Assessing the Effects of Climate on Global Fluvial Discharge Variability

Science.gov (United States)

Hansford, M. R.; Plink-Bjorklund, P.

2017-12-01

Plink-Bjorklund (2015) established the link between precipitation seasonality and river discharge variability in the monsoon domain and subtropical rivers (see also Leier et al, 2005; Fielding et al., 2009), resulting in distinct morphodynamic processes and a sedimentary record distinct from perennial precipitation zone in tropical rainforest zone and mid latitudes. This study further develops our understanding of discharge variability using a modern global river database created with data from the Global Runoff Data Centre (GRDC). The database consists of daily discharge for 595 river stations and examines them using a series of discharge variability indexes (DVI) on different temporal scales to examine how discharge variability occurs in river systems around the globe. These indexes examine discharge of individual days and monthly averages that allows for comparison of river systems against each other, regardless of size of the river. Comparing river discharge patterns in seven climate zones (arid, cold, humid subtropics, monsoonal, polar, rainforest, and temperate) based off the Koppen-Geiger climate classifications reveals a first order climatic control on discharge patterns and correspondingly sediment transport. Four groupings of discharge patterns emerge when coming climate zones and DVI: persistent, moderate, seasonal, and erratic. This dataset has incredible predictive power about the nature of discharge in fluvial systems around the world. These seasonal effects on surface water supply affects river morphodynamics and sedimentation on a wide timeframe, ranging from large single events to an inter-annual or even decadal timeframe. The resulting sedimentary deposits lead to differences in fluvial architecture on a range of depositional scales from sedimentary structures and bedforms to channel complex systems. These differences are important to accurately model for several reasons, ranging from stratigraphic and paleoenviromental reconstructions to more

Fluvial geomorphology on Earth-like planetary surfaces: A review.

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Baker, Victor R; Hamilton, Christopher W; Burr, Devon M; Gulick, Virginia C; Komatsu, Goro; Luo, Wei; Rice, James W; Rodriguez, J A P

2015-09-15

Morphological evidence for ancient channelized flows (fluvial and fluvial-like landforms) exists on the surfaces of all of the inner planets and on some of the satellites of the Solar System. In some cases, the relevant fluid flows are related to a planetary evolution that involves the global cycling of a volatile component (water for Earth and Mars; methane for Saturn's moon Titan). In other cases, as on Mercury, Venus, Earth's moon, and Jupiter's moon Io, the flows were of highly fluid lava. The discovery, in 1972, of what are now known to be fluvial channels and valleys on Mars sparked a major controversy over the role of water in shaping the surface of that planet. The recognition of the fluvial character of these features has opened unresolved fundamental questions about the geological history of water on Mars, including the presence of an ancient ocean and the operation of a hydrological cycle during the earliest phases of planetary history. Other fundamental questions posed by fluvial and fluvial-like features on planetary bodies include the possible erosive action of large-scale outpourings of very fluid lavas, such as those that may have produced the remarkable canali forms on Venus; the ability of exotic fluids, such as methane, to create fluvial-like landforms, as observed on Saturn's moon, Titan; and the nature of sedimentation and erosion under different conditions of planetary surface gravity. Planetary fluvial geomorphology also illustrates fundamental epistemological and methodological issues, including the role of analogy in geomorphological/geological inquiry.

Titan's fluvial valleys: Morphology, distribution, and spectral properties

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Langhans, M.H.; Jaumann, R.; Stephan, K.; Brown, R.H.; Buratti, B.J.; Clark, R.N.; Baines, K.H.; Nicholson, P.D.; Lorenz, R.D.; Soderblom, L.A.; Soderblom, J.M.; Sotin, Christophe; Barnes, J.W.; Nelson, R.

2012-01-01

Titan's fluvial channels have been investigated based on data obtained by the Synthetic Aperture Radar (SAR) instrument and the Visible and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft. In this paper, a database of fluvial features is created based on radar-SAR data aiming to unveil the distribution and the morphologic and spectral characteristics of valleys on Titan on a global scale. It will also study the spatial relations between fluvial valleys and Titan's geologic units and spectral surface units which have become accessible thanks to Cassini-VIMS data. Several distinct morphologic types of fluvial valleys can be discerned by SAR-images. Dendritic valley networks appear to have much in common with terrestrial dendritic systems owing to a hierarchical and tree-shaped arrangement of the tributaries which is indicative of an origin from precipitation. Dry valleys constitute another class of valleys resembling terrestrial wadis, an indication of episodic and strong flow events. Other valley types, such as putative canyons, cannot be correlated with rainfall based on their morphology alone, since it cannot be ruled out that they may have originated from volcanic/tectonic action or groundwater sapping. Highly developed and complex fluvial networks with channel lengths of up to 1200 km and widths of up to 10 km are concentrated only at a few locations whereas single valleys are scattered over all latitudes. Fluvial valleys are frequently found in mountainous areas. Some terrains, such as equatorial dune fields and undifferentiated plains at mid-latitudes, are almost entirely free of valleys. Spectrally, fluvial terrains are often characterized by a high reflectance in each of Titan's atmospheric windows, as most of them are located on Titan's bright 'continents'. Nevertheless, valleys are spatially associated with a surface unit appearing blue due to its higher reflection at 1.3??m in a VIMS false color RGB composite with R: 1.59/1.27??m, G: 2

Vision for a worldwide fluvial-sediment information network

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Gray, J.R.; Osterkamp, W.R.

2007-01-01

The nations of the world suffer both from the deleterious effects of some natural and human-altered fluxes of fluvial sediment and a lack of consistent and reliable information on the temporal and spatial occurrence of fluvial sediments. Decades ago, this difficulty was unavoidable due to a lack of understanding of the magnitude and scope of environmental influences exerted by fluvial sediment coupled with a dearth of tools for monitoring and studying the data. Such is no longer the case.

Riesgos vinculados a la exposición al radón

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Juan Miguel Barros Dios

2010-12-01

Full Text Available Se comentan las diferentes evidencias científicas de que el radón y sus descendientes de vida media corta son responsables de la aparición de un número no desdeñable de cánceres de pulmón entre la población expuesta en domicilios y edificios públicos (exposición laboral. Asimismo, se traza una pequeña aproximación al camino recorrido por este conocimiento y su difícil aceptación por parte de las diferentes Administraciones de numerosos países y, en concreto, de España, así como las diversas investigaciones que el Grupo Galego do Radon y el Laboratorio de Radón de Galicia, del Área de Salud Pública, de la Universidad de Santiago de Compostela, llevan aportando a ese conocimiento científico. Por último, se valoran las escasas iniciativas legislativas sobre el problema en España.

Arquitectura fluvial de las «Areniscas del río Arandilla». Triásico de Molina de Aragón (Guadalajara

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Sánchez-Moya, Y.

1989-08-01

Full Text Available The outstanding outcrops of Upper Buntsandstein sediments (Middle Triassic in Molina de Aragón (Guadalajara area, allow a detailed study of their characteristics and their associations which are described here. The fluvial architecture of the section indicates four main depositional episodes. The two lowest episodes were laid down by a fluvial system characterized by frequent channel shifting, low sinuosity and wide shallow channels. The drainage basin was controlled by highly seasonal discharge. The middle episode evolved into a more distal systems, with smaller higher sinuosity channels and fine overbank deposits. The uppermost episode is related to an increase of slope in the basin. That increase is probably related to tectonic movements recorded in this area. An attempt has been made to correlate the above events to the global sea level fluctuations (Haq et al., 1987. So, the low stage that have been stated occurred during Early Anisian can be tentatively correlated with the uppermost episode in Areniscas del río Arandilla.Los excelentes afloramientos de la parte superior del Buntsandstein (Triásico medio en Molina de Aragón (Guadalajara, han permitido llevar a cabo un análisis sedimentológico detallado de las facies fluviales y de su arquitectura. Se han distinguido doce diferentes facies cuyas características y asociaciones se describen en este trabajo. La evolución fluvial indica la existencia de cuatro episodios deposicionales. Los dos episodios inferiores son característicos de un sistema fluvial con canales de baja sinuosidad, inestables, de gran amplitud y poca profundidad. El drenaje de la cuenca estaba controlado por importantes descargas estacionales. El episodio intermedio es el resultado de la evolución del sistema hacia facies más distales. En esta etapa los canales son de menor tamaño, la sinuosidad es mayor y existe un mayor porcentaje de depósitos de granulometría fina relacionados con la llanura de inundaci

A fluvial mercury budget for Lake Ontario.

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Denkenberger, Joseph S; Driscoll, Charles T; Mason, Edward; Branfireun, Brian; Warnock, Ashley

2014-06-03

Watershed mercury (Hg) flux was calculated for ten inflowing rivers and the outlet for Lake Ontario using empirical measurements from two independent field-sampling programs. Total Hg (THg) flux for nine study watersheds that directly drain into the lake ranged from 0.2 kg/yr to 13 kg/yr, with the dominant fluvial THg load from the Niagara River at 154 kg/yr. THg loss at the outlet (St. Lawrence River) was 68 kg/yr and has declined approximately 40% over the past decade. Fluvial Hg inputs largely (62%) occur in the dissolved fraction and are similar to estimates of atmospheric Hg inputs. Fluvial mass balances suggest strong in-lake retention of particulate Hg inputs (99%), compared to dissolved total Hg (45%) and methyl Hg (22%) fractions. Wetland land cover is a good predictor of methyl Hg yield for Lake Ontario watersheds. Sediment deposition studies, coupled atmospheric and fluvial Hg fluxes, and a comparison of this work with previous measurements indicate that Lake Ontario is a net sink of Hg inputs and not at steady state likely because of recent decreases in point source inputs and atmospheric Hg deposition.

Análisis cualitativo de tópicos vinculados a la calidad de vida en personas con discapacidad

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María Victoria Martín Cilleros

Full Text Available Resumen La calidad de vida es un concepto que refleja la percepción subjetiva de la persona en relación al grado de satisfacción con sus condiciones de vida. Es un concepto que implica poner en primer plano a la persona, hablar sobre la calidad de los profesionales implicados e influye en el desarrollo de programas y la provisión de los servicios. El artículo refleja la opinión que tienen diferentes agentes relacionados con la discapacidad sobre determinados tópicos vinculados al modelo de calidad de vida como son: relación entre diferentes agentes, la formación necesaria en los profesionales del ámbito de la salud y/o de la discapacidad y el paso de la presencia a la participación en la sociedad de las personas con discapacidad. A través de una metodológica cualitativa, se analizan las argumentaciones de los participantes en estos tres temas. La nube de palabras, el mapa conceptual y el análisis de contenido, realizado tras la codificación de la información, permitieron conocer las necesidades percibidas y la satisfacción con la atención de los diferentes servicios. Se propone el perfil del profesional idóneo en el ámbito de la discapacidad. En las conclusiones obtenidas se recogen propuestas de futuro, facilitadoras de la mejora de la calidad de vida de las personas con discapacidad.

Geochemistry of Fluvial Sediments from Geregu, Southwest Nigeria

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Adiotomre Emmanuel E.

2017-03-01

Full Text Available Geochemical analysis of fluvial sediments on the banks of River Ero using inductively coupled plasma mass spectrometry illustrates their maturity, provenance and tectonic setting. The analysed sediment samples show low SiO2/Al2O3 ratios of 2.92-2.99 (units FL_A, FL_B and FL_E and high SiO2/Al2O3 ratios of 4.064-4.852 (units FL_C, FL_D, FL_F and FL_G. Sediments were geochemically classified as shales (units FL_A, FL_B and FL_E and greywackes (units FL_C, FL_D, FL_F and FL_G. Variability in sediment maturity (FL_F > FL_G >FL_C >FL_D >FL_A > FL_B > FL_E parallels a decreasing order in the ratios of SiO2/Al2O3 and K2O/Al2O3, as well as the proportion of quartz grains and matrix components. Evidence from Al2O3/TiO2, K2O, Rb, La/Co, Th/Co, Cr/ Th, Th/Cr, La/Th-Hf, Th-Hf-Co and rare earth element contents of sediment samples suggest felsic protoliths of upper continental crust in a passive margin tectonic setting. An insignificant contribution of mafic components from the source is, however, inferred based on the Ni and Cr contents of the sediment samples. Combined Eu anomalies <0.85 and (Gd/Ybn ratios <2.0 (1.53- 1.82, average 1.65 suggest post-Archean protoliths.

Field migration rates of tidal meanders recapitulate fluvial morphodynamics

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Finotello, Alvise; Lanzoni, Stefano; Ghinassi, Massimiliano; Marani, Marco; Rinaldo, Andrea; D'Alpaos, Andrea

2018-02-01

The majority of tidal channels display marked meandering features. Despite their importance in oil-reservoir formation and tidal landscape morphology, questions remain on whether tidal-meander dynamics could be understood in terms of fluvial processes and theory. Key differences suggest otherwise, like the periodic reversal of landscape-forming tidal flows and the widely accepted empirical notion that tidal meanders are stable landscape features, in stark contrast with their migrating fluvial counterparts. On the contrary, here we show that, once properly normalized, observed migration rates of tidal and fluvial meanders are remarkably similar. Key to normalization is the role of tidal channel width that responds to the strong spatial gradients of landscape-forming flow rates and tidal prisms. We find that migration dynamics of tidal meanders agree with nonlinear theories for river meander evolution. Our results challenge the conventional view of tidal channels as stable landscape features and suggest that meandering tidal channels recapitulate many fluvial counterparts owing to large gradients of tidal prisms across meander wavelengths.

The contribution of bank and surface sediments to fluvial sediment ...

African Journals Online (AJOL)

The contribution of bank and surface sediments to fluvial sediment transport of the Pra River. ... the relative contribution of surface and bank sediments to the fluvial sediment transport. ... EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT

Fluvial to Lacustrine Facies Transitions in Gale Crater, Mars

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Sumner, Dawn Y.; Williams, Rebecca M. E.; Schieber, Juergen; Palucis, Marisa C.; Oehler, Dorothy Z.; Mangold, Nicolas; Kah, Linda C.; Gupta, Sanjeev; Grotzinger, John P.; Grant, John A., III;

Field migration rates of tidal meanders recapitulate fluvial morphodynamics.

Science.gov (United States)

Finotello, Alvise; Lanzoni, Stefano; Ghinassi, Massimiliano; Marani, Marco; Rinaldo, Andrea; D'Alpaos, Andrea

2018-02-13

The majority of tidal channels display marked meandering features. Despite their importance in oil-reservoir formation and tidal landscape morphology, questions remain on whether tidal-meander dynamics could be understood in terms of fluvial processes and theory. Key differences suggest otherwise, like the periodic reversal of landscape-forming tidal flows and the widely accepted empirical notion that tidal meanders are stable landscape features, in stark contrast with their migrating fluvial counterparts. On the contrary, here we show that, once properly normalized, observed migration rates of tidal and fluvial meanders are remarkably similar. Key to normalization is the role of tidal channel width that responds to the strong spatial gradients of landscape-forming flow rates and tidal prisms. We find that migration dynamics of tidal meanders agree with nonlinear theories for river meander evolution. Our results challenge the conventional view of tidal channels as stable landscape features and suggest that meandering tidal channels recapitulate many fluvial counterparts owing to large gradients of tidal prisms across meander wavelengths. Copyright © 2018 the Author(s). Published by PNAS.

Fluvial hydrology and geomorphology of Monsoon-dominated Indian rivers

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Vishwas S. Kale

2005-11-01

Full Text Available The Indian rivers are dominantly monsoon rainfed. As a result, their regime characteristics are dictated by the spatio-temporal variations in the monsoon rainfall. Although the rivers carry out most of the geomorphic work during 4-5 months of the monsoon season, the nature and magnitude of response to variations in the discharge and sediment load varies with the basin size and relief characteristics. Large monsoon floods play a role of great importance on all the rivers. This paper describes the hydrological and geomorphological characteristics of the two major fluvial systems of the Indian region, namely the Himalayan fluvial system and the Peninsular fluvial system. Large number of studies published so far indicate that there are noteworthy differences between the two river systems, with respect to river hydrology, channel morphology, sediment load and behaviour. The nature of alterations in the fluvial system due to increased human interference is also briefly mentioned. This short review demonstrates that there is immense variety of rivers in India. This makes India one of the best places to study rivers and their forms and processes.

Fluvial organic carbon losses from oil palm plantations on tropical peat, Sarawak, Southeast Asia

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Cook, Sarah; Page, Susan; Evans, Chris; Whelan, Mick; Gauci, Vincent; Lip Khoon, Kho

2017-04-01

Tropical peatlands are valuable stores of carbon. However, tropical peat swamp forests (TPSFs) in Southeast Asia have increasingly been converted to other land-uses. For example, more than 25% of TPSFs are now under oil palm plantations. This conversion - requiring felling and burning of trees and drainage of the peat - can enhance carbon mineralization, dissolved organic carbon (DOC) losses and can contribute significantly to global anthropogenic greenhouse gas emissions, changing these natural carbon sinks into carbon sources. At present, relatively few scientifically sound studies provide dependable estimates of gaseous and fluvial carbon losses from oil palm plantations or from drained tropical peat in general. Here we present an annual (54 week) estimate of the export of dissolved and particulate organic carbon in water draining two oil palm estates and nearby stands of TPSF in Sarawak, Malaysia, subjected to varying degrees of past anthropogenic disturbance. Spectrophotometric techniques including SUVA254 (Specific Ultra-Violet Absorption) were used to gain insight into the aromaticity and subsequent bioavailability of the exported DOC. Water draining plantation and deforested land had a higher proportion of labile carbon compared to water draining forested areas. Preliminary data suggest a total fluvial DOC flux from plantations of ca. 190 g C m-2 year-1; nearly three times estimates from intact TPSFs (63 g C m-2 year-1). DOC accounted for between 86 % - 94 % of the total organic carbon lost (most of which was bioavailable). Wit et al. (2015) estimates that an average of 53 % of peat-derived DOC is decomposed and emitted as CO2, on a monthly basis. Based on these estimates our data suggests an additional 101 g CO2 m-2 may be emitted indirectly from fluvial organic carbon in degraded TPSFs per year. Overall, these findings emphasize the importance of including fluvial organic carbon fluxes when quantifying the impact of anthropogenic disturbance on the

Evaluating process origins of sand-dominated fluvial stratigraphy

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Chamberlin, E.; Hajek, E. A.

2015-12-01

Sand-dominated fluvial stratigraphy is often interpreted as indicating times of relatively slow subsidence because of the assumption that fine sediment (silt and clay) is reworked or bypassed during periods of low accommodation. However, sand-dominated successions may instead represent proximal, coarse-grained reaches of paleo-river basins and/or fluvial systems with a sandy sediment supply. Differentiating between these cases is critical for accurately interpreting mass-extraction profiles, basin-subsidence rates, and paleo-river avulsion and migration behavior from ancient fluvial deposits. We explore the degree to which sand-rich accumulations reflect supply-driven progradation or accommodation-limited reworking, by re-evaluating the Castlegate Sandstone (Utah, USA) and the upper Williams Fork Formation (Colorado, USA) - two Upper Cretaceous sandy fluvial deposits previously interpreted as having formed during periods of relatively low accommodation. Both units comprise amalgamated channel and bar deposits with minor intra-channel and overbank mudstones. To constrain relative reworking, we quantify the preservation of bar deposits in each unit using detailed facies and channel-deposit mapping, and compare bar-deposit preservation to expected preservation statistics generated with object-based models spanning a range of boundary conditions. To estimate the grain-size distribution of paleo-sediment input, we leverage results of experimental work that shows both bed-material deposits and accumulations on the downstream side of bars ("interbar fines") sample suspended and wash loads of active flows. We measure grain-size distributions of bar deposits and interbar fines to reconstruct the relative sandiness of paleo-sediment supplies for both systems. By using these novel approaches to test whether sand-rich fluvial deposits reflect river systems with accommodation-limited reworking and/or particularly sand-rich sediment loads, we can gain insight into large

Unsteady Landscapes: Climatic and Tectonic Controls on Fluvial Terrace Formation

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Clubb, F. J.; Mudd, S. M.

2017-12-01

Fluvial terraces are common landforms throughout mountainous regions which represent abandoned remnants of active river systems and their floodplains. The formation of these landforms points to a fundamental unsteadiness in the incision rate of the fluvial network, providing important information on channel response to climatic, tectonic, and base-level forcing, sediment storage and dynamics within mountainous systems, and the relative importance of lateral and vertical incision rates. In his 1877 Report on the Geology of the Henry Mountains, G.K. Gilbert suggested that strath terraces may form due to climatically-driven increase in sediment supply, causing armouring of the channel bed and hindering vertical incision. An alternative hypothesis suggests that strath terraces may be preserved through progressive tectonic uplift or base-level fall. These different formation mechanisms should result in varying distribution of terrace elevations along channels: if terraces are formed through climate-driven variations in sediment supply, we might expect that terrace elevations would be random, whereas progressive fluvial incision should result in a series of terraces with a systematic elevation pattern. Here we test alternative hypotheses for strath terrace formation using a new method for objectively and rapidly identifying terrace surfaces from digital elevation models (DEMs) over large spatial scales. Our new method identifies fluvial terraces using their gradient and elevation compared to the modern channel, thresholds of which are statistically calculated from the DEM and do not need to be set manually by the user. We use this method to extract fluvial terraces for every major river along the coast of California, and quantify their distribution and elevation along the fluvial long profile. Our results show that there is no systematic pattern in terrace elevations despite a well-constrained spatial variation in uplift rates, suggesting that terraces in this region do

Fluvial deposits as an archive of early human activity: Progress during the 20 years of the Fluvial Archives Group

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Chauhan, Parth R.; Bridgland, David R.; Moncel, Marie-Hélène; Antoine, Pierre; Bahain, Jean-Jacques; Briant, Rebecca; Cunha, Pedro P.; Despriée, Jackie; Limondin-Lozouet, Nicole; Locht, Jean-Luc; Martins, Antonio A.; Schreve, Danielle C.; Shaw, Andrew D.; Voinchet, Pierre; Westaway, Rob; White, Mark J.; White, Tom S.

2017-06-01

Fluvial sedimentary archives are important repositories for Lower and Middle Palaeolithic artefacts throughout the 'Old World', especially in Europe, where the beginning of their study coincided with the realisation that early humans were of great antiquity. Now that many river terrace sequences can be reliably dated and correlated with the globally valid marine isotope record, potentially useful patterns can be recognized in the distribution of the find-spots of the artefacts that constitute the large collections that were assembled during the years of manual gravel extraction. This paper reviews the advances during the past two decades in knowledge of hominin occupation based on artefact occurrences in fluvial contexts, in Europe, Asia and Africa. As such it is an update of a comparable review in 2007, at the end of IGCP Project no. 449, which had instigated the compilation of fluvial records from around the world during 2000-2004, under the auspices of the Fluvial Archives Group. An overarching finding is the confirmation of the well-established view that in Europe there is a demarcation between handaxe making in the west and flake-core industries in the east, although on a wider scale that pattern is undermined by the increased numbers of Lower Palaeolithic bifaces now recognized in East Asia. It is also apparent that, although it seems to have appeared at different places and at different times in the later Lower Palaeolithic, the arrival of Levallois technology as a global phenomenon was similarly timed across the area occupied by Middle Pleistocene hominins, at around 0.3 Ma.

Martian Fluvial Conglomerates at Gale Crater

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Williams, R. M. E.; Grotzinger, J. P.; Dietrich, W. E.; Gupta, S.; Sumner, D. Y.; Wiens, R. C.; Mangold, N.; Malin, M. C.; Edgett, K. S.; Maurice, S.; Forni, O.; Gasnault, O.; Ollila, A.; Newsom, H. E.; Dromart, G.; Palucis, M. C.; Yingst, R. A.; Anderson, R. B.; Herkenhoff, K. E.; Le Mouélic, S.; Goetz, W.; Madsen, M. B.; Koefoed, A.; Jensen, J. K.; Bridges, J. C.; Schwenzer, S. P.; Lewis, K. W.; Stack, K. M.; Rubin, D.; Kah, L. C.; Bell, J. F.; Farmer, J. D.; Sullivan, R.; Van Beek, T.; Blaney, D. L.; Pariser, O.; Deen, R. G.; Kemppinen, Osku; Bridges, Nathan; Johnson, Jeffrey R.; Minitti, Michelle; Cremers, David; Edgar, Lauren; Godber, Austin; Wadhwa, Meenakshi; Wellington, Danika; McEwan, Ian; Newman, Claire; Richardson, Mark; Charpentier, Antoine; Peret, Laurent; King, Penelope; Blank, Jennifer; Weigle, Gerald; Schmidt, Mariek; Li, Shuai; Milliken, Ralph; Robertson, Kevin; Sun, Vivian; Baker, Michael; Edwards, Christopher; Ehlmann, Bethany; Farley, Kenneth; Griffes, Jennifer; Miller, Hayden; Newcombe, Megan; Pilorget, Cedric; Rice, Melissa; Siebach, Kirsten; Stolper, Edward; Brunet, Claude; Hipkin, Victoria; Léveillé, Richard; Marchand, Geneviève; Sobrón Sánchez, Pablo; Favot, Laurent; Cody, George; Steele, Andrew; Flückiger, Lorenzo; Lees, David; Nefian, Ara; Martin, Mildred; Gailhanou, Marc; Westall, Frances; Israël, Guy; Agard, Christophe; Baroukh, Julien; Donny, Christophe; Gaboriaud, Alain; Guillemot, Philippe; Lafaille, Vivian; Lorigny, Eric; Paillet, Alexis; Pérez, René; Saccoccio, Muriel; Yana, Charles; Aparicio, Carlos Armiens; Caride Rodríguez, Javier; Carrasco Blázquez, Isaías; Gómez Gómez, Felipe; Elvira, Javier Gómez; Hettrich, Sebastian; Lepinette Malvitte, Alain; Marín Jiménez, Mercedes; Frías, Jesús Martínez; Soler, Javier Martín; Torres, F. Javier Martín; Molina Jurado, Antonio; Sotomayor, Luis Mora; Muñoz Caro, Guillermo; Navarro López, Sara; González, Verónica Peinado; García, Jorge Pla; Rodriguez Manfredi, José Antonio; Planelló, Julio José Romeral; Alejandra Sans Fuentes, Sara; Sebastian Martinez, Eduardo; Torres Redondo, Josefina; O'Callaghan, Roser Urqui; Zorzano Mier, María-Paz; Chipera, Steve; Lacour, Jean-Luc; Mauchien, Patrick; Sirven, Jean-Baptiste; Manning, Heidi; Fairén, Alberto; Hayes, Alexander; Joseph, Jonathan; Squyres, Steven; Thomas, Peter; Dupont, Audrey; Lundberg, Angela; Melikechi, Noureddine; Mezzacappa, Alissa; DeMarines, Julia; Grinspoon, David; Reitz, Günther; Prats, Benito; Atlaskin, Evgeny; Genzer, Maria; Harri, Ari-Matti; Haukka, Harri; Kahanpää, Henrik; Kauhanen, Janne; Paton, Mark; Polkko, Jouni; Schmidt, Walter; Siili, Tero; Fabre, Cécile; Wray, James; Wilhelm, Mary Beth; Poitrasson, Franck; Patel, Kiran; Gorevan, Stephen; Indyk, Stephen; Paulsen, Gale; Bish, David; Schieber, Juergen; Gondet, Brigitte; Langevin, Yves; Geffroy, Claude; Baratoux, David; Berger, Gilles; Cros, Alain; Uston, Claude d.; Lasue, Jérémie; Lee, Qiu-Mei; Meslin, Pierre-Yves; Pallier, Etienne; Parot, Yann; Pinet, Patrick; Schröder, Susanne; Toplis, Mike; Lewin, Éric; Brunner, Will; Heydari, Ezat; Achilles, Cherie; Oehler, Dorothy; Sutter, Brad; Cabane, Michel; Coscia, David; Szopa, Cyril; Robert, François; Sautter, Violaine; Nachon, Marion; Buch, Arnaud; Stalport, Fabien; Coll, Patrice; François, Pascaline; Raulin, François; Teinturier, Samuel; Cameron, James; Clegg, Sam; Cousin, Agnès; DeLapp, Dorothea; Dingler, Robert; Jackson, Ryan Steele; Johnstone, Stephen; Lanza, Nina; Little, Cynthia; Nelson, Tony; Williams, Richard B.; Jones, Andrea; Kirkland, Laurel; Treiman, Allan; Baker, Burt; Cantor, Bruce; Caplinger, Michael; Davis, Scott; Duston, Brian; Fay, Donald; Hardgrove, Craig; Harker, David; Herrera, Paul; Jensen, Elsa; Kennedy, Megan R.; Krezoski, Gillian; Krysak, Daniel; Lipkaman, Leslie; McCartney, Elaina; McNair, Sean; Nixon, Brian; Posiolova, Liliya; Ravine, Michael; Salamon, Andrew; Saper, Lee; Stoiber, Kevin; Supulver, Kimberley; Van Beek, Jason; Zimdar, Robert; French, Katherine Louise; Iagnemma, Karl; Miller, Kristen; Summons, Roger; Goesmann, Fred; Hviid, Stubbe; Johnson, Micah; Lefavor, Matthew; Lyness, Eric; Breves, Elly; Dyar, M. Darby; Fassett, Caleb; Blake, David F.; Bristow, Thomas; DesMarais, David; Edwards, Laurence; Haberle, Robert; Hoehler, Tori; Hollingsworth, Jeff; Kahre, Melinda; Keely, Leslie; McKay, Christopher; Bleacher, Lora; Brinckerhoff, William; Choi, David; Conrad, Pamela; Dworkin, Jason P.; Eigenbrode, Jennifer; Floyd, Melissa; Freissinet, Caroline; Garvin, James; Glavin, Daniel; Harpold, Daniel; Mahaffy, Paul; Martin, David K.; McAdam, Amy; Pavlov, Alexander; Raaen, Eric; Smith, Michael D.; Stern, Jennifer; Tan, Florence; Trainer, Melissa; Meyer, Michael; Posner, Arik; Voytek, Mary; Anderson, Robert C.; Aubrey, Andrew; Beegle, Luther W.; Behar, Alberto; Brinza, David; Calef, Fred; Christensen, Lance; Crisp, Joy A.; DeFlores, Lauren; Feldman, Jason; Feldman, Sabrina; Flesch, Gregory; Hurowitz, Joel; Jun, Insoo; Keymeulen, Didier; Maki, Justin; Mischna, Michael; Morookian, John Michael; Parker, Timothy; Pavri, Betina; Schoppers, Marcel; Sengstacken, Aaron; Simmonds, John J.; Spanovich, Nicole; de la Torre Juarez, Manuel; Vasavada, Ashwin R.; Webster, Christopher R.; Yen, Albert; Archer, Paul Douglas; Cucinotta, Francis; Jones, John H.; Ming, Douglas; Morris, Richard V.; Niles, Paul; Rampe, Elizabeth; Nolan, Thomas; Fisk, Martin; Radziemski, Leon; Barraclough, Bruce; Bender, Steve; Berman, Daniel; Dobrea, Eldar Noe; Tokar, Robert; Vaniman, David; Leshin, Laurie; Cleghorn, Timothy; Huntress, Wesley; Manhès, Gérard; Hudgins, Judy; Olson, Timothy; Stewart, Noel; Sarrazin, Philippe; Grant, John; Vicenzi, Edward; Wilson, Sharon A.; Bullock, Mark; Ehresmann, Bent; Hamilton, Victoria; Hassler, Donald; Peterson, Joseph; Rafkin, Scot; Zeitlin, Cary; Fedosov, Fedor; Golovin, Dmitry; Karpushkina, Natalya; Kozyrev, Alexander; Litvak, Maxim; Malakhov, Alexey; Mitrofanov, Igor; Mokrousov, Maxim; Nikiforov, Sergey; Prokhorov, Vasily; Sanin, Anton; Tretyakov, Vladislav; Varenikov, Alexey; Vostrukhin, Andrey; Kuzmin, Ruslan; Clark, Benton; Wolff, Michael; McLennan, Scott; Botta, Oliver; Drake, Darrell; Bean, Keri; Lemmon, Mark; Lee, Ella Mae; Sucharski, Robert; Hernández, Miguel Ángel de Pablo; Blanco Ávalos, Juan José; Ramos, Miguel; Kim, Myung-Hee; Malespin, Charles; Plante, Ianik; Muller, Jan-Peter; González, Rafael Navarro; Ewing, Ryan; Boynton, William; Downs, Robert; Fitzgibbon, Mike; Harshman, Karl; Morrison, Shaunna; Kortmann, Onno; Williams, Amy; Lugmair, Günter; Wilson, Michael A.; Jakosky, Bruce; Zunic, Tonci Balic; Frydenvang, Jens; Kinch, Kjartan; Stipp, Susan Louise Svane; Boyd, Nick; Campbell, John L.; Gellert, Ralf; Perrett, Glynis; Pradler, Irina; VanBommel, Scott; Jacob, Samantha; Owen, Tobias; Rowland, Scott; Savijärvi, Hannu; Boehm, Eckart; Böttcher, Stephan; Burmeister, Sönke; Guo, Jingnan; Köhler, Jan; García, César Martín; Mellin, Reinhold Mueller; Schweingruber, Robert Wimmer; McConnochie, Timothy; Benna, Mehdi; Franz, Heather; Bower, Hannah; Brunner, Anna; Blau, Hannah; Boucher, Thomas; Carmosino, Marco; Atreya, Sushil; Elliott, Harvey; Halleaux, Douglas; Rennó, Nilton; Wong, Michael; Pepin, Robert; Elliott, Beverley; Spray, John; Thompson, Lucy; Gordon, Suzanne; Williams, Joshua; Vasconcelos, Paulo; Bentz, Jennifer; Nealson, Kenneth; Popa, Radu; Moersch, Jeffrey; Tate, Christopher; Day, Mackenzie; Kocurek, Gary; Hallet, Bernard; Sletten, Ronald; Francis, Raymond; McCullough, Emily; Cloutis, Ed; ten Kate, Inge Loes; Arvidson, Raymond; Fraeman, Abigail; Scholes, Daniel; Slavney, Susan; Stein, Thomas; Ward, Jennifer; Berger, Jeffrey; Moores, John E.

2013-05-01

Observations by the Mars Science Laboratory Mast Camera (Mastcam) in Gale crater reveal isolated outcrops of cemented pebbles (2 to 40 millimeters in diameter) and sand grains with textures typical of fluvial sedimentary conglomerates. Rounded pebbles in the conglomerates indicate substantial fluvial abrasion. ChemCam emission spectra at one outcrop show a predominantly feldspathic composition, consistent with minimal aqueous alteration of sediments. Sediment was mobilized in ancient water flows that likely exceeded the threshold conditions (depth 0.03 to 0.9 meter, average velocity 0.20 to 0.75 meter per second) required to transport the pebbles. Climate conditions at the time sediment was transported must have differed substantially from the cold, hyper-arid modern environment to permit aqueous flows across several kilometers.

Utilization of alternatives fuels in a fluvial convoy; Utilizacao de combustiveis alternativos em um comboio fluvial

Energy Technology Data Exchange (ETDEWEB)

Padovezi, Carlos D; Giraldo, Arnaldo

1987-12-31

This work presents the results of tests performed with ethanol and methanol in a fluvial convoy in Tiete river, Sao Paulo State - Southeast Brazil. It also outlines a comparison and evaluation methodology. 9 figs., 3 tabs.

Utilization of alternatives fuels in a fluvial convoy; Utilizacao de combustiveis alternativos em um comboio fluvial

Energy Technology Data Exchange (ETDEWEB)

Padovezi, Carlos D.; Giraldo, Arnaldo

1986-12-31

This work presents the results of tests performed with ethanol and methanol in a fluvial convoy in Tiete river, Sao Paulo State - Southeast Brazil. It also outlines a comparison and evaluation methodology. 9 figs., 3 tabs.

Landform Evolution Modeling of Specific Fluvially Eroded Physiographic Units on Titan

Science.gov (United States)

Moore, J. M.; Howard, A. D.; Schenk, P. M.

2015-01-01

Several recent studies have proposed certain terrain types (i.e., physiographic units) on Titan thought to be formed by fluvial processes acting on local uplands of bedrock or in some cases sediment. We have earlier used our landform evolution models to make general comparisons between Titan and other ice world landscapes (principally those of the Galilean satellites) that we have modeled the action of fluvial processes. Here we give examples of specific landscapes that, subsequent to modeled fluvial work acting on the surfaces, produce landscapes which resemble mapped terrain types on Titan.

Púrpura Alérgica Trombocitopénica

OpenAIRE

Zegarra Puppi, José

2014-01-01

En el amplio campo de la Patología Médica los síndromes purpúricos vinculados a fenómenos alérgicos han adquirido singular importancia debido a los progresos de la Medicina en el terreno de la inmuno-hematología. En estos estudios cobra singular relieve la patogenia inmunitaria de las trombocitopenias. Hasta hace 15 años las teorías que explicaban las púrpuras trombocitopénicas se referían principalmente a la hiperfunción esplénica que deprimía la maduración de los megacariocitos o la salida...

Riparian shrub metal concentrations and growth in amended fluvial mine tailings

Science.gov (United States)

Fluvial mine tailing deposition has caused extensive riparian damage throughout the western United States. Willows are often used for fluvial mine tailing revegetation, but some species accumulate excessive metal concentrations which could be detrimental to browsers. In a greenhouse experiment, gr...

Morphology of fluvial levee series along a river under human influence, Maros River, Hungary

Science.gov (United States)

Kiss, Tímea; Balogh, Márton; Fiala, Károly; Sipos, György

2018-02-01

The development and morphometry of fluvial levees reflect the connection between channel and overbank processes, which can be altered by various human activities. The aims of this study are to investigate the morphology and spatial characteristics of fluvial levees and evaluate the role of some local- and catchment-scale human activities on their medium-term (150 years) development. This study applies LiDAR data along a 53-km-long reach of the Maros River in Hungary. Six fluvial levee types are identified based on the beginning and end of their evolution. These levee types were generated by local nineteenth century channel regulation works (cutoffs) and mid-twentieth century channel narrowing, which was caused by gravel mining and water impoundment in the upstream sections. However, other human activities also influenced the development of active fluvial levees because their horizontal evolution could have been limited by embanked flood-protection levees or the widening of low-lying floodplain benches that were generated by channel narrowing. Additionally, revetment constructions influenced their vertical parameters as higher fluvial levees developed along the fixed banks. Generally, the older active fluvial levees are wider, while the younger active levees are narrower with steeper slopes but not always lower. On the low-lying floodplain levels (benches), the youngest fluvial levees evolved quite rapidly and consist of coarser material. Currently, only 9.8- to 38-year return-period floods could cover the fluvial levees, contributing to their evolution. This fact and the development of fluvial levee series with two-three members reflect a gradual decoupling of the channel from the floodplain.

Heavy mineral analyses as a powerful tool in fluvial geomorphology

Science.gov (United States)

von Suchodoletz, Hans; Gärtner, Andreas; Faust, Dominik

2014-05-01

The Marneuli depression is a tectonic sub-basin of the Transcaucasian depression in eastern Georgia, filled with several decametres of fluvial, lacustrine and aeolian Quaternary sediments. In order to reconstruct past landscape evolution of the region we studied Late Quaternary fluvial sediments found along several rivers that flow through that depression. Whereas Holocene river sediments could generally easily be assigned to corresponding rivers, this was not always the case for older fluvial sediments. For this reason, we studied the heavy mineral contents of five recent rivers and of four sedimentary deposits of potential precursors. A total of 4088 analysed heavy mineral grains enabled us to set up the characteristic heavy mineral distribution pattern for each sample. Using these data, we were able to reconstruct the most likely source areas of the Late Pleistocene fluvial sediments and to link them with the catchment areas of recent rivers. This allowed us to identify and to substantiate significant Late Quaternary river diversions that could at least partly be assigned to ongoing tectonic processes.

Fluvial response to the last Holocene rapid climate change in the Northwestern Mediterranean coastlands

Science.gov (United States)

Degeai, Jean-Philippe; Devillers, Benoît; Blanchemanche, Philippe; Dezileau, Laurent; Oueslati, Hamza; Tillier, Margaux; Bohbot, Hervé

2017-05-01

The variability of fluvial activity in the Northwestern Mediterranean coastal lowlands and its relationship with modes of climate change were analysed from the late 9th to the 18th centuries CE. Geochemical analyses were undertaken from a lagoonal sequence and surrounding sediments in order to track the fluvial inputs into the lagoon. An index based on the K/S and Rb/S ratios was used to evidence the main periods of fluvial activity. This index reveals that the Medieval Climate Anomaly (MCA) was a drier period characterized by a lower fluvial activity, while the Little Ice Age (LIA) was a wetter period with an increase of the river dynamics. Three periods of higher than average fluvial activity were evidenced at the end of the first millennium CE (ca. 900-950 cal yr CE), in the first half of the second millennium CE (ca. 1150-1550 cal yr CE), and during the 1600s-1700s CE (ca. 1650-1800 cal yr CE). The comparison of these fluvial periods with other records of riverine or lacustrine floods in Spain, Italy, and South of France seems to indicate a general increase in fluvial and flood patterns in the Northwestern Mediterranean in response to the climate change from the MCA to the LIA, although some episodes of flooding are not found in all records. Besides, the phases of higher than average fluvial dynamics are in good agreement with the North Atlantic cold events evidenced from records of ice-rafted debris. The evolution of fluvial activity in the Northwestern Mediterranean coastlands during the last millennium could have been driven by atmospheric and oceanic circulation patterns.

La Pérdida de Espacios Fluviales en Andalucía (1956-2007. Una Aproximación Escalar.

Directory of Open Access Journals (Sweden)

David González-Rojas

2017-12-01

Full Text Available Desde mediados del siglo pasado, los espacios fluviales andaluces han conocido un acelerado proceso de degradación. En el presente artículo se realiza una aproximación histórica y multiescalar de la distribución de estos espacios a partir de los mapas de usos y coberturas vegetales. A escala regional, se evidencia que Andalucía ha perdido una décima parte de los espacios fluviales en seis décadas. En segundo lugar, se analiza, a escala local, dos casos paradigmáticos (río Guadalmina y río Guadalquivir y extensibles al resto del territorio. El esfuerzo realizado para la ordenación de los ríos no ha tenido su reflejo en los resultados obtenidos, siendo las interrelaciones entre la gestión del agua y del territorio (regional, subregional y municipal una cuestión no resuelta.

Geomorphic Unit Tool (GUT): Applications of Fluvial Mapping

Science.gov (United States)

Kramer, N.; Bangen, S. G.; Wheaton, J. M.; Bouwes, N.; Wall, E.; Saunders, C.; Bennett, S.; Fortney, S.

2017-12-01

Geomorphic units are the building blocks of rivers and represent distinct habitat patches for many fluvial organisms. We present the Geomorphic Unit Toolkit (GUT), a flexible GIS geomorphic unit mapping tool, to generate maps of fluvial landforms from topography. GUT applies attributes to landforms based on flow stage (Tier 1), topographic signatures (Tier 2), geomorphic characteristics (Tier 3) and patch characteristics (Tier 4) to derive attributed maps at the level of detail required by analysts. We hypothesize that if more rigorous and consistent geomorphic mapping is conducted, better correlations between physical habitat units and ecohydraulic model results will be obtained compared to past work. Using output from GUT for coarse bed tributary streams in the Columbia River Basin, we explore relationships between salmonid habitat and geomorphic spatial metrics. We also highlight case studies of how GUT can be used to showcase geomorphic impact from large wood restoration efforts. Provided high resolution topography exists, this tool can be used to quickly assess changes in fluvial geomorphology in watersheds impacted by human activities.

Modeling plan-form deltaic response to changes in fluvial sediment supply

NARCIS (Netherlands)

Nienhuis, J.H.; Ashton, A.D.; Roos, Pieter C.; Hulscher, Suzanne J.M.H.; Giosan, L.; Kranenburg, W.M.; Horstman, E.M.; Wijnberg, K.M.

2012-01-01

This study focuses on the effects of changes in fluvial sediment supply on the plan-form shape of wave-dominated deltas. We apply a one-line numerical shoreline model to calculate shoreline evolution after (I) elimination and (II) time-periodic variation of fluvial input. Model results suggest four

Shaler: in situ analysis of a fluvial sedimentary deposit on Mars

Science.gov (United States)

Edgar, Lauren; Gupta, Sanjeev; Rubin, David M.; Lewis, Kevin W.; Kocurek, Gary A.; Anderson, Ryan; Bell, James F.; Dromart, Gilles; Edgett, Kenneth S.; Grotzinger, John P.; Hardgrove, Craig; Kah, Linda C.; LeVeille, Richard A.; Malin, Michael C.; Mangold, Nicholas; Milliken, Ralph E.; Minitti, Michelle; Palucis, Marisa C.; Rice, Melissa; Rowland, Scott K.; Schieber, Juergen; Stack, Kathryn M.; Sumner, Dawn Y.; Wiens, Roger C.; Williams, Rebecca M.E.; Williams, Amy J.

2018-01-01

This paper characterizes the detailed sedimentology of a fluvial sandbody on Mars for the first time, and interprets its depositional processes and palaeoenvironmental setting. Despite numerous orbital observations of fluvial landforms on the surface of Mars, ground-based characterization of the sedimentology of such fluvial deposits has not previously been possible. Results from the NASA Mars Science Laboratory Curiosity rover provide an opportunity to reconstruct at fine scale the sedimentary architecture and palaeomorphology of a fluvial environment on Mars. This work describes the grain size, texture, and sedimentary facies of the Shaler outcrop, reconstructs the bedding architecture, and analyses cross-stratification to determine palaeocurrents. On the basis of bedset geometry and inclination, grain-size distribution, and bedform migration direction, this study concludes that the Shaler outcrop likely records the accretion of a fluvial barform. The majority of the outcrop consists of large-scale trough cross-bedding of coarse sand and granules. Palaeocurrent analyses and bedform reconstruction indicate that the beds were deposited by bedforms that migrated towards the northeast, across the surface of a bar that migrated southeast. Stacked cosets of dune cross-bedding suggest aggradation of multiple bedforms, which provides evidence for short periods of sustained flow during Shaler deposition. However, local evidence for aeolian reworking and the presence of potential desiccation cracks within the outcrop suggests that fluvial deposition may have been intermittent. The uppermost strata at Shaler are distinct in terms of texture and chemistry, and are inferred to record deposition from a different sediment dispersal system with a contrasting provenance. The outcrop as a whole is a testament to the availability of liquid water on the surface of Mars in its early history.

Expansión urbana, PRMS y el corredor fluvial del Rio Mapocho inferior /Urban growth, planning instruments and the lower Mapocho River basin

Directory of Open Access Journals (Sweden)

Francisco Ferrando Acuña

2010-06-01

Full Text Available Se analiza la relevancia de los servicios ambientales de los corredores fluviales en el ámbito de la planificación urbana sustentable, al tenor de la realidad y falencias de los instrumentos territoriales vigentes en esta temática. Dados los múltiples servicios ambientales de esto tipo de sistema natural, escasamente valorizado y nada incorporado en los IOT en Chile, al contrario de experiencias extranjeras como las españolas, se rescata y explicitan las características del corredor inferior del Río Mapocho entre la Comuna de Maipú y el Monte desde el punto de vista geomorfológico, hidrológico y ambiental, y se señala la relevancia de su temprana incorporación en los proyectos de urbanización de este territorio, los cuales ya se encuentran en marcha a propósito del progresivo cambio de uso del suelo de rural a urbano. /In Chile there's no correlation between the environmental relevance of the fluvial corridors and its many benefic functions for the urban climate and quality of life of his inhabitants with planning instruments. Consequently these fluvial systems aren't the basis of city planning setting aside its environmental services not only for cities, also for regions and more. The lower Río Mapocho corridor is evaluated considering the land use change in its surroundings. A review is presentes of international experiences on this matter, particularly from Spain.

Contemporary Conceptual Approaches in Fluvial Geomorphology

Directory of Open Access Journals (Sweden)

Mônica dos Santos Marçal

2016-06-01

Full Text Available Contemporary fluvial geomorphology faces challenging questions, especially as it goes by understanding the Late Holocene/Anthropocene period, which has repercussions today and are intrinsically important to understand the human river disturbance. Given the scale that physical rates operate in complex river systems, two conceptual paths were developed to analyze the spatial and temporal organization. The network view emphasizes controls on catchment-scale and a reach approach focuses on discontinuity and local controls. Fluvial geomorphology has seek to understand the organization of complex river systems from the integrated view of the continuity and discontinuity paradigm. This integrated approach has stimulated within the geomorphology, the emergence of new theoretical-methodological instruments. It is recognized that rivers management is an ongoing process, part of the socio-cultural development, which refers to both a social movement and scientific exercise.

Protracted fluvial recovery from medieval earthquakes, Pokhara, Nepal

Science.gov (United States)

Stolle, Amelie; Bernhardt, Anne; Schwanghart, Wolfgang; Andermann, Christoff; Schönfeldt, Elisabeth; Seidemann, Jan; Adhikari, Basanta R.; Merchel, Silke; Rugel, Georg; Fort, Monique; Korup, Oliver

2016-04-01

River response to strong earthquake shaking in mountainous terrain often entails the flushing of sediments delivered by widespread co-seismic landsliding. Detailed mass-balance studies following major earthquakes in China, Taiwan, and New Zealand suggest fluvial recovery times ranging from several years to decades. We report a detailed chronology of earthquake-induced valley fills in the Pokhara region of western-central Nepal, and demonstrate that rivers continue to adjust to several large medieval earthquakes to the present day, thus challenging the notion of transient fluvial response to seismic disturbance. The Pokhara valley features one of the largest and most extensively dated sedimentary records of earthquake-triggered sedimentation in the Himalayas, and independently augments paleo-seismological archives obtained mainly from fault trenches and historic documents. New radiocarbon dates from the catastrophically deposited Pokhara Formation document multiple phases of extremely high geomorphic activity between ˜700 and ˜1700 AD, preserved in thick sequences of alternating fluvial conglomerates, massive mud and silt beds, and cohesive debris-flow deposits. These dated fan-marginal slackwater sediments indicate pronounced sediment pulses in the wake of at least three large medieval earthquakes in ˜1100, 1255, and 1344 AD. We combine these dates with digital elevation models, geological maps, differential GPS data, and sediment logs to estimate the extent of these three pulses that are characterized by sedimentation rates of ˜200 mm yr-1 and peak rates as high as 1,000 mm yr-1. Some 5.5 to 9 km3 of material infilled the pre-existing topography, and is now prone to ongoing fluvial dissection along major canyons. Contemporary river incision into the Pokhara Formation is rapid (120-170 mm yr-1), triggering widespread bank erosion, channel changes, and very high sediment yields of the order of 103 to 105 t km-2 yr-1, that by far outweigh bedrock denudation rates

Modeling Long-Term Fluvial Incision : Shall we Care for the Details of Short-Term Fluvial Dynamics?

Science.gov (United States)

Lague, D.; Davy, P.

2008-12-01

Fluvial incision laws used in numerical models of coupled climate, erosion and tectonics systems are mainly based on the family of stream power laws for which the rate of local erosion E is a power function of the topographic slope S and the local mean discharge Q : E = K Qm Sn. The exponents m and n are generally taken as (0.35, 0.7) or (0.5, 1), and K is chosen such that the predicted topographic elevation given the prevailing rates of precipitation and tectonics stay within realistic values. The resulting topographies are reasonably realistic, and the coupled system dynamics behaves somehow as expected : more precipitation induces increased erosion and localization of the deformation. Yet, if we now focus on smaller scale fluvial dynamics (the reach scale), recent advances have suggested that discharge variability, channel width dynamics or sediment flux effects may play a significant role in controlling incision rates. These are not factored in the simple stream power law model. In this work, we study how these short- term details propagate into long-term incision dynamics within the framework of surface/tectonics coupled numerical models. To upscale the short term dynamics to geological timescales, we use a numerical model of a trapezoidal river in which vertical and lateral incision processes are computed from fluid shear stress at a daily timescale, sediment transport and protection effects are factored in, as well as a variable discharge. We show that the stream power law model might still be a valid model but that as soon as realistic effects are included such as a threshold for sediment transport, variable discharge and dynamic width the resulting exponents m and n can be as high as 2 and 4. This high non-linearity has a profound consequence on the sensitivity of fluvial relief to incision rate. We also show that additional complexity does not systematically translates into more non-linear behaviour. For instance, considering only a dynamical width

The influence of basin slope and fluvial flow on deltaic built-up processes off mountainous, seasonal rivers

Science.gov (United States)

Bárcenas, Patricia; Macías, Jorge; Fernández-Salas, Luis Miguel; López-González, Nieves; José Lobo, Francisco

2016-04-01

The construction and evolution of submarine deltaic deposits are influenced by a combination of allogenic factors, such as fluvial flow (Q), and autogenic factors, such as basin slope (BS). Numerical simulations of turbidity currents are used to propose a morphodynamic model that quantifies the effect of both the slope and river input variations on the development of small deltaic environments in the northern shelf of the Alborán Sea, western Mediterranean Basin, that are linked to short and mountainous fluvial systems controlled by a seasonal Mediterranean climate. Traditionally, this type of model has been used for simulating hyperpycnal flows (Parker et al. (1986), Kubo (2004), Khan et al. (2005) & Morales et al. (2009)). In this study, the turbidity-HySEA model has been used taken into account the parameter settings and the numerical resolution specified in Bárcenas (2013) and Morales et al. (2009), respectively. These simulations were performed along a time period of eight days under two different fluvial flow conditions (constant and variable flow during the simulation period). Two different types of bathymetric profiles have been considered: a) piecewise linear profile and b) real bathymetric profiles from EM3000D multibeam echosounder data obtained off the present-day and artificial mouths of the Adra River. Five morphometric parameters were measured for each simulation (time and slope necessary for the formation of the topset, offlap break distance to the coastline, distal boundary depth and submarine delta length). The numerical experiments performed demonstrate the nonlinear relationship between the input variables (Q and BS) and the measured morphometric parameters. The morphodynamic of the sedimentary wedges considering the sediment dispersion and the offlap-break distance to the coastline can be represented by two extreme cases with many intermediate cases in between. The first case would be conditioned by proximal sedimentation while in the second

Do river channels decrease in width downstream on Distributive Fluvial Systems? An evaluation of modern mega-fans

Science.gov (United States)

Espinoza, T. N.; Scuderi, L. A.; Weissmann, G. S.; Hartley, A. J.

2014-12-01

Recent studies on aggradational continental sedimentary basins globally show that fluvial deposits in most modern sedimentary basins are dominated Distributive Fluvial Systems (DFS). DFS's are identified by: (1) pattern of channels and floodplain deposits that radiate outward from an apex located where the river enters the sedimentary basin, (2) deposition where an alluvial system becomes unconfined upon entering the sedimentary basin, (3) broadly fan shaped deposit that is convex upward across the DFS and concave upward down-fan, and (4) if the DFS is incised, an intersection point above which the alluvial system is held in an incised valley and below which it distributes sediment across an active depositional lobe. Several papers about DFS hypothesized that rivers on DFS decrease in size down-fan. We are testing this hypothesis through evaluation of LANDSAT and STRM data from large DFS described by Hartley et al (2010). We use ArcGIS to: (1) open the images and merge them together if there are more than one image corresponding to the DFS being studied, (2) use a Maximum Likelihood Analysis in six classes to segment different features on the DFS (e.g. exposed sands, water, vegetation, and other fan environments), (3) isolate the classes that correspond to the active channel belt (e.g., exposed sand bars and water), (4) divide the active channel belt into 1000 m long sections, (5) determine the area of active channel belt in each section, and (6) calculate the average width of the river in each section (e.g., W = area/1000m). We present our result for each DFS river on a graph that shows the change in width downstream. Our final product will be a dataset that contains width versus distance down-fan from the apex for as many of the large DFS from Hartley et al (2010) as possible. If the hypothesis is supported, the decrease in width could have a substantial predictive significance on sandstone geometry in fluvial successions.

Experimental investigation of fluvial dike breaching due to flow overtopping

Science.gov (United States)

El Kadi Abderrezzak, K.; Rifai, I.; Erpicum, S.; Archambeau, P.; Violeau, D.; Pirotton, M.; Dewals, B.

2017-12-01

The failure of fluvial dikes (levees) often leads to devastating floods that cause loss of life and damages to public infrastructure. Overtopping flows have been recognized as one of the most frequent cause of dike erosion and breaching. Fluvial dike breaching is different from frontal dike (embankments) breaching, because of specific geometry and boundary conditions. The current knowledge on the physical processes underpinning fluvial dike failure due to overtopping remains limited. In addition, there is a lack of a continuous monitoring of the 3D breach formation, limiting the analysis of the key mechanisms governing the breach development and the validation of conceptual or physically-based models. Laboratory tests on breach growth in homogeneous, non-cohesive sandy fluvial dikes due to flow overtopping have been performed. Two experimental setups have been constructed, permitting the investigation of various hydraulic and geometric parameters. Each experimental setup includes a main channel, separated from a floodplain by a dike. A rectangular initial notch is cut in the crest to initiate dike breaching. The breach development is monitored continuously using a specific developed laser profilometry technique. The observations have shown that the breach develops in two stages: first the breach deepens and widens with the breach centerline being gradually shifted toward the downstream side of the main channel. This behavior underlines the influence of the flow momentum component parallel to the dike crest. Second, the dike geometry upstream of the breach stops evolving and the breach widening continues only toward the downstream side of the main channel. The breach evolution has been found strongly affected by the flow conditions (i.e. inflow discharge in the main channel, downstream boundary condition) and floodplain confinement. The findings of this work shed light on key mechanisms of fluvial dike breaching, which differ substantially from those of dam

Characterizing fluvial heavy metal pollutions under different rainfall conditions: Implication for aquatic environment protection.

Science.gov (United States)

Zhang, Lixun; Zhao, Bo; Xu, Gang; Guan, Yuntao

2018-09-01

Globally, fluvial heavy metal (HM) pollution has recently become an increasingly severe problem. However, few studies have investigated the variational characteristics of fluvial HMs after rain over long periods (≥1 year). The Dakan River in Xili Reservoir watershed (China) was selected as a case study to investigate pollution levels, influencing factors, and sources of HMs under different rainfall conditions during 2015 and 2016. Fluvial HMs showed evident spatiotemporal variations attributable to the coupled effects of pollution generation and rainfall diffusion. Fluvial HM concentrations were significantly associated with rainfall characteristics (e.g., rainfall intensity, rainfall amount, and antecedent dry period) and river flow, which influenced the generation and the transmission of fluvial HMs in various ways. Moreover, this interrelationship depended considerably on the HM type and particle size distribution. Mn, Pb, Cr, and Ni were major contributors to high values of the comprehensive pollution index; therefore, they should be afforded special attention. Additionally, quantitative source apportionment of fluvial HMs was conducted by combining principal component analysis with multiple linear regression and chemical mass balance models to obtain comprehensive source profiles. Finally, an environment-friendly control strategy coupling "source elimination" and "transport barriers" was proposed for aquatic environment protection. Copyright © 2018 Elsevier B.V. All rights reserved.

Signatures of Late Pleistocene fluvial incision in an Alpine landscape

Science.gov (United States)

Leith, Kerry; Fox, Matthew; Moore, Jeffrey R.

2018-02-01

Uncertainty regarding the relative efficacy of fluvial and glacial erosion has hindered attempts to quantitatively analyse the Pleistocene evolution of alpine landscapes. Here we show that the morphology of major tributaries of the Rhone River, Switzerland, is consistent with that predicted for a landscape shaped primarily by multiple phases of fluvial incision following a period of intense glacial erosion after the mid-Pleistocene transition (∼0.7 Ma). This is despite major ice sheets reoccupying the region during cold intervals since the mid-Pleistocene. We use high-resolution LiDAR data to identify a series of convex reaches within the long-profiles of 18 tributary channels. We propose these reaches represent knickpoints, which developed as regional uplift raised tributary bedrock channels above the local fluvial baselevel during glacial intervals, and migrated upstream as the fluvial system was re-established during interglacial periods. Using a combination of integral long-profile analysis and stream-power modelling, we find that the locations of ∼80% of knickpoints in our study region are consistent with that predicted for a fluvial origin, while the mean residual error over ∼100 km of modelled channels is just 26.3 m. Breaks in cross-valley profiles project toward the elevation of former end-of-interglacial channel elevations, supporting our model results. Calculated long-term uplift rates are within ∼15% of present-day measurements, while modelled rates of bedrock incision range from ∼1 mm/yr for low gradient reaches between knickpoints to ∼6-10 mm/yr close to retreating knickpoints, typical of observed rates in alpine settings. Together, our results reveal approximately 800 m of regional uplift, river incision, and hillslope erosion in the lower half of each tributary catchment since 0.7 Ma.

Aeolian and fluvial processes in dryland regions: the need for integrated studies

Science.gov (United States)

Belnap, Jayne; Munson, Seth M.; Field, Jason P.

2011-01-01

Aeolian and fluvial processes play a fundamental role in dryland regions of the world and have important environmental and ecological consequences from local to global scales. Although both processes operate over similar spatial and temporal scales and are likely strongly coupled in many dryland systems, aeolian and fluvial processes have traditionally been studied separately, making it difficult to assess their relative importance in drylands, as well as their potential for synergistic interaction. Land degradation by accelerated wind and water erosion is a major problem throughout the world's drylands, and although recent studies suggest that these processes likely interact across broad spatial and temporal scales to amplify the transport of soil resources from and within drylands, many researchers and land managers continue to view them as separate and unrelated processes. Here, we illustrate how aeolian and fluvial sediment transport is coupled at multiple spatial and temporal scales and highlight the need for these interrelated processes to be studied from a more integrated perspective that crosses traditional disciplinary boundaries. Special attention is given to how the growing threat of climate change and land-use disturbance will influence linkages between aeolian and fluvial processes in the future. We also present emerging directions for interdisciplinary needs within the aeolian and fluvial research communities that call for better integration across a broad range of traditional disciplines such as ecology, biogeochemistry, agronomy, and soil conservation.

Estudio comparativo del rendimiento de las funciones ejecutivas en la corteza prefrontal dorsolateral, orbitofrontal y frontomedial en adolescentes policonsumidores de sustancias psicoactivas, vinculados al sistema de responsabilidad penal en paralelo con adolescentes que no se encuentran bajo esta misma condición

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Diego Alejandro Calle Sandoval

2017-07-01

Full Text Available La presente investigación se realizó bajo una metodología cuantitativa comparativa y de corte transversal, la cual tuvo como objetivo la realización de un estudio del rendimiento de las funciones ejecutivas en la corteza prefrontal dorsolateral, orbitofrontal y frontomedial en adolescentes, entre los 14 y 18 años de edad, policonsumidores de sustancias psicoactivas (SPA y vinculados al sistema de responsabilidad penal, en paralelo con adolescentes pertenecientes a una institución educativa que no se encuentran bajo esta misma condición; todos ellos del departamento del Quindío. A la población estudio se le aplicó una prueba neuropsicológica de funciones ejecutivas y lóbulos frontales (BANFE 2, cuyos resultados dan cuenta de que el grado de escolaridad –sea alto o inferior– no es un factor influyente en el rendimiento ejecutivo; además, evidencian diferencias significativas en el rendimiento de las funciones ejecutivas en la población bajo responsabilidad penal con antecedentes de policonsumo, encontrándose alteración en la corteza prefrontal dorsolateral, orbitofrontal y frontomedial, a diferencia de la población estudiantil que no cumple con esta condición.

Fluvial-deltaic sedimentation and stratigraphy of the ferron sandstone

Science.gov (United States)

Anderson, P.B.; Chidsey, T.C.; Ryer, T.A.

1997-01-01

East-central Utah has world-class outcrops of dominantly fluvial-deltaic Turonian to Coniacian aged strata deposited in the Cretaceous foreland basin. The Ferron Sandstone Member of the Mancos Shale records the influences of both tidal and wave energy on fluvial-dominated deltas on the western margin of the Cretaceous western interior seaway. Revisions of the stratigraphy are proposed for the Ferron Sandstone. Facies representing a variety of environments of deposition are well exposed, including delta-front, strandline, marginal marine, and coastal-plain. Some of these facies are described in detail for use in petroleum reservoir characterization and include permeability structure.

Sediment dynamics in the Rhine catchment : Quantification of fluvial response to climate change and human impact

NARCIS (Netherlands)

Erkens, G.

2009-01-01

Fluvial systems are strongly responsive to changes in climate and land use — but take their time to show it. Accurate prediction of the timing and degree of future fluvial response requires comprehensive understanding of fluvial response in the past. This PhD-thesis studied the response of the river

GOEMORFOLOGIA FLUVIAL DA BACIA HIDROGRÁFICA DO RIO DE ONDAS

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Ossifleres Silva Damasceno

2011-10-01

Full Text Available Os estudos de Geomorfologia Fluvial para analise de Bacias Hidrográficas vêm tendo nos últimos tempos grande importância, tanto para se conhecer as características de determinadas bacias como para se planejar o uso de tais recursos. Neste sentido, este trabalho foi efetuado no intuito de somar aos estudos anteriormente executados nessa bacia, levantando algumas características geomorfológicas, o uso e ocupação atual. Palavras-chaves: geomorfologia fluvial, hidrografia, agricultura irrigada.

Surficial geological tools in fluvial geomorphology: Chapter 2

Science.gov (United States)

Jacobson, Robert B.; O'Connor, James E.; Oguchi, Takashi

2016-01-01

Increasingly, environmental scientists are being asked to develop an understanding of how rivers and streams have been altered by environmental stresses, whether rivers are subject to physical or chemical hazards, how they can be restored, and how they will respond to future environmental change. These questions present substantive challenges to the discipline of fluvial geomorphology, especially since decades of geomorphologic research have demonstrated the general complexity of fluvial systems. It follows from the concept of complex response that synoptic and short-term historical views of rivers will often give misleading understanding of future behavior. Nevertheless, broadly trained geomorphologists can address questions involving complex natural systems by drawing from a tool box that commonly includes the principles and methods of geology, hydrology, hydraulics, engineering, and ecology.

Fluvial system response to Late Devensian (Weichselian) aridity, Baston, Lincolnshire, England

Science.gov (United States)

Briant, Rebecca M.; Coope, G. Russell; Preece, Richard C.; Keen, David H.; Boreham, Steve; Griffiths, Huw I.; Seddon, Mary B.; Gibbard, Philip L.

2004-07-01

Little is known about the impact of Late Devensian (Weichselian) aridity on lowland British landscapes, largely because they lack the widespread coversand deposits of the adjacent continent. The concentration of large interformational ice-wedge casts in the upper part of many Devensian fluvial sequences suggests that fluvial activity may have decreased considerably during this time. The development of optically stimulated luminescence (OSL) dating enables this period of ice-wedge cast formation to be constrained for the first time in eastern England, where a marked horizon of ice-wedge casts is found between two distinctive dateable facies associations. Contrasts between this horizon and adjacent sediments show clear changes in environment and fluvial system behaviour in response to changing water supply, in line with palaeontological evidence. In addition to providing chronological control on the period of ice-wedge formation, the study shows good agreement of the radiocarbon and OSL dating techniques during the Middle and Late Devensian, with direct comparison of these techniques beyond 15 000 yr for the first time in Britain. It is suggested that aridity during the Late Devensian forced a significant decrease in fluvial activity compared with preceding and following periods, initiating a system with low peak flows and widespread permafrost development. Copyright

Lacustrine-fluvial interactions in Australia's Riverine Plains

Science.gov (United States)

Kemp, Justine; Pietsch, Timothy; Gontz, Allen; Olley, Jon

2017-06-01

Climatic forcing of fluvial systems has been a pre-occupation of geomorphological studies in Australia since the 1940s. In the Riverine Plain, southeastern Australia, the stable tectonic setting and absence of glaciation have combined to produce sediment loads that are amongst the lowest in the world. Surficial sediments and landforms exceed 140,000 yr in age, and geomorphological change recorded in the fluvial, fluvio-lacustrine and aeolian features have provided a well-studied record of Quaternary environmental change over the last glacial cycle. The region includes the Willandra Lakes, whose distinctive lunette lakes preserve a history of water-level variations and ecological change that is the cornerstone of Australian Quaternary chronostratigraphy. The lunette sediments also contain an ancient record of human occupation that includes the earliest human fossils yet found on the Australian continent. To date, the lake-level and palaeochannel records in the Lachlan-Willandra system have not been fully integrated, making it difficult to establish the regional significance of hydrological change. Here, we compare the Willandra Lakes environmental record with the morphology and location of fluvial systems in the lower Lachlan. An ancient channel belt of the Lachlan, Willandra Creek, acted as the main feeder channel to Willandra Lakes before channel avulsion caused the lakes to dry out in the late Pleistocene. Electromagnetic surveys, geomorphological and sedimentary evidence are used to reconstruct the evolution of the first new channel belt following the avulsion. Single grain optical dating of floodplain sediments indicates that sedimentation in the new Middle Billabong Palaeochannel had commenced before 18.4 ± 1.1 ka. A second avulsion shifted its upper reaches to the location of the present Lachlan River by 16.2 ± 0.9 ka. The timing of these events is consistent with palaeohydrological records reconstructed from Willandra Lakes and with the record of

The Gediz River fluvial archive : A benchmark for Quaternary research in Western Anatolia

NARCIS (Netherlands)

Maddy, D.; Veldkamp, A.; Demir, T.; van Gorp, W.; Wijbrans, J.R.; van Hinsbergen, D.J.J.; Dekkers, M.J.; Schreve, D.; Schoorl, J.M.; Scaife, R.; Stemerdink, C.; van der Schriek, T.; Bridgland, D.R.; Aytaç, A.S.

2017-01-01

The Gediz River, one of the principal rivers of Western Anatolia, has an extensive Pleistocene fluvial archive that potentially offers a unique window into fluvial system behaviour on the western margins of Asia during the Quaternary. In this paper we review our work on the Quaternary Gediz River

Evidence of anthropogenic tipping points in fluvial dynamics in Europe

Science.gov (United States)

Notebaert, Bastiaan; Broothaerts, Nils; Verstraeten, Gert

2018-05-01

In this study the occurrence of thresholds in fluvial style changes during the Holocene are discussed for three different catchments: the Dijle and Amblève catchments (Belgium) and the Valdaine Region (France). We consider tipping points to be a specific type of threshold, defined as relatively rapid and irreversible changes in the system. Field data demonstrate that fluvial style has varied in all three catchments over time, and that different tipping points can be identified. An increase in sediment load as a result of human induced soil erosion lead to a permanent change in the Dijle floodplains from a forested peaty marsh towards open landscape with clastic deposition and a well-defined river channel. In the Valdaine catchment, an increase in coarse sediment load, caused by increased erosion in the mountainous upper catchment, altered the floodplains from a meandering pattern to a braided pattern. Other changes in fluvial style appeared to be reversible. Rivers in the Valdaine were prone to different aggradation and incision phases due to changes in peak water discharge and sediment delivery, but the impact was too low for these changes to be irreversible. Likewise the Dijle River has recently be prone to an incision phase due to a clear water effect, and also this change is expected to be reversible. Finally, the Amblève River did not undergo major changes in style during the last 2000 to 5000 years, even though floodplain sedimentation rates increased tenfold during the last 600 years. Overall, these examples demonstrate how changes in fluvial style depend on the crossing of thresholds in sediment supply and water discharge. Although changes in these controlling parameters are caused by anthropogenic land use changes, the link between those land use changes and changes in fluvial style is not linear. This is due to the temporal variability in landscape connectivity and sediment transport and the non-linear relationship between land use intensity and soil

Recuperación del paisaje con fines de ocio. Parque fluvial del Jarama. Comunidad de Madrid. España

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Pinedo, Alejandro

1990-10-01

Full Text Available This paper focuses on a rivershore reclamation scheme for an area of the Community of Madrid (Spain. Due to its location not far from the City of Madrid, recreational water based use was proposed as the final use for this disturbed river environment. The reclamation plan proposes the creation of the Jarama River Park (Parque Fluvial del Jarama that would be integrated into the Rivershore Reclamation Program of the Integral Water Plan of Madrid (Plan Integral del Agua en Madrid-PIAM. Several sets of actions are considered for the reclamation of the river and ponds system. Some of them are: — Reclamation of the old railway corridor located along the river. — Reclamation of the river bed and banks. — Reclamation of the Campillo Pond area.

El plan de recuperación de márgenes y riberas que se describe en el presente artículo, trata de salir al paso y aportar soluciones a los cada vez más frecuentes problemas de restauración y aprovechamiento de terrenos degradados que se plantean en los ámbitos urbanos y periurbano. El plan se localiza geográficamente en un área de la Comunidad de Madrid que posee un alto nivel de degradación y al mismo tiempo un gran potencial recreativo, se trata de el Parque Fluvial del Jarama, situado en el tramo del río Jarama comprendido entre la desembocadura del arroyo de la Vega y la del Manzanares; el Parque Fluvial del Jarama constituye la actuación más ambiciosa dentro del Programa de Recuperación de Márgenes del Plan Integral del Agua en Madrid (PIAM y en él se contemplan una serie de actuaciones que se pueden agrupar en los bloques siguientes: — Restauración de la explanación del ferrocarril. — Restauración y adecuación del cauce y márgenes. — Restauración de la Laguna del Campillo.

Geological aspects of paleoseismicity and archaeosismology in the fluvial alluvial Rimac valley

OpenAIRE

Jacay, Javier

2017-01-01

The sedimentary fill of the Rimac River fluvial-alluvial plain (Upper Miocene-Quaternary) consists of a thick sequence of unconsolidated material that corresponds to fluvial deposits. A record of seismotectonic activity is presentedin the sedimentary levels of fine facie within numerous paleoseismic structures such as contoured layers, pseudonodules, load figures, and material injections. Additionally, wall inclination and collapse, as well as displacement and partialfracturing, and pavement ...

Natural radionuclide behaviour in the fluvial environment

International Nuclear Information System (INIS)

Murray, A.S.; Olley, J.M.; Wallbrink, P.J.

1992-01-01

Variable concentrations of uranium and thorium series nuclides and 7 Be have been measured in soils and sediments. Strong correlations between 226 Ra and thorium series nuclides were found in sediments but not in soils. Laboratory measurements suggest the correlations arise from particle size and density dependent transport, and transport-related abrasion of iron oxide coatings. These correlations are characteristic of the sampled location, and provide a method for identifying the source areas which dominate the fluvial nuclide flux, and by implication, the associated sediment flux. Cosmogenic 7 Be (half-life 53 d) also contributes to nuclide fluxes. Over an 18 month period, individual rainstorms increased the 7 Be soil inventory by 10% on average. Dry precipitation contributed less than 10% to the total. Most 7 Be was retained within the top few millimetres of soil. It is deduced that 7 Be presence in fluvial sediments indicates a significant surface source contribution to the overall nuclide and sediment flux. (author)

The influence of fluvial reservoir architecture on geothermal energy production in Hot Sedimentary Aquifers

NARCIS (Netherlands)

Willems, C.J.L.

2014-01-01

Currently six geothermal doublets are realized in the WNB. Five of these doublets target the same Lower Cretaceous fluvial sandstone interval, the Nieuwerkerk Formation. About 40 exploration licences are granted. Many of them also have sandstones in the same fluvial interval, the Nieuwerkerk

A Field Exercise in Fluvial Sediment Transport.

Science.gov (United States)

Tharp, Thomas M.

1983-01-01

Describes an investigation which introduces the mathematical principles of stream hydraulics and fluvial sediment in a practical context. The investigation has four stages: defining hydrology of the stream; defining channel hydraulics in a study reach; measuring grain size; and calculating transportable grain size and comparing measure stream-bed…

DOS SISTEMAS AMBIENTAIS AO SISTEMA FLUVIAL – UMA REVISÃO DE CONCEITOS

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Jonas Otaviano Praça de Souza

2013-10-01

Full Text Available Tentando consolidar as noções de totalidade, a geografia física passa a utilizar a noção de sistemas dinâmicos, não lineares e de comportamento caótico. Deste modo, a abordagem sistêmica/complexa apresenta-se como meio de compreensão do mundo natural, assim possibilitando a previsão de mudanças, avaliação dos sistemas ambientais, distúrbios e limiares do sistema. Nota-se, assim, a importância dos estudos processuais para o gerenciamento de recursos hídricos, tornando imprescindíveis estudos sistêmicos que analisem os diversos elementos importantes para a análise dos recursos hídricos, dentre eles as questões processuais. Deste modo, a necessidade de se trabalhar o gerenciamento integrado de recursos hídricos, enquadrado na perspectiva sistêmica, solidificou a bacia hidrográfica e/ou bacia de drenagem como recorte espacial sistêmico. Delimitada a área pode-se compreender a bacia hidrográfica como um Sistema Fluvial, conceituado por Schumm (1977, que é analisado a partir da zona fonte de sedimentos, da rede de transporte e dos sítios de deposição. Esses elementos não são espacialmente excludentes, interagindo entre si, além de apresentar escalas diferenciadas. Para o estudo do sistema fluvial é necessário levar em consideração quatro conceitos: uniformidade dos processos, limiares de mudança, evolução da paisagem e respostas complexas.

Climate-sensitive feedbacks between hillslope processes and fluvial erosion in sediment-driven incision models

Science.gov (United States)

Skov, Daniel S.; Egholm, David L.

2016-04-01

Surface erosion and sediment production seem to have accelerated globally as climate cooled in the Late Cenozoic, [Molnar, P. 2004, Herman et al 2013]. Glaciers emerged in many high mountain ranges during the Quaternary, and glaciation therefore represents a likely explanation for faster erosion in such places. Still, observations and measurements point to increases in erosion rates also in landscapes where erosion is driven mainly by fluvial processes [Lease and Ehlers (2013), Reusser (2004)]. Flume experiments and fieldwork have shown that rates of incision are to a large degree controlled by the sediment load of streams [e.g. Sklar and Dietrich (2001), Beer and Turowski (2015)]. This realization led to the formulation of sediment-flux dependent incision models [Sklar and Dietrich (2004)]. The sediment-flux dependence links incision in the channels to hillslope processes that supply sediment to the channels. The rates of weathering and soil transport on the hillslopes are processes that are likely to respond to changing temperatures, e.g. because of vegetation changes or the occurrence of frost. In this study, we perform computational landscape evolution experiments, where the coupling between fluvial incision and hillslope processes is accounted for by coupling a sediment-flux-dependent model for fluvial incision to a climate-dependent model for weathering and hillslope sediment transport. The computational experiments first of all demonstrate a strong positive feedback between channel and hillslope processes. In general, faster weathering leads to higher rates of channel incision, which further increases the weathering rates, mainly because of hillslope steepening. Slower weathering leads to the opposite result. The experiments also demonstrate, however, that the feedbacks vary significantly between different parts of a drainage network. For example, increasing hillslope sediment production may accelerate incision in the upper parts of the catchment, while at

Fluvial facies reservoir productivity prediction method based on principal component analysis and artificial neural network

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Pengyu Gao

2016-03-01

Full Text Available It is difficult to forecast the well productivity because of the complexity of vertical and horizontal developments in fluvial facies reservoir. This paper proposes a method based on Principal Component Analysis and Artificial Neural Network to predict well productivity of fluvial facies reservoir. The method summarizes the statistical reservoir factors and engineering factors that affect the well productivity, extracts information by applying the principal component analysis method and approximates arbitrary functions of the neural network to realize an accurate and efficient prediction on the fluvial facies reservoir well productivity. This method provides an effective way for forecasting the productivity of fluvial facies reservoir which is affected by multi-factors and complex mechanism. The study result shows that this method is a practical, effective, accurate and indirect productivity forecast method and is suitable for field application.

Gold-bearing fluvial and associated tidal marine sediments of Proterozoic age in the Mporokoso Basin, northern Zambia

Science.gov (United States)

Andrews-Speed, C. P.

1986-07-01

The structurally defined Mporokoso Basin contains up to 5000 m of continental and marine clastic sediments and minor silicic volcanics which together form the Mporokoso Group. These rocks overlie unconformably a basement of silicic-intermediate igneous rocks and accumulated within the interval 1830-1130 Ma. This sedimentological study was restricted to the eastern end of the basin and was part of an assessment of the potential for palaeoplacer gold in the Mporokoso Group. At the base of the Mporokoso Group, the Mbala Formation consists of 1000-1500 m of purple sandstones and conglomerates deposited in a braided-stream system overlain by 500-1000 m of mature quartz arenites deposited in a tidal marine setting. A general coarsening-upward trend exists within the fluvial sediments. Sandy, distal braided-stream facies passes upwards into more proximal conglomeratic facies. In proximal sections, poorly sorted conglomerates form the top of the coarsening-up sequence which is 500-700 m thick. The overlying fluvial sediments fine upwards. The tidal marine sandstones at the top of the Mbala Formation resulted from reworking of fluvial sediments during a marine transgression. Well-exposed sections with fluvial conglomerates were studied in detail. Individual conglomerate bodies form sheets extending for hundreds of metres downstream and at least one hundred metres across stream, with little sign of deep scouring or channelling. They are generally matrix-supported. The whole fluvial sequence is characterised by a paucity of mud or silt. These conglomerates were deposited by large velocity, sheet flows of water which transported a bed-load of pebbles and sand. Most fine material settling out from suspension was eroded by the next flow. The great lateral and vertical extent and the uniformity of the fluvial sediments suggest that the sediments accumulated over an unconfined alluvial plain and that the tectonic evolution of the source area was relatively continuous and not

La géoarchéologie fluviale

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Gilles Arnaud-Fassetta

2008-03-01

Full Text Available Les recherches des hydrogéomorphologues ont des applications nombreuses dans le vaste champ des sciences géoarchéologiques. Elles fournissent des réponses précises sur la façon dont l’environnement des anciens lieux de passage et de vie humaine a évolué. Le propos n’est pas seulement de définir les causes des grands changements environnementaux, mais aussi de juger de la vulnérabilité sociétale face aux contraintes hydroclimatiques. Pour cela, les méthodes d’étude doivent nécessairement prendre en compte les trois facettes de la géomorphologie fluviale : la paléohydrographie, la paléohydrologie et la paléohydraulique. La pertinence de cette approche est montrée en milieu rural et urbain dans les plaines deltaïques du Rhône (France du Sud et de l’Isonzo (Italie du Nord.Current research led by hydrogeomorphologists has numerous applications in the vast field of geoarchaeological sciences. It brings precise answers on environmental characteristics around the ancient places of passage and human life. The goal is not only to define the causes of global environmental changes, but also to precise the links between river dynamics and human societies in terms of fluvial risk. Therefore, the studied methods should simultaneously take into account the three facets of the fluvial geomorphology, i.e., the palaeohydrography, the palaeohydrology, and the palaeohydraulics. The pertinence of this combinatorial approach is deduced from the work of the author led both in rural and urban areas of the deltaic plains of the Rhône (South of France and Isonzo (northern Italy rivers.

Fluvial processes and channel morphometry of the upper Orashi ...

African Journals Online (AJOL)

Fluvial processes and channel morphometry of the upper Orashi basin in ... of channel equilibrium between morphology and hydrology, the Orashi channel is not well ... Drainage basins, watershed morphology, morphometric analysis, Nigeria ...

Fluvial Channel Networks as Analogs for the Ridge-Forming Unit, Sinus Meridiani, Mars

Science.gov (United States)

Wilkinson, M. J.; du Bois, J. B.

2010-01-01

Fluvial models have been generally discounted as analogs for the younger layered rock units of Sinus Meridiani. A fluvial model based on the large fluvial fan provides a possibly close analog for various features of the sinuous ridges of the etched, ridge-forming unit (RFU) in particular. The close spacing of the RFU ridges, their apparently chaotic orientations, and their organization in dense networks all appear unlike classical stream channel patterns. However, drainage patterns on large fluvial fans low-angle, fluvial aggradational features, 100s of km long, documented worldwide by us provide parallels. Some large fan characteristics resemble those of classical floodplains, but many differences have been demonstrated. One major distinction relevant to the RFU is that channel landscapes of large fans can dominate large areas (1.2 million km2 in one S. American study area). We compare channel morphologies on large fans in the southern Sahara Desert with ridge patterns in Sinus Meridiani (fig 1). Stream channels are the dominant landform on large terrestrial fans: they may equate to the ubiquitous, sinuous, elongated ridges of the RFU that cover areas region wide. Networks of convergent/divergent and crossing channels may equate to similar features in the ridge networks. Downslope divergence is absent in channels of terrestrial upland erosional landscapes (fig. 1, left), whereas it is common to both large fans (fig. 1, center) and RFU ridge patterns (fig 1, right downslope defined as the regional NW slope of Sinus Meridiani). RFU ridge orientation, judged from those areas apparently devoid of impact crater control, is broadly parallel with the regional slope (arrow, fig. 1, right), as is mean orientation of major channels on large fans (arrow, fig. 1, center). High densities per unit area characterize fan channels and martian ridges reaching an order of magnitude higher than those in uplands just upstream of the terrestrial study areas fig. 1. In concert with

Ridge Orientations of the Ridge-Forming Unit, Sinus Meridiani, Mars-A Fluvial Explanation

Science.gov (United States)

Wilkinson, M. Justin; Herridge, A.

2013-01-01

Imagery and MOLA data were used in an analysis of the ridge-forming rock unit (RFU) exposed in Sinus Meridiani (SM). This unit shows parallels at different scales with fluvial sedimentary bodies. We propose the terrestrial megafan as the prime analog for the RFU, and likely for other members of the layered units. Megafans are partial cones of fluvial sediment, with radii up to hundreds of km. Although recent reviews of hypotheses for the RFU units exclude fluvial hypotheses [1], inverted ridges in the deserts of Oman have been suggested as putative analogs for some ridges [2], apparently without appreciating The wider context in which these ridges have formed is a series of megafans [3], a relatively unappreciated geomorphic feature. It has been argued that these units conform to the megafan model at the regional, subregional and local scales [4]. At the regional scale suites of terrestrial megafans are known to cover large areas at the foot of uplands on all continents - a close parallel with the setting of the Meridiani sediments at the foot of the southern uplands of Mars, with its incised fluvial systems leading down the regional NW slope [2, 3] towards the sedimentary units. At the subregional scale the layering and internal discontinuities of the Meridiani rocks are consistent, inter alia, with stacked fluvial units [4]. Although poorly recognized as such, the prime geomorphic environment in which stream channel networks cover large areas, without intervening hillslopes, is the megafan [see e.g. 4]. Single megafans can reach 200,000 km2 [5]. Megafans thus supply an analog for areas where channel-like ridges (as a palimpsest of a prior landscape) cover the intercrater plains of Meridiani [6]. At the local, or river-reach scale, the numerous sinuous features of the RFU are suggestive of fluvial channels. Cross-cutting relationships, a common feature of channels on terrestrial megafans, are ubiquitous. Desert megafans show cemented paleo-channels as inverted

A model of plant strategies in fluvial hydrosystems

NARCIS (Netherlands)

Bornette, G.; Tabacchi, E.; Hupp, C.; Puijalon, S.; Rostan, J.C.

2008-01-01

1. We propose a model of plant strategies in temperate fluvial hydrosystems that considers the hydraulic and geomorphic features that control plant recruitment, establishment and growth in river floodplains. 2. The model describes first how the disturbance gradient and the grain-size of the river

The origin of dose distributions in fluvial sediments, and the prospect of dating single grains from fluvial deposits using optically stimulated luminescence

International Nuclear Information System (INIS)

Olley, J.M.; Caitcheon, G.G.; Roberts, R.G.

1999-01-01

We examine the causes of the asymmetric distributions of dose observed from measurements of the optically stimulated luminescence emitted by small aliquots of fluvial quartz, and deduce that the asymmetry arises as a result of samples being composed of a mix of mainly well bleached grains with grains that were effectively unbleached at the time of deposition. We demonstrate that the shapes of the dose distributions can be used to assess the likelihood that aliquots consist only of grains that were well-bleached at the time of deposition. The more asymmetric the distribution, the greater the probability that the aliquots with the lowest dose most closely represent the true burial dose. Single grains with differing doses are present in each of the samples examined, and the population with the lowest dose gives an optical age consistent with the expected burial age. This result implies that the beta-dose heterogeneity in these deposits is small, and that the effects of micro-dosimetric variations on optical dating of individual grains are not significant for these samples. We demonstrate that single-grain dating of fluvial material is possible and practicable using standard Risoe optical dating equipment, and we conclude that application of a new regenerative-dose protocol to single grains of quartz, using the lowest dose population to estimate the burial dose, is the best available means of obtaining reliable luminescence ages for heterogeneously bleached fluvial sediments

Diagnòstics d'infermeria vinculats al procés migratori: visió dels inmigrants

OpenAIRE

Rifà i Ros, Maria Rosa

2012-01-01

El objetivo general de esta investigación pretende identificar los diagnósticos de enfermería NANDA predominantes en la población inmigrante, vinculados al proceso migratorio y está enmarcada en el Modelo de Competencia Cultural de Purnell y en el modelo Outcome Present State Test (OPT) de razonamiento clínico de Pesut y Herman. Considerando los objetivos de la investigación, ésta se aborda desde el paradigma cualitativo siguiendo las propuestas de la investigación fenomenológica que busca d...

A geologic approach to field methods in fluvial geomorphology

Science.gov (United States)

Fitzpatrick, Faith A.; Thornbush, Mary J; Allen, Casey D; Fitzpatrick, Faith A.

2014-01-01

A geologic approach to field methods in fluvial geomorphology is useful for understanding causes and consequences of past, present, and possible future perturbations in river behavior and floodplain dynamics. Field methods include characterizing river planform and morphology changes and floodplain sedimentary sequences over long periods of time along a longitudinal river continuum. Techniques include topographic and bathymetric surveying of fluvial landforms in valley bottoms and describing floodplain sedimentary sequences through coring, trenching, and examining pits and exposures. Historical sediment budgets that include floodplain sedimentary records can characterize past and present sources and sinks of sediment along a longitudinal river continuum. Describing paleochannels and floodplain vertical accretion deposits, estimating long-term sedimentation rates, and constructing historical sediment budgets can assist in management of aquatic resources, habitat, sedimentation, and flooding issues.

Implications from Sedimentary records in Fluvial Terraces for Geomorphological Evolution in the Puli Basin, Taiwan

NARCIS (Netherlands)

Tseng, C.H.; Wenske, D.; Böse, M.; Reimann, T.; Lüthgens, C.; Frechen, Manfred

2013-01-01

Fluvial terraces play an important role for research on previous geomorphic processes as their sediments can record various sedimentation stages. In the mountains of central Taiwan, however, the formation time of sediments in the Puli Basin is still unclear. In this study, we investigate the fluvial

A regional sediment transport modeling for fluvial influx and redistribution of suspended radionuclide in the Fukushima coast

International Nuclear Information System (INIS)

Uchiyama, Yusuke; Yamanishi, Takafumi; Tsumune, Daisuke; Miyazawa, Yasumasa

2014-01-01

Fluvial discharge from the rivers is viewed as a missing piece for the inventory of the radionuclides in the ocean during the accident at the Fukushima Daiichi Nuclear Power Plant. The land-derived input introduces a time lag behind the direct release through hydrological process because these radionuclides mostly attach to suspended particles (sediments) that are transported quite differently to the dissolved matter in the ocean. We therefore develop a regional sediment transport model consisting of a multi-class non-cohesive sediment transport module, a wave-enhanced bed boundary layer model and a stratigraphy model proposed by Blaas et al. (2007) based on ROMS. (author)

Combined fluvial and pluvial urban flood hazard analysis: concept development and application to Can Tho city, Mekong Delta, Vietnam

Science.gov (United States)

Apel, Heiko; Martínez Trepat, Oriol; Nghia Hung, Nguyen; Thi Chinh, Do; Merz, Bruno; Viet Dung, Nguyen

2016-04-01

Many urban areas experience both fluvial and pluvial floods, because locations next to rivers are preferred settlement areas and the predominantly sealed urban surface prevents infiltration and facilitates surface inundation. The latter problem is enhanced in cities with insufficient or non-existent sewer systems. While there are a number of approaches to analyse either a fluvial or pluvial flood hazard, studies of a combined fluvial and pluvial flood hazard are hardly available. Thus this study aims to analyse a fluvial and a pluvial flood hazard individually, but also to develop a method for the analysis of a combined pluvial and fluvial flood hazard. This combined fluvial-pluvial flood hazard analysis is performed taking Can Tho city, the largest city in the Vietnamese part of the Mekong Delta, as an example. In this tropical environment the annual monsoon triggered floods of the Mekong River, which can coincide with heavy local convective precipitation events, causing both fluvial and pluvial flooding at the same time. The fluvial flood hazard was estimated with a copula-based bivariate extreme value statistic for the gauge Kratie at the upper boundary of the Mekong Delta and a large-scale hydrodynamic model of the Mekong Delta. This provided the boundaries for 2-dimensional hydrodynamic inundation simulation for Can Tho city. The pluvial hazard was estimated by a peak-over-threshold frequency estimation based on local rain gauge data and a stochastic rainstorm generator. Inundation for all flood scenarios was simulated by a 2-dimensional hydrodynamic model implemented on a Graphics Processing Unit (GPU) for time-efficient flood propagation modelling. The combined fluvial-pluvial flood scenarios were derived by adding rainstorms to the fluvial flood events during the highest fluvial water levels. The probabilities of occurrence of the combined events were determined assuming independence of the two flood types and taking the seasonality and probability of

Ephemeral-fluvial sediments as potential hydrocarbon reservoirs. Vol. 1: Sedimentology

Energy Technology Data Exchange (ETDEWEB)

Taylor, K.S.

1994-12-31

Although reservoirs formed from ephemeral-fluvial sandstones have previously been considered relatively simple, unresolved problems of sandbody correlation and production anomalies demonstrate the need for improved understanding of their internal complexity. Outcropping ephemeral-fluvial systems have been studied in order to determine the main features and processes occurring in sand-rich ephemeral systems and to identify which features will be of importance in a hydrocarbon reservoir. The Lower Jurassic Upper Moenave and Kayenta Formations of south-eastern Utah and northern Arizona comprise series of stacked, sand-dominated sheet-like palaeochannels suggestive of low sinuosity, braided systems. Low subsidence rates and rapid lateral migration rates enabled channels to significantly modify their widths during high discharge. (author)

EL PRECURSOR DEL NEUROPEPTIDO CART POSEE UNA SEÑAL DE DESTINACION A LAS VESICULAS DE SECRECION REGULADA

OpenAIRE

BLANCO NAHUELQUEO, ELIAS HUMBERTO; BLANCO NAHUELQUEO, ELIAS HUMBERTO

2011-01-01

CART (Cocaine- Amphetamine Regulated Transcript} fue descubierto como un RNAm que es inducido por una dosis aguda de cocaína y también de anfetamina en el estriado de cerebro de rata. A partir de su descubrimiento el neuropéptido CART fue vinculado a drogas de abuso, sin embargo existe mayor evidencia que lo vincula al control del apetito. El neuropéptido CART inhibe potentemente el apetito (efecto anorexigénico} cuando es administrado intra-cerebralmente a roedores. Una subregión de...

Global effects of agriculture on fluvial dissolved organic matter

DEFF Research Database (Denmark)

Graeber, Daniel; Boëchat, Iola; Encina, Francisco

2015-01-01

Agricultural land covers approximately 40% of Earth’s land surface and affects hydromorphological, biogeochemical and ecological characteristics of fluvial networks. In the northern temperate region, agriculture also strongly affects the amount and molecular composition of dissolved organic matter...

Fluvial processes on Mars: Erosion and sedimentation

Science.gov (United States)

Squyres, Steven W.

1988-01-01

One of the most important discoveries of the Mariner 9 and Viking missions to Mars was evidence of change of the Martian surface by the action of liquid water. From the standpoint of a Mars Rover/Sample Return Mission, fluvial activity on Mars is important in two ways: (1) channel formation has deeply eroded the Martian crust, providing access to relatively undisturbed subsurface units; and (2) much of the material eroded from channels may have been deposited in standing bodies of liquid water. The most striking fluvial erosion features on Mars are the outflow channels. A second type of channel apparently caused by flow of liquid water is the valley systems. These are similar to terrestial drainage systems. The sedimentary deposits of outflow channels are often difficult to identfy. No obvious deposits such as deltaic accumulations are visible in Viking images. Another set of deposits that may be water lain and that date approx. from the epoch of outflow channels are the layered deposits in the Valles Marineris. From the standpoint of a Mars Rover/Sample Return mission, the problem with all of these water-lain sediments is their age, or rather the lack of it.

Fluvial geomorphology: where do we go from here?

Science.gov (United States)

Smith, Derald G.

1993-07-01

The evolution of geomorphology and in particular, fluvial geomorphology, is at a crossroads. Currently, the discipline is dismally organized, without focus or direction, and is practised by individualists who rarely collaborate in numbers significant enough to generate major research initiatives. If the discipline is to mature and to prosper, we must make some very difficult decisions that will require major changes in our ways of thinking and operating. Either the field stays in its current operational mode and becomes a backwater science, or it moves forward and adopts the ways of the more competitive sectors of the earth and biosciences. For the discipline to evolve, fluvial geomorphologists must first organize an association within North America or at the international level. The 3rd International Geomorphology Conference may be a start, but within that organization we must develop our own divisional and/or regional organizations. Within the Quaternary geology/geomorphology divisions of the Geological Socieity of America (GSA), Association of American Geographers (AAG), American Geophysical Union (AGU) and British Geomorphology Research Group (BGRG) the voice of fluvial geomorphology is lost in a sea of diverse and competitive interests, though there is reason for hope resulting from some recent initiatives. In Canada, we have no national geomorphology organization per se; our closest organization is Canqua (Canadian Quaternary Association). Next, fluvial researchers must collaborate, by whatever means, to develop "scientific critical mass" in order to generate ideas and long-range goals of modest and major scientific importance. These projects will help secure major research funding without which, research opportunities will diminish and initiating major new research will become nearly impossible. Currently, we are being surpassed by the glaciologists, remote sensors, ecologists, oceanographers, climatologists-atmospheric researchers and some Quaternary

Fluvial archives, a valuable record of vertical crustal deformation

Science.gov (United States)

Demoulin, A.; Mather, A.; Whittaker, A.

2017-06-01

The study of drainage network response to uplift is important not only for understanding river system dynamics and associated channel properties and fluvial landforms, but also for identifying the nature of crustal deformation and its history. In recent decades, geomorphic analysis of rivers has proved powerful in elucidating the tectonic evolution of actively uplifting and eroding orogens. Here, we review the main recent developments that have improved and expanded qualitative and quantitative information about vertical tectonic motions (the effects of horizontal deformation are not addressed). Channel long profiles have received considerable attention in the literature, and we briefly introduce basic aspects of the behaviour of bedrock rivers from field and numerical modelling perspectives, before describing the various metrics that have been proposed to identify the information on crustal deformation contained within their steady-state characteristics. Then, we review the literature dealing with the transient response of rivers to tectonic perturbation, through the production of knickpoints propagating through the drainage network. Inverse modelling of river profiles for uplift in time and space is also shown to be very effective in reconstructing regional tectonic histories. Finally, we present a synthetic morphometric approach for deducing the tectonic record of fluvial landscapes. As well as the erosional imprint of tectonic forcing, sedimentary deposits, such as fluvial terrace staircases, are also considered as a classical component of tectonic geomorphology. We show that these studies have recently benefited from rapid advances in dating techniques, allowing more reliable reconstruction of incision histories and estimation of incision rates. The combination of progress in the understanding of transient river profiles and larger, more rigorous data sets of terrace ages has led to improved understanding of river erosion and the implications for terrace

Model Projections of Future Fluvial Sediment Delivery to Major Deltas Under Environmental Change

Science.gov (United States)

Darby, S. E.; Dunn, F.; Nicholls, R. J.; Cohen, S.; Zarfl, C.

2017-12-01

Deltas are important hot spots for climate change impacts on which over half a billion people live worldwide. Most of the world's deltas are sinking as a result of natural and anthropogenic subsidence and due to eustatic sea level rise. The ability to predict rates of delta aggradation is therefore critical to assessments of the extent to which sedimentation can potentially offset sea level rise, but our ability to make such predictions is severely hindered by a lack of insight into future trends of the fluvial sediment load supplied to their deltas by feeder watersheds. To address this gap we investigate fluvial sediment fluxes under future environmental change for a selection (47) of the world's major river deltas. Specifically, we employed the numerical model WBMsed to project future variations in mean annual fluvial sediment loads under a range of environmental change scenarios that account for changes in climate, socio-economics and dam construction. Our projections indicate a clear decrease (by 34 to 41% on average, depending on the specific scenario) in future fluvial sediment supply to most of the 47 deltas. These reductions in sediment delivery are driven primarily by anthropogenic disturbances, with reservoir construction being the most influential factor globally. Our results indicate the importance of developing new management strategies for reservoir construction and operation.

Influence of fluvial sandstone architecture on geothermal energy production

NARCIS (Netherlands)

Willems, C.J.L.; Maghami Nick, Hamidreza M.; Weltje, G.J.; Donselaar, M.E.; Bruhn, D.F.

2015-01-01

Fluvial sandstone reservoirs composed of stacked meander belts are considered as potential geothermal resources in the Netherlands. Net-to-gross, orientation and stacking pattern of the channel belts is of major importance for the connectivity between the injection and production well in such

Reservoirs as hotspots of fluvial carbon cycling in peatland catchments.

Science.gov (United States)

Stimson, A G; Allott, T E H; Boult, S; Evans, M G

2017-02-15

Inland water bodies are recognised as dynamic sites of carbon processing, and lakes and reservoirs draining peatland soils are particularly important, due to the potential for high carbon inputs combined with long water residence times. A carbon budget is presented here for a water supply reservoir (catchment area~9km 2 ) draining an area of heavily eroded upland peat in the South Pennines, UK. It encompasses a two year dataset and quantifies reservoir dissolved organic carbon (DOC), particulate organic carbon (POC) and aqueous carbon dioxide (CO 2 (aq)) inputs and outputs. The budget shows the reservoir to be a hotspot of fluvial carbon cycling, as with high levels of POC influx it acts as a net sink of fluvial carbon and has the potential for significant gaseous carbon export. The reservoir alternates between acting as a producer and consumer of DOC (a pattern linked to rainfall and temperature) which provides evidence for transformations between different carbon species. In particular, the budget data accompanied by 14 C (radiocarbon) analyses provide evidence that POC-DOC transformations are a key process, occurring at rates which could represent at least ~10% of the fluvial carbon sink. To enable informed catchment management further research is needed to produce carbon cycle models more applicable to these environments, and on the implications of high POC levels for DOC composition. Copyright © 2016 Elsevier B.V. All rights reserved.

Variability in fluvial geomorphic response to anthropogenic disturbance

Science.gov (United States)

Verstraeten, Gert; Broothaerts, Nils; Van Loo, Maarten; Notebaert, Bastiaan; D'Haen, Koen; Dusar, Bert; De Brue, Hanne

2017-10-01

Humans have greatly impacted the processes and intensities of erosion, sediment transport and storage since the introduction of agriculture. In many regions around the world, accelerated floodplain sedimentation can be related to increases in human pressure on the environment. However, the relation between the intensity of anthropogenic disturbance and the magnitude of change in fluvial sediment dynamics is not straightforward and often non-linear. Here, we review a number of case studies from contrasting environmental settings in the European loess belt, the Eastern Mediterranean mountain ranges and the eastern USA. Detailed field-based sediment archive studies and sediment budgets covering time periods ranging from 200 to over 5000 year, as well as the use of pollen and sediment provenance techniques, show that no overarching concept of changes in floodplain sedimentation following anthropogenic disturbance can be established. Slope-channel (dis)connectivity controls the existence of thresholds or tipping points that need to be crossed before significant changes in downstream sediment dynamics are recorded following human impact. This coupling can be related to characteristics of human pressure such as its duration, intensity and spatial patterns, but also to the geomorphic and tectonic setting. Furthermore, internal feedback mechanisms, such as those between erosion and soil thickness, further complicate the story. All these factors controlling the propagation of sediment from eroding hillslopes to river channels vary between regions. Hence, only unique patterns of fluvial geomorphic response can be identified. As a result, unravelling the human impact from current-day sediment archives and predicting the impact of future human disturbances on fluvial sediment dynamics remain a major challenge. This has important implications for interpreting contemporary sediment yields as well as downstream sediment records in large floodplains, deltas and the marine

Combined fluvial and pluvial urban flood hazard analysis: method development and application to Can Tho City, Mekong Delta, Vietnam

Science.gov (United States)

Apel, H.; Trepat, O. M.; Hung, N. N.; Chinh, D. T.; Merz, B.; Dung, N. V.

2015-08-01

Many urban areas experience both fluvial and pluvial floods, because locations next to rivers are preferred settlement areas, and the predominantly sealed urban surface prevents infiltration and facilitates surface inundation. The latter problem is enhanced in cities with insufficient or non-existent sewer systems. While there are a number of approaches to analyse either fluvial or pluvial flood hazard, studies of combined fluvial and pluvial flood hazard are hardly available. Thus this study aims at the analysis of fluvial and pluvial flood hazard individually, but also at developing a method for the analysis of combined pluvial and fluvial flood hazard. This combined fluvial-pluvial flood hazard analysis is performed taking Can Tho city, the largest city in the Vietnamese part of the Mekong Delta, as example. In this tropical environment the annual monsoon triggered floods of the Mekong River can coincide with heavy local convective precipitation events causing both fluvial and pluvial flooding at the same time. Fluvial flood hazard was estimated with a copula based bivariate extreme value statistic for the gauge Kratie at the upper boundary of the Mekong Delta and a large-scale hydrodynamic model of the Mekong Delta. This provided the boundaries for 2-dimensional hydrodynamic inundation simulation for Can Tho city. Pluvial hazard was estimated by a peak-over-threshold frequency estimation based on local rain gauge data, and a stochastic rain storm generator. Inundation was simulated by a 2-dimensional hydrodynamic model implemented on a Graphical Processor Unit (GPU) for time-efficient flood propagation modelling. All hazards - fluvial, pluvial and combined - were accompanied by an uncertainty estimation considering the natural variability of the flood events. This resulted in probabilistic flood hazard maps showing the maximum inundation depths for a selected set of probabilities of occurrence, with maps showing the expectation (median) and the uncertainty by

Suspended sediment transport trough a large fluvial-tidal channel network

Science.gov (United States)

Wright, Scott A.; Morgan-King, Tara L.

2015-01-01

The confluence of the Sacramento and San Joaquin Rivers, CA, forms a large network of interconnected channels, referred to as the Sacramento-San Joaquin Delta (the Delta). The Delta comprises the transition zone from the fluvial influences of the upstream rivers and tidal influences of San Francisco Bay downstream. Formerly an extensive tidal marsh, the hydrodynamics and geomorphology of Delta have been substantially modified by humans to support agriculture, navigation, and water supply. These modifications, including construction of new channels, diking and draining of tidal wetlands, dredging of navigation channels, and the operation of large pumping facilities for distribution of freshwater from the Delta to other parts of the state, have had a dramatic impact on the physical and ecological processes within the Delta. To better understand the current physical processes, and their linkages to ecological processes, the USGS maintains an extensive network of flow, sediment, and water quality gages in the Delta. Flow gaging is accomplished through use of the index-velocity method, and sediment monitoring uses turbidity as a surrogate for suspended-sediment concentration. Herein, we present analyses of the transport and dispersal of suspended sediment through the complex network of channels in the Delta. The primary source of sediment to the Delta is the Sacramento River, which delivers pulses of sediment primarily during winter and spring runoff events. Upon reaching the Delta, the sediment pulses move through the fluvial-tidal transition while also encountering numerous channel junctions as the Sacramento River branches into several distributary channels. The monitoring network allows us to track these pulses through the network and document the dominant transport pathways for suspended sediment. Further, the flow gaging allows for an assessment of the relative effects of advection (the fluvial signal) and dispersion (from the tides) on the sediment pulses as they

Mapping Variability in the Medusae Fossae Formation: Yardang Morphologies, Fluvial Reworking, and Crater Depth to Diameter Ratios

Science.gov (United States)

Khuller, A. R.; Kerber, L.

2017-12-01

The Medusae Fossae Formation (MFF) is a voluminous, fine-grained deposit thought to be of pyroclastic origin. While it contains widespread, well-preserved inverted fluvial features, its pervasive cover of dust means that little is known about its composition, and indirect means must be used to characterize its material properties. This project aims to correlate fluvial features in the Western MFF with other indicators of material strength: yardang morphology and crater depth-to-diameter ratios. For this work, Context Camera (CTX) images were used to map features of fluvial origin (inverted channels, sinuous ridges, alluvial fans). The presence of rounded, meso-yardangs in close proximity to fluvial features was also mapped. Crater depth-diameter (d/D) ratios (for craters 1-512km) were analyzed using a global Mars crater database (Robbins and Hynek, 2012) as a proxy for material strength. Approximately 1400 fluvial segments were mapped, with the most populous cluster located in Aeolis and Zephyria Plana. Rounded meso-yardangs were found to be common in areas that also have fluvial features. In agreement with previous work (Barlow, 1993), MFF craters were found to have a greater d/D ratio (0.0523) than the global mean (0.0511). Ratios between MFF lobes differ significantly, providing insight into the heterogeneity of induration within the formation. The deepest craters are found in Eumenides Dorsum and the shallowest in Aeolis Planum, consistent with a greater degree of induration and reworking in the western part of the formation where the fluvial features and "salt-playa" meso-yardangs are found. It also suggests that Eumenides, which is the tallest MFF outcrop, could also be the least compacted. The presence of long, complex, and sometimes overlapping branching networks imply multiple relative episodes of channel formation. Rounded meso-yardangs, which are associated with salt playa surfaces on Earth, provide additional evidence for the presence of liquid water

Volcanogenic Fluvial-Lacustrine Environments in Iceland and Their Utility for Identifying Past Habitability on Mars

Directory of Open Access Journals (Sweden)

Claire Cousins

2015-02-01

Full Text Available The search for once-habitable locations on Mars is increasingly focused on environments dominated by fluvial and lacustrine processes, such as those investigated by the Mars Science Laboratory Curiosity rover. The availability of liquid water coupled with the potential longevity of such systems renders these localities prime targets for the future exploration of Martian biosignatures. Fluvial-lacustrine environments associated with basaltic volcanism are highly relevant to Mars, but their terrestrial counterparts have been largely overlooked as a field analogue. Such environments are common in Iceland, where basaltic volcanism interacts with glacial ice and surface snow to produce large volumes of meltwater within an otherwise cold and dry environment. This meltwater can be stored to create subglacial, englacial, and proglacial lakes, or be released as catastrophic floods and proglacial fluvial systems. Sedimentary deposits produced by the resulting fluvial-lacustrine activity are extensive, with lithologies dominated by basaltic minerals, low-temperature alteration assemblages (e.g., smectite clays, calcite, and amorphous, poorly crystalline phases (basaltic glass, palagonite, nanophase iron oxides. This paper reviews examples of these environments, including their sedimentary deposits and microbiology, within the context of utilising these localities for future Mars analogue studies and instrument testing.

Volcanogenic fluvial-lacustrine environments in iceland and their utility for identifying past habitability on Mars.

Science.gov (United States)

Cousins, Claire

2015-02-16

The search for once-habitable locations on Mars is increasingly focused on environments dominated by fluvial and lacustrine processes, such as those investigated by the Mars Science Laboratory Curiosity rover. The availability of liquid water coupled with the potential longevity of such systems renders these localities prime targets for the future exploration of Martian biosignatures. Fluvial-lacustrine environments associated with basaltic volcanism are highly relevant to Mars, but their terrestrial counterparts have been largely overlooked as a field analogue. Such environments are common in Iceland, where basaltic volcanism interacts with glacial ice and surface snow to produce large volumes of meltwater within an otherwise cold and dry environment. This meltwater can be stored to create subglacial, englacial, and proglacial lakes, or be released as catastrophic floods and proglacial fluvial systems. Sedimentary deposits produced by the resulting fluvial-lacustrine activity are extensive, with lithologies dominated by basaltic minerals, low-temperature alteration assemblages (e.g., smectite clays, calcite), and amorphous, poorly crystalline phases (basaltic glass, palagonite, nanophase iron oxides). This paper reviews examples of these environments, including their sedimentary deposits and microbiology, within the context of utilising these localities for future Mars analogue studies and instrument testing.

Study on detailed geological modelling for fluvial sandstone reservoir in Daqing oil field

Energy Technology Data Exchange (ETDEWEB)

Zhao Hanqing; Fu Zhiguo; Lu Xiaoguang [Institute of Petroleum Exploration and Development, Daqing (China)

1997-08-01

Guided by the sedimentation theory and knowledge of modern and ancient fluvial deposition and utilizing the abundant information of sedimentary series, microfacies type and petrophysical parameters from well logging curves of close spaced thousands of wells located in a large area. A new method for establishing detailed sedimentation and permeability distribution models for fluvial reservoirs have been developed successfully. This study aimed at the geometry and internal architecture of sandbodies, in accordance to their hierarchical levels of heterogeneity and building up sedimentation and permeability distribution models of fluvial reservoirs, describing the reservoir heterogeneity on the light of the river sedimentary rules. The results and methods obtained in outcrop and modem sedimentation studies have successfully supported the study. Taking advantage of this method, the major producing layers (PI{sub 1-2}), which have been considered as heterogeneous and thick fluvial reservoirs extending widely in lateral are researched in detail. These layers are subdivided into single sedimentary units vertically and the microfacies are identified horizontally. Furthermore, a complex system is recognized according to their hierarchical levels from large to small, meander belt, single channel sandbody, meander scroll, point bar, and lateral accretion bodies of point bar. The achieved results improved the description of areal distribution of point bar sandbodies, provide an accurate and detailed framework model for establishing high resolution predicting model. By using geostatistic technique, it also plays an important role in searching for enriched zone of residual oil distribution.

Variables and potential models for the bleaching of luminescence signals in fluvial environments

Science.gov (United States)

Gray, Harrison J.; Mahan, Shannon

2015-01-01

Luminescence dating of fluvial sediments rests on the assumption that sufficient sunlight is available to remove a previously obtained signal in a process deemed bleaching. However, luminescence signals obtained from sediment in the active channels of rivers often contain residual signals. This paper explores and attempts to build theoretical models for the bleaching of luminescence signals in fluvial settings. We present two models, one for sediment transported in an episodic manner, such as flood-driven washes in arid environments, and one for sediment transported in a continuous manner, such as in large continental scale rivers. The episodic flow model assumes that the majority of sediment is bleached while exposed to sunlight at the near surface between flood events and predicts a power-law decay in luminescence signal with downstream transport distance. The continuous flow model is developed by combining the Beer–Lambert law for the attenuation of light through a water column with a general-order kinetics equation to produce an equation with the form of a double negative exponential. The inflection point of this equation is compared with the sediment concentration from a Rouse profile to derive a non-dimensional number capable of assessing the likely extent of bleaching for a given set of luminescence and fluvial parameters. Although these models are theoretically based and not yet necessarily applicable to real-world fluvial systems, we introduce these ideas to stimulate discussion and encourage the development of comprehensive bleaching models with predictive power.

A multi-scale approach of fluvial biogeomorphic dynamics using photogrammetry.

Science.gov (United States)

Hortobágyi, Borbála; Corenblit, Dov; Vautier, Franck; Steiger, Johannes; Roussel, Erwan; Burkart, Andreas; Peiry, Jean-Luc

2017-11-01

Over the last twenty years, significant technical advances turned photogrammetry into a relevant tool for the integrated analysis of biogeomorphic cross-scale interactions within vegetated fluvial corridors, which will largely contribute to the development and improvement of self-sustainable river restoration efforts. Here, we propose a cost-effective, easily reproducible approach based on stereophotogrammetry and Structure from Motion (SfM) technique to study feedbacks between fluvial geomorphology and riparian vegetation at different nested spatiotemporal scales. We combined different photogrammetric methods and thus were able to investigate biogeomorphic feedbacks at all three spatial scales (i.e., corridor, alluvial bar and micro-site) and at three different temporal scales, i.e., present, recent past and long term evolution on a diversified riparian landscape mosaic. We evaluate the performance and the limits of photogrammetric methods by targeting a set of fundamental parameters necessary to study biogeomorphic feedbacks at each of the three nested spatial scales and, when possible, propose appropriate solutions. The RMSE varies between 0.01 and 2 m depending on spatial scale and photogrammetric methods. Despite some remaining difficulties to properly apply them with current technologies under all circumstances in fluvial biogeomorphic studies, e.g. the detection of vegetation density or landform topography under a dense vegetation canopy, we suggest that photogrammetry is a promising instrument for the quantification of biogeomorphic feedbacks at nested spatial scales within river systems and for developing appropriate river management tools and strategies. Copyright © 2016 Elsevier Ltd. All rights reserved.

Environmental changes in the central Po Plain (northern Italy) due to fluvial modifications and anthropogenic activities

Science.gov (United States)

Marchetti, Mauro

2002-05-01

The fluvial environment of the central Po Plain, the largest plain in Italy, is discussed in this paper. Bounded by the mountain chains of the Alps and the Apennines, this plain is a link between the Mediterranean environment and the cultural and continental influences of both western and eastern Europe. In the past decades, economic development has been responsible for many changes in the fluvial environment of the area. This paper discusses the changes in fluvial dynamics that started from Late Pleistocene and Early Holocene due to distinct climatic changes. The discussion is based on geomorphological, pedological, and archaeological evidences and radiocarbon dating. In the northern foothills, Late Pleistocene palaeochannels indicate several cases of underfit streams among the northern tributaries of the River Po. On the other hand, on the southern side of the Po Plain, no geomorphological evidence of similar discharge reduction has been found. Here, stratigraphic sections, together with archaeological remains buried under the fluvial deposits, show a reduction in the size of fluvial sediments after the 10th millennium BC. During the Holocene, fluvial sedimentation became finer, and was characterised by minor fluctuations in the rate of deposition, probably related to short and less intense climatic fluctuations. Given the high rate of population growth and the development of human activities since the Neolithic Age, human influence on fluvial dynamics, especially since the Roman Age, prevailed over other factors (i.e., climate, tectonics, vegetation, etc.). During the Holocene, the most important changes in the Po Plain were not modifications in water discharge but in sediment. From the 1st to 3rd Century AD, land grants to war veterans caused almost complete deforestation, generalised soil erosion, and maximum progradation of the River Po delta. At present, land abandonment in the mountainous region has led to reafforestation. Artificial channel control in the

Analytically based forward and inverse models of fluvial landscape evolution during temporally continuous climatic and tectonic variations

Science.gov (United States)

Goren, Liran; Petit, Carole

2017-04-01

Fluvial channels respond to changing tectonic and climatic conditions by adjusting their patterns of erosion and relief. It is therefore expected that by examining these patterns, we can infer the tectonic and climatic conditions that shaped the channels. However, the potential interference between climatic and tectonic signals complicates this inference. Within the framework of the stream power model that describes incision rate of mountainous bedrock rivers, climate variability has two effects: it influences the erosive power of the river, causing local slope change, and it changes the fluvial response time that controls the rate at which tectonically and climatically induced slope breaks are communicated upstream. Because of this dual role, the fluvial response time during continuous climate change has so far been elusive, which hinders our understanding of environmental signal propagation and preservation in the fluvial topography. An analytic solution of the stream power model during general tectonic and climatic histories gives rise to a new definition of the fluvial response time. The analytic solution offers accurate predictions for landscape evolution that are hard to achieve with classical numerical schemes and thus can be used to validate and evaluate the accuracy of numerical landscape evolution models. The analytic solution together with the new definition of the fluvial response time allow inferring either the tectonic history or the climatic history from river long profiles by using simple linear inversion schemes. Analytic study of landscape evolution during periodic climate change reveals that high frequency (10-100 kyr) climatic oscillations with respect to the response time, such as Milankovitch cycles, are not expected to leave significant fingerprints in the upstream reaches of fluvial channels. Linear inversion schemes are applied to the Tinee river tributaries in the southern French Alps, where tributary long profiles are used to recover the

Does deposition depth control the OSL bleaching of fluvial sediment?

NARCIS (Netherlands)

Cunningham, A. C.; Wallinga, J.; Hobo, N.; Versendaal, A. J.; Makaske, B.; Middelkoop, H.

2014-01-01

The Optically Stimulated Luminescence (OSL) signal from fluvial sediment often contains a remnant from the previous deposition cycle, leading to a partially bleached equivalent-dose distribution. Although identification of the burial dose is of primary concern, the degree of bleaching could

Stability of Fluvial and Gravity-flow Antidunes

Science.gov (United States)

Fedele, J. J.; Hoyal, D. C. J. D.; Demko, T. M.

2017-12-01

Antidunes develop as a consequence of interface (free surface) deformation and sediment transport feedback in supercritical flows. Fluvial (open-channel flow) antidunes have been studied extensively in the laboratory and the field, and recognized in ancient sedimentary deposits. Experiments on gravity flow (turbidity and density currents) antidunes indicate that they are more stable and long-lived than their fluvial counterpart but the mechanism controlling this stability is poorly understood. Sea floor bathymetric and subsurface data suggest that large-scale, antidune-like sediment waves are extremely common in deep-water, found in a wide range of settings and sediment characteristics. While most of these large features have been interpreted as cyclic steps, the term has been most likely overused due to the lack of recognition criteria and basic understanding on the differences between antidunes and cyclic steps formed under gravity flows. In principle, cyclic steps should be more common in confined or channel-lobe transition settings where flows tend to be more energetic or focused, while antidunes should prevail in regions of less confinement, under sheet-like or expanding flows. Using published, fluvial stable-antidune data, we show that the simplified 1D, mechanical-energy based analysis of flow over a localized fixed obstacle (Long, 1954; Baines, 1995; Kubo and Yokokawa, 2001) is inaccurate for representing flow over antidunes and their stability. Instead, a more detailed analysis of a flow along a long-wavelength (in relation to flow thickness) wavy bed that also considers the interactions between flow and sediment transport is used to infer conditions of antidune stability and the breaking of surface waves. In particular, the position of the surface wave crest in relation to the bedform crest, along with the role of average flow velocity, surface velocity, and surface wave celerity appear relevant in determining antidune instability. The analysis is

Nove interpretacije fluvialnih sedimentov na krasu = New interpretations of fluvial sediments from the Kras

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Andrej Mihevc

2007-01-01

Full Text Available Important unroofed caves with fluvial sediments from Divaški kras, Matarsko podoljePodgorski kras are presented. Extend of the phenomena and relation to the existingand karst surface and geomorphological meaning of them are described. Sedimentsthem were analysed and dated with different methods. The largest age of the sedimentfound in the unroofed cave excavated in Črnotiče quarry. In the cave wall fossil remainsstygobiont Marifugia cavatica were covered by 3.2-4.1 Ma old fluvial sediments.

Precambrian fluvial deposits: Enigmatic palaeohydrological data from the c. 2 1.9 Ga Waterberg Group, South Africa

Science.gov (United States)

Eriksson, Patrick G.; Bumby, Adam J.; Brümer, Jacobus J.; van der Neut, Markus

2006-08-01

Precambrian fluvial systems, lacking the influence of rooted vegetation, probably were characterised by flashy surface runoff, low bank stability, broad channels with abundant bedload, and faster rates of channel migration; consequently, a braided fluvial style is generally accepted. Pre-vegetational braided river systems, active under highly variable palaeoclimatic conditions, may have been more widespread than are modern, ephemeral dry-land braided systems. Aeolian deflation of fine fluvial detritus does not appear to have been prevalent. With the onset of large cratons by the Neoarchaean-Palaeoproterozoic, very large, perennial braided river systems became typical. The c. 2.06-1.88 Ga Waterberg Group, preserved within a Main and a smaller Middelburg basin on the Kaapvaal craton, was deposited largely by alluvial/braided-fluvial and subordinate palaeo-desert environments, within fault-bounded, possibly pull-apart type depositories. Palaeohydrological data obtained from earlier work in the Middelburg basin (Wilgerivier Formation) are compared to such data derived from the correlated Blouberg Formation, situated along the NE margin of the Main basin. Within the preserved Blouberg depository, palaeohydrological parameters estimated from clast size and cross-bed set thickness data, exhibit rational changes in their values, either in a down-palaeocurrent direction, or from inferred basin margin to palaeo-basin centre. In both the Wilgerivier and Blouberg Formations, calculated palaeoslope values (derived from two separate formulae) plot within the gap separating typical alluvial fan gradients from those which characterise rivers (cf. [Blair, T.C., McPherson, J.G., 1994. Alluvial fans and their natural distinction from rivers based on morphology, hydraulic processes, sedimentary processes, and facies assemblages. J. Sediment. Res. A64, 450-489.]). Although it may be argued that such data support possibly unique fluvial styles within the Precambrian, perhaps related to

Fluvial landscape development in the southwestern Kalahari during the Holocene - Chronology and provenance of fluvial deposits in the Molopo Canyon

DEFF Research Database (Denmark)

Ramisch, Arne; Bens, Oliver; Buylaert, Jan-Pieter

2017-01-01

are sparse and often discontinuous. Hence, little is known about Holocene environmental change in this region. This study focuses on reconstructing paleoenvironmental change from the timing and provenance of fluvial deposits located within the Molopo Canyon, which connects the southern Kalahari drainage...... to the deposition of alluvial fills. These results suggest that the southern Kalahari Drainage remained endorheic and therefore disconnected from the Orange River throughout the Holocene....

Late Cenozoic fluvial successions in northern and western India: an overview and synthesis

Science.gov (United States)

Sinha, R.; Kumar, R.; Sinha, S.; Tandon, S. K.; Gibling, M. R.

2007-11-01

Late Cenozoic fluvial successions are widespread in India. They include the deposits of the Siwalik basin which represent the accumulations of the ancient river systems of the Himalayan foreland basin. Palaeomagnetic studies reveal that fluvial architecture and styles of deposition were controlled by Himalayan tectonics as well as by major climatic fluctuations during the long (∼13 Ma) span of formation. The Indo-Gangetic plains form the world's most extensive Quaternary alluvial plains, and display spatially variable controls on sedimentation: Himalayan tectonics in the frontal parts, climate in the middle reaches, and eustasy in the lower reaches close to the Ganga-Brahmaputra delta. Climatic effects were mediated by strong fluctuations in the SW Indian Monsoon, and Himalayan rivers occupy deep valleys in the western Ganga plains where stream power is high, cut in part during early Holocene monsoon intensification; the broad interfluves record the simultaneous aggradation of plains-fed rivers since ∼100 ka. The eastward increase in precipitation across the Ganga Plains results in rivers with low stream power and a very high sediment flux, resulting in an aggradational mode and little incision. The river deposits of semi-arid to arid western India form important archives of Quaternary climate change through their intercalation with the eolian deposits of the Thar Desert. Although the synthesis documents strong variability-both spatial and temporal-in fluvial stratigraphy, climatic events such as the decline in precipitation during the Last Glacial Maximum and monsoon intensification in the early Holocene have influenced fluvial dynamics throughout the region.

Factores socioculturales y psicológicos vinculados a la lactancia materna exclusiva Sociocultural and psychological factors linked to exclusive breastfeeding

Directory of Open Access Journals (Sweden)

Regla Caridad Broche Candó

2011-06-01

Full Text Available Introducción: la lactancia materna ha sido la forma de alimentación más segura para el ser humano en toda su historia. Esta leche es la única que asegura al niño pequeño una alimentación adecuada y le protege de las infecciones. Objetivo: determinar el comportamiento de los principales factores socioculturales y psicológicos vinculados a la práctica y abandono de la lactancia materna exclusiva y su repercusión en el estado de salud de los lactantes. Métodos: se realizó un estudio descriptivo de corte transversal, en el municipio Diego Ibarra, Estado de Carabobo, en el año 2008. La muestra estuvo conformada por 96 lactantes cuyas madres dieron su consentimiento informado para participar en este. Resultados: se observó un predominio de las madres adolescentes asociado al abandono de la lactancia materna antes de los 4 meses, la secundaria fue el nivel escolar más frecuente en la serie, sin embargo, el predominio de la categoría de obrera o técnica se asoció a una lactancia menor de 4 meses. Conclusiones: al nacimiento predominó la lactancia materna mixta, con una tendencia progresiva al uso de la lactancia artificial a partir del cuarto mes. Se encontró mayor frecuencia de madres con conocimientos deficientes sobre la lactancia materna, y fueron estas las que lactaron a sus bebés por menor tiempo. Más de las tres cuartas partes de las mujeres refirieron como causa de abandono de la lactancia materna exclusiva, que el niño se quedaba con hambre y la insuficiente disponibilidad de leche en las mamas.Introduction: the breastfeeding has been the more safe feeding way for human being in all its history. This type of milk is the only assuring the infant a proper feeding while protecting him of infections. Objective: to determine the behavior of main sociocultural and psychological factors linked to practice and giving up of the exclusive breastfeeding and its repercussion on infant health status. Methods: a cross-sectional and

Beaver ponds' impact on fluvial processes (Beskid Niski Mts., SE Poland).

Science.gov (United States)

Giriat, Dorota; Gorczyca, Elżbieta; Sobucki, Mateusz

2016-02-15

Beaver (Castor sp.) can change the riverine environment through dam-building and other activities. The European beaver (Castor fiber) was extirpated in Poland by the nineteenth century, but populations are again present as a result of reintroductions that began in 1974. The goal of this paper is to assess the impact of beaver activity on montane fluvial system development by identifying and analysing changes in channel and valley morphology following expansion of beaver into a 7.5 km-long headwater reach of the upper Wisłoka River in southeast Poland. We document the distribution of beaver in the reach, the change in river profile, sedimentation type and storage in beaver ponds, and assess how beaver dams and ponds have altered channel and valley bottom morphology. The upper Wisłoka River fluvial system underwent a series of anthropogenic disturbances during the last few centuries. The rapid spread of C. fiber in the upper Wisłoka River valley was promoted by the valley's morphology, including a low-gradient channel and silty-sand deposits in the valley bottom. At the time of our survey (2011), beaver ponds occupied 17% of the length of the study reach channel. Two types of beaver dams were noted: in-channel dams and valley-wide dams. The primary effect of dams, investigated in an intensively studied 300-m long subreach (Radocyna Pond), was a change in the longitudinal profile from smooth to stepped, a local reduction of the water surface slope, and an increase in the variability of both the thalweg profile and surface water depths. We estimate the current rate of sedimentation in beaver ponds to be about 14 cm per year. A three-stage scheme of fluvial processes in the longitudinal and transverse profile of the river channel is proposed. C. fiber reintroduction may be considered as another important stage of the upper Wisłoka fluvial system development. Copyright © 2015 Elsevier B.V. All rights reserved.

Fluvial sediment inputs to upland gravel bed rivers draining forested catchments: potential ecological impacts

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S. D. Marks

1997-01-01

Full Text Available As identified by the detailed long-term monitoring networks at Plynlimon, increased sediment supply to upland fluvial systems is often associated with forestry land-use and practice. Literature is reviewed, in the light of recent results from Plynlimon sediment studies, to enable identification of the potential ecological impacts of fluvial particulate inputs to upland gravel bed rivers draining forested catchments similar to the headwaters of the River Severn. Both sediment transport and deposition can have significant impacts upon aquatic vertebrates, invertebrates and plants.

Hydrodynamic and sedimentological controls governing formation of fluvial levees

Science.gov (United States)

Johnston, G. H.; Edmonds, D. A.; David, S. R.; Czuba, J. A.

2017-12-01

Fluvial levees are familiar features found on the margins of river channels, yet we know little about what controls their presence, height, and shape. These attributes of levees are important because they control sediment transfer from channel to floodplain and flooding patterns along a river system. Despite the familiarity and importance of levees, there is a surprising lack of basic geomorphic data on fluvial levees. Because of this we seek to understand: 1) where along rivers do levees tend to occur?; 2) what geomorphic and hydrodynamic variables control cross-sectional shape of levees? We address these questions by extracting levee shape from LiDAR data and by collecting hydrodynamic and sedimentological data from reaches of the Tippecanoe River, the White River, and the Muscatatuck River, Indiana, USA. Fluvial levees are extracted from a 1.5-m resolution LiDAR bare surface model and compared to hydrological, sedimentological, and geomorphological data from USGS stream gages. We digitized banklines and extracted levee cross-sections to calculate levee slope, taper, height, e-folding length, and e-folding width. To answer the research questions, we performed a multivariable regression between the independent variables—channel geometry, sediment grain size and concentration, flooding conditions, and slope—and the dependent levee variables. We find considerable variation in levee presence and shape in our field data. On the Muscatatuck River levees occur on 30% of the banks compared to 10% on the White River. Moreover, levees on the Muscatatuck are on average 3 times wider than the White River. This is consistent with the observation that the Muscatatuck is finer-grained compared to the White River and points to sedimentology being an important control on levee geomorphology. Future work includes building a morphodynamic model to understand how different hydrodynamic and geomorphic conditions control levee geometry.

Two depositional models for Pliocene coastal plain fluvial systems, Goliad Formation, south Texas Gulf Coastal plain

International Nuclear Information System (INIS)

Hoel, H.D.; Galloway, W.E.

1983-01-01

The Goliad Formation consists of four depositional systems-the Realitos and Mathis bed-load fluvial systems in the southwest and the Cuero and Eagle Lake mixed-load fluvial systems in the northeast. Five facies are recognized in the Realitos and Mathis bed-load fluvial systems: (1) primary channel-fill facies, (2) chaotic flood channel-fill facies, (3) complex splay facies, (4) flood plain facies, and (5) playa facies. A model for Realitos-Mathis depositional environments shows arid-climate braided stream complexes with extremely coarse sediment load, highly variable discharge, and marked channel instability. Broad, shallow, straight to slightly sinuous primary channels were flanked by wide flood channels. Flood channels passed laterally into broad, low-relief flood plains. Small playas occupied topographic lows near large channel axes. Three facies are recognized in the Cuero and Eagle Lake mixed-load fluvial systems: (1) channel-fill facies, (2) crevasse splay facies, and (3) flood plain facies. A model for Cuero-Eagle Lake depositional environments shows coarse-grained meander belts in a semi-arid climate. Slightly to moderately sinuous meandering streams were flanked by low, poorly developed natural levees. Crevasse splays were common, but tended to be broad and ill-defined. Extensive, low-relief flood plains occupied interaxial areas. The model proposed for the Realitos and Mathis fluvial systems may aid in recognition of analogous ancient depositional systems. In addition, since facies characteristics exercise broad controls on Goliad uranium mineralization, the proposed depositional models aid in defining target zones for Goliad uranium exploration

Salmon habitat use, tidal-fluvial estuary - Columbia River Estuary Tidal Habitats

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The goal of the tidal-fluvial estuary study is to determine the estuary's contribution to the spatial structure and life history diversity of Columbia River salmon...

Reconstructing paleo-discharge from geometries of fluvial sinuous ridges on Earth and Mars

Science.gov (United States)

Hayden, A.; Lamb, M. P.; Mohrig, D. C.; Williams, R. M. E.; Myrow, P.; Ewing, R. C.; Cardenas, B. T.; Findlay, C. P., III

2017-12-01

Sinuous, branching networks of topographic ridges resembling river networks are common across Mars, and show promise for quantifying ancient martian surface hydrology. There are two leading formation mechanisms for ridges with a fluvial origin. Inverted channels are ridges that represent casts (e.g., due to lava fill) of relict river channel topography, whereas exhumed channel deposits are eroded remnants of a more extensive fluvial deposit, such as a channel belt. The inverted channel model is often assumed on Mars; however, we currently lack the ability to distinguish these ridge formation mechanisms, motivating the need for Earth-analog study. To address this issue, we studied the extensive networks of sinuous ridges in the Ebro basin of northeast Spain. The Ebro ridges stand 3-15 meters above the surrounding plains and are capped by a cliff-forming sandstone unit 3-10 meters thick and 20-50 meters in breadth. The caprock sandstone bodies contain bar-scale cross stratification, point-bar deposits, levee deposits, and lenses of mudstone, indicating that these are channel-belt deposits, rather than casts of channels formed from lateral channel migration, avulsion and reoccupation. In plan view, ridges form segments branching outward to the north resembling a distributary network; however, crosscutting relationships indicate that ridges cross at different stratigraphic levels. Thus, the apparent network in planview reflects non-uniform exhumation of channel-belt deposits from multiple stratigraphic positions, rather than an inverted coeval river network. As compared to the inverted channel model, exhumed fluvial deposits indicate persistent fluvial activity over geologic timescales, indicating the potential for long-lived surface water on ancient Mars.

Anguilles estuariennes et fluviales : apports de l'otolithométrie

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MOUNAIX B.

1994-10-01

La zonation de l'otolithe, interprétée par rapport à la croissance des poissons, décrit deux écotypes dans la population d'anguilles de la Vilaine : un écotype fluvial dont la croissance est perturbée et ralentie, et un écotype estuarien dont la croissance est plus régulière. Cette partition de la population est cohérente avec les caractéristiques environnementales des deux milieux. Elle pourrait par ailleurs constituer un indice de l'impact des aménagements des bassins versants sur la croissance, la durée du cycle biologique et la dynamique des populations d'anguilles. Il apparaît alors nécessaire de considérer séparément les sous-unités estuariennes et fluviales des stocks d'anguilles des bassins versants de la Vilaine et de la Loire, en particulier pour étudier la diminution des abondances.

Complejidad ambiental en el Bajío mexicano: implicaciones del proyecto civilizatorio vinculado al crecimiento económico

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Daniel Tagle Zamora

2017-01-01

Full Text Available El objetivo de este artículo es visibilizar las contradicciones ambientales de la lógica del crecimiento económico adoptada en el Bajío guanajuatense, en el marco de la economía ecológica, que muestra la inviabilidad socioambiental de las políticas públicas en Guanajuato. El índice del desarrollo humano municipal, la compilación de informes ambientales del estado, los talleres con actores clave, así como la retroalimentación con pares académicos, expertos en la temática ambiental, reflejan el contraste ambiental del modelo de desarrollo que impera y opera de manera normalizada en esta región. Es notoria la desarticulación deliberada entre las políticas económica y ambiental, que favorece a la primera gracias a la permisibilidad de la segunda, lo que se traduce en la trasferencia de los costos socioambientales del sector privado al público, y apoya la lógica de la acumulación frente al interés común. Esto a través de la contaminación y la sobreexplotación de los cuerpos de agua, la contaminación atmosférica, el extractivismo, la sobregeneración de residuos sólidos, la pérdida de calidad de los suelos que, entre otros, son algunos elementos que tensionan la capacidad de resiliencia social y ambiental de esta zona. Esta visibilización de la crisis ambiental refleja la pertinencia de incorporar un enfoque analítico capaz de abordar una crisis multidimensional, y comprender que ésta se encuentra en la parte ilógica de la lógica del crecimiento económico.

Analysis of groundwater flow and stream depletion in L-shaped fluvial aquifers

Science.gov (United States)

Lin, Chao-Chih; Chang, Ya-Chi; Yeh, Hund-Der

2018-04-01

Understanding the head distribution in aquifers is crucial for the evaluation of groundwater resources. This article develops a model for describing flow induced by pumping in an L-shaped fluvial aquifer bounded by impermeable bedrocks and two nearly fully penetrating streams. A similar scenario for numerical studies was reported in Kihm et al. (2007). The water level of the streams is assumed to be linearly varying with distance. The aquifer is divided into two subregions and the continuity conditions of the hydraulic head and flux are imposed at the interface of the subregions. The steady-state solution describing the head distribution for the model without pumping is first developed by the method of separation of variables. The transient solution for the head distribution induced by pumping is then derived based on the steady-state solution as initial condition and the methods of finite Fourier transform and Laplace transform. Moreover, the solution for stream depletion rate (SDR) from each of the two streams is also developed based on the head solution and Darcy's law. Both head and SDR solutions in the real time domain are obtained by a numerical inversion scheme called the Stehfest algorithm. The software MODFLOW is chosen to compare with the proposed head solution for the L-shaped aquifer. The steady-state and transient head distributions within the L-shaped aquifer predicted by the present solution are compared with the numerical simulations and measurement data presented in Kihm et al. (2007).

The impact of urban expansion and agricultural legacies on trace metal accumulation in fluvial and lacustrine sediments of the lower Chesapeake Bay basin, USA

International Nuclear Information System (INIS)

Coxon, T.M.; Odhiambo, B.K.; Giancarlo, L.C.

2016-01-01

The progressively declining ecological condition of the Chesapeake Bay is attributed to the influx of contaminants associated with sediment loads supplied by its largest tributaries. The continued urban expansion in the suburbs of Virginia cities, modern agricultural activities in the Shenandoah Valley, the anthropogenic and climate driven changes in fluvial system hydrodynamics and their potential associated impacts on trace metals enrichment in the bay's tributaries necessitate constant environmental monitoring of these important water bodies. Eight "2"1"0Pb and "1"3"7Cs dated sediment cores and seventy two sediment grab samples were used to analyze the spatial and temporal distributions of Al, Ca, Mg, Cr, Cd, As, Se, Pb, Cu, Zn, Mn, and Fe in the waterways of the Virginia portion of the Chesapeake Bay basin. The sediment cores for trace metal historical fluctuation analysis were obtained in lower fluvial-estuarine environments and reservoirs in the upper reaches of the basin. The trace metal profiles revealed high basal enrichment factors (EF) of between 0.05 and 40.24, which are interpreted to represent early nineteenth century agricultural activity and primary resource extraction. Surficial enrichment factors on both cores and surface grab samples ranged from 0.01 (Cu) to 1421 (Cd), with Pb, Cu, Zn, and Cd enrichments a plausible consequence of modern urban expansion and industrial development along major transportation corridors. Contemporary surficial enrichments of As, Se, and Cr also ranged between 0 and 137, with the higher values likely influenced by lithological and atmospheric sources. Pearson correlation analyses suggest mining and agricultural legacies, coupled with aerosol deposition, are responsible for high metal concentrations in western lakes and headwater reaches of fluvial systems, while metal accumulation in estuarine reaches of the major rivers can be attributed to urban effluence and the remobilization of legacy sediments. - Highlights: �

The impact of urban expansion and agricultural legacies on trace metal accumulation in fluvial and lacustrine sediments of the lower Chesapeake Bay basin, USA

Energy Technology Data Exchange (ETDEWEB)

Coxon, T.M. [Department of Earth and Environmental Sciences, University of Mary Washington, 1301 College Avenue Fredericksburg, Virginia 22401 (United States); Odhiambo, B.K., E-mail: bkisila@umw.edu [Department of Earth and Environmental Sciences, University of Mary Washington, 1301 College Avenue Fredericksburg, Virginia 22401 (United States); Giancarlo, L.C. [Department of Chemistry, University of Mary Washington, Fredericksburg, VA 22401 (United States)

2016-10-15

The progressively declining ecological condition of the Chesapeake Bay is attributed to the influx of contaminants associated with sediment loads supplied by its largest tributaries. The continued urban expansion in the suburbs of Virginia cities, modern agricultural activities in the Shenandoah Valley, the anthropogenic and climate driven changes in fluvial system hydrodynamics and their potential associated impacts on trace metals enrichment in the bay's tributaries necessitate constant environmental monitoring of these important water bodies. Eight {sup 210}Pb and {sup 137}Cs dated sediment cores and seventy two sediment grab samples were used to analyze the spatial and temporal distributions of Al, Ca, Mg, Cr, Cd, As, Se, Pb, Cu, Zn, Mn, and Fe in the waterways of the Virginia portion of the Chesapeake Bay basin. The sediment cores for trace metal historical fluctuation analysis were obtained in lower fluvial-estuarine environments and reservoirs in the upper reaches of the basin. The trace metal profiles revealed high basal enrichment factors (EF) of between 0.05 and 40.24, which are interpreted to represent early nineteenth century agricultural activity and primary resource extraction. Surficial enrichment factors on both cores and surface grab samples ranged from 0.01 (Cu) to 1421 (Cd), with Pb, Cu, Zn, and Cd enrichments a plausible consequence of modern urban expansion and industrial development along major transportation corridors. Contemporary surficial enrichments of As, Se, and Cr also ranged between 0 and 137, with the higher values likely influenced by lithological and atmospheric sources. Pearson correlation analyses suggest mining and agricultural legacies, coupled with aerosol deposition, are responsible for high metal concentrations in western lakes and headwater reaches of fluvial systems, while metal accumulation in estuarine reaches of the major rivers can be attributed to urban effluence and the remobilization of legacy sediments

Late Holocene lowland fluvial archives and geoarchaeology : Utrecht's case study of Rhine river abandonment under Roman and Medieval settlement

NARCIS (Netherlands)

van Dinter, M.; Cohen, K.M.; Hoek, W.Z.; Stouthamer, E.; Jansma, E.; Middelkoop, H.

2017-01-01

Fluvial lowlands have become attractive human settling areas all around the world over the last few millennia. Because rivers kept changing their course and networks due to avulsion, the sedimentary sequences in these areas are archives of both fluvial geomorphological and archaeological

Pre- and post-remediation characterization of acid-generating fluvial tailings material

Science.gov (United States)

Smith, Kathleen S.; Walton-Day, Katherine; Hoal, Karin O.; Driscoll, Rhonda L.; Pietersen, K.

2012-01-01

The upper Arkansas River south of Leadville, Colorado, USA, contains deposits of fluvial tailings from historical mining operations in the Leadville area. These deposits are potential non-point sources of acid and metal contamination to surface- and groundwater systems. We are investigating a site that recently underwent in situ remediation treatment with lime, fertilizer, and compost. Pre- and post-remediation fluvial tailings material was collected from a variety of depths to examine changes in mineralogy, acid generation, and extractable nutrients. Results indicate sufficient nutrient availability in the post-remediation near-surface material, but pyrite and acid generation persist below the depth of lime and fertilizer addition. Mineralogical characterization performed using semi-quantitative X-ray diffraction and quantitative SEM-based micro-mineralogy (Mineral Liberation Analysis, MLA) reveal formation of gypsum, jarosite, and complex coatings surrounding mineral grains in post-remediation samples.

Introduction to the special issue on discontinuity of fluvial systems

Science.gov (United States)

Burchsted, Denise; Daniels, Melinda; Wohl, Ellen E.

2014-01-01

Fluvial systems include natural and human-created barriers that modify local base level; as such, these discontinuities alter the longitudinal flux of water and sediment by storing, releasing, or changing the flow path of those materials. Even in the absence of distinct barriers, fluvial systems are typically discontinuous and patchy. The size of fluvial discontinuities ranges across scales from 100 m, such as riffles, to 104 m, such as lava dams or major landslides. The frequency of occurrence appears to be inversely related to size, with creation and failure of the small features, such as beaver dams, occurring on a time scale of 100 to 101 years and a frequency of occurrence at scales as low as 101 m. In contrast, larger scale discontinuities, such as lava dams, can last for time scales up to 105 years and have a frequency of occurrence of approximately 104 m. The heterogeneity generated by features is an essential part of river networks and should be considered as part of river management. Therefore, we suggest that "natural" dams are a useful analog for human dams when evaluating options for river restoration. This collection of papers on the studies of natural dams includes bedrock barriers, log jams and beaver dams. The collection also addresses the discontinuity generated by a floodplain — in the absence of an obvious barrier in the channel — and tools for evaluation of riverbed heterogeneity. It is completed with a study of impact of human dams on floodplain sedimentation. These papers will help geomorphologists and river managers understand the factors that control river heterogeneity across scales and around the world.

Examining fluvial fish range loss with SDMs

Science.gov (United States)

Taylor, Andrew T.; Papeş, Monica; Long, James M.

2018-01-01

Fluvial fishes face increased imperilment from anthropogenic activities, but the specific factors contributing most to range declines are often poorly understood. For example, the range of the fluvial‐specialist shoal bass (Micropterus cataractae) continues to decrease, yet how perceived threats have contributed to range loss is largely unknown. We used species distribution models to determine which factors contributed most to shoal bass range loss. We estimated a potential distribution based on natural abiotic factors and a series of currently occupied distributions that incorporated variables characterizing land cover, non‐native species, and river fragmentation intensity (no fragmentation, dams only, and dams and large impoundments). We allowed interspecific relationships between non‐native congeners and shoal bass to vary across fragmentation intensities. Results from the potential distribution model estimated shoal bass presence throughout much of their native basin, whereas models of currently occupied distribution showed that range loss increased as fragmentation intensified. Response curves from models of currently occupied distribution indicated a potential interaction between fragmentation intensity and the relationship between shoal bass and non‐native congeners, wherein non‐natives may be favored at the highest fragmentation intensity. Response curves also suggested that >100 km of interconnected, free‐flowing stream fragments were necessary to support shoal bass presence. Model evaluation, including an independent validation, suggested that models had favorable predictive and discriminative abilities. Similar approaches that use readily available, diverse, geospatial data sets may deliver insights into the biology and conservation needs of other fluvial species facing similar threats.

Deciphering Fluvial-Capture-Induced Erosional Patterns at the Continental Scale on the Iberian Peninsula

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Anton, L.; Munoz Martin, A.; De Vicente, G.; Finnegan, N. J.

2017-12-01

The process of river incision into bedrock dictates the landscape response to changes in climate and bedrock uplift in most unglaciated settings. Hence, understanding processes of river incision into bedrock and their topographic signatures are a basic goal of geomorphology. Formerly closed drainage basins provide an exceptional setting for the quantification of long term fluvial dissection and landscape change, making them valuable natural laboratories. Internally drained basins are peculiar because they trap all the sediment eroded within the watershed; as closed systems they do not respond to the base level of the global ocean and deposition is the dominant process. In that context, the opening of an outward drainage involves a sudden lowering of the base level, which is transmitted upstream along fluvial channels in the form of erosional waves, leading to high incision and denudation rates within the intrabasinal areas. Through digital topographic analysis and paleolandscape reconstruction based on relict deposits and landscapes on the Iberian Peninsula, we quantify the volume of sediments eroded from formerly internally drained basins since capture. Mapping of fluvial dissection patterns reveals how, and how far, regional waves of incision have propagated upstream. In our analysis, erosional patterns are consistent with the progressive establishment of an outward drainage system, providing a relative capture chronology for the different studied basins. Divide migration inferred from chi maps supports the interpretations based on fluvial dissection patterns and volumes, providing clues on how landscaped changed and how drainage integration occurred within the studied watersheds. [Funded by S2013/MAE-2739 and CGL2014-59516].

Heterogeneity in a Suburban River Network: Understanding the Impact of Fluvial Wetlands on Dissolved Oxygen and Metabolism in Headwater Streams

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Cain, J. S.; Wollheim, W. M.; Sheehan, K.; Lightbody, A.

2014-12-01

Low dissolved oxygen content in rivers threatens fish populations, aquatic organisms, and the health of entire ecosystems. River systems with high fluvial wetland abundance and organic matter, may result in high metabolism that in conjunction with low re-aeration rates, lead to low oxygen conditions. Increasing abundance of beaver ponds in many areas may exacerbate this phenomenon. This research aims to understand the impact of fluvial wetlands, including beaver ponds, on dissolved oxygen (D.O.) and metabolism throughout the headwaters of the Ipswich R. watershed, MA, USA. In several fluvial wetland dominated systems, we measured diel D.O. and metabolism in the upstream inflow, the surface water transient storage zones of fluvial wetland sidepools, and at the outflow to understand how the wetlands modify dissolved oxygen. D.O. was also measured longitudinally along entire surface water flow paths (x-y km long) to determine how low levels of D.O. propagate downstream. Nutrient samples were also collected to understand how their behavior was related to D.O. behavior. Results show that D.O. in fluvial wetlands has large swings with periods of very low D.O. at night. D.O. swings were also seen in downstream outflow, though lagged and somewhat attenuated. Flow conditions affect the level of inundation and the subsequent effects of fluvial wetlands on main channel D.O.. Understanding the D.O. behavior throughout river systems has important implications for the ability of river systems to remove anthropogenic nitrogen.

Experimental insights into organic carbon oxidation potential during fluvial transport without floodplain storage

Science.gov (United States)

Scheingross, J. S.; Hovius, N.; Sachse, D.; Vieth-Hillebrand, A.; Turowski, J. M.; Hilton, R. G.

2016-12-01

Over geologic timescales, the exchange of organic carbon (OC) between the atmosphere, rock, and biosphere is thought to be a major control on global climate. CO2 flux estimates from oxidation of rock-derived OC and sequestration of biospheric OC during fluvial transit from source to sink are approximately the same order of magnitude or larger than those from silicate weathering. Despite field data showing loss of OC moving downstream in lowland rivers, it is unclear if losses occur primarily during active fluvial transport within the river, where OC is in continual motion within an aerated environment, or during longer periods when OC is temporarily stored in river floodplains which may be anoxic. This represents a major knowledge gap, as the unknown location of OC oxidation (i.e., river vs. floodplain) limits our ability to develop process-based models that can be employed to predict OC losses, constrain carbon budgets, and unravel links between climate, tectonics, and erosion. To fill this gap, we investigated the potential for OC oxidation in laboratory experiments simulating fluvial transport without floodplain storage. Mixtures of OC-rich and siliciclastic sediment were transported for distances of 2000 km in annular flumes while making time-series measurements of sediment TOC and water DOC concentrations. Initial results for transport of OC-rich soil show increasing DOC with transport distance to levels that represent a transfer of 2% of the total OC from the solid to the dissolved phase; however, we observed no detectable change in the solid-phase TOC. Similar results were obtained in a control experiment with identical sediment in still water. These preliminary results suggest minimal OC oxidation within our experiment, and, to the extent that such experiments represent natural transport through river systems, are consistent with the hypothesis that OC losses may occur primarily during floodplain storage rather than fluvial transport.

Spatial and temporal modelling of fluvial aggradation in the Hasli Valley (Swiss Alps) during the last 1300 years

Science.gov (United States)

Llorca, Jaime; Schulte, Lothar; Carvalho, Filipe

2016-04-01

The Haslital delta (upper Aare River catchment, Bernese Alps) progradated into the Lake Brienz after the retreat of the Aare Glacier (post-LGM). Present delta plain geomorphology and spatial distribution of sedimentary facies result from historical fluvial dynamics and aggradation. Over centuries, local communities have struggled to control the Aare floods and to mitigate their effects on the floodplain (by means of raising artificial levees, channelizing the course, creating an underground drainage network, constructing dams at the basin headwaters). This study focuses on the spatial and temporal evolution of sediment dynamics of the floodplain by analyzing fluvial sedimentary records . The internal variability of lithostratigraphic sequences is a key issue to understand hydrological processes in the basin under the effect of environmental and anthropogenic changes of the past. The floodplain lithostratigraphy was reconstructed by coring alongside four cross-sections; each one is composed of more than 25 shallow boreholes (2 m deep) and two long drillings (variable depth, up to 9 m). The chronostratigraphical models were obtained by AMS 14C dating, and information of paleofloods and channel migration were reconstructed from historical sources (Schulte et al., 2015). The identification of different sedimentary facies, associated with the fluvial architecture structures, provides information on variations of vertical and lateral accretion processes (Houben, 2007). The location and geometry of buried channel-levee facies (gravel and coarse sand layers) indicate a significant mobility of the riverbed of the Hasli-Aare river, following an oscillatory pattern during the last millennia. Furthermore, fine sedimentary deposits and peat layers represent the existence of stable areas where floods have a low incidence. Once the different types of deposits were identified, aggradation rates were estimated in order to determine the spatial variability of the accumulation

Cuerpo y casa : hacia el espacio doméstico contemporáneo desde las transformaciones de la cocina y el cuarto de baño

OpenAIRE

Pardo Díaz, Gonzalo

2016-01-01

Los ámbitos vinculados tanto a la preparación de los alimentos como al cuidado del cuerpo revelan las transformaciones de la domesticidad a lo largo de la historia y permiten analizar los cambios más radicales de la casa y sus habitantes. Desde las primeras hogueras, el cocinar ha implicado un lugar, que una vez vinculado al habitar construido ha ido desplazándose por el espacio doméstico, ampliándose y reduciéndose, alejándose o acercándose al resto de los espacios de la casa en función de ...

Utilization of ancient permafrost carbon in headwaters of Arctic fluvial networks

NARCIS (Netherlands)

Mann, Paul J.; Eglinton, Timothy I.; McIntyre, Cameron P.; Zimov, Nikita; Davydova, Anna; Vonk, Jorien E.; Holmes, Robert M.; Spencer, Robert G M

2015-01-01

Northern high-latitude rivers are major conduits of carbon from land to coastal seas and the Arctic Ocean. Arctic warming is promoting terrestrial permafrost thaw and shifting hydrologic flowpaths, leading to fluvial mobilization of ancient carbon stores. Here we describe 14 C and 13 C

When do plants modify fluvial processes? Plant-hydraulic interactions under variable flow and sediment supply rates

Science.gov (United States)

Manners, Rebecca B.; Wilcox, Andrew C.; Kui, Li; Lightbody, Anne F.; Stella, John C.; Sklar, Leonard S.

2015-02-01

Flow and sediment regimes shape alluvial river channels; yet the influence of these abiotic drivers can be strongly mediated by biotic factors such as the size and density of riparian vegetation. We present results from an experiment designed to identify when plants control fluvial processes and to investigate the sensitivity of fluvial processes to changes in plant characteristics versus changes in flow rate or sediment supply. Live seedlings of two species with distinct morphologies, tamarisk (Tamarix spp.) and cottonwood (Populus fremontii), were placed in different configurations in a mobile sand-bed flume. We measured the hydraulic and sediment flux responses of the channel at different flow rates and sediment supply conditions representing equilibrium (sediment supply = transport rate) and deficit (sediment supply plant species and configuration. Species-specific traits controlled the hydraulic response: compared to cottonwood, which has a more tree-like morphology, the shrubby morphology of tamarisk resulted in less pronation and greater reductions in near-bed velocities, Reynolds stress, and sediment flux rates. Under sediment-deficit conditions, on the other hand, abiotic factors dampened the effect of variations in plant characteristics on the hydraulic response. We identified scenarios for which the highest stem-density patch, independent of abiotic factors, dominated the fluvial response. These results provide insight into how and when plants influence fluvial processes in natural systems.

The Brahmaputra River: a stratigraphic analysis of Holocene avulsion and fluvial valley reoccupation history

Science.gov (United States)

Hartzog, T. R.; Goodbred, S. L.

2011-12-01

The Brahmaputra River, one of the world's largest braided streams, is a major component of commerce, agriculture, and transportation in India and Bangladesh. Hence any significant change in course, morphology, or behavior would be likely to influence the regional culture and economy that relies on this major river system. The history of such changes is recorded in the stratigraphy deposited by the Brahmaputra River during the Holocene. Here we present stratigraphic analysis of sediment samples from the boring of 41 tube wells over a 120 km transect in the upper Bengal Basin of northern Bangladesh. The transect crosses both the modern fluvial valley and an abandoned fluvial valley about 60 km downstream of a major avulsion node. Although the modern Brahmaputra does not transport gravel, gravel strata are common below 20 m with fluvial sand deposits dominating most of the stratigraphy. Furthermore, the stratigraphy preserves very few floodplain mud strata below the modern floodplain mud cap. These preliminary findings will be assessed to determine their importance in defining past channel migration, avulsion frequency, and the reoccupation of abandoned fluvial valleys. Understanding the avulsion and valley reoccupation history of the Brahmaputra River is important to assess the risk involved with developing agriculture, business, and infrastructure on the banks of modern and abandoned channels. Based on the correlation of stratigraphy and digital surface elevation data, we hypothesize that the towns of Jamalpur and Sherpur in northern Bangladesh were once major ports on the Brahmaputra River even though they now lie on the banks of small underfit stream channels. If Jamalpur and Sherpur represent the outer extent of the Brahmaputra River braid-belt before the last major avulsion, these cities and any communities developed in the abandoned braid-belt assume a high risk of devastation if the next major avulsion reoccupies this fluvial valley. It is important to

Fluvial biogeomorphology in the Anthropocene: Managing rivers and managing landscapes.

Science.gov (United States)

Viles, Heather

2015-04-01

Biogeomorphology considers the many, and often complex, interactions between ecological and geomorphological processes. The concept of the Anthropocene deserves greater attention by scientists working on biogeomorphology, as will be demonstrated in this talk though a focus on fluvial environments. Rivers and river systems have been the subject of long-term human interference and management across the world, often in the form of direct manipulation of biogeomorphic interactions. Up to the present three broadly-defined phases of the Anthropocene can be identified - the Palaeoanthropocene, the Industrial Revolution and the Great Acceleration. Each of these broad phases of the Anthropocene has different implications for fluvial biogeomorphology and river management. The nature and dynamics of tufa-depositing systems provide good examples of the differing Anthropocene situations and will be focused on in this talk. We may now be entering a fourth phase of the Anthropocene called 'Earth system stewardship'. In terms of better understanding and managing the biogeomorphic interactions within rivers in such a phase, an improved conceptualisation of the Anthropocene and the complex web of interactions between human, ecological and geomorphological processes is needed.

Tratamiento de los espacios fluviales urbanos andaluces en la planificación territorial y sectorial

Directory of Open Access Journals (Sweden)

David González Rojas

2017-01-01

Full Text Available La recuperación y conservación de los espacios fluviales urbanos debe insertarse dentro de los procesos de planificación territorial y sectorial. El presente trabajo analiza la evolución y las transformaciones de los espacios fluviales urbanos en Andalucía durante las últimas décadas, a través del análisis de los distintos planes. Para el estudio de las relaciones entre el planeamiento territorial y sectorial y los espacios fluviales urbanos se ha realizado una recopilación de los documentos actualmente aprobados o en tramitación. En el artículo se destacan los avances durante el periodo estudiado, pero también las inercias, resistencias y nuevos problemas asociados. El esfuerzo realizado para la ordenación de los ríos a su paso por las ciudades no ha tenido su reflejo en los resultados obtenidos, siendo las interrelaciones entre la gestión del agua y del territorio (regional, subregional y municipal una cuestión no resuelta.

Optimizing sampling strategy for radiocarbon dating of Holocene fluvial systems in a vertically aggrading setting

International Nuclear Information System (INIS)

Toernqvist, T.E.; Dijk, G.J. Van

1993-01-01

The authors address the question of how to determine the period of activity (sedimentation) of fossil (Holocene) fluvial systems in vertically aggrading environments. The available data base consists of almost 100 14 C ages from the Rhine-Meuse delta. Radiocarbon samples from the tops of lithostratigraphically correlative organic beds underneath overbank deposits (sample type 1) yield consistent ages, indicating a synchronous onset of overbank deposition over distances of at least up to 20 km along channel belts. Similarly, 14 C ages from the base of organic residual channel fills (sample type 3) generally indicate a clear termination of within-channel sedimentation. In contrast, 14 C ages from the base of organic beds overlying overbank deposits (sample type 2), commonly assumed to represent the end of fluvial sedimentation, show a large scatter reaching up to 1000 14 C years. It is concluded that a combination of sample types 1 and 3 generally yields a satisfactory delimitation of the period of activity of a fossil fluvial system. 30 refs., 11 figs., 4 tabs

Analysis of groundwater flow and stream depletion in L-shaped fluvial aquifers

Directory of Open Access Journals (Sweden)

C.-C. Lin

2018-04-01

Full Text Available Understanding the head distribution in aquifers is crucial for the evaluation of groundwater resources. This article develops a model for describing flow induced by pumping in an L-shaped fluvial aquifer bounded by impermeable bedrocks and two nearly fully penetrating streams. A similar scenario for numerical studies was reported in Kihm et al. (2007. The water level of the streams is assumed to be linearly varying with distance. The aquifer is divided into two subregions and the continuity conditions of the hydraulic head and flux are imposed at the interface of the subregions. The steady-state solution describing the head distribution for the model without pumping is first developed by the method of separation of variables. The transient solution for the head distribution induced by pumping is then derived based on the steady-state solution as initial condition and the methods of finite Fourier transform and Laplace transform. Moreover, the solution for stream depletion rate (SDR from each of the two streams is also developed based on the head solution and Darcy's law. Both head and SDR solutions in the real time domain are obtained by a numerical inversion scheme called the Stehfest algorithm. The software MODFLOW is chosen to compare with the proposed head solution for the L-shaped aquifer. The steady-state and transient head distributions within the L-shaped aquifer predicted by the present solution are compared with the numerical simulations and measurement data presented in Kihm et al. (2007.

Fluvial-aeolian interactions in sediment routing and sedimentary signal buffering: an example from the Indus Basin and Thar Desert

Science.gov (United States)

East, Amy E.; Clift, Peter D.; Carter, Andrew; Alizai, Anwar; VanLaningham, Sam

2015-01-01

Sediment production and its subsequent preservation in the marine stratigraphic record offshore of large rivers are linked by complex sediment-transfer systems. To interpret the stratigraphic record it is critical to understand how environmental signals transfer from sedimentary source regions to depositional sinks, and in particular to understand the role of buffering in obscuring climatic or tectonic signals. In dryland regions, signal buffering can include sediment cycling through linked fluvial and eolian systems. We investigate sediment-routing connectivity between the Indus River and the Thar Desert, where fluvial and eolian systems exchanged sediment over large spatial scales (hundreds of kilometers). Summer monsoon winds recycle sediment from the lower Indus River and delta northeastward, i.e., downwind and upstream, into the desert. Far-field eolian recycling of Indus sediment is important enough to control sediment provenance at the downwind end of the desert substantially, although the proportion of Indus sediment of various ages varies regionally within the desert; dune sands in the northwestern Thar Desert resemble the Late Holocene–Recent Indus delta, requiring short transport and reworking times. On smaller spatial scales (1–10 m) along fluvial channels in the northern Thar Desert, there is also stratigraphic evidence of fluvial and eolian sediment reworking from local rivers. In terms of sediment volume, we estimate that the Thar Desert could be a more substantial sedimentary store than all other known buffer regions in the Indus basin combined. Thus, since the mid-Holocene, when the desert expanded as the summer monsoon rainfall decreased, fluvial-eolian recycling has been an important but little recognized process buffering sediment flux to the ocean. Similar fluvial-eolian connectivity likely also affects sediment routing and signal transfer in other dryland regions globally.

Fluvial particle characterization using artificial neural network and spectral image processing

Science.gov (United States)

Shrestha, Bim Prasad; Gautam, Bijaya; Nagata, Masateru

2008-03-01

Sand, chemical waste, microbes and other solid materials flowing with the water bodies are of great significance to us as they cause substantial impact to different sectors including drinking water management, hydropower generation, irrigation, aquatic life preservation and various other socio-ecological factors. Such particles can't completely be avoided due to the high cost of construction and maintenance of the waste-treatment methods. A detailed understanding of solid particles in surface water system can have benefit in effective, economic, environmental and social management of water resources. This paper describes an automated system of fluvial particle characterization based on spectral image processing that lead to the development of devices for monitoring flowing particles in river. Previous research in coherent field has shown that it is possible to automatically classify shapes and sizes of solid particles ranging from 300-400 μm using artificial neural networks (ANN) and image processing. Computer facilitated with hyper spectral and multi spectral images using ANN can further classify fluvial materials into organic, inorganic, biodegradable, bio non degradable and microbes. This makes the method attractive for real time monitoring of particles, sand and microorganism in water bodies at strategic locations. Continuous monitoring can be used to determine the effect of socio-economic activities in upstream rivers, or to monitor solid waste disposal from treatment plants and industries or to monitor erosive characteristic of sand and its contribution to degradation of efficiency of hydropower plant or to identify microorganism, calculate their population and study the impact of their presence. Such system can also be used to characterize fluvial particles for planning effective utilization of water resources in micro-mega hydropower plant, irrigation, aquatic life preservation etc.

Insights into organic carbon oxidation potential during fluvial transport from laboratory and field experiments

Science.gov (United States)

Scheingross, J. S.; Dellinger, M.; Eglinton, T. I.; Fuchs, M. C.; Golombek, N.; Hilton, R. G.; Hovius, N.; Lupker, M.; Repasch, M. N.; Sachse, D.; Turowski, J. M.; Vieth-Hillebrand, A.; Wittmann, H.

2017-12-01

Over geologic timescales, the exchange of organic carbon (OC) between the atmosphere, hydropshere, biosphere and geosphere can be a major control on atmospheric carbon dioxide concentrations. The carbon fluxes from the oxidation of rock-derived OC (a CO2 source) and erosion, transport, and burial of biospheric OC (a potential CO2 sink) during fluvial transit are approximately the same order of magnitude or larger than those from silicate weathering. Despite field data showing increasing oxidation of OC moving downstream in lowland rivers, it is unclear if losses occur primarily during active fluvial transport, where OC is in continual motion within an aerated river, or during periods of temporary storage in river floodplains which may be anoxic. The unknown location of OC oxidation (i.e., river vs. floodplain) limits our ability to mechanistically link geochemical and geomorphic processes which are required to develop models capable of predicting OC losses, constrain carbon budgets, and unravel links between climate, tectonics, and erosion. To fill this knowledge gap, we investigated OC oxidation in controlled laboratory experiments and a simplified field setting. We performed experiments in annular flumes that simulate fluvial transport without floodplain storage, allowing mixtures of OC-rich and siliciclastic sediment to be transported for distances of 1000 km. Preliminary experiments exploring both rock-derived and biospheric OC sources show minimal OC oxidation during active river transport, consistent with the idea that the majority of OC loss occurs during transient floodplain storage. These results are also consistent with new field data collected in the Rio Bermejo, Argentina, a lowland river traversing 800 km with no tributary inputs, where aged floodplain deposits have 3 to 10 times lower OC concentrations compared to modern river sediments. Together our field data and experiments support the hypothesis that oxidation of OC occurs primarily during

A fast, parallel algorithm to solve the basic fluvial erosion/transport equations

Science.gov (United States)

Braun, J.

2012-04-01

Quantitative models of landform evolution are commonly based on the solution of a set of equations representing the processes of fluvial erosion, transport and deposition, which leads to predict the geometry of a river channel network and its evolution through time. The river network is often regarded as the backbone of any surface processes model (SPM) that might include other physical processes acting at a range of spatial and temporal scales along hill slopes. The basic laws of fluvial erosion requires the computation of local (slope) and non-local (drainage area) quantities at every point of a given landscape, a computationally expensive operation which limits the resolution of most SPMs. I present here an algorithm to compute the various components required in the parameterization of fluvial erosion (and transport) and thus solve the basic fluvial geomorphic equation, that is very efficient because it is O(n) (the number of required arithmetic operations is linearly proportional to the number of nodes defining the landscape), and is fully parallelizable (the computation cost decreases in a direct inverse proportion to the number of processors used to solve the problem). The algorithm is ideally suited for use on latest multi-core processors. Using this new technique, geomorphic problems can be solved at an unprecedented resolution (typically of the order of 10,000 X 10,000 nodes) while keeping the computational cost reasonable (order 1 sec per time step). Furthermore, I will show that the algorithm is applicable to any regular or irregular representation of the landform, and is such that the temporal evolution of the landform can be discretized by a fully implicit time-marching algorithm, making it unconditionally stable. I will demonstrate that such an efficient algorithm is ideally suited to produce a fully predictive SPM that links observationally based parameterizations of small-scale processes to the evolution of large-scale features of the landscapes on

Excursions in fluvial (dis)continuity

Science.gov (United States)

Grant, Gordon E.; O'Connor, James E.; Safran, Elizabeth

2017-01-01

Lurking below the twin concepts of connectivity and disconnectivity are their first, and in some ways, richer cousins: continuity and discontinuity. In this paper we explore how continuity and discontinuity represent fundamental and complementary perspectives in fluvial geomorphology, and how these perspectives inform and underlie our conceptions of connectivity in landscapes and rivers. We examine the historical roots of continuum and discontinuum thinking, and how much of our understanding of geomorphology rests on contrasting views of continuity and discontinuity. By continuum thinking we refer to a conception of geomorphic processes as well as geomorphic features that are expressed along continuous gradients without abrupt changes, transitions, or thresholds. Balance of forces, graded streams, and hydraulic geometry are all examples of this perspective. The continuum view has played a prominent role in diverse disciplinary fields, including ecology, paleontology, and evolutionary biology, in large part because it allows us to treat complex phenomena as orderly progressions and invoke or assume equilibrium processes that introduce order and prediction into our sciences.In contrast the discontinuous view is a distinct though complementary conceptual framework that incorporates non-uniform, non-progressive, and non-equilibrium thinking into understanding geomorphic processes and landscapes. We distinguish and discuss examples of three different ways in which discontinuous thinking can be expressed: 1) discontinuous spatial arrangements or singular events; 2) specific process domains generally associated with thresholds, either intrinsic or extrinsic; and 3) physical dynamics or changes in state, again often threshold-linked. In moving beyond the continuous perspective, a fertile set of ideas comes into focus: thresholds, non-equilibrium states, heterogeneity, catastrophe. The range of phenomena that is thereby opened up to scientific exploration similarly expands

Large Fluvial Fans: Aspects of the Attribute Array

Science.gov (United States)

Wilkinson, Justin M.

2015-01-01

In arguing for a strict definition of the alluvial fan (coarse-grained with radii less than10 km, in mountain-front settings), Blair and McPherson (1994) proposed that there is no meaningful difference between large fluvial fans (LFF) and floodplains, because the building blocks of both are channel-levee-overbank deposits. Sediment bodies at the LFF scale (greater than 100 km long, fan-shaped in planform), are relatively unstudied although greater than 160 are now identified globally. The following perspectives suggest that the significance of LFF needs to be reconsidered.

Pleistocene-Holocene sedimentation of Solimões-Amazon fluvial system between the tributaries Negro and Madeira, Central Amazon

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Eliezer Senna Gonçalves Júnior

Full Text Available ABSTRACT: In the scope of Solimões-Amazon fluvial system between the Negro and Madeira tributaries, three levels of Quaternary fluvial terraces overlie the Alter do Chão and Novo Remanso formations further than 100 km southward its current main channel. Smooth undulated topography presenting low drainages density formed by sparse secondary plain channels and rounded lakes characterizes these deposits. Internally, they show point bars morphology constituted by intercalated layers of mud (silt and clay and sand forming an inclined heterolithic stratification. The asymmetric distribution of fluvial terraces allied to the records of old scroll-bars features and paleochannels in many extensions of the Solimões River suggests the predominance of a meander pattern between 240 to 6 kyears. On the other hand, the development of the current anabranching pattern took place in the last six kyears due to the Holocene sea-level rise, besides the action of neotectonics and rainforest establishment related to the increase of humidity in Amazonia.

A new ‘superassemblage’ model explaining proximal-to-distal and lateral facies changes in fluvial environments, based on the Proterozoic Sanjauli Formation (Lesser Himalaya, India

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Ananya Mukhopadhyay

2016-09-01

Full Text Available Facies analysis of fluvial deposits of the Proterozoic Sanjauli Formation in the Lesser Himalaya was combined with an architectural analysis. On this basis, a model was developed that may be applied to other fluvial systems as well, whether old or recent. The new model, which might be considered as an assemblage of previous models, explains lateral variations in architecture and facies but is not in all respects consistent with the standard fluvial models. The Sanjauli fluvial model is unique in that it deals with lateral facies variations due to shifts of the base-level along with fluctuations in accommodation space owing to changes in palaeoclimate.

The impact of urban expansion and agricultural legacies on trace metal accumulation in fluvial and lacustrine sediments of the lower Chesapeake Bay basin, USA.

Science.gov (United States)

Coxon, T M; Odhiambo, B K; Giancarlo, L C

2016-10-15

The progressively declining ecological condition of the Chesapeake Bay is attributed to the influx of contaminants associated with sediment loads supplied by its largest tributaries. The continued urban expansion in the suburbs of Virginia cities, modern agricultural activities in the Shenandoah Valley, the anthropogenic and climate driven changes in fluvial system hydrodynamics and their potential associated impacts on trace metals enrichment in the bay's tributaries necessitate constant environmental monitoring of these important water bodies. Eight (210)Pb and (137)Cs dated sediment cores and seventy two sediment grab samples were used to analyze the spatial and temporal distributions of Al, Ca, Mg, Cr, Cd, As, Se, Pb, Cu, Zn, Mn, and Fe in the waterways of the Virginia portion of the Chesapeake Bay basin. The sediment cores for trace metal historical fluctuation analysis were obtained in lower fluvial-estuarine environments and reservoirs in the upper reaches of the basin. The trace metal profiles revealed high basal enrichment factors (EF) of between 0.05 and 40.24, which are interpreted to represent early nineteenth century agricultural activity and primary resource extraction. Surficial enrichment factors on both cores and surface grab samples ranged from 0.01 (Cu) to 1421 (Cd), with Pb, Cu, Zn, and Cd enrichments a plausible consequence of modern urban expansion and industrial development along major transportation corridors. Contemporary surficial enrichments of As, Se, and Cr also ranged between 0 and 137, with the higher values likely influenced by lithological and atmospheric sources. Pearson correlation analyses suggest mining and agricultural legacies, coupled with aerosol deposition, are responsible for high metal concentrations in western lakes and headwater reaches of fluvial systems, while metal accumulation in estuarine reaches of the major rivers can be attributed to urban effluence and the remobilization of legacy sediments. Copyright © 2016

A multiple dating approach (luminescence and electron spin resonance) to assess rates of crustal deformation using Quaternary fluvial terraces of the lower Moulouya River (NE Morocco)

Science.gov (United States)

Bartz, Melanie; Rixhon, Gilles; Duval, Mathieu; King, Georgina; Brückner, Helmut

2017-04-01

The Moulouya River, the largest catchment in Morocco, drains an area characterized by active crustal deformation during the Late Cenozoic due to the convergence between the African and Eurasian plates. Our study focuses on the lowermost reach of the river in NE Morocco, where a thrust zone associated with N-S compressive shortening in this region was identified (Barcos et al., 2014; Rixhon et al., 2017). New geomorphological results demonstrate contrasting fluvial environments on each side of the thrust: long-lasting fluvial aggradation, materialized by >37 m-thick stacked fill terraces, and the development of a well-preserved terrace staircase, with three Pleistocene terrace levels, occurred in the footwall and the hanging wall, respectively (Rixhon et al., 2017). Here, we present a preliminary geochronological background for these contrasting terrace systems based on a multiple dating approach. Samples for (i) luminescence (pIRIR225 and pIRIR290 dating of coarse-grained K-feldspars) and (ii) electron spin resonance (ESR dating of coarse-grained quartz) from four different profiles were collected. (i) Due to the application of the athermal detrapping model by Huntley (2006) (modified after Kars et al., 2008), it appears that the feldspar signals are in sample specific field saturation. Our results yielded minimum ages of 0.9 Ma and 0.7 Ma for the footwall and hanging wall, respectively. (ii) Using the multiple centre approach with ESR dating (Duval et al., 2015), we measured both the aluminium (Al) and the titanium (Ti) centres in order to evaluate whether they would provide consistent results. Results indicate that De values of the Al centre are either slightly higher compared to those of the Ti centre or they agree within a 1σ-error range, which may simply be due to the slower bleaching kinetics of the Al centre. Thus, the ESR ages were inferred from the Ti centre. Ages between 1.35±0.10 and 1.17±0.10 Ma in the footwall show sediment aggradation between MIS

Reservoir architecture and tough gas reservoir potential of fluvial crevasse-splay deposits

NARCIS (Netherlands)

Van Toorenenburg, K.A.; Donselaar, M.E.; Weltje, G.J.

2015-01-01

Unconventional tough gas reservoirs in low-net-to-gross fluvial stratigraphic intervals may constitute a secondary source of fossil energy to prolong the gas supply in the future. To date, however, production from these thin-bedded, fine-grained reservoirs has been hampered by the economic risks

Extreme Changes in Stream Geomorphic Conditions induced by Fluvial Scour in Bridges

Science.gov (United States)

Özcan, O.; Ozcan, O.

2016-12-01

The numerous complexities associated with bridge scour have caused scour to be one of the most active topics of stream geomorphic research. The assessment of local scouring mechanism around bridge piers provides information for decision-making regarding the pile footing design, predicting the safety of bridges under critical scoured conditions, and as a result, may help prevent unnecessary loses. In the study, bridge design plans and HEC-RAS modeling were used for the assessment of changes in stream geomorphic conditions. The derived fluvial scour depths were compared with the field measurements and the empirical formula which is based on stream flow discharge rate, streambed condition and shape of river. Preliminary results revealed that bridge damage resulting from the flood event in 2003 induced substantial scour around bridge piles. Afterwards, significant stream bed change was observed under the influence of fluvial scour in another flood occurred in 2009. Consequently, geomorphic conditions of the stream bed should be considered in the structural design of the bridges.

Results of radiocarbon dating of Holocene fluvial sediments from Northeastern Bohemia

International Nuclear Information System (INIS)

Silar, J.; Zeman, A.

1989-01-01

Samples of wood and charcoal from the latest Holocene fluvial sediments under the lowest surface of alluvial plains were dated by radiocarbon in order to check paleomagnetic data at four sites in northeastern Bohemia. The results are presented as funcorrected 14 C ages and dendrochronologically corrected ages. Two samples were recent. 4 figs., 1 tab., 3 refs

Climatic implications of correlated upper Pleistocene glacial and fluvial deposits on the Cinca and Gallego rivers, NE Spain

Energy Technology Data Exchange (ETDEWEB)

Lewis, Claudia J [Los Alamos National Laboratory; Mcdonald, Eric [NON LANL; Sancho, Carlos [NON LANL; Pena, Jose- Luis [NON LANL

2008-01-01

We correlate Upper Pleistocene glacial and fluvial deposits of the Cinca and Gallego River valleys (south central Pyrenees and Ebro basin, Spain) using geomorphic position, luminescence dates, and time-related trends in soil development. The ages obtained from glacial deposits indicate glacial periods at 85 {+-} 5 ka, 64 {+-} 11 ka, and 36 {+-} 3 ka (from glacial till) and 20 {+-} 3 ka (from loess). The fluvial drainage system, fed by glaciers in the headwaters, developed extensive terrace systems in the Cinca River valley at 178 {+-} 21 ka, 97 {+-} 16 ka, 61 {+-} 4 ka, 47 {+-} 4 ka, and 11 {+-} 1 ka, and in the Gallego River valley at 151 {+-} 11 ka, 68 {+-} 7 ka, and 45 {+-} 3 ka. The times of maximum geomorphic activity related to cold phases coincide with Late Pleistocene marine isotope stages and heinrich events. The maximum extent of glaciers during the last glacial occurred at 64 {+-} 11 ka, and the terraces correlated with this glacial phase are the most extensive in both the Cinca (61 {+-} 4 ka) and Gallego (68 {+-} 7 ka) valleys, indicating a strong increase in fluvial discharge and availability of sediments related to the transition to deglaciation. The global Last Glacial Maximum is scarcely represented in the south central Pyrenees owing to dominantly dry conditions at that time. Precipitation must be controlled by the position of the Iberian Peninsula with respect to the North Atlantic atmospheric circulation system. The glacial systems and the associated fluvial dynamic seem sensitive to (1) global climate changes controlled by insolation, (2) North Atlantic thermohaline circulation influenced by freshwater pulses into the North Atlantic, and (3) anomalies in atmospheric circulation in the North Atlantic controlling precipitation on the Iberian peninsula. The model of glacial and fluvial evolution during the Late Pleistocene in northern Spain could be extrapolated to other glaciated mountainous areas in southern Europe.

Reflexiones y enfoques en la conservación y restauración de ríos: georrestauración y pensamiento fluvial

OpenAIRE

Horacio, Jesús

2015-01-01

En los últimos años las sociedades más avanzadas se comienzan a replantear los principios y métodos aplicados para la gestión de los ríos. Este cambio de tendencia en la forma de pensar acerca de nuestro patrimonio fluvial es lo que se denomina en este trabajo: pensamiento fluvial. Este pensamiento implica derrocar ideas incompletas o erróneas sobre qué es un río y aceptarlo como un sistema natural dinámico. Pero el pensamiento fluvial invita también a discutir sobre la forma de conservar y r...

Stratigraphic architecture of a fluvial-lacustrine basin-fill succession at Desolation Canyon, Uinta Basin, Utah: Reference to Walthers’ Law and implications for the petroleum industry

Science.gov (United States)

Ford, Grace L.; David R. Pyles,; Dechesne, Marieke

2016-01-01

A continuous window into the fluvial-lacustrine basin-fill succession of the Uinta Basin is exposed along a 48-mile (77-kilometer) transect up the modern Green River from Three Fords to Sand Wash in Desolation Canyon, Utah. In ascending order the stratigraphic units are: 1) Flagstaff Limestone, 2) lower Wasatch member of the Wasatch Formation, 3) middle Wasatch member of the Wasatch Formation, 4) upper Wasatch member of the Wasatch Formation, 5) Uteland Butte member of the lower Green River Formation, 6) lower Green River Formation, 7) Renegade Tongue of the lower Green River Formation, 8) middle Green River Formation, and 9) the Mahogany oil shale zone marking the boundary between the middle and upper Green River Formations. This article uses regional field mapping, geologic maps, photographs, and descriptions of the stratigraphic unit including: 1) bounding surfaces, 2) key upward stratigraphic characteristics within the unit, and 3) longitudinal changes along the river transect. This information is used to create a north-south cross section through the basin-fill succession and a detailed geologic map of Desolation Canyon. The cross section documents stratigraphic relationships previously unreported and contrasts with earlier interpretations in two ways: 1) abrupt upward shifts in the stratigraphy documented herein, contrast with the gradual interfingering relationships proposed by Ryder et al., (1976) and Fouch et al., (1994), 2) we document fluvial deposits of the lower and middle Wasatch to be distinct and more widespread than previously recognized. In addition, we document that the Uteland Butte member of the lower Green River Formation was deposited in a lacustrine environment in Desolation Canyon.

Fluvial geomorphology and aquatic-to-terrestrial Hg export are weakly coupled in small urban streams of Columbus, Ohio

Science.gov (United States)

Sullivan, S. Mažeika P.; Boaz, Lindsey E.; Hossler, Katie

2016-04-01

Although mercury (Hg) contamination is common in stream ecosystems, mechanisms governing bioavailability and bioaccumulation in fluvial systems remain poorly resolved as compared to lentic systems. In particular, streams in urbanized catchments are subject to fluvial geomorphic alterations that may contribute to Hg distribution, bioaccumulation, and export across the aquatic-to-terrestrial boundary. In 12 streams of urban Columbus, Ohio, we investigated the influence of fluvial geomorphic characteristics related to channel geometry, streamflow, and sediment size and distribution on (1) Hg concentrations in sediment and body burdens in benthic larval and adult emergent aquatic insects and (2) aquatic-to-terrestrial contaminant transfer to common riparian spiders of the families Pisauridae and Tetragnathidae via changes in aquatic insect Hg body burdens as well as in aquatic insect density and community composition. Hydrogeomorphic characteristics were weakly related to Hg body burdens in emergent insects (channel geometry) and tetragnathid spiders (streamflow), but not to Hg concentrations in sediment or benthic insects. Streamflow characteristics were also related to emergent insect density, while wider channels were associated with benthic insect community shifts toward smaller-bodied and more tolerant taxa (e.g., Chironomidae). Thus, our results provide initial evidence that fluvial geomorphology may influence aquatic-to-terrestrial contaminant Hg transfer through the collective effects on emergent insect body burdens as well as on aquatic insect community composition and abundance.

Fluvial incision by the Qingyijiang River on the northern fringe of Mt. Huangshan, eastern China: Responses to weakening of the East Asian summer monsoon

Science.gov (United States)

Hu, Chunsheng; Liu, Shaochen; Hu, Chenqi; Xu, Guanglai; Zhou, Yingqiu

2017-12-01

This paper focuses on climatic and tectonic controls to determine their relative importance to the Quaternary fluvial incision by the Qingyijiang River, eastern China. The Qingyijiang, which is one of longest tributaries of the lower Yangtze River, drains the northern piedmont of Mt. Huangshan. A field survey focused on three natural sections of the Qingyijiang in the Jingxian basin, where a well-preserved sequence of one alluvial platform (P) and three fluvial terraces (T3, T2, and T1) is presented. The heights of the platform and the terraces above river level are 65, 40, 20, and 7 m respectively. In this study, electron spin resonance (ESR), optical stimulated luminescence (OSL), and palaeomagnetic dating were applied to reconstruct the fluvial incision history of the Qingyijiang and evaluate the possible influence of tectonic uplift and/or climate change on the fluvial incision. The main results show that (1) the ages of P, T3, T2, and T1 were determined to be ∼ 1300, ∼ 900, ∼ 600, and ∼ 1.5 ka respectively, corresponding to four incision events in the Qingyijiang; (2) the East Asian summer monsoon (EASM) experienced four significant weakening events at 1300, 900, 600, and ∼ 1.5 ka, according to previous research. Correspondingly, we propose that four significant increased periods of regional precipitation occurred at 1300, 900, 600, and ∼ 1.5 ka in the study area because of the negative correlation between the intensity of the EASM and regional precipitation from 1960 to 2012; and (3) fluvial incision by the Qingyijiang arose as a result of the weakening of the EASM in combination with tectonic uplift, determined by matching fluvial incision history of the Qingyijiang with tectonic movement and EASM change. In addition, the weakening of the EASM climatically triggered fluvial incision by the Qingyijiang. This study supports the conclusion that major fluvial incision has been climatically triggered; however, it also suggests that the mechanism of

Insights into organic carbon oxidation potential during fluvial transport from controlled laboratory and natural field experiments

Science.gov (United States)

Scheingross, Joel S.; Dellinger, Mathieu; Golombek, Nina; Hilton, Robert G.; Hovius, Niels; Sachse, Dirk; Turowski, Jens M.; Vieth-Hillebrand, Andrea; Wittmann, Hella

2017-04-01

Over geologic timescales, the exchange of organic carbon (OC) between the atmosphere, biosphere and geosphere is thought to be a major control on atmospheric carbon dioxide (CO2) concentrations, and hence global climate. The carbon fluxes from the oxidation of rock-derived OC (a CO2 source) and erosion and transport of biospheric OC (a potential CO2 sink) during fluvial transit are approximately the same order of magnitude or larger than those from silicate weathering (France-Lanord and Derry, 1997; Bouchez et al., 2010). Despite field data showing oxidation of OC moving downstream in lowland rivers, it is unclear if losses occur primarily during active fluvial transport within the river, where OC is in continual motion within an aerated environment, or during longer periods when OC is temporarily stored in river floodplains which may be anoxic. This represents a major knowledge gap, as the unknown location of OC oxidation (i.e., river vs. floodplain) limits our ability to develop process-based models that can be employed to predict OC losses, constrain carbon budgets, and unravel links between climate, tectonics, and erosion. To fill this gap, we investigated the potential for OC oxidation in both controlled laboratory experiments and a simplified field setting. We consider both rock-derived and biospheric OC. Our experiments simulated fluvial transport without floodplain storage, allowing mixtures of OC-rich and siliciclastic sediment to be transported for distances of 1000 km in annular flumes while making time-series measurements of OC concentration in both the solid (POC) and dissolved (DOC) loads, as well as measurements of rhenium concentration, which serves as a proxy for the oxidation of rock-derived OC. These transport experiments were compared to static, control experiments where water and sediment in the same proportion were placed in still water. Initial results for transport of OC-rich soil show similar behavior between the transport and static

Phosphorus and nitrogen loading depths in fluvial sediments following manure spill simulations

Science.gov (United States)

Manure spills that enter streams can devastate the aquatic ecosystem. The depth of nitrogen (N) and phosphorus (P) loading in fluvial sediments following a manure spill have not been documented. Thus, the objectives of this study were (i) to determine the depth of N and P contamination as a result o...

Middle Moscovian climate of eastern equatorial Pangea recorded in paleosols and fluvial architecture

Czech Academy of Sciences Publication Activity Database

Opluštil, S.; Lojka, R.; Rosenau, N.A.; Strnad, L.; Sýkorová, Ivana

2015-01-01

Roč. 440, DEC (2015), s. 328-352 ISSN 0031-0182 Institutional support: RVO:67985891 Keywords : Carboniferous paleoclimate * fluvial architectures * paleosols * geochemistry Subject RIV: DB - Geology ; Mineralogy Impact factor: 2.525, year: 2015 http://www.sciencedirect.com/science/article/pii/S0031018215004939

High temporal resolution in situ measurement of the effective particle size characteristics of fluvial suspended sediment.

Science.gov (United States)

Williams, N D; Walling, D E; Leeks, G J L

2007-03-01

This paper reports the use of a LISST-100 device to monitor the effective particle size characteristics of suspended sediment in situ, and at a quasi-continuous temporal resolution. The study site was located on the River Exe at Thorverton, Devon, UK. This device has not previously been utilized in studies of fluvial suspended sediment at the storm event scale, and existing studies of suspended sediment dynamics have not involved such a high temporal resolution for extended periods. An evaluation of the field performance of the instrument is presented, with respect to innovative data collection and analysis techniques. It was found that trends in the effective particle size distribution (EPSD) and degree of flocculation of suspended sediment at the study site were highly complex, and showed significant short-term variability that has not previously been documented in the fluvial environment. The collection of detailed records of EPSD facilitated interpretation of the dynamic evolution of the size characteristics of suspended sediment, in relation to its likely source and delivery and flocculation mechanisms. The influence of measurement frequency is considered in terms of its implications for future studies of the particle size of fluvial suspended sediment employing in situ data acquisition.

Characterization and 3D reservoir modelling of fluvial sandstones of the Williams Fork Formation, Rulison Field, Piceance Basin, Colorado, USA

International Nuclear Information System (INIS)

Pranter, Matthew J; Vargas, Marielis F; Davis, Thomas L

2008-01-01

This study describes the stratigraphic characteristics and distribution of fluvial deposits of the Upper Cretaceous Williams Fork Formation in a portion of Rulison Field and addresses 3D geologic modelling of reservoir sand bodies and their associated connectivity. Fluvial deposits include isolated and stacked point-bar deposits, crevasse splays and overbank (floodplain) mudrock. Within the Williams Fork Formation, the distribution and connectivity of fluvial sandstones significantly impact reservoir productivity and ultimate recovery. The reservoir sandstones are primarily fluvial point-bar deposits interbedded with shales and coals. Because of the lenticular geometry and limited lateral extent of the reservoir sandstones (common apparent widths of ∼500–1000 ft; ∼150–300 m), relatively high well densities (e.g. 10 acre (660 ft; 200 m) spacing) are often required to deplete the reservoir. Heterogeneity of these fluvial deposits includes larger scale stratigraphic variability associated with vertical stacking patterns and structural heterogeneities associated with faults that exhibit lateral and reverse offsets. The discontinuous character of the fluvial sandstones and lack of distinct marker beds in the middle and upper parts of the Williams Fork Formation make correlation between wells tenuous, even at a 10 acre well spacing. Some intervals of thicker and amalgamated sandstones within the middle and upper Williams Fork Formation can be correlated across greater distances. To aid correlation and for 3D reservoir modelling, vertical lithology proportion curves were used to estimate stratigraphic trends and define the stratigraphic zonation within the reservoir interval. Object-based and indicator-based modelling methods have been applied to the same data and results from the models were compared. Results from the 3D modelling indicate that sandstone connectivity increases with net-to-gross ratio and, at lower net-to-gross ratios (<30%), differences exist in

Consentimiento estatal al arbitraje del CIADI

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Pérez Pacheco , Yaritza

2013-12-01

Full Text Available El arbitraje en materia de inversión extranjera con especial atención a la jurisdicción del Centro Internacional de Arreglo de Diferencias Relativas a Inversiones, conocido como CIADI, es parte del Derecho Internacional de las Inversiones. El CIADI creado en el Convenio de Washington de 1965 se ha constituido en el foro natural para conocer de las controversias entre un Estado receptor y un inversor nacional de otro Estado. En este contexto se cuestionan varios aspectos vinculados a la formación del consentimiento para someterse al arbitraje internacional, en particular las modalidades (contrato, legislación y tratados y efectos de la manifestación del consentimiento por parte del Estado receptor de la inversión. En este trabajo se ha empleado el método de análisis de casos para extraer parámetros generales en la materia. En la actualidad el arbitraje internacional es una garantía ofrecida por el Estado, lo cual ha generado un clima de mayor seguridad para los inversores extranjeros en el trato con los Estados receptores de inversión y ha incentivado el crecimiento del comercio internacional.

A Late Pleistocene linear dune dam record of aeolian-fluvial dynamics at the fringes of the northwestern Negev dunefield

Science.gov (United States)

Roskin, Joel; Bookman, Revital; Friesem, David; Vardi, Jacob

2017-04-01

The paper presents a late Pleistocene aeolian-fluvial record within a linear dune-like structure that partway served as a dune dam. Situated along the southern fringe of the northwestern Negev desert dunefield (Israel) the structure's morphology, orientation, and some of its stratigraphic units partly resemble adjacent west-east extending vegetated linear dunes. Uneven levels of light-colored, fine-grained fluvial deposits (LFFDs) extend to the north and south from the flanks of the studied structure. Abundant Epipalaeolithic sites line the fringes of the LFFDs. The LFFD microstructures of fine graded bedding and clay blocky peds indicate sorting and shrinking of saturated clays in transitional environments between low energy flows to shallow standing water formed by dunes damming a mid-sized drainage system. The structure's architecture of interchanging units of sand with LFFDs indicates interchanging dominances between aeolian sand incursion and winter floods. Sand mobilization associated with powerful winds during the Heinrich 1 event led to dune damming downstream of the structure and within the structure to in-situ sand deposition, partial fluvial erosion, reworking of the sand, and LFFD deposition. Increased sand deposition led to structure growth and blockage of its drainage system that in turn accumulated LFFD units up stream of the structure. Extrapolation of current local fluvial sediment yields indicate that LFFD accretion up to the structure's brim occurred over a short period of several decades. Thin layers of Geometric Kebaran (c. 17.5-14.5 ka cal BP) to Harifian (12-11 ka BP) artifacts within the structure's surface indicates intermittent, repetitive, and short term camping utilizing adjacent water along a timespan of 4-6 kyr. The finds directly imply that the NW Negev LFFDs formed in dune-dammed water bodies which themselves were formed following events of vegetated linear dune elongation. LFFD accumulation persisted as a result of dune dam

Risks related to exposure to radon Riesgos vinculados a la exposición al radón

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Juan Miguel Barros Dios

2010-12-01

Full Text Available They discuss the different scientific evidence that radon and its short half-life descendants are responsible for the appearance of a considerable number of lung cancers among the exposed population in homes and public buildings (occupational exposure. It also draws a small glimpse at the road traveled by this knowledge and acceptance difficult administrations in many countries and, in particular, of Spain, as well as the various investigations that the team do Galego Radon and Radon Laboratory from Galicia, the area of Public Health, University of Santiago de Compostela (USC, are contributing to scientific knowledge. Finally, they appreciate the few legislative initiatives on the problem in Spain.Se comentan las diferentes evidencias científicas de que el radón y sus descendientes de vida media corta son responsables de la aparición de un número no desdeñable de cánceres de pulmón entre la población expuesta en domicilios y edificios públicos (exposición laboral. Asimismo, se traza una pequeña aproximación al camino recorrido por este conocimiento y su difícil aceptación por parte de las diferentes Administraciones de numerosos países y, en concreto, de España, así como las diversas investigaciones que el Grupo Galego do Radon y el Laboratorio de Radón de Galicia, del Área de Salud Pública, de la Universidad de Santiago de Compostela, llevan aportando a ese conocimiento científico. Por último, se valoran las escasas iniciativas legislativas sobre el problema en España.

Transport and redistribution of Chernobyl fallout radionuclides by fluvial processes: some preliminary evidence

International Nuclear Information System (INIS)

Walling, D.E.; Bradley, S.B.

1988-01-01

Several measurements of 137 Cs concentrations in suspended sediment transported by the River Severn during the post-Chernobyl period and in recent channel and floodplain deposits along the river emphasise the potential significance of fluvial processes in the transport and concentration of fallout radionuclides. (author)

The impact of disturbance on the dynamics of fluvial processes in mountain landscapes

Czech Academy of Sciences Publication Activity Database

Langhammer, J.; Hartvich, Filip; Kliment, Z.; Jeníček, M.; Bernsteinová (Kaiglová), J.; Vlček, L.; Su, Y.; Štych, P.; Miřijovský, J.

2015-01-01

Roč. 21, č. 1 (2015), s. 105-116 ISSN 1211-7420 Institutional support: RVO:67985891 Keywords : runoff * fluvial dynamics * forest disturbance * climate change * Bohemian Forest Subject RIV: DE - Earth Magnetism, Geodesy, Geography http://www.npsumava.cz/gallery/31/9345-sg_21_1_langhammeretal.pdf

Modelling the impact of regional uplift and local tectonics on fluvial terrace preservation.

NARCIS (Netherlands)

Viveen, W.; Schoorl, J.M.; Veldkamp, A.; Balen, van R.T.

2014-01-01

A terrace formation model (TERRACE) combined with a longitudinal river profile model (FLUVER) was used to simulate fluvial terrace formation and preservation in the northwest Iberian lower Miño River basin under the influence of three tectonic conditions; namely regional vertical uplift, local basin

MIRAR AL CLAUSTRO. ACERCA DE LO CONVENTUAL EN LA OBRA DE JUANA MANUELA GORRITI

Directory of Open Access Journals (Sweden)

Victoria Cohen Imach

2010-01-01

Full Text Available En la narrativa y en cartas de Juana Manuela Gorriti (Salta, 1816?-Buenos Aires, 1892 emergen figuras adscribibles, en tránsito hacia o afines a diferentes formas de la existencia religiosa femenina: monjas de clausura, donadas, beatas y una modalidad característica del siglo XIX, las integrantes de congregaciones de vida activa. Focalizando el trazado del dominio monacal (al que pertenecen las dos primeras formas ofrecido por sus textos, este trabajo se interroga por los sentidos que parecen latir en ese rasgo. Considerando que para comprenderlo es necesario tener en cuenta la situación y las representaciones relativas a los claustros en la centuria en algunos de los ámbitos en los que la autora reside y que resultan escenario de episodios vinculados al tema en su escritura (Salta, Bolivia, Perú o bien en aquel que opera sólo en la segunda dirección (Chile, en particular, probablemente, Santiago, así como las ideas y la sensibilidad de la propia Gorriti acerca de tal dominio, él aspira centralmente a ofrecer un panorama articulado al respecto y a plantear de modo más sintético ciertos trazos de su construcción en el corpus indicado.

Effects of Wildfire on Fluvial Sediment Regime through Perturbations in Dry-Ravel

Science.gov (United States)

Florsheim, J. L.; Chin, A.; Kinoshita, A. M.; Nourbakhshbeidokhti, S.; Storesund, R.; Keller, E. A.

2015-12-01

In steep chaparral ecosystems with Mediterranean climate, dry ravel is a natural process resulting from wildfire disturbance that supplies sediment to fluvial systems. When dense chaparral vegetation burns, sediment accumulated on steep hillslopes is released for dry-season transport (dry ravel) down steep hillslopes during or soon after the wildfire. Results of a field study in southern California's Transverse Ranges illustrate the effect of wildfire on fluvial sediment regime in an unregulated chaparral system. Big Sycamore Canyon in the steep Santa Monica Mountains burned during the May 2013 Springs Fire and experienced one small sediment-transporting stormflow during the following winter. We conducted pre- and post-storm field campaigns during the fall and winter following the fire to quantify the effect of wildfire on the fluvial sediment regime. We utilized a sediment mass balance approach in which: 1) sediment supply, consisting primarily of dry ravel-derived deposits composed of relatively fine grained-sediment, was measured in the upstream basin and in the hillslope-channel margin adjacent to the study reach; 2) changes in storage in the study reach were quantified by analyzing the difference between pre- and post-storm channel topography derived from Terrestrial LiDAR Scanning (TLS) and field surveys; and 3) transport from the study reach was estimated as the difference between supply and change in storage where uncertainty is estimated using calculated sediment transport as a comparison. Results demonstrate channel deposition caused by changes in the short-term post-wildfire sediment regime. The increased sediment supply and storage are associated with significant changes in morphology, channel bed-material characteristics, and ecology. These results suggest that dry-ravel processes are an important factor to consider in post-wildfire sediment management.

Facies architecture and high resolution sequence stratigraphy of an aeolian, fluvial and shallow marine system in the Pennsylvanian Piauí Formation, Parnaíba Basin, Brazil

Science.gov (United States)

Vieira, Lucas Valadares; Scherer, Claiton Marlon dos Santos

2017-07-01

The Pennsylvanian Piauí Formation records the deposition of aeolian, fluvial and shallow marine systems accumulated in the cratonic sag Parnaíba basin. Characterization of the facies associations and sequence stratigraphic framework was done by detailed description and logging of outcrops. Six facies associations were recognized: aeolian dunes and interdunes, aeolian sandsheets, fluvial channels, tidally-influenced fluvial channels, shoreface and shoreface-shelf transition. Through correlation of stratigraphic surfaces, the facies associations were organized in system tracts, which formed eight high frequency depositional sequences, bounded by subaerial unconformities. These sequences are composed of a lowstand system tract (LST), that is aeolian-dominated or fluvial-dominated, a transgressive system tract (TST) that is formed by tidally-influenced fluvial channels and/or shoreface and shoreface-shelf transition deposits with retrogradational stacking, and a highstand system tract (HST), which is formed by shoreface-shelf transition and shoreface deposits with progradational stacking. Two low frequency cycles were determined by observing the stacking of the high frequency cycles. The Lower Sequence is characterized by aeolian deposits of the LST and an aggradational base followed by a progressive transgression, defining a general TST. The Upper Sequence is characterized by fluvial deposits and interfluve pedogenesis concurring with the aeolian deposits of the LST and records a subtle regression followed by transgression. The main control on sedimentation in the Piauí Formation was glacioeustasy, which was responsible for the changes in relative sea level. Even though, climate changes were associated with glacioeustatic phases and influenced the aeolian and fluvial deposition.

Fluvial organic carbon flux from an eroding peatland catchment, southern Pennines, UK

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R. R. Pawson

2008-03-01

Full Text Available This study investigates for the first time the relative importance of dissolved organic carbon (DOC and particulate organic carbon (POC in the fluvial carbon flux from an actively eroding peatland catchment in the southern Pennines, UK. Event scale variability in DOC and POC was examined and the annual flux of fluvial organic carbon was estimated for the catchment. At the event scale, both DOC and POC were found to increase with discharge, with event based POC export accounting for 95% of flux in only 8% of the time. On an annual cycle, exports of 35.14 t organic carbon (OC are estimated from the catchment, which represents an areal value of 92.47 g C m⁻² a⁻¹. POC was the most significant form of organic carbon export, accounting for 80% of the estimated flux. This suggests that more research is required on both the fate of POC and the rates of POC export in eroding peatland catchments.

The Amazonian Craton and its influence on past fluvial systems (Mesozoic-Cenozoic, Amazonia)

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Hoorn, C.; Roddaz, M.; Dino, R.; Soares, E.; Uba, C.; Ochoa-Lozano, D.; Mapes, R.; Hoorn, C.; Wesselingh, F.P.

2010-01-01

The Amazonian Craton is an old geological feature of Archaean/Proterozoic age that has determined the character of fluvial systems in Amazonia throughout most of its past. This situation radically changed during the Cenozoic, when uplift of the Andes reshaped the relief and drainage patterns of

New Mesoscale Fluvial Landscapes - Seismic Geomorphology and Exploration

Science.gov (United States)

Wilkinson, M. J.

2013-01-01

Megafans (100-600 km radius) are very large alluvial fans that cover significant areas on most continents, the surprising finding of recent global surveys. The number of such fans and patterns of sedimentation on them provides new mesoscale architectures that can now be applied on continental fluvial depositional systems, and therefore on. Megafan-scale reconstructions underground as yet have not been attempted. Seismic surveys offer new possibilities in identifying the following prospective situations at potentially unsuspected locations: (i) sand concentrations points, (ii) sand-mud continuums at the mesoscale, (iii) paleo-valley forms in these generally unvalleyed landscapes, (iv) stratigraphic traps, and (v) structural traps.

Transport and deposition of plutonium-contaminated sediments by fluvial processes, Los Alamos Canyon, New Mexico

International Nuclear Information System (INIS)

Graf, W.L.

1996-01-01

Between 1945 and 1952 the development of nuclear weapons at Los Alamos National Laboratory, New Mexico, resulted in the disposal of plutonium into the alluvium of nearby Acid and (to a lesser degree) DP Canyons. The purpose of this paper is to explore the connection between the disposal sites and the main river, a 20 km link formed by the fluvial system of Acid, Pueblo, DP, and Los Alamos Canyons. Empirical data from 15 yr of annual sediment sampling throughout the canyon system has produced 458 observations of plutonium concentration in fluvial sediments. These data show that, overall, mean plutonium concentrations in fluvial sediment decline from 10,000 fCi/g near the disposal area to 100 fCi/g at the confluence of the canyon system and the Rio Grande. Simulations using a computer model for water, sediment, and plutonium routing in the canyon system show that discharges as large as the 25 yr event would fail to develop enough transport capacity to completely remove the contaminated sediments from Pueblo Canyon. Lesser flows would move some materials to the Rio Grande by remobilization of stored sediments. The simulations also show that the deposits and their contaminants have a predictable geography because they occur where stream power is low, hydraulic resistance is high, and the geologic and/or geomorphic conditions provide enough space for storage. 38 refs., 13 figs., 1 tab

Re-evaluating luminescence burial doses and bleaching of fluvial deposits using Bayesian computational statistics.

NARCIS (Netherlands)

Cunningham, A.C.; Wallinga, J.; Versendaal, Alice; Makaske, A.; Middelkoop, H.; Hobo, N.

2015-01-01

The optically stimulated luminescence (OSL) signal from fluvial sediment often contains a remnant from the previous deposition cycle, leading to a partially bleached equivalent-dose distribution. Although identification of the burial dose is of primary concern, the degree of bleaching could

Re-evaluating luminescence burial doses and bleaching of fluvial deposits using Bayesian computational statistics

NARCIS (Netherlands)

Cunningham, A. C.; Wallinga, J.; Hobo, N.; Versendaal, A. J.; Makaske, B.; Middelkoop, H.

2015-01-01

The optically stimulated luminescence (OSL) signal from fluvial sediment often contains a remnant from the previous deposition cycle, leading to a partially bleached equivalent-dose distribution. Although identification of the burial dose is of primary concern, the degree of bleaching could

Study on fine geological modelling of the fluvial sandstone reservoir in Daqing oilfield

Energy Technology Data Exchange (ETDEWEB)

Zhoa Han-Qing [Daqing Research Institute, Helongjiang (China)

1997-08-01

These paper aims at developing a method for fine reservoir description in maturing oilfields by using close spaced well logging data. The main productive reservoirs in Daqing oilfield is a set of large fluvial-deltaic deposits in the Songliao Lake Basin, characterized by multi-layers and serious heterogeneities. Various fluvial channel sandstone reservoirs cover a fairly important proportion of reserves. After a long period of water flooding, most of them have turned into high water cut layers, but there are considerable residual reserves within them, which are difficult to find and tap. Making fine reservoir description and developing sound a geological model is essential for tapping residual oil and enhancing oil recovery. The principal reason for relative lower precision of predicting model developed by using geostatistics is incomplete recognition of complex distribution of fluvial reservoirs and their internal architecture`s. Tasking advantage of limited outcrop data from other regions (suppose no outcrop data available in oilfield) can only provide the knowledge of subtle changing of reservoir parameters and internal architecture. For the specific geometry distribution and internal architecture of subsurface reservoirs (such as in produced regions) can be gained only from continuous infilling logging well data available from studied areas. For developing a geological model, we think the first important thing is to characterize sandbodies geometries and their general architecture`s, which are the framework of models, and then the slight changing of interwell parameters and internal architecture`s, which are the contents and cells of the model. An excellent model should possess both of them, but the geometry is the key to model, because it controls the contents and cells distribution within a model.

On the Application of an Enthalpy Method to the Evolution of Fluvial Deltas Under Sea-Level Changes

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Anderson, W.; Lorenzo-Trueba, J.; Voller, V. R.

2017-12-01

Fluvial deltas are composites of two primary sedimentary environments: a depositional fluvial region and an offshore region. The fluvial region is defined by two geomorphic moving boundaries: an alluvial-bedrock transition (ABT), which separates the sediment prism from the non-erodible bedrock basement, and the shoreline (SH), where the delta meets the ocean. The trajectories of these boundaries in time and space define the evolution of the shape of the sedimentary prism, and are often used as stratigraphic indicators, particularly in seismic studies, of changes in relative sea level and the identification of stratigraphic sequences. In order to better understand the relative role of sea-level variations, tectonics, and sediment supply on the evolution of these boundaries, we develop a forward stratigraphic model that captures the dynamic behavior of the fluvial surface and treats the SH and ABT as moving boundaries (i.e., internal boundaries whose location must be determined as part of the solution to the overall morphological evolution problem). This forward model extends a numerical technique from heat transfer (i.e., enthalpy method), previously applied to the evolution of sedimentary basins, to account for sea-level changes. The mathematics of the approach are verified by comparing predictions from the numerical model with both existing and newly developed closed form analytical solutions. Model results support previous work, which suggests that the migration of the ABT can respond very differently to the sea-level signal. This response depends on factors such as sediment supply and delta length, which can vary greatly between basins. These results can have important implications for the reconstruction of past sea-level changes from the stratigraphic record of sedimentary basins.

Assessing Potential Algal Blooms in a Shallow Fluvial Lake by Combining Hydrodynamic Modelling and Remote-Sensed Images

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Monica Pinardi

2015-04-01

Full Text Available Shallow fluvial lakes are dynamic ecosystems shaped by physical and biological factors and characterized by the coexistence of phytoplankton and macrophytes. Due to multiple interplaying factors, understanding the distribution of phytoplankton in fluvial lakes is a complex but fundamental issue, in the context of increasing eutrophication, climate change, and multiple water uses. We analyze the distribution of phytoplankton by combining remotely sensed maps of chlorophyll-a with a hydrodynamic model in a dammed fluvial lake (Mantua Superior Lake, Northern Italy. The numerical simulation of different conditions shows that the main hydrodynamic effects which influence algal distribution are related to the combined effect of advection due to wind forces and local currents, as well as to the presence of large gyres which induce recirculation and stagnation regions, favoring phytoplankton accumulation. Therefore, the general characters of the phytoplankton horizontal patchiness can be inferred from the results of the hydrodynamic model. Conversely, hyperspectral remote-sensing products can be used to validate this model, as they provide chlorophyll-a distribution maps. The integration of ecological, hydraulic, and remote-sensing techniques may therefore help the monitoring and protection of inland water quality, with important improvements in management actions by policy makers.

Analysis of Fluvial Bed Sediments Along the Apalachicola River, Florida through Field Reconnaissance Studies

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Passeri, D.; Hagen, S. C.; Daranpob, A.; Smar, D. E.

2011-12-01

River competence is an important parameter in understanding sediment transport in fluvial systems. Competence is defined as the measure of a stream's ability to transport a certain maximum grain size of sediment. Studies have shown that bed sediment particle size in rivers and streams tends to vary spatially along the direction of stream flow. Over a river section several reaches long, variability of sediment particle sizes can be seen, often becoming finer downstream. This phenomenon is attributed to mechanisms such as local control of stream gradient, coarse tributary sediment supply or particle breakdown. Average particle size may also be smaller in tributary sections of rivers due to river morphology. The relationship between river mean velocity and particle size that can be transported has also been explored. The Hjulstrom curve classifies this relationship by relating particle size to velocity, dividing the regions of sedimentation, transportation, and erosion. The curve can also be used to find values such as the critical erosion velocity (the velocity required to transport particles of various sizes in suspension) and settling velocity (the velocity at which particles of a given size become too heavy to be transported and fall out of suspension, consequently causing deposition). The purpose of this research is to explore the principles of river competence through field reconnaissance collection and laboratory analysis of fluvial sediment core samples along the Apalachicola River, FL and its distributaries. Sediment core samples were collected in the wetlands and estuarine regions of the Apalachicola River. Sieve and hydrometer analyses were performed to determine the spatial distribution of particle sizes along the river. An existing high resolution hydrodynamic model of the study domain was used to simulate tides and generate river velocities. The Hjulstrom curve and the generated river velocities were used to define whether sediment was being transported

Rapid fluvial incision of a late Holocene lava flow: Insights from LiDAR, alluvial stratigraphy, and numerical modeling

Science.gov (United States)

Sweeney, Kristin; Roering, Joshua J.

2016-01-01

Volcanic eruptions fundamentally alter landscapes, paving over channels, decimating biota, and emplacing fresh, unweathered material. The fluvial incision of blocky lava flows is a geomorphic puzzle. First, high surface permeability and lack of sediment should preclude geomorphically effective surface runoff and dissection. Furthermore, past work has demonstrated the importance of extreme floods in driving incision via column toppling and plucking in columnar basalt, but it is unclear how incision occurs in systems where surface blocks are readily mobile. We examine rapid fluvial incision of the Collier lava flow, an andesitic Holocene lava flow in the High Cascades of Oregon. Since lava flow emplacement ∼1600 yr ago, White Branch Creek has incised bedrock gorges up to 8 m deep into the coherent core of the lava flow and deposited >0.2 km3 of sediment on the lava flow surface. Field observation points to a bimodal discharge regime in the channel, with evidence for both annual snowmelt runoff and outburst floods from Collier glacier, as well as historical evidence of vigorous glacial meltwater. To determine the range of discharge events capable of incision in White Branch Creek, we used a mechanistic model of fluvial abrasion. We show that the observed incision implies that moderate flows are capable of both initiating channel formation and sustaining incision. Our results have implications for the evolution of volcanic systems worldwide, where glaciation and/or mass wasting may accelerate fluvial processes by providing large amounts of sediment to otherwise porous, sediment-starved landscapes.

Applying fluvial geomorphology to river channel management: Background for progress towards a palaeohydrology protocol

Science.gov (United States)

Gregory, K. J.; Benito, G.; Downs, P. W.

2008-06-01

Significant developments have been achieved in applicable and applied fluvial geomorphology as shown in publications of the last three decades, analyzed as the basis for using results of studies of environmental change as a basis for management. The range of types of publications and of activities are more pertinent to river channel management as a result of concern with sustainability, global climate change, environmental ethics, ecosystem health concepts and public participation. Possible applications, with particular reference to river channel changes, include those concerned with form and process, assessment of channel change, urbanization, channelization, extractive industries, impact of engineering works, historical changes in land use, and restoration with specific examples illustrated in Table 1. In order to achieve general significance for fluvial geomorphology, more theory and extension by modelling methods is needed, and examples related to morphology and process characteristics, integrated approaches, and changes of the fluvial system are collected in Table 2. The ways in which potential applications are communicated to decision-makers range from applicable outputs including publications ranging from review papers, book chapters, and books, to applied outputs which include interdisciplinary problem solving, educational outreach, and direct involvement, with examples summarized in Table 3. On the basis of results gained from investigations covering periods longer than continuous records, a protocol embracing palaeohydrological inputs for application to river channel management is illustrated and developed as a synopsis version (Table 4), demonstrating how conclusions from geomorphological research can be expressed in a format which can be considered by managers.

Tamarix, hydrology and fluvial geomorphology: Chapter 7

Science.gov (United States)

Auerbach, Daniel A.; Merritt, David M.; Shafroth, Patrick B.; Sher, Anna A; Quigley, Martin F.

2013-01-01

This chapter explores the impact of hydrology and fluvial geomorphology on the distribution and abundance of Tamarix as well as the reciprocal effects of Tamarix on hydrologic and geomorphic conditions. It examines whether flow-regime alteration favors Tamarix establishment over native species, and how Tamarix stands modify processes involved in the narrowing of river channels and the formation of floodplains. It begins with an overview of the basic geomorphic and hydrologic character of rivers in the western United States before analyzing how this setting has contributed to the regional success of Tamarix. It then considers the influence of Tamarix on the hydrogeomorphic form and function of rivers and concludes by discussing how a changing climate, vegetation management, and continued water-resource development affect the future role of Tamarix in these ecosystems.

A method of fingerprinting the sources of fluvial sediment using environmental radionuclides. A case study of Tsuzura river watershed

International Nuclear Information System (INIS)

Mizugaki, Shigeru; Onda, Yuichi; Fukuyama, Taijiro; Koga, Satoko; Hiramatsu, Shinya

2006-01-01

To study the fluvial sediment sources in forested watershed in Shikoku Island, Japan, the concentration of Cs-137 and Pb-210 ex and U decay series radionuclides were analyzed. The study area in the midstream of Shimanto River basin, located 700 km southwest of Tokyo. The 0.33 km 2 area watershed ranges in elevation from 170 m to 560 m above sea level. The soil sampling was conducted in hillslopes in various locations such as landslide scar, soil surface in unmanaged Hinoki (Chamacecyparis obtusa) plantation and unsealed forest road, and detailed sampling in the stream bed and bank was also conducted in several tributaries. Time-integrated suspended sediment sampler was adopted to obtain enough volume of sample to determine the radionuclides. The activities of Cs-137, Pb-210, Pb-214 and Bi-214 of soils and fluvial sediments were determined by gamma-ray spectrometry. Correction for the effect of particle size distribution and organic matter content on the radionuclides were conducted to compare the radionuclides concentration between the soils of potential suspended sediment sources and fluvial sediments. It was found that there were significant differences of Cs-137 and Pb-210 ex concentration between forest floor or runoff sediment and forest road or stream bank. The Cs-137 and Pb-210 ex concentration of suspended sediment varied among them, suggesting the possibility of fingerprinting the sources of fluvial sediment by Cs-137 and Pb-210 ex . (author)

Stable carbon isotope analysis of fluvial sediment fluxes over two contrasting C(4) -C(3) semi-arid vegetation transitions.

Science.gov (United States)

Puttock, Alan; Dungait, Jennifer A J; Bol, Roland; Dixon, Elizabeth R; Macleod, Christopher J A; Brazier, Richard E

2012-10-30

Globally, many drylands are experiencing the encroachment of woody vegetation into grasslands. These changes in ecosystem structure and processes can result in increased sediment and nutrient fluxes due to fluvial erosion. As these changes are often accompanied by a shift from C(4) to C(3) vegetation with characteristic δ(13) C values, stable isotope analysis provides a promising mechanism for tracing these fluxes. Input vegetation, surface sediment and fluvially eroded sediment samples were collected across two contrasting C(4) -C(3) dryland vegetation transitions in New Mexico, USA. Isotope ratio mass spectrometric analyses were performed using a Carlo Erba NA2000 analyser interfaced to a SerCon 20-22 isotope ratio mass spectrometer to determine bulk δ(13) C values. Stable isotope analyses of contemporary input vegetation and surface sediments over the monitored transitions showed significant differences (p fluvially eroded sediment from each of the sites, with no significant variation between surface sediment and eroded sediment values. The significant differences in bulk δ(13) C values between sites were dependent on vegetation input. Importantly, these values were robustly expressed in fluvially eroded sediments, suggesting that stable isotope analysis is suitable for tracing sediment fluxes. Due to the prevalent nature of these dryland vegetation transitions in the USA and globally, further development of stable isotope ratio mass spectrometry has provided a valuable tool for enhanced understanding of functional changes in these ecosystems. Copyright © 2012 John Wiley & Sons, Ltd.

Influencia de tres tipos de vegetación riberena en el control de la erosión fluvial en Pantanos de Centla, México

NARCIS (Netherlands)

Sepúlveda, A.; Geissen, V.; Ochoa-Gaona, S.; Jarquin-Sanchez, A.; Hernandez de la Cruz, S.; Zamora-Cornelio, L.F.

2009-01-01

Influence of three types of riparian vegetation on fluvial erosion control in Pantanos de Centla, Mexico. Wetlands constitute very important ecological areas. The aim of this study was to quantify the soil losses due to fluvial erosion from 2006 to 2008 in two riverbanks under three types of vegetal

Climate evolution during the Pleniglacial and Late Glacial as recorded in quartz grain morphoscopy of fluvial to aeolian successions of the European Sand Belt

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Woronko Barbara

2015-06-01

Full Text Available We present results of research into fluvial to aeolian successions at four sites in the foreland of the Last Glacial Maximum, i.e., the central part of the “European Sand Belt”. These sites include dune fields on higher-lying river terraces and alluvial fans. Sediments were subjected to detailed lithofacies analyses and sampling for morphoscopic assessment of quartz grains. Based on these results, three units were identified in the sedimentary succession: fluvial, fluvio-aeolian and aeolian. Material with traces of aeolian origin predominate in these sediments and this enabled conclusions on the activity of aeolian processes during the Pleniglacial and Late Glacial, and the source of sediment supply to be drawn. Aeolian processes played a major role in the deposition of the lower portions of the fluvial and fluvio-aeolian units. Aeolian material in the fluvial unit stems from aeolian accumulation of fluvial sediments within the valley as well as particles transported by wind from beyond the valley. The fluvio-aeolian unit is composed mainly of fluvial sediments that were subject to multiple redeposition, and long-term, intensive processing in an aeolian environment. In spite of the asynchronous onset of deposition of the fluvio-aeolian unit, it is characterised by the greatest homogeneity of structural and textural characteristics. Although the aeolian unit was laid down simultaneously, it is typified by the widest range of variation in quartz morphoscopic traits. It reflects local factors, mainly the origin of the source material, rather than climate. The duration of dune-formation processes was too short to be reflected in the morphoscopy of quartz grains.

El impacto de los procesos fluviales en la formación de los yacimientos arqueológicos al aire libre : pautas de análisis experimental

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Ignacio de la Torre Sáinz

2001-01-01

Full Text Available El análisis de los procesos de formación del registro es un requisito básico para la interpretación correcta de los yacimientos arqueológicos. Un agente fundamental en la configuración de los conjuntos ai aire libre es la acción hidráulica, que condiciona la preservación de muchos yacimientos, especialmente los correspondientes a los momentos más antiguos del Paleolítico. Asumiendo los principios del uniformitarismo geológico, podemos proponer que el análisis de fenómenos actuales permite generar marcos referenciales que después sean aplicados como instrumentos analíticos para la interpretación de los conjuntos arqueológicos. En el presente trabajo son revisados los estudios experimentales existentes sobre la problemática del arrastre fluvial, y la relevancia de los resultados a la hora de establecer modelos actualistas que sirvan como referencia para el análisis del registro arqueológico.The analysis of formation processes of the record is a basic issue for the correct interpretation of archaeological sites. A Key agent in the configuration of open air sites is the action of water, which affects the site's preservation, especially those sites corresponding to the most ancient paleolithic times. Assuming the principes ofgeological uniformitarism, it is possible to propose that analysis of modern phenomena allows US to créate referential frameworks which can be applied as means of analysis for tfie interpretation of archaeological sites. In this paper, available experimental studies relating the problems of fluvial disturbance are revised. Furthermore, the relevance of the results to build actualistic models which work as a reference for the analysis of the archaeological record is considered.

UN DEBATE EN TORNO AL TRATO PREFERENCIAL: LA REIVINDICACIÓN DEL DERECHO A LA IGUALDAD DE TRATO Y NO DISCRIMINACIÓN DEL COLECTIVO DE DESPLAZADOS POR EL CONFLICTO ARMADO INTERNO

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Paula Andrea Ramírez Monsalve

2011-01-01

Full Text Available La violación masiva y sistemática de los derechos constitucionales fundamentales al colectivo de desplazados por parte de los actores vinculados al conflicto armado interno, no deja de ser un fenómeno que hoy exige, más que nunca, de un profundo análisis que ayude a dimensionar dinámicas de cambio frente a la forma como el Estado interviene y regula, aun considerando la atención especial, la protección y reivindicación de sus derechos constitucionales fundamentales. Particularmente su derecho a la igualdadde trato y no discriminación. Es aquí donde la atención de la población desplazada, a través de políticas públicas en materia de discriminación positiva, protagoniza de manera coyuntural un quehacer jurídico que tiende a discriminar al ya discriminado.

Chronology of fluvial terrace sequences for large Atlantic rivers in the Iberian Peninsula (Upper Tagus and Duero drainage basins, Central Spain)

Science.gov (United States)

Silva, Pablo G.; Roquero, Elvira; López-Recio, Mario; Huerta, Pedro; Martínez-Graña, Antonio M.

2017-06-01

This work analyses the chronology of fluvial terrace sequences of the two most important fluvial basins from central Spain draining to the Atlantic Ocean (Upper Tagus and Duero drainage basins). Both basins evolved under similar Mediterranean climatic conditions throughout the Pleistocene and present comparable number of fluvial terraces (16-17) after excluding the higher terrace levels of the Tagus (T1-T5) entrenched in the Raña surface. These higher ;rañizo terraces; was formed in response to fan-head trenching in this high alluvial piedmont (+220 m) and therefore not properly controlled by Quaternary fluvial downcutting. The study accomplishes the implementation of multiple regression analyses for terrace height-age relationships. To transform relative terrace heights above the present river thalwegs (i.e. +100 m) in numerical ages a ;height-age transference function; has been developed on the basis of preliminary statistical geochronological approaches proposed for Central Spain. The resultant height-age transference function gather 73 published geochronological data for terrace sequences, featuring a 3rd Order Polynomial Function (R2 0.90). This function describes the overall trend of valley downcutting for the last c. 2.3 Ma in Central Spain and is used to assign numerical ages to terrace levels at different relative elevation.

Arsenic and fluvial biofilms: biogeochemistry, toxicity and biotic interactions

OpenAIRE

Barral Fraga, Laura

2017-01-01

Basándonos en los conocimientos actuales sobre la ecotoxicología del biofilm y la biogeoquímica del arsénico en ecosistemas dulceacuícolas, esta tesis estudió, bajo concentraciones ambientales realistas, i) el papel de los biofilms bentónicos en la biodisponibilidad y destoxificación del arsénico, ii) los efectos tóxicos del arsénico sobre la estructura y función de los biofilms bentónicos fluviales, prestando especial atención a las respuestas de las diatomeas, y iii) la interacción entre es...

Contribution of radioactive tracers to sediment transport study in fluvial flows

International Nuclear Information System (INIS)

Wilson Junior, G.

1995-01-01

The uses of radioactive tracers in sediment transport studies are presented in this report to evidence the importance of: Open channel researches, to describe field applications in waterways; Simultaneous utilization of classical methods and radiotracer techniques, in fluvial and estuarine environments; Development of radiotracers techniques applied in dynamic sedimentology. The report illustrated with some experiments carried out in Brazil and France, in open channel and natural flows. (author). 5 refs, 4 figs

Gully annealing by fluvially-sourced Aeolian sand: remote sensing investigations of connectivity along the Fluvial-Aeolian-hillslope continuum on the Colorado River

Science.gov (United States)

Sankey, Joel B.; East, Amy E.; Collins, Brian D.; Caster, Joshua J.

2015-01-01

Processes contributing to development of ephemeral gully channels are of great importance to landscapes worldwide, and particularly in dryland regions where soil loss and land degradation from gully erosion pose long-term, land-management problems. Whereas gully formation has been relatively well studied, much less is known of the processes that anneal gullies and impede their growth. This work investigates gully annealing by aeolian sediment, along the Colorado River downstream of Glen Canyon Dam in Glen, Marble, and Grand Canyons, Arizona, USA (Figure 1). In this segment of the Colorado River, gully erosion potentially affects the stability and preservation of archaeological sites that are located within valley margins. Gully erosion occurs as a function of ephemeral, rainfall-induced overland flow associated with intense episodes of seasonal precipitation. Measurements of sediment transport and topographic change have demonstrated that fluvial sand in some locations is transported inland and upslope by aeolian processes to areas affected by gully erosion, and aeolian sediment activity can be locally effective at counteracting gully erosion (Draut, 2012; Collins and others, 2009, 2012; Sankey and Draut, 2014). The degree to which specific locations are affected by upslope wind redistribution of sand from active channel sandbars to higher elevation valley margins is termed “connectivity”. Connectivity is controlled spatially throughout the river by (1) the presence of upwind sources of fluvial sand within the contemporary active river channel (e.g., sandbars), and (2) bio-physical barriers that include vegetation and topography that might impede aeolian sediment transport. The primary hypothesis of this work is that high degrees of connectivity lead to less gullying potential.

Fluvial diffluence episodes reflected in the Pleistocene tufa deposits of the River Piedra (Iberian Range, NE Spain)

Science.gov (United States)

Vázquez-Urbez, M.; Pardo, G.; Arenas, C.; Sancho, C.

2011-01-01

The Pleistocene deposits of the valley of the River Piedra (NE Spain) are represented by thick tufas with small amounts of detrital material; the development of these deposits correlates with marine isotopic stages 9, 7, 6, and 5. The sedimentary scenario in which they formed mostly corresponded to stepped fluvial systems with barrage-cascade and associated dammed areas separated by low gradient fluvial stretches. Mapping and determining the sedimentology and chronology of these deposits distinguished two main episodes of fluvial diffluence that originated as a result of the temporary blockage of the river — a consequence of the vertical growth of tufa barrages in the main channel. In both episodes, water spilt out toward a secondary course from areas upstream of barrages where the water level surpassed the height of the divide between the main and secondary course. As a consequence, extensive and distinct tufa deposits with very varied facies formed over a gently inclined area toward and, indeed, within the secondary course. The hydrology of this secondary course was episodic, fed only by surface water. The two diffluence episodes detected occurred during MIS 7 and 7-6 and were interrupted by incision events, reflected by detrital deposits at the base of each tufa sedimentation stage in the main channel. Incision, which caused the breakage of the barrages, allowed water to again flow through the main channel. No evidence of diffluence was seen in any younger (MIS 5 to present-day) tufa deposits. The proposed diffluence model might help explain other carbonate fluvial systems in which (1) tufas appear in areas with no permanent water supply, and (2) tufas are absent over extensive areas despite conditions favourable to their formation.

Entre puertos, campos y acopios: Trabajo y transporte de granos en torno al Sudeste bonaerense.

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Paula Tagliabue

2014-12-01

Full Text Available En este artículo, se analiza el proceso de trabajo en el transporte automotor de granos en torno al sudeste bonaerense. Desde un abordaje cualitativo, se describen y analizan las prácticas durante la cosecha y pos-cosecha, y los trayectos campo-acopio, acopio-puerto. También se analizan las relaciones laborales a partir de una perspectiva ampliada de las relaciones laborales clásicas (asalariadas, estables, protegidas.Los rasgos que asume el trabajo en el transporte de granos están asociados a los cambios técnicos y tecnológicos de la producción de granos, así como a procesos de flexibilización laboral, vinculados a la disponibilidad permanente para fletar, la extensión de la jornada laboral y la intensidad del trabajo camionero.

Characterizing Feedbacks Between Environmental Forcing and Sediment Characteristics in Fluvial and Coastal Systems

Science.gov (United States)

Feehan, S.; Ruggiero, P.; Hempel, L. A.; Anderson, D. L.; Cohn, N.

2016-12-01

Characterizing Feedbacks Between Environmental Forcing and Sediment Characteristics in Fluvial and Coastal Systems American Geophysical Union, 2016 Fall Meeting: San Francisco, CA Authors: Scott Feehan, Peter Ruggiero, Laura Hempel, and Dylan Anderson Linking transport processes and sediment characteristics within different environments along the source to sink continuum provides critical insight into the dominant feedbacks between grain size distributions and morphological evolution. This research is focused on evaluating differences in sediment size distributions across both fluvial and coastal environments in the U.S. Pacific Northwest. The Cascades' high relief is characterized by diverse flow regimes with high peak/flashy flows and sub-threshold flows occurring in relative proximity and one of the most energetic wave climates in the world. Combining analyses of both fluvial and coastal environments provides a broader understanding of the dominant forces driving differences between each system's grain size distributions, sediment transport processes, and resultant evolution. We consider sediment samples taken during a large-scale flume experiment that simulated floods representative of both high/flashy peak flows analogous to runoff dominated rivers and sub-threshold flows, analogous to spring-fed rivers. High discharge flows resulted in narrower grain size distributions while low flows where less skewed. Relative sediment size showed clear dependence on distance from source and the environments' dominant fluid motion. Grain size distributions and sediment transport rates were also quantified in both wave dominated nearshore and aeolian dominated backshore portions of Long Beach Peninsula, Washington during SEDEX2, the Sandbar-aEolian-Dune EXchange Experiment of summer 2016. The distributions showed spatial patterns in mean grain size, skewness, and kurtosis dependent on the dominant sediment transport process. The feedback between these grain size

Quantifying bleaching for zero-age fluvial sediment: A Bayesian approach

International Nuclear Information System (INIS)

Cunningham, Alastair C.; Evans, Mary; Knight, Jasper

2015-01-01

Luminescence dating of sediment requires the sand grains to have been exposed to sunlight prior to their most recent burial. Under fluvial transport, the amount of sunlight exposure may not always be sufficient to reset the luminescence signal, a phenomenon known as ‘partial bleaching'. The extent of bleaching is dependent on a combination of geomorphic, sedimentological and fluvial processes. If bleaching can be quantified, and the relationship with these processes understood, it could potentially be used as a new environmental proxy for changes in the dynamics of river systems. Here, we use a recently developed statistical model to evaluate the extent of bleaching, by inferring the proportion of well-bleached grains in the small-aliquot population. We sampled low-flow and flood deposits at a single site on the River Sabie, South Africa. We show that the low-flow sediment is almost perfectly bleached (>80% of grains well bleached), while sediment at flood elevations is partially bleached (20–70 % of grains well bleached). The degree of bleaching may show a relationship with flood magnitude as defined by elevation above normal river level, and we speculate on the causes of variability in bleaching between flood samples. - Highlights: • We sampled modern river sediment from low-flow and flood elevations. • The unbleached OSL dose was measured. • Bayesian methods can estimate the proportion of well-bleached grains. • Low-flow sediments are well bleached; flood deposits are poorly bleached.

Glacial vs. Interglacial Period Contrasts in Midlatitude Fluvial Systems, with Examples from Western Europe and the Texas Coastal Plain

Science.gov (United States)

Blum, M.

2001-12-01

Mixed bedrock-alluvial valleys are the conveyor belts for sediment delivery to passive continental margins. Mapping, stratigraphic and sedimentologic investigations, and development of geochronological frameworks for large midlatitude rivers of this type, in Western Europe and the Texas Coastal Plain, provide for evaluation of fluvial responses to climate change over the last glacial-interglacial period, and the foundations for future quantitative evaluation of long profile evolution, changes through time in flood magnitude, and changes in storage and flux of sediments. This paper focuses on two issues. First, glacial vs. interglacial period fluvial systems are fundamentally different in terms of channel geometry, depositional style, and patterns of sediment storage. Glacial-period systems were dominated by coarse-grained channel belts (braided channels in Europe, large-wavelength meandering in Texas), and lacked fine-grained flood-plain deposits, whereas Holocene units, especially those of late Holocene age, contain appreciable thicknesses of flood-plain facies. Hence, extreme overbank flooding was not significant during the long glacial period, most flood events were contained within bankfull channel perimeters, and fine sediments were bypassed through the system to marine basins. By contrast, extreme overbank floods have been increasingly important during the relatively short Holocene, and a significant volume of fine sediment is sequestered in flood-plain settings. Second, glacial vs. interglacial systems exhibit different amplitudes and frequencies of fluvial adjustment to climate change. High-amplitude but low-frequency adjustments characterized the long glacial period, with 2-3 extended periods of lateral migration and sediment storage puncuated by episodes of valley incision. Low-amplitude but high-frequency adjustments have been more typical of the short Holocene, when there has been little net valley incision or net changes in sediment storage, but

The microfauna assemblages as indicators of paleoenvironmental changes in the Miocene fluvial- lacustrine cycles (NE Duero Basin, Spain

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A. Herrero-Hernández

2016-11-01

Full Text Available The siliclastic and carbonate deposits are interbedded in the Villadiego area (Miocene, NE Duero Basin. They have been subdivided into two high-rank depositional sequences: DDS and CDS. The sedimentary analysis of these units and the study of the microfauna content, mainly ostracods, led to the identification of lacustrine-fluvial interaction systems. The sedimentary characteristics reveal the existence of fluvial systems of gravel, flood plains and lacustrine systems that were interconnected and intimately related in north-south direction. In the sedimentological analysis, thirteen types of fluvial and lacustrine lithofacies and six genetic facies associations were recognized. The top of DDS is the result of lake level risings. The CDS shows a deepening-shallowing cycle. The ostracod micropaleontological analysis of the sediments have been studied, with the aim of reconstructing the palaeoenvironmental evolution of this area. These microfauna assemblages integrated with the analysis of the sedimentary facies allowed to conclude the existence of lakes with a water-bearing level of few tens of meters. A change in the chemical conditions of the waters, which evolved from oligohaline and carbonated to mesohaline and sulphated is concluded.

Evidence for an early land use in the Rhône delta (Mediterranean France) as recorded by late Holocene fluvial paleoenvironments (1640-100 BC)

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Arnaud-Fassetta, Gilles; De Beaulieu, Jacques-Louis; Suc, Jean-Pierre; Provansal, Mireille; Williamson, David; Leveau, Philippe; Aloïsi, Jean-Claude; Gadel, François; Giresse, Pierre; Oberlin, Christine; Duzer, Danièle

The overall objective of this paper is to describe the late Holocene (1640-100 BC) sedimentary and biological evolution of the Rhône-delta-plain, to interpret the sedimentary facies and palynofacies as the result of the effects of fluvial dynamic fluctuations and relative sea level change and to evaluate the paleohydrological constraints in the development of the land use and settlements of the Camargue. Focus is made on the upper part of V III core drilled on NE of the Vaccarès lagoon. By combining sedimentology, palynology, magnetic susceptibility and archeological data, this study allowed to identify the superposition of three types of paleo-environments (marsh, fluvial floodplain, levee/crevasse splay). This sequence indicates a gradual extension of fluvial environments between the end of the second millennium BC and the 1st century BC. The variability of fluvial dynamic is evident during this period with important flood events which contrast with periods of low flow. Pollen record can be a good marker of the fluvial dynamic variability. The expression of the riparian tree pollen grains in the coarser floodplain deposits could correspond to increased fluvial influence and probably to erosion of riverbank during flood events. The local plants are associated to the low energy sedimentary environments. Focuses are made on the relations between the evolution of the environment and land use. The development of the cereal culture in the floodplain of the Rhône delta has been demonstrated between 1640-1410 and 100 BC. The last alluviation of the Rhône perturbs the research of the archaeological sites in the central part of the delta but the existence of the rural villages from the first part of the first millennium BC is highly possible.

Fluvial wood function downstream of beaver versus man-made dams in headwater streams in Massachusetts, USA

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David, G. C.; DeVito, L. F.; Munz, K. T.; Lisius, G.

2014-12-01

Fluvial wood is an essential component of stream ecosystems by providing habitat, increasing accumulation of organic matter, and increasing the processing of nutrients and other materials. However, years of channel alterations in Massachusetts have resulted in low wood loads despite the afforestation that has occurred since the early 1900s. Streams have also been impacted by a large density of dams, built during industrialization, and reduction of the beaver population. Beavers were reintroduced to Massachusetts in the 1940s and they have since migrated throughout the state. Beaver dams impound water, which traps sediment and results in the development of complex channel patterns and more ecologically productive and diverse habitats than those found adjacent to man-made dams. To develop better management practices for dam removal it is essential that we understand the geomorphic and ecologic function of wood in these channels and the interconnections with floodplain dynamics and stream water chemistry. We investigate the connections among fluvial wood, channel morphology, floodplain soil moisture dynamics, and stream water chemistry in six watersheds in Massachusetts that have been impacted by either beaver or man-made dams. We hypothesize that wood load will be significantly higher below beaver dams, subsequently altering channel morphology, water chemistry, and floodplain soil moisture. Reaches are surveyed up- and downstream of each type of dam to better understand the impact dams have on the fluvial system. Surveys include a longitudinal profile, paired with dissolved oxygen and ammonium measurements, cross-section and fluvial wood surveys, hydraulic measurements, and floodplain soil moisture mapping. We found that dissolved oxygen mirrored the channel morphology, but did not vary significantly between reaches. Wood loads were significantly larger downstream of beaver dams, which resulted in significant changes to the ammonium levels. Floodplain soil moisture

Mechanosensory based orienting behaviors in fluvial and lacustrine populations of mottled sculpin (Cottus bairdi)

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Sheryl Coombs; Gary D. Grossman

2006-01-01

We compared prey-orienting and rheotactic behaviors in a fluvial (Coweeta Creek) and lacustrine (Lake Michigan) population of mottled sculpin. Blinded sculpin from both populations exhibited unconditioned, mechanosensory based rheotaxis to low velocity flows. Whereas Lake Michigan sculpin generally showed increasing levels of positive rheotaxis to increasing velocities...

Calculation of paleohydraulic parameters of a fluvial system under spatially variable subsidence, of the Ericson sandstone, South western Wyoming

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Snyder, H.; Leva-Lopez, J.

2017-12-01

During the late Campanian age in North America fluvial systems drained the highlands of the Sevier orogenic belt and travelled east towards the Western Interior Seaway. One of such systems deposited the Canyon Creek Member (CCM) of the Ericson Formation in south-western Wyoming. At this time the fluvial system was being partially controlled by laterally variable subsidence caused by incipient Laramide uplifts. These uplifts rather than real topographic features were only areas of reduced subsidence at the time of deposition of the CCM. Surface expression at that time must have been minimum, only minute changes in slope and accommodation. Outcrops around these Laramide structures, in particular both flanks of the Rock Springs Uplift, the western side of the Rawlins uplift and the north flank of the Uinta Mountains, have been sampled to study the petrography, grain size, roundness and sorting of the CCM, which along with the cross-bed thickness and bar thickness allowed calculation of the hydraulic parameters of the rivers that deposited the CCM. This study reveals how the fluvial system evolved and responded to the very small changes in subsidence and slope. Furthermore, the petrography will shed light on the provenance of these sandstones and on the relative importance of Sevier sources versus Laramide sources. This work is framed in a larger study that shows how incipient Laramide structural highs modified the behavior, style and architecture of the fluvial system, affecting its thickness, facies characteristics and net-to-gross both down-dip and along strike across the basin.

Detrital shadows: estuarine food web connectivity depends on fluvial influence and consumer feeding mode.

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Howe, Emily; Simenstad, Charles A; Ogston, Andrea

2017-10-01

We measured the influence of landscape setting on estuarine food web connectivity in five macrotidal Pacific Northwest estuaries across a gradient of freshwater influence. We used stable isotopes (δ 13 C, δ 15 N, δ 34 S) in combination with a Bayesian mixing model to trace primary producer contributions to suspension- and deposit-feeding bivalve consumers (Mytilus trossulus and Macoma nasuta) transplanted into three estuarine vegetation zones: emergent marsh, mudflat, and eelgrass. Eelgrass includes both Japanese eelgrass (Zostera japonica) and native eelgrass (Zostera marina). Fluvial discharge and consumer feeding mode strongly influenced the strength and spatial scale of observed food web linkages, while season played a secondary role. Mussels displayed strong cross-ecosystem connectivity in all estuaries, with decreasing marine influence in the more fluvial estuaries. Mussel diets indicated homogenization of detrital sources within the water column of each estuary. In contrast, the diets of benthic deposit-feeding clams indicated stronger compartmentalization in food web connectivity, especially in the largest river delta where clam diets were trophically disconnected from marsh sources of detritus. This suggests detritus deposition is patchy across space, and less homogenous than the suspended detritus pool. In addition to fluvial setting, other estuary-specific environmental drivers, such as marsh area or particle transport speed, influenced the degree of food web linkages across space and time, often accounting for unexpected patterns in food web connectivity. Transformations of the estuarine landscape that alter river hydrology or availability of detritus sources can thus potentially disrupt natural food web connectivity at the landscape scale, especially for sedentary organisms, which cannot track their food sources through space. © 2017 by the Ecological Society of America.

Teoría de la mente en un grupo de personas vinculadas al conflicto armado y en proceso de resocialización

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Mónica Gómez

2013-12-01

Full Text Available La teoría de la mente es la capacidad de inferir, predecir y atribuir estados mentales a otras personas. Este constructo ha sido estudiado desde numerosas patologías, como el autismo, la esquizofrenia y el síndrome de down. Estudios recientes han mostrado que las alteraciones de la teoría de la mente pueden ser observadas en los diferentes cuadros clínicos derivados de alteraciones del lóbulo frontal, como la personalidad antisocial. Algunos autores plantean que un aspecto esencial de la teoría de la mente es la empatía. Sin embargo, este constructo no ha sido estudiado en población normal colombiana con conductas violentas y delictivas que han estado vinculadas al conflicto armado. Este artículo tiene como propósito describir algunas características de la tom en sujetos que estuvieron vinculados al conflicto armado en antioquia con manifestaciones sintomáticas relacionadas con comportamientos violentos y delictivos.

Revisiting geochemical methods of distinguishing natural concentrations and pollution by risk elements in fluvial sediments

Czech Academy of Sciences Publication Activity Database

Matys Grygar, Tomáš; Popelka, J.

2016-01-01

Roč. 170, NOV (2016), s. 39-57 ISSN 0375-6742 R&D Projects: GA ČR(CZ) GA15-00340S Institutional support: RVO:61388980 Keywords : Enrichment * Fluvial sediments * Heavy metals Subject RIV: DD - Geochemistry Impact factor: 2.464, year: 2016

Large-scale coastal and fluvial models constrain the late Holocene evolution of the Ebro Delta

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J. H. Nienhuis

2017-09-01

Full Text Available The distinctive plan-view shape of the Ebro Delta coast reveals a rich morphologic history. The degree to which the form and depositional history of the Ebro and other deltas represent autogenic (internal dynamics or allogenic (external forcing remains a prominent challenge for paleo-environmental reconstructions. Here we use simple coastal and fluvial morphodynamic models to quantify paleo-environmental changes affecting the Ebro Delta over the late Holocene. Our findings show that these models are able to broadly reproduce the Ebro Delta morphology, with simple fluvial and wave climate histories. Based on numerical model experiments and the preserved and modern shape of the Ebro Delta plain, we estimate that a phase of rapid shoreline progradation began approximately 2100 years BP, requiring approximately a doubling in coarse-grained fluvial sediment supply to the delta. River profile simulations suggest that an instantaneous and sustained increase in coarse-grained sediment supply to the delta requires a combined increase in both flood discharge and sediment supply from the drainage basin. The persistence of rapid delta progradation throughout the last 2100 years suggests an anthropogenic control on sediment supply and flood intensity. Using proxy records of the North Atlantic Oscillation, we do not find evidence that changes in wave climate aided this delta expansion. Our findings highlight how scenario-based investigations of deltaic systems using simple models can assist first-order quantitative paleo-environmental reconstructions, elucidating the effects of past human influence and climate change, and allowing a better understanding of the future of deltaic landforms.

Depositional Architecture of Late Cambrian-Early Ordovician Siliciclastic Barik Formation; Al Huqf Area, Oman

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Abbasi, Iftikhar Ahmed

2017-04-01

Early Paleozoic siliciclastics sediments of the Haima Supergroup are subdivided into a number of formations and members based on lithological characteristics of various rock sequences. One of the distinct sandstone sequence, the Barik Formation (Late Cambrian-Early Ordovician) of the Andam Group is a major deep gas reservoir in central Oman. The sandstone bodies are prospective reservoir rocks while thick shale and clay interbeds act as effective seal. Part of the Barik Formation (lower and middle part) is exposed in isolated outcrops in Al Huqf area as interbedded multistoried sandstone, and green and red shale. The sandstone bodies are up to 2 meters thick and can be traced laterally for 300 m to over 1 km. Most of sandstone bodies show both lateral and vertical stacking. Two types of sandstone lithofacies are identified on the basis of field characteristics; a plane-bedded sandstone lithofacies capping thick red and green color shale beds, and a cross-bedded sandstone lithofacies overlying the plane-bedded sandstone defining coarsening upward sequences. The plane-bedded sandstone at places contains Cruziana ichnofacies and bivalve fragments indicating deposition by shoreface processes. Thick cross-bedded sandstone is interpreted to be deposited by the fluvial dominated deltaic processes. Load-casts, climbing ripples and flaser-bedding in siltstone and red shale indicate influence of tidal processes at times during the deposition of the formation. This paper summarizes results of a study carried out in Al Huqf area outcrops to analyze the characteristics of the sandstone-body geometry, internal architecture, provenance and diagenetic changes in the lower and middle part of the formation. The study shows build-up of a delta complex and its progradation over a broad, low-angle shelf where fluvial processes operate beside shoreface processes in a vegetation free setting. Keywords: Andam Group, Barik Formation, Ordovician sandstone, Al Huqf, Central Oman,

Quantitative reconstruction of cross-sectional dimensions and hydrological parameters of gravelly fluvial channels developed in a forearc basin setting under a temperate climatic condition, central Japan

Science.gov (United States)

Shibata, Kenichiro; Adhiperdana, Billy G.; Ito, Makoto

2018-01-01

Reconstructions of the dimensions and hydrological features of ancient fluvial channels, such as bankfull depth, bankfull width, and water discharges, have used empirical equations developed from compiled data-sets, mainly from modern meandering rivers, in various tectonic and climatic settings. However, the application of the proposed empirical equations to an ancient fluvial succession should be carefully examined with respect to the tectonic and climatic settings of the objective deposits. In this study, we developed empirical relationships among the mean bankfull channel depth, bankfull channel depth, drainage area, bankfull channel width, mean discharge, and bankfull discharge using data from 24 observation sites of modern gravelly rivers in the Kanto region, central Japan. Some of the equations among these parameters are different from those proposed by previous studies. The discrepancies are considered to reflect tectonic and climatic settings of the present river systems, which are characterized by relatively steeper valley slope, active supply of volcaniclastic sediments, and seasonal precipitation in the Kanto region. The empirical relationships derived from the present study can be applied to modern and ancient gravelly fluvial channels with multiple and alternate bars, developed in convergent margin settings under a temperate climatic condition. The developed empirical equations were applied to a transgressive gravelly fluvial succession of the Paleogene Iwaki Formation, Northeast Japan as a case study. Stratigraphic thicknesses of bar deposits were used for estimation of the bankfull channel depth. In addition, some other geomorphological and hydrological parameters were calculated using the empirical equations developed by the present study. The results indicate that the Iwaki Formation fluvial deposits were formed by a fluvial system that was represented by the dimensions and discharges of channels similar to those of the middle to lower reaches of

External controls on Quaternary fluvial incision and terrace formation at the Segre River, Southern Pyrenees

NARCIS (Netherlands)

Stange, K.M.; van Balen, R.T.; Vandenberghe, J.; Peña, J.L.; Sancho, C.

2013-01-01

Focusing on climatic- and structural (tectonic) controls, we aim to determine their relative importance for the (Pliocene to Quaternary) fluvial landscape evolution in the Southern Pyrenees foreland. We investigate the Segre River, which is one of the major streams of the Southern Pyrenees that

Curso virtual de educación continuada para los profesionales de la salud vinculados a los ensayos clínicos

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Migdacelys Arboláez Estrada

2009-04-01

Full Text Available Se realizó un estudio cuasi-experimental para elevar la competencia y desempeño de profesionales de la salud vinculados a ensayos clínicos. El estudio contó de 3 fases: diagnóstico de las necesidades de información sobre la temática e identificación de las dificultades en el desempeño de la actividad; diseño y valoración de un curso virtual de ensayos clínicos; y aplicación y evaluación de la efectividad del curso. En el diagnóstico el 92,0 % de los evaluados presentaron altas necesidades de información y el 52 % fueron evaluados con un desempeño malo. En función de estos resultados se diseñó un curso virtual de ensayos clínicos a través de un sitio Web. La implementación del curso fue aprobada por los expertos con un porcentaje de aceptación general del 95 %. Una vez finalizado, el curso fue evaluado como efectivo pues más del 80 % de los profesionales fueron evaluados sin necesidades de información y un desempeño bueno.

Pemaknaan Filsafati Kearifan Lokal untuk Adaptasi Masyarakat terhadap Ancaman Bencana Marin dan Fluvial di Lingkungan Kepesisiran

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S Sunarto

2011-07-01

Full Text Available The purpose of this research was to study the philosophical meaning of local wisdom that developed in the communities in the coastal environment, particularly in the eastern coast of Central Java. The method used for this philosophical meaning using the approach of geomorphological hermeneutics and disaster semiotics. The results of this research indicate that identified local wisdom in the form of cultural semiotics and faunal semiotics to anticipate the hazards of climate change as marine hazard and fluvial hazard. Cultural semiotics found in the form of advice that still need to be interpreted with a geomorphological hermeneutics approach order to use it to adapt to the coastal environment against marine hazard. The cultural semiotics has a geomorphological philosophical meaning as natural cycle that leads to dynamic equilibrium, not the philosophical meaning that leads to the view of anthropocentrism. In addition, also found cultural semiotics of “Dina Rèntèng” based on the philosophical views of ecocentrism. The cultural semiotics is used in society to adapt to the fluvial hazard. Faunal semiotics found in the form of anomalous crab behavior as a form of adaptation due to its response to environmental condition. The faunal semiotics has been used as a guide for the community to adapt to the fluvial hazard. Because of the local wisdom is loaded with philosophical meaning, it can be metatourism assets, so it can convert harm into benefit.

Geoarchaeology, the four dimensional (4D) fluvial matrix and climatic causality

Science.gov (United States)

Brown, A. G.

2008-10-01

Geoarchaeology is the application of geological and geomorphological techniques to archaeology and the study of the interactions of hominins with the natural environment at a variety of temporal and spatial scales. Geoarchaeology in the UK over the last twenty years has flourished largely because it has gone beyond technological and scientific applications. Over the same period our ability to reconstruct the 3-dimensional stratigraphy of fluvial deposits and the matrix of fluvial sites has increased dramatically because of a number of technological advances. These have included the use of LiDAR (laser imaging) and radar to produce high-resolution digital surface models, the use of geophysics, particularly ground penetrating radar and electrical resistivity, to produce sediment depth models, and the use of GIS and data visualisation techniques to manipulate and display the data. These techniques along with more systematic and detailed sedimentological recording of exposed sections have allowed the construction of more precise 3-dimensional (volumetric) models of the matrix of artefacts within fluvial deposits. Additionally a revolution in dating techniques, particularly direct sediment dating by luminescence methods, has enabled the creation of 4-dimensional models of the creation and preservation of these sites. These 4-dimensional models have the ability to provide far more information about the processes of site creation, preservation and even destruction, and also allow the integration of these processes with independent data sources concerning cultural evolution and climatic change. All improvements in the precision of dating fluvial deposits have archaeological importance in our need to translate events from a sequential or geological timeframe to human timescales. This allows geoarchaeology to make a more direct contribution to cultural history through the recognition of agency at the individual or group level. This data can then form a component of

Allogenic controls on the fluvial architecture and fossil preservation of the Upper Triassic Ischigualasto Formation, NW Argentina

Science.gov (United States)

Colombi, Carina E.; Limarino, Carlos O.; Alcober, Oscar A.

2017-12-01

The Upper Triassic Ischigualasto Formation in NW Argentina was deposited in a fluvial system during the synrift filling of the extensional Ischigualasto-Villa Unión Basin. The expansive exposures of the fluvial architecture and paleosols provide a framework to reconstruct the paleoenvironmental evolution of this basin during the Upper Triassic using continental sequence stratigraphy. The Ischigualasto Formation deposition can be divided into seven sequential sedimentary stages: the 1) Bypass stage; 2) Confined low-accommodation stage; 3) Confined high accommodation stage; 4) Unstable-accommodation stage; 5) Unconfined high-accommodation stage; 6) Unconfined low-accommodation stage; and finally, 7) Unconfined high-accommodation stage. The sedimentary evolution of the Ischigualasto Formation was driven by different allogenic controls such as rises and falls in lake levels, local tectonism, subsidence, volcanism, and climate, which also produced modifications of the equilibrium profile of the fluvial systems. All of these factors result in different accommodations in central and flank areas of the basin, which led to different architectural configurations of channels and floodplains. Allogenic processes affected not only the sequence stratigraphy of the basin but also the vertebrate and plant taphocenosis. Therefore, the sequence stratigraphy can be used not only as a predictive tool related to fossil occurrence but also to understand the taphonomic history of the basin at each temporal interval.

Avulsion and its implications for fluvial-deltaic architecture: insights from the Holocene Rhine-Meuse delta

NARCIS (Netherlands)

Stouthamer, E.; Cohen, K.M.; Gouw, M.J.P.

2010-01-01

Avulsion is a key process in the formation of fluvial-deltaic successions and a primary control on deltaic architecture. It determines the distribution of sediment and water and hence which location in the delta receives clastic sedimentation for what time. This makes the avulsion process an

Avulsion and its implications for fluvial-deltaic architecture: insights from the Holocene Rhine-Meuse delta

NARCIS (Netherlands)

Stouthamer, E.; Cohen, K.M.; Gouw, M.J.P.

2010-01-01

Avulsion is a principal process in the formation of fluvial-deltaic successions and a primary control on deltaic architecture. It determines the distribution of sediment and water and hence influences which location in the delta receives clastic sedimentation in what amounts for what time. It also

Evolution of tertiary intermontane fluvial system of Powder River Basin, Wyoming and Montana

International Nuclear Information System (INIS)

Flores, R.M.; Ethridge, F.G.

1985-01-01

Exploration and development of economic coal and uranium deposits of the Tertiary Fort Union and Wasatch Formations provided data related to the evolution of depositional systems in the Powder River Basin. In ascending order, the Paleocene Fort Union Formation consists of the Tullock, Lebo, and Tongue River Members. The overlying Eocene Wasatch Formation consists of the conglomeratic Kingsbury and Moncrief Members and laterally equivalent finer grained deposits. Evolution of fluvial deposition in the basin was determined from sandstone percent maps. A high proportion of sandstones in the Tullock Member and combined Tongue River Member and Wasatch Formation formed in interconnected east-west and north-south belts. The east-west belts represent alluvial fans, as well as braided and meandering tributary streams. The north-south belts reflect meandering and anastomosing trunk streams fed by basin margin tributaries. The sandstones of the Lebo Shale show east-west trends and represent deposits of fluvio-deltaic systems that filled a western, closed-lacustrine basin. The lake in this basin may have formed during localized subsidence along the Buffalo deep fault. These contrasting styles of fluvial deposition were largely controlled by extrabasinal and intrabasinal tectonics associated with Laramide orogeny

Distribution of uranium and thorium in sediments and plants from a granitic fluvial area

International Nuclear Information System (INIS)

Vargas, M.J.; Tome, F.V.; Sanchez, A.M.; Vazquez, M.T.C.; Murillo, J.L.G.

1997-01-01

A study of the presence of natural uranium and thorium isotopes in sediments and plants belonging to a granitic fluvial region of the Ortigas river (west of Spain) has been carried out. The existence of two uranium mines in the neighbourhood of the sampled sites and the granitic characteristics of the zone produce significant concentrations of natural radionuclides. Temporal and spatial variations of uranium and thorium concentrations and the activity ratios 234 U/ 238 U, 228 Th/ 232 Th and Th/U were studied to better understand the mobilization mechanisms such as leaching and transport at play in the studied system. These determinations were made using alpha-particle spectrometry with silicon detectors. The measurements were also compared with the results previously found for waters of this fluvial area. Uranium in sediments showed variations due to changes in rainfall, but thorium content was nearly constant. Uranium and thorium concentrations in plants were lower after rainfall. Incorporation of uranium into the plants seemed to be mainly from water, whereas incorporation of thorium seemed to be from both sediments and water. (Author)

Modelling sediment dynamics due to hillslope-river interactions : incorporating fluvial behaviour in landscape evolution model LAPSUS

NARCIS (Netherlands)

Baartman, Jantiene E. M.; van Gorp, Wouter; Temme, Arnaud J. A. M.; Schoorl, Jeroen M.

Landscape evolution models (LEMs) simulate the three-dimensional development of landscapes over time. Different LEMs have different foci, e.g. erosional behaviour, river dynamics, the fluvial domain, hillslopes or a combination. LEM LAPSUS is a relatively simple cellular model operating on

Fluvial fluxes from the Magdalena River into Cartagena Bay, Caribbean Colombia: Trends, future scenarios, and connections with upstream human impacts

Science.gov (United States)

Restrepo, Juan D.; Escobar, Rogger; Tosic, Marko

2018-02-01

Fluxes of continental runoff and sediments as well as downstream deposition of eroded soils have severely altered the structure and function of fluvial and deltaic-estuarine ecosystems. The Magdalena River, the main contributor of continental fluxes into the Caribbean Sea, delivers important amounts of water and sediments into Cartagena Bay, a major estuarine system in northern Colombia. Until now, trends in fluvial fluxes into the bay, as well as the relationship between these tendencies in fluvial inputs and associated upstream changes in the Magdalena catchment, have not been studied. Here we explore the interannual trends of water discharge and sediment load flowing from the Magdalena River-Canal del Dique system into Cartagena Bay during the last three decades, forecast future scenarios of fluxes into the bay, and discuss possible connections between observed trends in fluvial inputs and trends in human intervention in the Magdalena River basin. Significant upward trends in annual runoff and sediment load during the mid-1980s, 1990s, and post-2000 are observed in the Magdalena and in the Canal del Dique flowing into Cartagena Bay. During the last decade, Magdalena streamflow and sediment load experienced increases of 24% and 33%, respectively, compared to the pre-2000 year period. Meanwhile, the Canal del Dique witnessed increases in water discharge and sediment load of 28% and 48%, respectively. During 26 y of monitoring, the Canal del Dique has discharged 177 Mt of sediment to the coastal zone, of which 52 Mt was discharged into Cartagena Bay. Currently, the Canal drains 6.5% and transports 5.1% of the Magdalena water discharge and sediment load. By 2020, water discharge and sediment flux from the Canal del Dique flowing to the coastal zone will witness increments of 164% and 260%, respectively. Consequently, sediment fluxes into Cartagena Bay will witness increments as high as 8.2 Mt y- 1 or 317%. Further analyses of upstream sediment load series for 21

10Be and 26Al dating of river terraces and quaternary incision rates in the Ardenne massif (eastern Belgium)

Science.gov (United States)

Rixhon, G.; Braucher, R.; Siame, L.; Bourlès, D.; Demoulin, A.

2009-04-01

Because of the lack of reliable chronological data, the Quaternary evolution of the hydrographic network of the Ardennes (western continuation of the Rhenish shield, western Europe) remains still poorly known. Therefore, we measured the cosmogenic nuclides content (10Be and 26Al) of terrace sediments of Ardennian rivers (Meuse, Ourthe & Amblève) in order to date several terrace levels and to better constrain the Quaternary incision of the network. Though these dating methods are successfully used to determine ages of superficial (e.g., glacial) deposits, dating of fluvial terraces remains difficult. Possible predepositional exposures of the sampled material (inherited 10Be and 26Al) may indeed bias the measurements towards higher nuclide concentrations while several postdepositional processes (burial, erosion) may cause a lowering of the 10Be and 26Al concentrations. In an attempt to overcome these difficulties, the selected fluvial deposits (six locations) were sampled using a profiling technique on as thick as possible sections (more than 3 m). While previous studies assigned an early middle Pleistocene age (around 800 ka) to the main terrace level in the Rhine-Meuse system, our 10Be dates for the same terrace level (according to geometrical correlation) in the Amblève River, a Meuse subtributary, are much younger (upper Pleistocene). To explain this age discrepancy, we suggest that the incision was strongly diachronous from the Meuse valley towards its Ardennian headwaters, as a result of a delayed upstream propagation of the incision wave when it passes tributary junctions.

Estuary-wide genetic stock distribution and salmon habitat use, tidal-fluvial estuary - Columbia River Estuary Tidal Habitats

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The goal of the tidal-fluvial estuary study is to determine the estuary's contribution to the spatial structure and life history diversity of Columbia River salmon...

The phosphorus content of fluvial sediment in rural and industrialized river basins.

Science.gov (United States)

Owens, Philip N; Walling, Desmond E

2002-02-01

The phosphorus content of fluvial sediment (suspended sediment and the sediment) has been examined in contrasting rural (moorland and agricultural) and industrialized catchments in Yorkshire, UK. The River Swale drains a rural catchment with no major urban and industrial areas, and the total phosphorus (TP) content of fluvial sediment is generally within the range 500-1,500 microg g(-1). There is little evidence of any major downstream increase in TP content. In contrast, fluvial sediment from the industrialized catchments of the Rivers Aire and Calder exhibits both higher levels of TP content and marked downstream increases, with values of TP content ranging from 7,000 microg g(-1) at downstream sites. These elevated levels reflect P inputs from point sources, such as sewage treatment works (STWs) and combined sewer overflows. The influence of STWs is further demonstrated by the downstream increase in the inorganic P/organic P ratio from 4 in the lower reaches. Comparison of the P content of suspended sediment with that of the sediment and both discharge and suspended sediment concentration, reflecting changes in sediment and P sources during high flow events. Spatial variations in the P contents of the sediment evidence a similar pattern as those for suspended sediment, with relatively low levels of TP in the River Swale and elevated levels in the middle and downstream reaches of the Rivers Aire and Calder. The PP concentrations associated with floodplain and channel bed sediment are, however, lower than equivalent values for suspended sediment, and this primarily reflects the differences in the particle size composition between the three types of sediments. Rates of floodplain deposition and the amounts of fine-grained sediment stored in the river channels are relatively high, and suggest that such environments may represent important sinks for PP. Based on the sediment samples collected from the study basins, a simple four-fold classification which relates the

The Pliocene initiation and Early Pleistocene volcanic disruption of the palaeo-Gediz fluvial system, Western Turkey

NARCIS (Netherlands)

Maddy, D.; Demir, T.; Bridgland, D.R.; Veldkamp, A.; Stemerdink, C.; Schriek, van der T.; Schreve, D.

2007-01-01

In this paper, we report our latest observations concerning a Pliocene and Early Pleistocene record from Western Turkey. The sedimentary sequence described comprises the fluvial deposits of an Early Pleistocene palaeo-Gediz river system and its tributaries prior to the onset of volcanism around Kula

Buried late Pleistocene fluvial channels on the inner continental shelf off Vengurla, west coast of India

Digital Repository Service at National Institute of Oceanography (India)

SubbaRaju, L.V.; Krishna, K.S.; Chaubey, A.K.

with sediments. Cross sectional dimensions between 15 to 100 m width and 2 to 6 m depth suggest a fluvial origin of the channels. These buried channels appear to mark former positions of rivers flowing from the nearby coast and debouching into the Arabian Sea...

Estuarine abandoned channel sedimentation rates record peak fluvial discharge magnitudes

Science.gov (United States)

Gray, A. B.; Pasternack, G. B.; Watson, E. B.

2018-04-01

Fluvial sediment deposits can provide useful records of integrated watershed expressions including flood event magnitudes. However, floodplain and estuarine sediment deposits evolve through the interaction of watershed/marine sediment supply and transport characteristics with the local depositional environment. Thus extraction of watershed scale signals depends upon accounting for local scale effects on sediment deposition rates and character. This study presents an examination of the balance of fluvial sediment dynamics and local scale hydro-geomorphic controls on alluviation of an abandoned channel in the Salinas River Lagoon, CA. A set of three sediment cores contained discrete flood deposits that corresponded to the largest flood events over the period of accretion from 1969 to 2007. Sedimentation rates scaled with peak flood discharge and event scale sediment flux, but were not influenced by longer scale hydro-meteorological activities such as annual precipitation and water yield. Furthermore, the particle size distributions of flood deposits showed no relationship to event magnitudes. Both the responsiveness of sedimentation and unresponsiveness of particle size distributions to hydro-sedimentological event magnitudes appear to be controlled by aspects of local geomorphology that influence the connectivity of the abandoned channel to the Salinas River mainstem. Well-developed upstream plug bar formation precluded the entrainment of coarser bedload into the abandoned channel, while Salinas River mouth conditions (open/closed) in conjunction with tidal and storm surge conditions may play a role in influencing the delivery of coarser suspended load fractions. Channel adjacent sediment deposition can be valuable records of hydro-meteorological and sedimentological regimes, but local depositional settings may dominate the character of short term (interdecadal) signatures.

Impact of phenomenological theory of turbulence on pragmatic approach to fluvial hydraulics

Science.gov (United States)

Ali, Sk Zeeshan; Dey, Subhasish

2018-04-01

The phenomenological theory of turbulence (PTT) remains a long-standing and fascinating theory in turbulence research. In this review article, we highlight the state-of-the-science of the impact of the PTT on the pragmatic approach to fluvial hydraulics, explored over recent decades, discussing the salient and the subtle roles that the turbulence plays in governing many physical processes. To acquire a theoretical explanation of this pragmatic approach necessitates an intuitive thought that can bring together the background mechanisms of all the physical processes under one law—a thought that is capable of finding their inextricable links with the turbulent energy spectrum. We begin here with emphasizing the spectral and the co-spectral origin of the well-recognized laws of the wall, the resistance equation, and the turbulence intensities by portraying the typical momentum transfer mechanism of eddies in a turbulent flow. Next, we focus on the scaling laws of key fluvial processes derived from the perspective of the PTT, enlightening their physical insight and ability to judge how far the so-called empirical formulas can be used with confidence. The PTT has been able to disclose the origin of several primeval empirical formulas that have been used over many years without having any theoretical clarification and confirmation. Finally, we make an effort to describe some unsolved issues to be resolved as a future scope of research.

Human impact on fluvial regimes and sediment flux during the Holocene: review and future research agenda

NARCIS (Netherlands)

Hoffmann, T.; Thorndycraft, V.R.; Brown, A.G.; Coulthard, T.J.; Damnati, B.; Kale, V.S.; Middelkoop, H.; Notebaert, B.; Walling, D.E.

2010-01-01

There is a long history of human–riverine interactions throughout the period of agriculture that in some regions of the world started several thousand years ago. These interactions have altered rivers to human dominated systems with often negative impacts on fluvial environments. To achieve a good

Depositional record of an avulsive fluvial system controlled by peat compaction (Neogene, Most Basin, Czech Republic)

Czech Academy of Sciences Publication Activity Database

Rajchl, M.; Uličný, David

2005-01-01

Roč. 52, č. 3 (2005), s. 601-625 ISSN 0037-0746 R&D Projects: GA ČR GA205/01/0629 Institutional research plan: CEZ:AV0Z30120515 Keywords : avulsion * Eger Graben * fluvial channels Subject RIV: DB - Geology ; Mineralogy Impact factor: 1.876, year: 2005

A conceptual connectivity framework for understanding geomorphic change in human-impacted fluvial systems

Science.gov (United States)

Pöppl, Ronald; Keesstra, Saskia; Maroulis, Jerry

2017-04-01

Human-induced landscape change is difficult to predict due to the complexity inherent in both geomorphic and social systems as well as due to emerging coupling relationships between them. To better understand system complexity and system response to change, connectivity has become an important research paradigm within various disciplines including geomorphology, hydrology and ecology. With the proposed conceptual connectivity framework on geomorphic change in human-impacted fluvial systems a cautionary note is flagged regarding the need (i) to include and to systematically conceptualise the role of different types of human agency in altering connectivity relationships in geomorphic systems and (ii) to integrate notions of human-environment interactions to connectivity concepts in geomorphology to better explain causes and trajectories of landscape change. Underpinned by case study examples, the presented conceptual framework is able to explain how geomorphic response of fluvial systems to human disturbance is determined by system-specific boundary conditions (incl. system history, related legacy effects and lag times), vegetation dynamics and human-induced functional relationships (i.e. feedback mechanisms) between the different spatial dimensions of connectivity. It is further demonstrated how changes in social systems can trigger a process-response feedback loop between social and geomorphic systems that further governs the trajectory of landscape change in coupled human-geomorphic systems.

MODELLING LANDSCAPE MORPHODYNAMICS BY TERRESTRIAL PHOTOGRAMMETRY: AN APPLICATION TO BEACH AND FLUVIAL SYSTEMS

Directory of Open Access Journals (Sweden)

E. Sánchez-García

2016-06-01

Full Text Available Beach and fluvial systems are highly dynamic environments, being constantly modified by the action of different natural and anthropic phenomena. To understand their behaviour and to support a sustainable management of these fragile environments, it is very important to have access to cost-effective tools. These methods should be supported on cutting-edge technologies that allow monitoring the dynamics of the natural systems with high periodicity and repeatability at different temporal and spatial scales instead the tedious and expensive field-work that has been carried out up to date. The work herein presented analyses the potential of terrestrial photogrammetry to describe beach morphology. Data processing and generation of high resolution 3D point clouds and derived DEMs is supported by the commercial Agisoft PhotoScan. Model validation is done by comparison of the differences in the elevation among the photogrammetric point cloud and the GPS data along different beach profiles. Results obtained denote the potential that the photogrammetry 3D modelling has to monitor morphological changes and natural events getting differences between 6 and 25 cm. Furthermore, the usefulness of these techniques to control the layout of a fluvial system is tested by the performance of some modeling essays in a hydraulic pilot channel.

Some relationships between finances, payment systems, and provision

OpenAIRE

García U., Juan Carlos; Agudelo C., Carlos A.

2010-01-01

Los hospitales públicos ubicados en el Sur Occidente de Bogotá recibieron sus recursos en el período 1996-2000, principalmente por la atención a la población sin capacidad de pago, afiliada al régimen subsidiado o del régimen de vinculados. El Fondo Financiero Distrital de Salud fue el pagador de estos servicios. Para los vinculados utilizó tres formas de pago: presupuesto histórico, pago por actividad acompañado de transferencias y pago prospectivo por actividad final, acompañado de convenio...

Elementos inherentes a la dignidad y libre desarrollo de la personalidad desde el enfoque jurídico español de los usos inadecuados en menores de las nuevas tecnologías de la información aplicadas al ámbito turístico

OpenAIRE

Sacristán Romero, Francisco

2014-01-01

La irrupción masiva de las nuevas tecnologías de la información y comunicación han proyectado consecuencias jurídicas de primer orden en el ámbito turístico, especialmente en el turismo sexual, y en un segundo término en el denominado turismo de ferias y congresos que, en numerosas ocasiones, aparece vinculado al primero en concentraciones y eventos multitudinarios que se celebran en las grandes ciudades del planeta. La aparición del escenario virtual que conforma el ciberespacio ha afectado ...

On the connectivity anisotropy in fluvial Hot Sedimentary Aquifers and its influence on geothermal doublet performance

DEFF Research Database (Denmark)

Willems, Cees J.L.; Nick, Hamid; Donselaar, Marinus E.

2017-01-01

This study finds that the geothermal doublet layout with respect to the paleo flow direction in fluvial sedimentary reservoirs could significantly affect pump energy losses. These losses can be reduced by up to 10% if a doublet well pair is oriented parallel to the paleo flow trend compared...

Fluvial response to Holocene volcanic damming and breaching in the Gediz and Geren rivers, western Turkey

NARCIS (Netherlands)

van Gorp, W.; Veldkamp, A.; Temme, A.J.A.M.; Maddy, D; Demir, T.; Schriek van der, T.; Reimann, T.; Wallinga, J.; Wijbrans, J.R.; Schoorl, J.M.

2013-01-01

This study discusses the complex late Holocene evolution of the Gediz River north of Kula, western Turkey, when a basaltic lava flow dammed and filled this river valley. Age control was obtained using established and novel feldspar luminescence techniques on fluvial sands below and on top of the

Fluvial response to abrupt global warming at the Palaeocene/Eocene boundary.

Science.gov (United States)

Foreman, Brady Z; Heller, Paul L; Clementz, Mark T

2012-11-01

Climate strongly affects the production of sediment from mountain catchments as well as its transport and deposition within adjacent sedimentary basins. However, identifying climatic influences on basin stratigraphy is complicated by nonlinearities, feedback loops, lag times, buffering and convergence among processes within the sediment routeing system. The Palaeocene/Eocene thermal maximum (PETM) arguably represents the most abrupt and dramatic instance of global warming in the Cenozoic era and has been proposed to be a geologic analogue for anthropogenic climate change. Here we evaluate the fluvial response in western Colorado to the PETM. Concomitant with the carbon isotope excursion marking the PETM we document a basin-wide shift to thick, multistoried, sheets of sandstone characterized by variable channel dimensions, dominance of upper flow regime sedimentary structures, and prevalent crevasse splay deposits. This progradation of coarse-grained lithofacies matches model predictions for rapid increases in sediment flux and discharge, instigated by regional vegetation overturn and enhanced monsoon precipitation. Yet the change in fluvial deposition persisted long after the approximately 200,000-year-long PETM with its increased carbon dioxide levels in the atmosphere, emphasizing the strong role the protracted transmission of catchment responses to distant depositional systems has in constructing large-scale basin stratigraphy. Our results, combined with evidence for increased dissolved loads and terrestrial clay export to world oceans, indicate that the transient hyper-greenhouse climate of the PETM may represent a major geomorphic 'system-clearing event', involving a global mobilization of dissolved and solid sediment loads on Earth's surface.

Hidrogeoquímica de Metais em Água Fluvial: Fontes Geológicas Graníticas e Gnáissicas - Bacia do Rio Paquequer, Teresópolis, Estado do Rio de Janeiro

Directory of Open Access Journals (Sweden)

Carla Semiramis Silveira

2014-07-01

Full Text Available A bacia de drenagem do rio Paquequer (269 km² faz parte da região hidrográfica do rio Paraíba do Sul e situa-se no município de Teresópolis no estado do Rio de Janeiro. A sua litologia é representativa dos granitos e gnaisses da Região Sudeste do Brasil. Objetiva-se avaliar o processo de intemperismo destas rochas e a mobilidade dos elementos químicos através da hidrogeoquímica fluvial. Foram amostrados 15 pontos fluviais (com medição de vazão e parâmetros físico-químicos sendo 9 no canal principal e 6 nos principais afluentes. As amostras foram analisadas por ICP-MS para Si, Fe, Mn, Al, Cu, Ni, Cr, Zn, Ba, Rb, Sr, Pb, Cd e Co e por cromatografia de íons para Na+ , K+ , Mg2+ e Ca2+. Dados da literatura referentes à composição elementar destas rochas foram utilizados. A hidrogeoquímica fluvial é dominada por Na, Ca e Si. Os metais Pb, Cd, Co e Cr apresentaram valores muito baixos refletindo a baixa abundância nas rochas e a inexistência de fontes antrópicas industriais. As concentrações encontradas para os elementos Ni, Zn e Cu foram baixas e relacionadas ao núcleo urbano. A análise estatística multivariada mostrou 4 grupos principais, sendo utilizado o grupo 2 (pontos do médio e baixo curso do canal principal para a estimativa de intemperismo. A composição geoquímica da Unidade Rio Negro (migmatito influenciou a hidrogeoquímica através da razão Mg/Fe, maior no afluente que drena esta litologia. A carga fluvial indicou a fonte principal litológica para Si, Mg, Na, K, Ca, Sr, Ba e Rb. A estimativa de taxa de intemperismo indicou 3 grupos de elementos: i os muito móveis (Ca e Sr; ii os pouco móveis (Mg, K, Mn, Rb, Ba e Si e iii os imóveis (Fe e Al. Desta forma sugere-se que o plagioclásio (com Ca e Sr na sua estrutura é o primeiro mineral a ser dissolvido e lixiviado na água percolante no perfil de intemperismo, seguido pelo K-feldspato e biotita. Parte do Si é retida para a cristalização de minerais

100 kyr fluvial cut-and-fill terrace cycles since the Middle Pleistocene in the southern Central Andes, NW Argentina

Science.gov (United States)

Tofelde, Stefanie; Schildgen, Taylor F.; Savi, Sara; Pingel, Heiko; Wickert, Andrew D.; Bookhagen, Bodo; Wittmann, Hella; Alonso, Ricardo N.; Cottle, John; Strecker, Manfred R.

2017-09-01

Fluvial fill terraces in intermontane basins are valuable geomorphic archives that can record tectonically and/or climatically driven changes of the Earth-surface process system. However, often the preservation of fill terrace sequences is incomplete and/or they may form far away from their source areas, complicating the identification of causal links between forcing mechanisms and landscape response, especially over multi-millennial timescales. The intermontane Toro Basin in the southern Central Andes exhibits at least five generations of fluvial terraces that have been sculpted into several-hundred-meter-thick Quaternary valley-fill conglomerates. New surface-exposure dating using nine cosmogenic 10Be depth profiles reveals the successive abandonment of these terraces with a 100 kyr cyclicity between 75 ± 7 and 487 ± 34 ka. Depositional ages of the conglomerates, determined by four 26Al/10Be burial samples and U-Pb zircon ages of three intercalated volcanic ash beds, range from 18 ± 141 to 936 ± 170 ka, indicating that there were multiple cut-and-fill episodes. Although the initial onset of aggradation at ∼1 Ma and the overall net incision since ca. 500 ka can be linked to tectonic processes at the narrow basin outlet, the superimposed 100 kyr cycles of aggradation and incision are best explained by eccentricity-driven climate change. Within these cycles, the onset of river incision can be correlated with global cold periods and enhanced humid phases recorded in paleoclimate archives on the adjacent Bolivian Altiplano, whereas deposition occurred mainly during more arid phases on the Altiplano and global interglacial periods. We suggest that enhanced runoff during global cold phases - due to increased regional precipitation rates, reduced evapotranspiration, or both - resulted in an increased sediment-transport capacity in the Toro Basin, which outweighed any possible increases in upstream sediment supply and thus triggered incision. Compared with two

depositional environment of the gombe formation in the gongola sub

African Journals Online (AJOL)

(Received 16 June 2016; Revision Accepted 25 July 2016) ... The morphometric analysis indicates both fluvial and beach environment with dominance of fluvial ... Formation, the Campano-Maastrichtian Deltaic Gombe ... dominated delta by Carter el al. ... Figure 2: Stratigraphy succession of Benue Trough (Tukur et al. 2015).

Tidal Simulations of an Incised-Valley Fluvial System with a Physics-Based Geologic Model

Science.gov (United States)

Ghayour, K.; Sun, T.

2012-12-01

Physics-based geologic modeling approaches use fluid flow in conjunction with sediment transport and deposition models to devise evolutionary geologic models that focus on underlying physical processes and attempt to resolve them at pertinent spatial and temporal scales. Physics-based models are particularly useful when the evolution of a depositional system is driven by the interplay of autogenic processes and their response to allogenic controls. This interplay can potentially create complex reservoir architectures with high permeability sedimentary bodies bounded by a hierarchy of shales that can effectively impede flow in the subsurface. The complex stratigraphy of tide-influenced fluvial systems is an example of such co-existing and interacting environments of deposition. The focus of this talk is a novel formulation of boundary conditions for hydrodynamics-driven models of sedimentary systems. In tidal simulations, a time-accurate boundary treatment is essential for proper imposition of tidal forcing and fluvial inlet conditions where the flow may be reversed at times within a tidal cycle. As such, the boundary treatment at the inlet has to accommodate for a smooth transition from inflow to outflow and vice-versa without creating numerical artifacts. Our numerical experimentations showed that boundary condition treatments based on a local (frozen) one-dimensional approach along the boundary normal which does not account for the variation of flow quantities in the tangential direction often lead to unsatisfactory results corrupted by numerical artifacts. In this talk, we propose a new boundary treatment that retains all spatial and temporal terms in the model and as such is capable to account for nonlinearities and sharp variations of model variables near boundaries. The proposed approach borrows heavily from the idea set forth by J. Sesterhenn1 for compressible Navier-Stokes equations. The methodology is successfully applied to a tide-influenced incised

Revitalización y promoción de la Ruta del Duero: las iniciativas de excelencia y las propuestas innovadoras

Directory of Open Access Journals (Sweden)

Luis Alfonso Hortelano Mínguez

2007-01-01

Full Text Available El río Duero constituye el eje natural que articula el territorio de la Comunidad Autónoma de Castilla y León porque surca de este a oeste toda la región, desde sus fuentes hasta la «raya» hispano-portuguesa, y ha condicionado históricamente las relaciones meridianas. Además, las tierras castellanoleonesas se identifican con la cuenca fluvial del Duero, excepto unas pequeñas zonas de los bordes que desagüan a los ríos del Norte, Ebro y Tajo. Las orientaciones emanadas de las instituciones europeas, en el umbral del siglo XXI, proponen una gestión compartida de los recursos naturales y culturales de la «eurorregión» del Duero/Douro. En este nuevo marco de cooperación transfronteriza juegan un papel esencial los proyectos vinculados a un turismo sostenible y de calidad. La propuesta de un aprovechamiento turístico integral del tramo castellanoleonés se materializó en la creación de la Ruta del Duero, con una base territorial ligada a las comarcas agrarias próximas al río, a la que se han sumado los esfuerzos económicos de diversas iniciativas.

Cross-stratified Wood: Enigmatic Woody Debris Deposits in Warm-Polar Fluvial Sediments (Pliocene Beaufort Formation, Nunavut)

Science.gov (United States)

Davies, N. S.; Gosse, J. C.; Rybczynski, N.

2012-04-01

Woody debris has been an important sediment component and a significant geomorphic agent in pristine fluvial systems since the Devonian. In recent years a large volume of research has focussed on various aspects of the importance of woody debris within the fluvial realm; from the evolutionary significance of fossil wood accumulations in the rock record to studies of the biogeomorphological and ecological importance of woody debris in modern rivers. In this presentation we describe cross-stratified woody debris deposits comprising organic detritus from a boreal-type treeline forest that included species of pine, birch, poplar, alder, spruce, eastern cedar, and larch, in both shrub and tree form. The cross-stratified wood is an enigmatic subset of fine woody debris which, to our knowledge, has never before been described from either the global stratigraphic record or modern fluvial environments. The deposits we describe are located within the Pliocene Beaufort Formation on Meighen Island, Nunavut, Canada, at a latitude of 80°N, and are compared with other cross-stratified woody debris deposits that have been noted elsewhere in the Pliocene of the Canadian Arctic. We make the robust observation that these deposits appear to be geographically and stratigraphically restricted to polar latitudes from a period of warm climatic conditions during the Pliocene (15-20 °C warmer mean annual temperature than the present day). In this regard it is possible to speculate that the transport of large amounts of woody debris as bedload is potentially a unique feature of forested high latitude rivers. Such bedload deposition requires a large amount of woody debris with a greater density than the fluid transporting it. The softwood composition of the debris suggests that this was most likely attained by saturation and subsequent entrainment of extensive accumulations of deadwood, promoted by unusually high rates of tree mortality and low rates of bacterial decomposition arising from

Formation of topographically inverted fluvial deposits on Earth and Mars

Science.gov (United States)

Hayden, A.; Lamb, M. P.; Fischer, W. W.; Ewing, R. C.; McElroy, B. J.

2016-12-01

Sinuous ridges interpreted as exhumed river deposits (so-called "inverted channels") are common features on Mars that show promise for quantifying ancient martian surface hydrology. Morphological similarity of these inverted channels to river channels led to a "landscape inversion hypothesis" in which the geometries of ridges and ridge networks accurately reflect the geometries of the paleo-river channels and networks. An alternative "deposit inversion hypothesis" proposes that ridges represent eroded fluvial channel-belt deposits with channel-body geometries that may differ significantly from those of the rivers that built the deposit. To investigate these hypotheses we studied the sedimentology and morphology of inverted channels in Jurassic and Cretaceous outcrops in Utah and the Aeolis Dorsa region of Mars. Ridges in Utah extend for hundreds of meters, are tens of meters wide, and stand up to 30 meters above the surrounding plain. A thick ribbon-geometry sandstone or conglomerate body caps overbank mudstone, paleosols, and thin crevasse-splay sandstone beds. Caprock beds consist of stacked dune- to bar-scale trough cross sets, mud intraclasts, and in cases scroll bars indicating meandering. In plan view, ridge networks bifurcate; however, crosscutting relationships show that distinct sandstone channel bodies at distinct stratigraphic levels intersect at these junctions. Ridge-forming sandstone bodies have been narrowed from their original dimensions by cliff retreat and bisected by modern fluvial erosion and mass wasting. We therefore interpret the sinuous ridges in Utah as eroded remnants of channel-belt sandstone bodies formed by laterally migrating and avulsing rivers rather than channel fills - consistent with deposit inversion. If the sinuous ridges in Aeolis Dorsa also formed by deposit inversion, river widths previously interpreted under the landscape inversion hypothesis are overestimated by up to a factor of 10 and discharges by up to a factor of 100.

Fluvial sediment transport in a glacier-fed high-mountain river (Riffler Bach, Austrian Alps)

Science.gov (United States)

Morche, David; Weber, Martin; Faust, Matthias; Schuchardt, Anne; Baewert, Henning

2017-04-01

High-alpine environments are strongly affected by glacier retreat since the Little Ice Age (LIA). Due to ongoing climate change the hydrology of proglacial rivers is also influenced. It is expected that the growing proportions of snow melt and rainfall events will change runoff characteristics of proglacial rivers. Additionally, the importance of paraglacial sediment sources in recently deglaciating glacier forefields is increasing, while the role of glacial erosion is declining. Thus complex environmental conditions leading to a complex pattern of fluvial sediment transport in partly glaciated catchments of the European Alps. Under the umbrella of the joint PROSA-project the fluvial sediment transport of the river Riffler Bach (Kaunertal, Tyrol, Austria) was studied in 3 consecutive ablation seasons in order to quantify sediment yields. In June 2012 a probe for water level and an automatic water sampler (AWS) were installed at the outlet of the catchment (20km2). In order to calculate annual stage-discharge-relations by the rating-curve approach, discharge (Q) was repeatedly measured with current meters and by salt dilution. Concurrent to the discharge measurements bed load was collected using a portable Helley-Smith sampler. Bed load samples were weighted and sieved in the laboratory to gain annual bed load rating curves and grain size distributions. In total 564 (2012: 154, 2013: 209, 2014: 201) water samples were collected and subsequently filtered to quantify suspended sediment concentrations (SSC). Q-SSC-relations were calculated for single flood events due to the high variability of suspended sediment transport. The results show a high inter- and intra-annual variability of solid fluvial sediment transport, which can be explained by the characteristics of suspended sediment transport. Only 13 of 22 event-based Q-SSC-relations show causal dependency. In 2012, during a period with multiple pluvial-induced peak discharges most sediment was transported. On the

Metodología para el empoderamiento en salud sexual de actores sociales vinculados a niños/as preescolares Methodology for empowerment in sexual health of social participants linked to preschool boys/girls

Directory of Open Access Journals (Sweden)

Guillermo Díaz Llanes

2010-12-01

Full Text Available INTRODUCCIÓN: la promoción de comportamientos sexuales salutógenos es uno de los principales retos de la salud pública contemporánea, por la gran complejidad que estos exhiben y su potencial beneficio al cuadro de salud de todos los países. Uno de los referentes teóricos que sustentan las intervenciones en esta dimensión de la salud, es el empoderamiento, sin embargo, todavía se carece de metodologías capaces de guiar las intervenciones al nivel comunitario. OBJETIVO: el presente estudio se propuso la construcción y validación de una metodología dirigida a empoderar en salud sexual a actores sociales de la comunidad, vinculados a la educación de niños preescolares. MÉTODOS: el estudio se vertebró en un diseño de investigación-acción participativa. RESULTADOS: se consiguió una metodología ajustada al empoderamiento con 3 etapas y subetapas diferenciadas, y a su vez, conectadas entre sí, con suficiente flexibilidad para ser adaptada a diversos entornos. Cada etapa contiene salidas esperadas a partir de procedimientos y técnicas lógicamente ordenadas, que parten de la acción, reflexionan críticamente sobre ella y la transforman.INTRODUCTION: the promotion of health sexual behaviors is one of the major challenges of current public health due to its great complexity and its potential benefit to health situation at world level. One of the concerning theoretical features supporting the interventions in this health dimension is the empowerment, however, still there is a lack of methodologies able to guide the interventions at community level. OBJECTIVE: the objective of present paper was to create and to validate the methodology directed to empower in sexual health to social participants of community, linked with the education of preschool children. METHODS: the study included a participation-research design. RESULTS: it was possible to obtain a methodology fitted to empowerment including three differentiated stages and

Characterization of organic matter in dusts and fluvial sediments from exposed areas of dowtown Prague, Czech Republic

Czech Academy of Sciences Publication Activity Database

Sýkorová, Ivana; Havelcová, Martina; Trejtnarová, Hana; Matysová, Petra; Vašíček, Michal; Suchý, V.; Kříbek, B.

2009-01-01

Roč. 80, č. 2 (2009), s. 69-86 ISSN 0166-5162 R&D Projects: GA AV ČR IAA300460804 Institutional research plan: CEZ:AV0Z30460519 Keywords : dust * fluvial sediment * carbonaceous particles Subject RIV: DD - Geochemistry Impact factor: 1.924, year: 2009

Middel Pleistocene to Holocene fluvial terrace development and uplift-driven valley incision in the SE Carpathians, Romania

NARCIS (Netherlands)

Necea, D.; Fielitz, W.; Andriessen, P.A.M.; Dinu, C.

2013-01-01

This study reveals that in the SE Carpathians terrace development and fluvial incision during the Middle Pleistocene-Holocene are predominantly controlled by tectonic uplift as shown by terrace distributions and uplift amounts and rates. The work focuses on a transect from the internal nappes and

Assessment of spatiotemporal variations in the fluvial wash-load component in the 21st century with regard to GCM climate change scenarios

International Nuclear Information System (INIS)

Mouri, Goro

2015-01-01

For stream water, in which a relationship exists between wash-load concentration and discharge, an estimate of fine-sediment delivery may be obtained from a traditional fluvial wash-load rating curve. Here, we demonstrate that the remaining wash-load material load can be estimated from a traditional empirical principle on a nationwide scale. The traditional technique was applied to stream water for the whole of Japan. Four typical GCMs were selected from the Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble to provide the driving fields for the following regional climate models to assess the wash-load component based on rating curves: the Model for Interdisciplinary Research on Climate (MIROC), the Meteorological Research Institute Atmospheric General Circulation Model (MRI-GCM), the Hadley Centre Global Environment Model (HadGEM) and the Geophysical Fluid Dynamics Laboratory (GFDL) climate model. The simulations consisted of an ensemble, including multiple physics configurations and different Representative Concentration Pathways (RCP2.6, RCP4.5 and RCP8.5), which was used to produce monthly datasets for the whole country of Japan. The impacts of future climate changes on fluvial wash load in Japanese stream water were based on the balance of changes in hydrological factors. The annual and seasonal variations of the fluvial wash load were assessed from the result of the ensemble analysis in consideration of the Greenhouse Gas (GHG) emission scenarios. The determined results for the amount of wash load increase range from approximately 20 to 110% in the 2040s, especially along part of the Pacific Ocean and the Sea of Japan regions. In the 2090s, the amount of wash load is projected to increase by more than 50% over the whole of Japan. The assessment indicates that seasonal variation is particularly important because the rainy and typhoon seasons, which include extreme events, are the dominant seasons. Because fluvial wash-load-component turbidity

Assessment of spatiotemporal variations in the fluvial wash-load component in the 21st century with regard to GCM climate change scenarios

Energy Technology Data Exchange (ETDEWEB)

Mouri, Goro, E-mail: mouri@rainbow.iis.u-tokyo.ac.jp

2015-11-15

For stream water, in which a relationship exists between wash-load concentration and discharge, an estimate of fine-sediment delivery may be obtained from a traditional fluvial wash-load rating curve. Here, we demonstrate that the remaining wash-load material load can be estimated from a traditional empirical principle on a nationwide scale. The traditional technique was applied to stream water for the whole of Japan. Four typical GCMs were selected from the Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble to provide the driving fields for the following regional climate models to assess the wash-load component based on rating curves: the Model for Interdisciplinary Research on Climate (MIROC), the Meteorological Research Institute Atmospheric General Circulation Model (MRI-GCM), the Hadley Centre Global Environment Model (HadGEM) and the Geophysical Fluid Dynamics Laboratory (GFDL) climate model. The simulations consisted of an ensemble, including multiple physics configurations and different Representative Concentration Pathways (RCP2.6, RCP4.5 and RCP8.5), which was used to produce monthly datasets for the whole country of Japan. The impacts of future climate changes on fluvial wash load in Japanese stream water were based on the balance of changes in hydrological factors. The annual and seasonal variations of the fluvial wash load were assessed from the result of the ensemble analysis in consideration of the Greenhouse Gas (GHG) emission scenarios. The determined results for the amount of wash load increase range from approximately 20 to 110% in the 2040s, especially along part of the Pacific Ocean and the Sea of Japan regions. In the 2090s, the amount of wash load is projected to increase by more than 50% over the whole of Japan. The assessment indicates that seasonal variation is particularly important because the rainy and typhoon seasons, which include extreme events, are the dominant seasons. Because fluvial wash-load-component turbidity

Geocronología de los yacimientos achelenses de Pinedo y Cien Fanegas (Valle del Tajo) e implicaciones en la evolución fluvial en el entorno de Toledo (España)

DEFF Research Database (Denmark)

López-Recio, M.; Silva, P. G.; Roquero, E.

2015-01-01

This study presents the first geochronological data from several research projects focused on the chronostratigraphy of the Tagus fluvial terraces in the environs of Toledo city (Central Spain). The research is centered on Middle to Late Pleistocene fluvial terraces with palaeontological and Ache...

Global map and spectroscopic analyses of Martian fluvial systems: paleoclimatic implications

Science.gov (United States)

Alemanno, Giulia; Orofino, Vincenzo; Mancarella, Francesca; Fonti, Sergio

2017-04-01

Currently environmental conditions on Mars do not allow the presence of liquid water on its surface for long periods of time. However, there are various evidences for past water flow at its surface. In fact, the ancient terrains of Mars are covered with fluvial and lacustrine features such as valley networks, longitudinal valleys and basin lakes. There are no doubts about the fact that the Martian valleys were originated by water flow. This led many researchers to think that probably, at the time of their formation, the conditions of atmospheric pressure and surface temperature were different from the present[1]. To infer the climate history of Mars from valley networks, a global approach is necessary. We produced a global map of Martian valleys. We manually mapped all the valleys (longer than 20 km) as vector-based polylines within the QGIS software, using THEMIS daytime IR (100 m/pixel), and where possible CTX images (up to 6 m/pixel), plus topographic MOLA data ( 500 m/pixel). Respect to the previous manual maps[1,2] data of higher image quality (new THEMIS mosaic) and topographic information allow us to identify new structures and more tributaries for a large number of systems. We also used the geologic map of Mars[3] in order to determine the valleys age distribution. Most valleys are too small for age determination from superposition of impact craters so we have assumed that a valley is as old as the terrain on which it has been carved[1]. Furthermore we are, currently, analyzing spectroscopic data from CRISM instrument (Compact Reconnaissance Imaging Spectrometer for Mars) onboard Mars Reconnaissance Orbiter, concerning the mapped valleys or associated basin lakes with the aim of assessing the mineralogy of these structures. Our attention is especially focused on the possible detection of any hydrated minerals (e.g. phyllosilicates, hydrated silica) or evaporites (e.g. carbonates, sulfates, chlorides). Phyllosilicates- bearing rocks are considered as an

Compound simulation of fluvial floods and storm surges in a global coupled river-coast flood model: Model development and its application to 2007 Cyclone Sidr in Bangladesh

Science.gov (United States)

Ikeuchi, Hiroaki; Hirabayashi, Yukiko; Yamazaki, Dai; Muis, Sanne; Ward, Philip J.; Winsemius, Hessel C.; Verlaan, Martin; Kanae, Shinjiro

2017-08-01

Water-related disasters, such as fluvial floods and cyclonic storm surges, are a major concern in the world's mega-delta regions. Furthermore, the simultaneous occurrence of extreme discharges from rivers and storm surges could exacerbate flood risk, compared to when they occur separately. Hence, it is of great importance to assess the compound risks of fluvial and coastal floods at a large scale, including mega-deltas. However, most studies on compound fluvial and coastal flooding have been limited to relatively small scales, and global-scale or large-scale studies have not yet addressed both of them. The objectives of this study are twofold: to develop a global coupled river-coast flood model; and to conduct a simulation of compound fluvial flooding and storm surges in Asian mega-delta regions. A state-of-the-art global river routing model was modified to represent the influence of dynamic sea surface levels on river discharges and water levels. We conducted the experiments by coupling a river model with a global tide and surge reanalysis data set. Results show that water levels in deltas and estuaries are greatly affected by the interaction between river discharge, ocean tides and storm surges. The effects of storm surges on fluvial flooding are further examined from a regional perspective, focusing on the case of Cyclone Sidr in the Ganges-Brahmaputra-Meghna Delta in 2007. Modeled results demonstrate that a >3 m storm surge propagated more than 200 km inland along rivers. We show that the performance of global river routing models can be improved by including sea level dynamics.

Reconstructing Early Pleistocene (1.3 Ma) terrestrial environmental change in western Anatolia: Did it drive fluvial terrace formation?

NARCIS (Netherlands)

Veldkamp, A.; Candy, I.; Jongmans, A.G.; Maddy, D.; Demir, T.; Schoorl, J.M.; Schreve, D.; Stemerdink, C.; Schriek, van der T.

2015-01-01

A terrestrial environmental reconstruction of an Early Pleistocene landscape from western Anatolia is presented. The basis of this reconstruction is a sedimentary stack comprising fluvial and colluvial slope deposits. Contained within this stack is a sequence comprising two massive laminar calcretes

Sediment Transport Dynamic in a Meandering Fluvial System: Case Study of Chini River

Science.gov (United States)

Nazir, M. H. M.; Awang, S.; Shaaban, A. J.; Yahaya, N. K. E. M.; Jusoh, A. M.; Arumugam, M. A. R. M. A.; Ghani, A. A.

2016-07-01

Sedimentation in river reduces the flood carrying capacity which lead to the increasing of inundation area in the river basin. Basic sediment transport can predict the fluvial processes in natural rivers and stream through modeling approaches. However, the sediment transport dynamic in a small meandering and low-lying fluvial system is considered scarce in Malaysia. The aim of this study was to analyze the current riverbed erosion and sedimentation scenarios along the Chini River, Pekan, Pahang. The present study revealed that silt and clay has potentially been eroded several parts of the river. Sinuosity index (1.98) indicates that Chini River is very unstable and continuous erosion process in waterways has increase the riverbank instability due to the meandering factors. The riverbed erosional and depositional process in the Chini River is a sluggish process since the lake reduces the flow velocity and causes the deposited particles into the silt and clay soil at the bed of the lake. Besides, the bed layer of the lake comprised of cohesive silt and clayey composition that tend to attach the larger grain size of sediment. The present study estimated the total sediment accumulated along the Chini River is 1.72 ton. The HEC-RAS was employed in the simulations and in general the model performed well, once all parameters were set within their effective ranges.

The evolution of a colluvial hollow to a fluvial channel with periodic steps following two transformational disturbances: A wildfire and a historic flood

Science.gov (United States)

Rengers, Francis K.; McGuire, Luke; Ebel, Brian A.; Tucker, G. E.

2018-01-01

The transition of a colluvial hollow to a fluvial channel with discrete steps was observed after two landscape-scale disturbances. The first disturbance, a high-severity wildfire, changed the catchment hydrology to favor overland flow, which incised a colluvial hollow, creating a channel in the same location. This incised channel became armored with cobbles and boulders following repeated post-wildfire overland flow events. Three years after the fire, a record rainstorm produced regional flooding and generated sufficient fluvial erosion and sorting to produce a fluvial channel with periodically spaced steps. An analysis of the step spacing shows that after the flood, newly formed steps retained a similar spacing to the topographic roughness spacing in the original colluvial hollow (prior to channelization). This suggests that despite a distinct change in channel form roughness and bedform morphology, the endogenous roughness periodicity was conserved. Variations in sediment erodibility helped to create the emergent steps as the largest particles ( >D84) remained immobile, becoming step features, and downstream soil was easily winnowed away.

The evolution of a colluvial hollow to a fluvial channel with periodic steps following two transformational disturbances: A wildfire and a historic flood

Science.gov (United States)

Rengers, F. K.; McGuire, L. A.; Ebel, B. A.; Tucker, G. E.

2018-05-01

The transition of a colluvial hollow to a fluvial channel with discrete steps was observed after two landscape-scale disturbances. The first disturbance, a high-severity wildfire, changed the catchment hydrology to favor overland flow, which incised a colluvial hollow, creating a channel in the same location. This incised channel became armored with cobbles and boulders following repeated post-wildfire overland flow events. Three years after the fire, a record rainstorm produced regional flooding and generated sufficient fluvial erosion and sorting to produce a fluvial channel with periodically spaced steps. An analysis of the step spacing shows that after the flood, newly formed steps retained a similar spacing to the topographic roughness spacing in the original colluvial hollow (prior to channelization). This suggests that despite a distinct change in channel form roughness and bedform morphology, the endogenous roughness periodicity was conserved. Variations in sediment erodibility helped to create the emergent steps as the largest particles (>D84) remained immobile, becoming step features, and downstream soil was easily winnowed away.

Evidence of population resistance to extreme low flows in a fluvial-dependent fish species

Science.gov (United States)

Katz, Rachel A.; Freeman, Mary C.

2015-01-01

Extreme low streamflows are natural disturbances to aquatic populations. Species in naturally intermittent streams display adaptations that enhance persistence during extreme events; however, the fate of populations in perennial streams during unprecedented low-flow periods is not well-understood. Biota requiring swift-flowing habitats may be especially vulnerable to flow reductions. We estimated the abundance and local survival of a native fluvial-dependent fish species (Etheostoma inscriptum) across 5 years encompassing historic low flows in a sixth-order southeastern USA perennial river. Based on capturemark-recapture data, the study shoal may have acted as a refuge during severe drought, with increased young-of-the-year (YOY) recruitment and occasionally high adult immigration. Contrary to expectations, summer and autumn survival rates (30 days) were not strongly depressed during low-flow periods, despite 25%-80% reductions in monthly discharge. Instead, YOY survival increased with lower minimum discharge and in response to small rain events that increased low-flow variability. Age-1+ fish showed the opposite pattern, with survival decreasing in response to increasing low-flow variability. Results from this population dynamics study of a small fish in a perennial river suggest that fluvial-dependent species can be resistant to extreme flow reductions through enhanced YOY recruitment and high survival

Caracterización estacional del hábitat fluvial del río Erro (Navarra

Directory of Open Access Journals (Sweden)

P.M. Leunda, R. Miranda, M.C. Escala

2004-01-01

Full Text Available Se presenta la descripción de catorce tramos representativos del río Erro (Navarra a partir de la caracterización del hábitat fluvial llevada a cabo en invierno, verano y otoño de 2002. Para este estudio se han considerado parámetros tanto del hábitat físico (profundidad, anchura del cauce, pendiente de las orillas, velocidad del agua, tipo de sustrato, vegetación acuática y sombreado como físico-químicos del agua (temperatura, pH, conductividad, sólicos disueltos y oxigeno disuelto. El análisis de las caracteristicas del rio Erro permite considerar su estado general como bueno, aunque se detecta la presencia de un tramo sensible aguas abajo de la localidad de Erro. Si bien este tramo sensible presenta niveles de conservación aceptables, es susceptible de deteriorarse si no de adoptan las medidas oportunas para su conservación. Se sugiere su inclusión en el Lugar de Interés Comunitario (Red Natura 2000 de Navarra de los "Sistemas Fluviales de lis Ríos Irati, Urrobi y Erro".

Milankovitch cyclicity in the paleotropical, fluvial, Late Triassic age strata recovered by the Colorado Plateau Coring Project (CPCP)

Science.gov (United States)

Olsen, P. E.; Mundil, R.; Kent, D.; Rasmussen, C.

2017-12-01

Two questions addressed by the CPCP are: 1) is Milankovitch-paced climate cyclicity recorded in the fluvial Late Triassic age Chinle Formation ( 227-202 Ma); and 2) do geochronological data from the Chinle support the Newark-Hartford astrochronological polarity time scale (1) (APTS). To these ends we examined the upper 157 m (stratigraphic thickness) of Petrified Forest National Park core 1A (Owl Rock, Petrified Forest, and upper Sonsela members), consisting mostly of massive red paleosols and less important fluvial sandstones. A linear age model tied to new U-Pb zircon CA ID-TIMS dates from core 1A, consistent with published data from outcrop (2), yields a duration of about 5 Myr for this interval. Magnetic susceptibility variations, interpreted as reflecting penecontemporaneous soil and sandstone redox conditions, show a clear 12 m cycle corresponding to a 400 kyr cycle based on Fourier analysis in both core and hole. Similar cyclicity is apparent in spectrophotometric data, largely reflecting hematite variability. Weak, higher frequency cycles are present consistent with 100 kyr variability. There is no interpretable 20 kyr signal. Such cyclicity is not an anticipated direct effect of Milankvitch insolation variations, but must reflect non-linear integration of variability that changes dramatically at the eccentricity-scale, brought about by the sedimentary and climate systems. Our results support a direct 405 kyr-level correlation between the fluvial medial Chinle and lacustrine Newark Basin section (middle Passaic Formation), consistent with new and published (3) paleomagnetic polarity stratigraphy from the Chinle, showing that the Milankovitch eccentricity cycles are recorded in lower accumulation rate fluvial systems. Our results also independently support the continuity of the Newark Basin section and corroborate the Newark-Hartford APTS, not allowing for a multi-million year hiatus in the Passaic Formation, as has been asserted (4). We anticipate further

Fluvial sedimentology of a major uranium-bearing sandstone - A study of the Westwater Canyon member of the Morrison Formation, San Juan Basin, New Mexico

International Nuclear Information System (INIS)

Turner-Peterson, C.E.

1986-01-01

The Westwater Canyon Member of the Morrison Formation, the main ore-bearing sandstone in the San Juan basin, consists of a sequence of vertically stacked braided stream deposits. Three fluvial units within the sequence can be delineated in the basin. Volcanic pebbles are abundant in the middle fluvial unit, in a zone that forms a crude time line. A pronounced thickening of sandstone in the Westwater Canyon Member north of Gallup, once believed to be the apex of a large alluvial fan, is now thought to merely reflect a greater accumulation of sediment in response to downwarping of the basin in that area. Provenance studies suggest that highlands that contributed detritus to Westwater Canyon streams were located several hundred kilometers to the west and southwest of the San Juan basin, and thus fan apices would also have been several hundred kilometers upstream. The fluvial units recognized in the basin may well be coalesced distal fan deposits, but are probably best interpreted as vertically stacked braided steam sequences. Facies changes in fine-grained interbeds of the Westwater Canyon probably have greater significance in terms of localizing ore than any special attribute of the fluvial sandstones themselves. Uranium ore generally occurs in sandstones that are interbedded with greenish-gray lacustrine mudstones. Pore waters that were expelled from these mudstones are thought to have been the source of the pore-filling organic matter (humate) associated with primary uranium ore in nearby sandstones

Reconstructing late quaternary fluvial process controls in the upper aller valley (north Germany) by means of numerical modeling

NARCIS (Netherlands)

Veldkamp, A.; Berg, van den M.; Dijke, van J.J.; Berg van Saparoea, van den R.M.

2002-01-01

The morpho-genetic evolution of the upper Aller valley (Weser basin, North Germany) was reconstructed using geological and geomorphologic data integrated within a numerical process model framework (FLUVER-2). The current relief was shaped by Pre-Elsterian fluvial processes, Elsterian and Saalian ice

Reconstructing Late Quaternary fluvial process controls in the upper Aller Valley (North Germany) by means of numerical modeling

NARCIS (Netherlands)

Veldkamp, A.; Berg, M.W. van den; Dijke, J.J. van; Berg van den; Saparoea, R.M. van

2002-01-01

The morpho-genetic evolution of the upper Aller valley (Weser basin, North Germany) was reconstructed using geological and geomorphologic data integrated within a numerical process model framework (FLUVER-2). The current relief was shaped by Pre-Elsterian fluvial processes, Elsterian and Saalian ice

Étude préliminaire de recrutement fluvial de l'anguille

Directory of Open Access Journals (Sweden)

LEGAULT A.

1994-10-01

La passe piège représente la seule voie de franchissement de l'obstacle. L'évaluation des captures permet d'estimer le taux de recrutement du bassin versant pour l'année 1992. Il s'établit à 561 individus par km2 de bassin versant. L'évaluation annuelle de ce taux pourrait être utilisée afin de suivre la dynamique du stock à l'échelle du bassin versant. Ces évaluations, conduites à l'échelle de l'aire de répartition européenne de l'anguille, pourraient permettre d'établir le recrutement fluvial annuel et ses fluctuations.

Gestión de la cultura literaria desde la economía política de la comunicación y la cultura : Desafíos de la era digital

OpenAIRE

Fernandez, Paola Elisabeth

2015-01-01

Los estudios de la Economía Política de la Comunicación y la Cultura se han vinculado históricamente y en paralelo a dos objetos parciales de estudio. El primero, vinculado a las artes gráficas y visuales, y el segundo, inspirado en los aportes de la escuela de Frankfurt; ambos limitaron su estudio a las industrias culturales y los medios de comunicación. El propósito de este artículo radica en plantear una integración conceptual en torno al libro como bien y obra intelectual, con l...

Gestión de la cultura literaria desde la economía política de la comunicación y la cultura. Desafíos en la era digital

OpenAIRE

Paola Elisabet Fernández

2015-01-01

Los estudios de la Economía Política de la Comunicación y la Cultura se han vinculado históricamente y en paralelo a dos objetos parciales de estudio. El primero, vinculado a las artes gráficas y visuales, y el segundo, inspirado en los aportes de la escuela de Frankfurt; ambos limitaron su estudio a las industrias culturales y los medios de comunicación. El propósito de este artículo radica en plantear una integración conceptual en torno al libro como bien y obra intelectual, con la inte...

Phytolith analysis in fluvial quaternary sediment (San Salvador and Palmar formation) Uruguay river and Argentina eastern

International Nuclear Information System (INIS)

Patterer, N.; Passeggi, E.; Zucol, A.; Brea, M.; Krohling, D.

2012-01-01

This work is about two microfossils fluvial units deposited by the Uruguay river during the Quaternary. These are San Salvador and Palmar formation (Plio-Pleistocene - Upper Pleistocene).The Palmar formation is a band of 4-15 km along the right bank of the Uruguay river outcropping from the eastern provinces of Corrientes and Entre Rios, to Concepcion del Uruguay

Relevance of the Paraná River hydrology on the fluvial water quality of the Delta Biosphere Reserve.

Science.gov (United States)

Puig, Alba; Olguín Salinas, Héctor F; Borús, Juan A

2016-06-01

The increasing frequency of extreme events in large rivers may affect not only their flow, but also their water quality. In the present study, spatial and temporal changes in fluvial physico-chemical variables were analyzed in a mega-river delta during two extreme hydrological years (La Niña-El Niño) and related to potential explanatory factors. Basic water variables were evaluated in situ at 13 points (distant 2-35 km from each other) in watercourses of the Delta Biosphere Reserve (890 km(2)) in the Lower Paraná River (Argentina) in nine surveys (October 2008-July 2010) without meteorological tides. Samples for laboratory analyses were collected from each main river. Multivariate tests by permutations were applied. The period studied was influenced by a drought, within a long period dominated by low flows combined with dry weather and wildfires, and a large (10 years of recurrence) and prolonged (7 months) flood. The hydrological phase, followed by the season and the hydrological year (according to the ENSO event) were the principal explanatory factors of the main water quality changes, whereas the drainage sub-basin and the fluvial environment (river or stream) were secondary explanatory factors. During the drought period, conductivity, turbidity, and associated variables (e.g., major ions, silicon, and iron concentrations) were maximal, whereas real color was minimal. In the overbanking flood phase, pH and dissolved oxygen concentration were minimal, whereas real color was maximal. Dissolved oxygen saturation was also low in the receding flood phase and total major ion load doubled after the arrival of the overbanking stage. The water quality of these watercourses may be affected by the combination of several influences, such as the Paraná River flow, the pulses with sediments and solutes from the Bermejo River, the export of the Delta floodplain properties mainly by the flood, the season, and the saline tributaries to the Lower Paraná River. The high

Implications of sedimentological studies for environmental pollution assessment and management: Examples from fluvial systems in North Queensland and Western Australia

Science.gov (United States)

Eyre, Bradley; McConchie, David

1993-05-01

Sedimentology is of increasing importance in environmental research, particularly environmental pollution studies, where past trends in environmental processes need to be combined with data on present conditions to predict likely future changes—the past and present as a key to the future. Two examples are used to illustrate the role of sedimentology in assessing the influence of major processes on the transport, accumulation, deposition and modification of contaminants in fluvial/estuarine systems and in developing environmental management plans. Example 1 shows that when assessing nutrient behaviour in fluvial/estuarine depositional settings, it is important to examine the partitioning of phosphorus between grain size fractions to evaluate the sedimentological processes which control the dispersion and trapping of these contaminants. Example 2 shows that in studies of anthropogenic metal inputs to modern depositional settings, lateral and stratigraphic trends in sediment texture and mineralogy should be examined, in addition to trends in metal loads and evaluation of the prevailing physical, chemical and biological processes that may influence metal mobility and dispersion. Clearly, basic sedimentological data should form part of any assessment of potentially contaminated sites and part of investigations into the dispersion and trapping of contaminants in fluvial systems. These data are also required for rational environmental management to ensure that planning decisions are compatible with natural environmental constraints.

Volcanic or Fluvial Channels on Ascraeus Mons: Focus on the Source Area of Sinuous Channels on the Southeast Rift Apron

Science.gov (United States)

Signorella, J. D.; de Wet, A. P.; Bleacher, J. E.; Collins, A.; Schierl, Z. P.; Schwans, B.

2012-03-01

This study focuses on the source area of sinuous channels on the southeast rift apron on Ascraeus Mons, Mars and attempts to understand whether the channels were formed through volcanic or fluvial processes.

La vegetación como indicador de la Geomorfología Fluvial

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Juan José Neiff

2005-11-01

Full Text Available Aguas abajo de la confluencia con el río Paraguay, el Paraná se expande en una ancha planicie lateral que, durante las inundaciones extraordinarias completa un área 2-10 veces mayor que el área ocupada por las aguas en los períodos de bajantes extraordinarias, en los que el curso queda aislado de la planicie inundable. El propósito de esta contribución es presentar las características más salientes de este tramo entrelazado del río, usando las unidades de paisaje y los tipos de vegetación, como indicadores de las formas del relieve. Imágenes satelitales Landsat TM5 y TM7 procesadas con el SIG IDRISI, de la inundación extrema de 1998 y de la sequía extrema de 2001, fueron usadas para la clasificación de los tipos de vegetación, usando el criterio propuesto por CET (Clasificación Ecológica de Tierras. Observaciones de campo fueron realizadas en ambas fases hidrológicas para obtener la posición topográfica de las unidades de vegetación y de los ensambles de comunidades vegetales. Nosotros encontramos que los albardones están ocupados por tipos de bosques, mientras que los bañados y cuerpos de aguas someros están cubiertos por plantas herbáceas y que las praderas flotantes de vegetación flotante libre, como el aguapé, crecen en lagos conectados al río una o más veces en el año. La vegetación acuática del curso principal es muy pobre como consecuencia del flujo del río y las fluctuaciones de nivel del agua. Sólo pequeñas manchas de carrizo se encontraron creciendo en barras de arena. La interrelación entre la vegetación y las formas del relieve es muy dinámica, con cambios drásticos en períodos de décadas o aún de pocos años, dependiendo del caudal y de la carga de sólidos transportados. En otro sentido, la vegetación fluvial tiene un importante rol en la fijación de depósitos fluviales y como núcleos de acreción en las barras o para entender la obstrucción de pequeños cursos de agua en la planicie

A hydro-geochemical study of Nahr-Ibrahim catchment area: Fluvial metal transport

International Nuclear Information System (INIS)

Korfali, Samira

2004-01-01

Author.Metals enter water bodies geological weathering, soil erosion, industrial and domestic waste discharges, as well as atmospheric deposition. The metal content in sediments is a reflection of the nature of their background whether of geologic and/or anthropogenic origin. The depositional process of metals in sediment are controlled by river discharge, turbulence of river, morphology and river geometry, as well as the geochemical phases of sediment and soils. Thus a study of metal content in river and /or metal transport with a water body should include a hydrological study of the river, types of minerals in sediment and soil, sediment and soil textures, and metal speciation in the different geochemical phases of sediment, bank and soils. A contaminated flood plain is a temporary storage system for pollutants and an understanding of soil-sediment-interactions is important prerequisite for modeling fluvial pollutant transport. The determination of metal speciation in sediment and soil chemical fraction can provide information on the way in which these metals are bound to sediment and soil, their mobilization potential, bioavailability and possible mechanism of fluvial pollutant transport. Sequential extraction techniques yielding operationally defined chemical pools have been used by many workers to examine the partitioning of metals among the various geochemical phases of sediment or soil. The sequential extraction method specifies metals in sediment fractions as: exchangeable, specifically sorbed, easily reducible, moderately reducible, organic, residual. Previously, I have conducted a study on speciation of metals (Fe, Mn, Zn, Cu, Pb and Cd) in the dry season bed-load sediments only at five sites 13 km stretch upstream from the mouth of Nahr Ibrahim. The reported data revealed that the specifically sorbed sediment fraction was the prime fraction for deposition of Mn, Z, CU, Pb and Cd metals in sediments. X-ray diffraction analysis of bed sediments showed

Enfoque por competencias, ¿una respuesta al fracaso escolar?

Directory of Open Access Journals (Sweden)

Philippe Perrenooud

2009-01-01

Full Text Available Son tiempos de reflexión sobre las competencias. Queda mucho por investigar acerca de sus posibilidades pero es cierto que, desde el punto de vista teórico, el enfoque por competencias se presenta como potente al complementar una pedagogía que, tradicionalmente, se ha centrado en las disciplinas y en los saberes. Pero también este enfoque aparece fuerte en el campo de la formación en la medida en que viene vinculado a las prácticas sociales y educativas, al trabajo pedagógico de los problemas educativos en las diferentes situaciones, a los proyectos que los educadores desean materializar en sus lugares de trabajo. Están por demostrar las expectativas puestas en el enfoque por competencias y este texto trata de pensar toda una serie de cuestiones relacionadas con su puesta en marcha en los contextos formativos.---------------------------------------------------------------------These are times for reflection on skills. There is much left to investigate on their possibilities but it is true that, from the theoretical point of view, the skill approach appears to be powerful by complementing a pedagogy which, tradicionally, has focused on the knowledge and disciplines. But this approach appears strongly in the training field as it is linked to the social and educational practices, to the pedagogic work on educative problems, to the different situations, to the project that teachers wish to materialize in the labor places. Still to be demonstrated are the expectations on the skills approach, and this text tries to think on a series of matters related with its set in motion in the learning contexts.

Temporal correlation of fluvial and alluvial sequences in the Makran Range, SE-Iran

Science.gov (United States)

Kober, F.; Zeilinger, G.; Ivy-Ochs, S.; Dolati, A.; Smit, J.; Burg, J.-P.; Bahroudi, A.; Kubik, P. W.; Baur, H.; Wieler, R.; Haghipour, N.

2009-04-01

The Makran region of southeastern Iran is an active accretionary wedge with a partially subaerial component. New investigations have revealed a rather complex geodynamic evolution of the Makran active accretionary wedge that is not yet fully understood in its entity. Ongoing convergence between the Arabian and Eurasian plates and tectonic activity since the late Mesozoic has extended all trough the Quaternary. We focus here on fluvial and alluvial sequences in tectonically separated basins that have been deposited probably in the Pliocene/Quaternary, based on stratigraphic classification in official geological maps, in order to understand the climatic and tectonic forces occurring during the ongoing accretionary wegde formation. Specifically, we investigate the influence of Quaternary climate variations (Pleistocene cold period, monsoonal variations) on erosional and depositional processes in the (semi)arid Makran as well as local and regional tectonic forces in the Coastal and Central Makran Range region. Necessary for such an analysis is a temporal calibration of alluvial and fluvial terrace sequences that will allow an inter-basin correlation. We utilize the exposure age dating method using terrestrial cosmogenic nuclides (TCN) due to the lack of otherwise datatable material in the arid Makran region. Limited radiocarbon data are only available for marine terraces (wave-cut platforms). Our preliminary 21Ne and 10Be TCN-ages of amalgamated clast samples from (un)deformed terrace and alluvial sequences range from ~250 ky to present day (modern wash). These ages agree in relative terms with sequences previously assigned by other investigations through correlation of Quaternary sequences from Central and Western Iran regions. However, our minimum ages suggest that all age sequences are of middle to late Pleistocene age, compared to Pliocene age estimates previously assigned for the oldest units. Although often suggested, a genetical relation and connection of those

Regional Contamination of Moravia (South-Eastern Czech Republic): Temporal Shift of Pb and Zn Loading in Fluvial Sediments

Czech Academy of Sciences Publication Activity Database

Matys Grygar, Tomáš; Sedláček, J.; Bábek, O.; Nováková, Tereza; Strnad, L.; Mihaljevič, M.

2012-01-01

Roč. 223, č. 2 (2012), s. 739-753 ISSN 0049-6979 R&D Projects: GA AV ČR IAAX00130801 Institutional research plan: CEZ:AV0Z40320502 Keywords : fluvial sediments * Pb * Zn * regional contamination Subject RIV: DD - Geochemistry Impact factor: 1.748, year: 2012

An inventory of published and unpublished fluvial-sediment data for California, 1956-70

Science.gov (United States)

Porterfield, George

1972-01-01

This inventory was prepared to provide a convenient reference to published and unpublished fluvial-sediment data for water years 1956-70, and updates substantially previous inventories. Sediment stations are listed in downstream order, and an alphabetical list of stations is also included. Figure 1 shows the approximate location of sediment stations in California. Most of the fluvial-sediment data in California were collected by the U.S. Geological Survey, under cooperative agreements with the following Federal, State, and local agencies: California Department of Water Resources, California Department of Navigation and Ocean Development, California Department of Fish and Game, Bolinas Harbor District, Monterey County Flood Control and Water Conservation District, Orange County Flood Control District, Riverside County Flood Control and Water Conservation District, San Diego County Department of Sanitation and Flood Control, San Luis Obispo County, San Mateo County, Santa Clara County Flood Control and Water District, Santa Cruz County Flood Control and Water Conservation District, Santa Cruz, city of, University of California, Ventura County Flood Control District, Forest Service, U.S. Department of Agriculture, Soil Conservation Service, U.S. Department of Agriculture, Corps of Engineers, U.S. Army, Bureau of Reclamation, U.S. Department of the Interior, National Park Service, U.S. Department of the Interior. This report was prepared by the Geological Survey under the general supervision of R. Stanley Lord, district chief in charge of water-resources investigations in California.

Floodplain forest succession reveals fluvial processes: A hydrogeomorphic model for temperate riparian woodlands.

Science.gov (United States)

Egger, Gregory; Politti, Emilio; Lautsch, Erwin; Benjankar, Rohan; Gill, Karen M; Rood, Stewart B

2015-09-15

River valley floodplains are physically-dynamic environments where fluvial processes determine habitat gradients for riparian vegetation. These zones support trees and shrubs whose life stages are adapted to specific habitat types and consequently forest composition and successional stage reflect the underlying hydrogeomorphic processes and history. In this study we investigated woodland vegetation composition, successional stage and habitat properties, and compared these with physically-based indicators of hydraulic processes. We thus sought to develop a hydrogeomorphic model to evaluate riparian woodland condition based on the spatial mosaic of successional phases of the floodplain forest. The study investigated free-flowing and dam-impacted reaches of the Kootenai and Flathead Rivers, in Idaho and Montana, USA and British Columbia, Canada. The analyses revealed strong correspondence between vegetation assessments and metrics of fluvial processes indicating morphodynamics (erosion and shear stress), inundation and depth to groundwater. The results indicated that common successional stages generally occupied similar hydraulic environments along the different river segments. Comparison of the spatial patterns between the free-flowing and regulated reaches revealed greater deviation from the natural condition for the braided channel segment than for the meandering segment. This demonstrates the utility of the hydrogeomorphic approach and suggests that riparian woodlands along braided channels could have lower resilience than those along meandering channels and might be more vulnerable to influences such as from river damming or climate change. Copyright © 2015 Elsevier Ltd. All rights reserved.

Arctic deltaic lake sediments as recorders of fluvial organic matter deposition

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Jorien E Vonk

2016-08-01

Full Text Available Arctic deltas are dynamic and vulnerable regions that play a key role in land-ocean interactions and the global carbon cycle. Delta lakes may provide valuable historical records of the quality and quantity of fluvial fluxes, parameters that are challenging to investigate in these remote regions. Here we study lakes from across the Mackenzie Delta, Arctic Canada, that receive fluvial sediments from the Mackenzie River when spring flood water levels rise above natural levees. We compare downcore lake sediments with suspended sediments collected during the spring flood, using bulk (% organic carbon, % total nitrogen, 13C, 14C and molecular organic geochemistry (lignin, leaf waxes. High-resolution age models (137Cs, 210Pb of downcore lake sediment records (n=11 along with lamina counting on high-resolution radiographs show sediment deposition frequencies ranging between annually to every 15 years. Down-core geochemical variability in a representative delta lake sediment core is consistent with historical variability in spring flood hydrology (variability in peak discharge, ice jamming, peak water levels. Comparison with earlier published Mackenzie River depth profiles shows that (i lake sediments reflect the riverine surface suspended load, and (ii hydrodynamic sorting patterns related to spring flood characteristics are reflected in the lake sediments. Bulk and molecular geochemistry of suspended particulate matter from the spring flood peak and lake sediments are relatively similar showing a mixture of modern higher-plant derived material, older terrestrial permafrost material, and old rock-derived material. This suggests that deltaic lake sedimentary records hold great promise as recorders of past (century-scale riverine fluxes and may prove instrumental in shedding light on past behaviour of arctic rivers, as well as how they respond to a changing climate.

Fluvial sedimentary styles and associated depositional environments in the buntsandstein west of river rhine in saar area and pfalz (F.R. Germany) and vosges (France)

Science.gov (United States)

Dachroth, Wolfgang

The Buntsandstein west of river Rhine in Saar area, Pfalz and Vosges consists of three fluvial magnacycles which are characterized by different associated non-alluvial environments. The stratigraphic sequence is divided by several unconformities reflecting tectonic movements which were connected with periods of extension of the depositional area. Two major phases and two minor events are recognized by the evaluation of the Pfalz unconformity and the Lothringen unconformity, and the Leuter unconformity and the Saar unconformity, respectively. The Lower Buntsandstein (including Zechstein) compries the first magnacycle and is built up of alluvial-fan deposits, fluvial braidplain sediments and marine to lagoonal deposits. Some aeolian sands as well as several palaeosols are also present. The palaeolandscape consists of alluvial fans seaming the margin of the basin and fluvial braidplains reaching from the toes of the fan belt to the centre of the depositional area which is occupied by a lagoonal sea that partially evolves into a playa-lake with progressive refreshment. The Middle Buntsandstein comprises the second magnacycle and is composed of an alternation of aeolian Dünnschichten and fluvial Felsbänke. The third facies are alluvial-fan deposits of palaeogeographically restricted distribution along the margins of the basin. The aeolian Dünnschichten originate in the marginal parts of chott-type depressions (in comparison with the recent Chott Djerid in Tunesia) where rising ground water moistens the dry sediments that are laid down on the playa floor and thus allows their enhanced preservation. In dry periods, wind-blown sand is spread out as plane sheets or as migrating wind ripple trains, or accumulates to barchanoid-type dunes that advance across the flat. Depending on supply of sand, all stages of transition between dune fields with only narrow interdune corridors between the ridges and interdune playas with isolated widely-spaced dunes are developed. The

Nuevos índices cronológicos de evolución de los suelos en terrazas fluviales

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Zazo, C.

1997-04-01

, contenido global de arcilla, que corresponde al producto del contenido de arcilla por el espesor del horizonte argílico en cm; ILU, índice de iluviación, relación entre el porcentaje de arcilla en el horizonte Bt/porcentaje de arcilla en el horizonte A; y, AC/L, índice de vejez, relación entre el porcentaje de arcilla/porcentaje de limo en el horizonte Bt. Se realiza el estudio estadístico de las correlaciones lineales entre estos índices y la edad relativa de los suelos estimada a través de la cota relativa de los niveles de terrazas correspondientes. El índice de vejez (AC/L es el que muestra los mejores resultados como criterio cronológico de evolución edáfica en la cronosecuencia estudiada. La aplicación de estos índices cronológicos a otras cronosecuencias de terrazas fluviales (río Henares y río Esla confirma la utilidad de estos criterios de la evolución del suelo. Los mejores resultados se obtienen para el índice de vejez, y en segundo lugar el contenido de arcilla, y el contenido global de arcilla. El índice de iluviación presenta una mayor variabilidad, y su uso como criterio cronológico de evolución es menos preciso, debido a que resulta más afectado por la conservación total o el truncamiento parcial del perfil original.

VARIAÇÃO ESPACIAL E CONDICIONANTES DO ENTALHAMENTO FLUVIAL NA BACIA DO RIO GRANDE, SUL DE MINAS GERAIS

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Éric Andrade Rezende

2016-12-01

Full Text Available O presente trabalho pretende avaliar as variações no aprofundamento da drenagem na alta/média bacia do Rio Grande, sul de Minas Gerais. Para a mensuração do entalhamento fluvial (amplitude altimétrica em cada trecho dos canais fluviais foi utilizada a base ottocodificada em conjunto com o modelo digital de elevação SRTM/Topodata. A distribuição das classes de amplitude mostrou que na maior parte da alta/média bacia do Rio Grande o entalhamento fluvial situa-se entre 40 e 120 m. Valores superiores a 120 m concentram-se principalmente na Serra da Mantiqueira, junto às cabeceiras dos principais rios. O controle litológico sobre a distribuição das classes de amplitude é espacialmente restrito, o que sugere que a tectônica cenozoica é o principal fator controlador da intensidade da incisão fluvial. A boa correspondência entre classes de amplitude e falhas mapeadas indica a atuação de soerguimentos diferenciais entre blocos, com o consequente rebaixamento de níveis de base regionais nos blocos baixos. Esse controle é mais evidente na porção sul da área, com destaque para a zona de cisalhamento de Jesuânia (ENE. Nesse contexto, as áreas mais soerguidas são as porções da Serra da Mantiqueira que reúnem as principais concentrações de amplitudes superiores a 200 m. Mais ao norte merecem destaque as áreas com concentrações anômalas de amplitudes relativamente elevadas ao norte de Três Corações e na média/baixa bacia do Rio Jacaré. No primeiro caso um considerável soerguimento neocenozoico também deve ter ocorrido, enquanto no segundo as amplitudes mais elevadas aparentemente estão relacionadas à retração erosiva de um knickpoint com o consequente rejuvenescimento do relevo. A predominância de amplitudes menores (< 80 m na porção oriental, drenada por afluentes do alto Rio Grande, em relação à porção ocidental (sub-bacia do Rio Sapucaí aparenta estar relacionada à presença de soleiras quartz

Fluvial sediment transport: Analytical techniques for measuring sediment load

International Nuclear Information System (INIS)

2005-07-01

Sediment transport data are often used for the evaluation of land surface erosion, reservoir sedimentation, ecological habitat quality and coastal sediment budgets. Sediment transport by rivers is usually considered to occur in two major ways: (1) in the flow as a suspended load and (2) along the bed as a bed load. This publication provides guidance on selected techniques for the measurement of particles moving in both modes in the fluvial environment. The relative importance of the transport mode is variable and depends on the hydraulic and sedimentary conditions. The potential user is directed in the selection of an appropriate technique through the presentation of operating principles, application guidelines and estimated costs. Techniques which require laboratory analysis are grab sample, pump sample, depth sample, point integrated and radioactive tracers. Techniques which will continuously record data are optical backscattering, nuclear transmission, single frequency acoustic and laser diffraction

Distribution and Potential Mobility of Selected Heavy Metals in a Fluvial Environment Under the Influence of Tanneries

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Rodrigues M. L. K.

2013-04-01

Full Text Available In this study we evaluated the occurrence of heavy metals in a fluvial environment under the influence of tanneries – the Cadeia and Feitoria rivers basin (RS, south Brazil, highlighting the distribution and potential mobility of the selected elements. Every three months, over one year-period, selected heavy metals and ancillary parameters were analyzed in water and sediment samples taken at ten sites along the rivers. Water analyses followed APHA recommendations, and sediment analyses were based on methods from USEPA (SW846 and European Community (BCR sequential extraction. The determinations were performed by ICP/OES, except for Hg (CV/ETA. Statistical factor analysis was applied to water and sediment data sets, in order to obtain a synthesis of the environmental diagnosis. The results revealed that water quality decreased along the rivers, and mainly on the dry period (January, showing the influence of tannery plants vicinity and flow variations. Except for Fe, Al, and eventually Mn, heavy metal contents in water were in agreement with Brazilian standards. Concerning sediments, Al, Cu, Fe, Ni, Mn, Ti, and Zn concentrations appeared to reflect the base levels, while Cr and Hg were enriched in the deposits from the lower part of the basin. The partition of heavy metals among the sediment geochemical phases showed higher mobility of Mn along the sampling sites, followed by Cr in the lower reach of the basin, most affected by tanneries. Since Cr was predominantly associated to the oxidizable fraction, its potential mobilization from contaminated sediments would be associated to redox conditions. The detection of Hg in the tissue of a bottom-fish species indicated that the environmental conditions are apparently favoring the remobilization of this metal from contaminated sediments.

Diagnostic sedimentary structures of the fluvial-tidal transition zone – Evidence from deposits of the Rhine and Meuse

NARCIS (Netherlands)

Berg, J.H. van den; Boersma, J.R.; Gelder, A. van

2007-01-01

n mesotidal settings the transition of a coastal plain estuary to the river is marked by the change of a multiple ebb and flood channel configurationto a single channel system. At high river discharge fluvial processes operate, whereas in periods of low discharge the flow is complicated by a

Morfometría fluvial aplicada a una cuenca urbana en Ingeniero White, República Argentina

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Alicia María Campo

2012-04-01

Full Text Available La morfometría fluvial estudia diversas variables que caracterizan la forma de una cuenca de drenaje. El objetivo de este trabajo es aplicar el método morfométrico de cuencas naturales a una cuenca urbana. El área en estudio (6 km2 drena sus aguas al frente costero y comprende la localidad de Ingeniero White, República Argentina. Se realizó la jerarquización de la red de drenaje. Se identificaron tres subcuencas con escasa pendiente que presentan eventos de inundación, con mayor peligrosidad con precipitaciones extremas. Los valores de relación de longitud indicaron mayor concentración de energía en eventos de grandes avenidas. Los valores de relación de elongación demostraron que una de las subcuencas es de forma circular y presenta mayor velocidad en las avenidas de la escorrentía. Las dos cuencas más elongadas tienen mayor retardo en las avenidas. El mayor caudal del área en estudio fluye por la cuenca que posee el mayor número de orden y la mayor superficie. Las otras dos cuencas están sujetas a crecientes instantáneas y de respuesta inmediata. Los valores de pendiente y de área aplicados a modelos hidrológicos e hidraúlico determinaron la sección de los conductos y canales. El caudal calculado para el área drenada fue de 22.41 m3/s.

Quaternary river incision in the uplifted Rhenish massif (Ardennes, Belgium) - Insights from 10Be/26Al dating of river terraces

Science.gov (United States)

Rixhon, Gilles; Bourlès, Didier; Braucher, Régis; Siame, Lionel; Bovy, Benoît.; Demoulin, Alain

2010-05-01

Although it constitutes the main tool to unravel the regional recent tectonics, the chronology of the Pleistocene river incision is still poorly constrained within the uplifted Rhenish-Ardennes massif (Belgium, western Europe). Here, we measure cosmogenic nuclides concentrations (10Be and 26Al) in terrace quartz or quartzite sediments of several Ardennian rivers (Meuse, Ourthe and Amblève) in order to date the so-called Younger Main Terrace (YMT), a key-level in the network evolution. Though these dating methods are successfully used to determine ages of superficial (e.g., glacial) deposits, dating of fluvial terraces remains difficult. Possible predepositional exposures of the sampled material (inherited 10Be and 26Al) may indeed bias the measurements towards higher nuclide concentrations while several postdepositional processes (burial, erosion) may cause a lowering of the 10Be and 26Al concentrations. In an attempt to overcome these difficulties, the selected fluvial deposits (five locations) were sampled using a profiling technique on as thick as possible sections (more than 3 m). We present the first absolute dating of the YMT in the lower Meuse valley (nearby the Dutch boundary), where we obtained an age of 630 ka for a terrace deposit buried beneath 3 m of Weichselian loess. This age is consistent with some previously published estimates based on paleomagnetic data and MIS correlations. However, our ages for the same terrace level within the Ardennes are significantly younger: >400 ka in the lower Ourthe, and only ~220 ka still farther upstream, in the lower Amblève. We thus demonstrate that the post-YMT incision occurred diachronically in NE Ardennes. The ~0.5 Ma timespan needed by the erosion wave to propagate from the lower Meuse towards the Ardennian headwaters contradicts the long-held statement of a climatically driven incision that would have been synchronous throughout the catchment.

The origin of dose distributions in fluvial sediments, and the prospect of dating single grains from fluvial deposits using optically stimulated luminescence

CERN Document Server

Olley, J M; Roberts, R G

1999-01-01

We examine the causes of the asymmetric distributions of dose observed from measurements of the optically stimulated luminescence emitted by small aliquots of fluvial quartz, and deduce that the asymmetry arises as a result of samples being composed of a mix of mainly well bleached grains with grains that were effectively unbleached at the time of deposition. We demonstrate that the shapes of the dose distributions can be used to assess the likelihood that aliquots consist only of grains that were well-bleached at the time of deposition. The more asymmetric the distribution, the greater the probability that the aliquots with the lowest dose most closely represent the true burial dose. Single grains with differing doses are present in each of the samples examined, and the population with the lowest dose gives an optical age consistent with the expected burial age. This result implies that the beta-dose heterogeneity in these deposits is small, and that the effects of micro-dosimetric variations on optical dati...

High-resolution urban flood modelling - a joint probability approach

Science.gov (United States)

Hartnett, Michael; Olbert, Agnieszka; Nash, Stephen

2017-04-01

The hydrodynamic modelling of rapid flood events due to extreme climatic events in urban environment is both a complex and challenging task. The horizontal resolution necessary to resolve complexity of urban flood dynamics is a critical issue; the presence of obstacles of varying shapes and length scales, gaps between buildings and the complex geometry of the city such as slopes affect flow paths and flood levels magnitudes. These small scale processes require a high resolution grid to be modelled accurately (2m or less, Olbert et al., 2015; Hunter et al., 2008; Brown et al., 2007) and, therefore, altimetry data of at least the same resolution. Along with availability of high-resolution LiDAR data and computational capabilities, as well as state of the art nested modelling approaches, these problems can now be overcome. Flooding and drying, domain definition, frictional resistance and boundary descriptions are all important issues to be addressed when modelling urban flooding. In recent years, the number of urban flood models dramatically increased giving a good insight into various modelling problems and solutions (Mark et al., 2004; Mason et al., 2007; Fewtrell et al., 2008; Shubert et al., 2008). Despite extensive modelling work conducted for fluvial (e.g. Mignot et al., 2006; Hunter et al., 2008; Yu and Lane, 2006) and coastal mechanisms of flooding (e.g. Gallien et al., 2011; Yang et al., 2012), the amount of investigations into combined coastal-fluvial flooding is still very limited (e.g. Orton et al., 2012; Lian et al., 2013). This is surprising giving the extent of flood consequences when both mechanisms occur simultaneously, which usually happens when they are driven by one process such as a storm. The reason for that could be the fact that the likelihood of joint event is much smaller than those of any of the two contributors occurring individually, because for fast moving storms the rainfall-driven fluvial flood arrives usually later than the storm surge

Assessment of spatiotemporal variations in the fluvial wash-load component in the 21st century with regard to GCM climate change scenarios.

Science.gov (United States)

Mouri, Goro

2015-11-15

For stream water, in which a relationship exists between wash-load concentration and discharge, an estimate of fine-sediment delivery may be obtained from a traditional fluvial wash-load rating curve. Here, we demonstrate that the remaining wash-load material load can be estimated from a traditional empirical principle on a nationwide scale. The traditional technique was applied to stream water for the whole of Japan. Four typical GCMs were selected from the Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble to provide the driving fields for the following regional climate models to assess the wash-load component based on rating curves: the Model for Interdisciplinary Research on Climate (MIROC), the Meteorological Research Institute Atmospheric General Circulation Model (MRI-GCM), the Hadley Centre Global Environment Model (HadGEM) and the Geophysical Fluid Dynamics Laboratory (GFDL) climate model. The simulations consisted of an ensemble, including multiple physics configurations and different Representative Concentration Pathways (RCP2.6, RCP4.5 and RCP8.5), which was used to produce monthly datasets for the whole country of Japan. The impacts of future climate changes on fluvial wash load in Japanese stream water were based on the balance of changes in hydrological factors. The annual and seasonal variations of the fluvial wash load were assessed from the result of the ensemble analysis in consideration of the Greenhouse Gas (GHG) emission scenarios. The determined results for the amount of wash load increase range from approximately 20 to 110% in the 2040s, especially along part of the Pacific Ocean and the Sea of Japan regions. In the 2090s, the amount of wash load is projected to increase by more than 50% over the whole of Japan. The assessment indicates that seasonal variation is particularly important because the rainy and typhoon seasons, which include extreme events, are the dominant seasons. Because fluvial wash-load-component turbidity

Predicting interwell heterogeneity in fluvial-deltaic reservoirs: Outcrop observations and applications of progressive facies variation through a depositional cycle

Energy Technology Data Exchange (ETDEWEB)

Knox, P.R.; Barton, M.D. [Univ. of Texas, Austin, TX (United States)

1997-08-01

Nearly 11 billion barrels of mobile oil remain in known domestic fluvial-deltaic reservoirs despite their mature status. A large percentage of this strategic resource is in danger of permanent loss through premature abandonment. Detailed reservoir characterization studies that integrate advanced technologies in geology, geophysics, and engineering are needed to identify remaining resources that can be targeted by near-term recovery methods, resulting in increased production and the postponement of abandonment. The first and most critical step of advanced characterization studies is the identification of reservoir architecture. However, existing subsurface information, primarily well logs, provides insufficient lateral resolution to identify low-permeability boundaries that exist between wells and compartmentalize the reservoir. Methods to predict lateral variability in fluvial-deltaic reservoirs have been developed on the basis of outcrop studies and incorporate identification of depositional setting and position within a depositional cycle. The position of a reservoir within the framework of a depositional cycle is critical. Outcrop studies of the Cretaceous Ferron Sandstone of Utah have demonstrated that the architecture and internal heterogeneity of sandstones deposited within a given depositional setting (for example, delta front) vary greatly depending upon whether they were deposited in the early, progradational part of a cycle or the late, retrogradational part of a cycle. The application of techniques similar to those used by this study in other fluvial-deltaic reservoirs will help to estimate the amount and style of remaining potential in mature reservoirs through a quicklook evaluation, allowing operators to focus characterization efforts on reservoirs that have the greatest potential to yield additional resources.

Mecanismos de explotación sexual de niñas y adolescentes en los alrededores del puerto fluvial de Pucallpa

Directory of Open Access Journals (Sweden)

Jaris Mujica

2011-12-01

Full Text Available La explotación sexual de niñas y adolescentes es un fenómeno que ha crecido con la expansión de las industrias extractivas (de madera, petróleo, minerales y gas en la Amazonía peruana. El artículo es parte de una larga investigación en la ciudad de Pucallpa y la ruta norte del río Ucayali, y tiene como objetivo central mostrar la dinámica económica de los mecanismos de explotación sexual comercial de niñas y adolescentes en los alrededores del principal puerto fluvial. Se estudia los mecanismos de explotación local de los bares y restaurantes del puerto, la demanda y las percepciones sobre la explotación sexual de las niñas, y las lógicas económicas que ello implica. Se trata de un negocio cuya rentabilidad está anexada al comercio de bebidas alcohólicas y alimentos; y que no obedece a una lógica criminal organizada sino a un conjunto de redes familiares.

A review on studies of the transport and the form of radionuclides in the fluvial environment

Energy Technology Data Exchange (ETDEWEB)

Matsunaga, Takeshi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

2001-06-01

The Japan Atomic Energy Research Institute has conducted studies with an aim to contribute to understanding the long-term behavior of atmospherically-derived radionuclides deposited on the ground. The present report reviews a series of studies among them which have especially dealt with the behavior of those radionuclides in a fluvial environment. The studies cited here include investigations of 1) the evaluation of the transport rate of the atmospherically-derived radionuclides from the ground via a river to the downstream areas where the affected water is consumed; 2) the physico-chemical form of the radionuclides in the fluvial environment. An investigation in the Kuji river watershed with {sup 137}Cs, {sup 210}Pb and {sup 7}Be has validated i) the importance of suspended particulate materials in the fluvial discharge of those radionuclides, and ii) a methodology to estimate the discharge of those radionuclides based on the regression analysis with the river water flow rate. From a viewpoint of their distribution between water and suspended particles, the form of radionuclides released by the Chernobyl accident in rivers and lakes in the vicinity of the Chernobyl Nuclear Power Plant were analyzed. As a result, a general reasonability and some cautions were suggested when commonly reported distribution ratios obtained in the laboratory and the different environment are applied to describe the partitioning of the radionuclides in specific natural environmental conditions. This experimental investigation in Chernobyl also revealed the role of natural dissolved organics in affecting the dissolution and transport of {sup 239,240}Pu, {sup 241}Am through complexation to form soluble species. Further, a chemical equilibrium model was applied to describe this complexation. The similar model was also applied for the behavior of iron and manganese (hydr)oxides in river recharged aquifers which can bear riverborne radionuclides and can influence their migration. The

A review on studies of the transport and the form of radionuclides in the fluvial environment

International Nuclear Information System (INIS)

Matsunaga, Takeshi

2001-06-01

The Japan Atomic Energy Research Institute has conducted studies with an aim to contribute to understanding the long-term behavior of atmospherically-derived radionuclides deposited on the ground. The present report reviews a series of studies among them which have especially dealt with the behavior of those radionuclides in a fluvial environment. The studies cited here include investigations of 1) the evaluation of the transport rate of the atmospherically-derived radionuclides from the ground via a river to the downstream areas where the affected water is consumed; 2) the physico-chemical form of the radionuclides in the fluvial environment. An investigation in the Kuji river watershed with 137 Cs, 210 Pb and 7 Be has validated i) the importance of suspended particulate materials in the fluvial discharge of those radionuclides, and ii) a methodology to estimate the discharge of those radionuclides based on the regression analysis with the river water flow rate. From a viewpoint of their distribution between water and suspended particles, the form of radionuclides released by the Chernobyl accident in rivers and lakes in the vicinity of the Chernobyl Nuclear Power Plant were analyzed. As a result, a general reasonability and some cautions were suggested when commonly reported distribution ratios obtained in the laboratory and the different environment are applied to describe the partitioning of the radionuclides in specific natural environmental conditions. This experimental investigation in Chernobyl also revealed the role of natural dissolved organics in affecting the dissolution and transport of 239,240 Pu, 241 Am through complexation to form soluble species. Further, a chemical equilibrium model was applied to describe this complexation. The similar model was also applied for the behavior of iron and manganese (hydr)oxides in river recharged aquifers which can bear riverborne radionuclides and can influence their migration. The obtained findings and the

Quality-Assurance Plan for the Analysis of Fluvial Sediment by the U. S. Geological Survey Kentucky Water Science Center Sediment Laboratory

National Research Council Canada - National Science Library

Shreve, Elizabeth A; Downs, Aimee C

2005-01-01

This report describes laboratory procedures used by the U. S. Geological Survey Kentucky Water Science Center Sediment Laboratory for the processing and analysis of fluvial sediment samples for concentration of sand and finer material...

Interculturalidad y educación. Aportación al estado del arte en Etnomatemáticas

Directory of Open Access Journals (Sweden)

Juan Luis Piñeiro

2016-07-01

Full Text Available Las investigaciones crecientes en el área de la Etnomatemática han generado un amplio escenario de discusión en el campo de la educación matemática, y por consiguiente es posible observar un gran número de aportes a nivel mundial. En este sentido, se plantea la necesidad de indagar sobre cuáles son los aspectos principales que preocupan en este campo de la educación y contribuir de esta manera, al estado del arte sobre la Etnomatemática, y por consiguiente a la educación matemática y la diversidad cultural. Para afrontar este problema, se realizó en primer lugar, una búsqueda sistemática de publicaciones científicas, en actas de congresos y revistas de impacto durante el periodo 2014-2015, de la cual se obtuvieron 48 documentos vinculados al área de la etnomatemática de manera explícita o implícita. En segundo lugar, se analizó la muestra teniendo en cuenta el modelo MOMUME de Oliveras (2000, 2008a, 2008b. Esta herramienta metodológica nos permitió reflexionar sobre las tendencias que se están configurando en Etnomatemática y contribuir al estado del arte en este programa. Los resultados muestran tendencia a tratar temas tales como: sociedad, cultura y modelo educativo, a través de experimentos de campo y con metodologías cualitativas, fundamentados en las matemáticas como un constructo social y cultural.

Identifying the source of fluvial terrace deposits using XRF scanning and Canonical Discriminant Analysis: A case study of the Chihshang terraces, eastern Taiwan

Science.gov (United States)

Chang, Queenie; Lee, Jian-Cheng; Hunag, Jyh-Jaan; Wei, Kuo-Yen; Chen, Yue-Gau; Byrne, Timothy B.

2018-05-01

The source of fluvial deposits in terraces provides important information about the catchment fluvial processes and landform evolution. In this study, we propose a novel approach that combines high-resolution Itrax-XRF scanning and Canonical Discriminant Analysis (CDA) to identify the source of fine-grained fluvial terrace deposits. We apply this approach to a group of terraces that are located on the hanging wall of the Chihshang Fault in eastern Taiwan with two possible sources, the Coastal Range on the east and the Central Range on the west. Our results of standard samples from the two potential sources show distinct ranges of canonical variables, which provided a better separation ability than individual chemical elements. We then tested the possibility of using this approach by applying it to several samples with known sediment sources and obtain positive results. Applying this same approach to the fine-grained sediments in Chihshang terraces indicates that they are mostly composed of Coastal Range material but also contain some inputs from the Central Range. In two lowest terraces T1 and T2, the fine-grained deposits show significant Central Range component. For terrace T4, the results show less Central Range input and a trend of decreasing Central Range influences up section. The Coastal Range material becomes dominant in the two highest terraces T7 and T10. Sediments in terrace T5 appear to have been potentially altered by post-deposition chemical alteration processes and are not included in the analysis. Our results show that the change in source material in the terraces deposits was relatively gradual rather than the sharp changes suggested by the composition of the gravels and conglomerates. We suggest that this change in sources is related to the change in dominant fluvial processes that controlled by the tectonic activity.

Determination of burial dose in incompletely bleached fluvial samples using single grains of quartz

DEFF Research Database (Denmark)

Thomsen, Kristina Jørkov; Murray, A.S.; Bøtter-Jensen, Lars

2007-01-01

We determine the burial dose in three known-age incompletely bleached fluvial samples using single grains of quartz. Estimation of burial dose in incompletely bleached samples requires that the characteristics of the well-bleached part of the distribution are known in order to distinguish between...... well-bleached and poorly bleached grains. It is especially important to investigate if the uncertainties assigned to individual estimates of dose adequately describe the observed variability in well-bleached dose distributions. We investigate this by quantifying the overdispersion in laboratory-bleached...

Sedimentological reservoir characteristics of the Paleocene fluvial/lacustrine Yabus Sandstone, Melut Basin, Sudan

Science.gov (United States)

Mahgoub, M. I.; Padmanabhan, E.; Abdullatif, O. M.

2016-11-01

Melut Basin in Sudan is regionally linked to the Mesozoic-Cenozoic Central and Western African Rift System (CWARS). The Paleocene Yabus Formation is the main oil producing reservoir in the basin. It is dominated by channel sandstone and shales deposited in fluvial/lacustrine environment during the third phase of rifting in the basin. Different scales of sedimentological heterogeneities influenced reservoir quality and architecture. The cores and well logs analyses revealed seven lithofacies representing fluvial, deltaic and lacustrine depositional environments. The sandstone is medium to coarse-grained, poorly to moderately-sorted and sub-angular to sub-rounded, arkosic-subarkosic to sublitharenite. On the basin scale, the Yabus Formation showed variation in sandstone bodies, thickness, geometry and architecture. On macro-scale, reservoir quality varies vertically and laterally within Yabus Sandstone where it shows progressive fining upward tendencies with different degrees of connectivity. The lower part of the reservoir showed well-connected and amalgamated sandstone bodies, the middle to the upper parts, however, have moderate to low sandstone bodies' connectivity and amalgamation. On micro-scale, sandstone reservoir quality is directly affected by textures and diagenetic changes such as compaction, cementation, alteration, dissolution and kaolinite clays pore fill and coat all have significantly reduced the reservoir porosity and permeability. The estimated porosity in Yabus Formation ranges from 2 to 20% with an average of 12%; while permeability varies from 200 to 500 mD and up to 1 Darcy. The understanding of different scales of sedimentological reservoir heterogeneities might contribute to better reservoir quality prediction, architecture, consequently enhancing development and productivity.

Radiocarbon constraints on the coupled growth of sediment and organic carbon reservoirs in fluvial systems

Science.gov (United States)

Torres, M. A.; Kemeny, P. C.; Fischer, W. W.; Lamb, M. P.

2017-12-01

Vast amounts of sediments are stored transiently in fluvial deposits as they move in rivers from source to sink. The timescale(s) of transient storage have the potential to set the cadence for biogeochemical reactions to occur in river sediments. However, the extent to which storage modulates the chemical composition of river sediments remains unclear. In case of the organic carbon (OC) cycle, transient sediment storage may leave an imprint in the radiocarbon (14C) content of riverine particulate OC (POC), offering a potential tool to trace the coupling of sediment storage and biogeochemical cycling in river systems. We investigated the modern and ancient budgets of sediments and POC in the Efi Haukadalsá River catchment in West Iceland to provide new empirical constraints on the role of sediment storage in the terrestrial OC cycle. This field site is attractive because the basaltic bedrock is free of rock-derived (i.e. "petrogenic") POC such that bulk 14C measurements can be interpreted more directly as constraints on catchment OC storage timescales. Additionally, Lake Haukadalsvatn at the outlet of the river catchment has captured sediment for nearly 13 ka, which offers a complementary record of the evolution of climate-sediment-OC linkages since deglaciation. New 14C measurements show that bulk POC in fine grained fluvial deposits within the Haukadalsá catchment is remarkably old (model ages between 1 and 10 ka). This evidence for "aged" POC in floodplain storage is consistent with previous measurements from Lake Haukadalsvatn, which show that POC is aged in the river system by thousands of years prior to deposition in the lake. Additionally, our estimate of the mean transit time of sediments through the river system matches the millennial-scale reservoir age of riverine POC derived from 14C, which implies a tight coupling between sediment storage and the OC cycle. We interpret the long-term increase in the 14C reservoir age of riverine POC over the last 10 ka

Fluvial depositional environment evolving into deltaic setting with marine influences in the buntsandstein of northern vosges (France)

Science.gov (United States)

Gall, Jean-Claude

The Buntsandstein in the Northern Vosges (France) originates mainly in an inland braidplain fluvial environment which passes in the upper part of the sequence into deltaic milieu in the coastal plain along the border of the sea, with the continental environment finally being drowned with the transgression of the shallow sea. The fluvial sedimentation is characterized by the presence of two facies throughout the Buntsandstein : channel facies and overbank plain facies. The channel facies comprises sandy and conglomeratic deposits forming within active streams by strong currents, whereas the overbank plain facies is built up of silty-clayey sandstones or silt/clay originating in stagnant water in abandoned watercourses, ponds, pools and puddles. The significance of particularly the floodplain sediments is subjected to considerable changes throughout the Buntsandstein sequence. There are all stages of transition between overbank plain deposits being only preserved in ghost-like facies as reworked clasts due to effective secondary removal of primarily occasionally formed suspension fines, and an abundance of autochthonous floodplain sediments in the depositional record resulting from favourable conditions of primary origin and secondary preservation. Reworked ventifacts within fluvial channel sediments testify to subordinate aeolian influences in the alluvial plain, with reasonable reworking, however, having removed all in situ traces of wind activity. Declining aridity of palaeoclimate towards the top is indicated by the appearance of violet horizon palaeosols in the Zone-Limite-Violette and the Couches intermédiaires being accompanied by Bröckelbank carbonate breccias originating from concentration of reworked fragments of pedogenic carbonate nodules. Biogenic traces are in the lower part of the sequence mainly present as Planolites burrows in the finer-grained sediments. Palaeosalinities as revealed from boron contents indicate progressively increasing

Using a Geospatial Model to Relate Fluvial Geomorphology to Macroinvertebrate Habitat in a Prairie River—Part 1: Genus-Level Relationships with Geomorphic Typologies

Directory of Open Access Journals (Sweden)

Anna G. N. Meissner

2016-01-01

Full Text Available Modern river ecosystems undergo constant stress from disturbances such as bank stabilization, channelization, dams, and municipal, agricultural, and industrial water use. As these anthropogenic water requirements persist, more efficient methods of characterizing river reaches are essential. Benthic macroinvertebrates are helpful when evaluating fluvial health, because they are often the first group to react to contaminants that can then be transferred through them to other trophic levels. Hence, the purpose of this research is to use a geospatial model to differentiate instream macroinvertebrate habitats, and determine if the model is a viable method for stream evaluation. Through the use of ArcGIS and digital elevation models, the fluvial geomorphology of the Qu’Appelle River in Saskatchewan (SK was assessed. Four geomorphological characteristics of the river were isolated (sinuosity, slope, fractal dimension, and stream width and clustered through Principle Component Analysis (PCA, yielding sets of river reaches with similar geomorphological characteristics, called typologies. These typologies were mapped to form a geospatial model of the river. Macroinvertebrate data were aligned to the locations of the typologies, revealing several relationships with the fluvial geomorphology. A Kruskal-Wallis analysis and post hoc pairwise multiple comparisons were completed with the macroinvertebrate data to pinpoint significant genera, as related to the geospatial model.

Controles fluviales del Rio Cauca en la región de La Mojana.

OpenAIRE

Posada García, Lilian; Rhenals Garrido, Remberto Luis

2006-01-01

Se realiza un análisis de fotografías aéreas, imágenes de satélite y cartografía de diferentes años que permiten identificar procesos importantes de divagación, erosión y sedimentación de la zona estudiada. La variación con el tiempo de las formas del canal (islas y barras), la aparición de complejos de orillares, madreviejas (canales abandonados y sedimentados), canales abandonados, cambios de curso del canal principal, entre otros procesos muestran la gran dinámica fluvial del sistema....

Dominant mechanisms for the delivery of fine sediment and phosphorus to fluvial networks draining grassland dominated headwater catchments.

Science.gov (United States)

Perks, M T; Owen, G J; Benskin, C McW H; Jonczyk, J; Deasy, C; Burke, S; Reaney, S M; Haygarth, P M

2015-08-01

Recent advances in monitoring technology have enabled high frequency, in-situ measurements of total phosphorus and total reactive phosphorus to be undertaken with high precision, whilst turbidity can provide an excellent surrogate for suspended sediment. Despite these measurements being fundamental to understanding the mechanisms and flow paths that deliver these constituents to river networks, there is a paucity of such data for headwater agricultural catchments. The aim of this paper is to deduce the dominant mechanisms for the delivery of fine sediment and phosphorus to an upland river network in the UK through characterisation of the temporal variability of hydrological fluxes, and associated soluble and particulate concentrations for the period spanning March 2012-February 2013. An assessment of the factors producing constituent hysteresis is undertaken following factor analysis (FA) on a suite of measured environmental variables representing the fluvial and wider catchment conditions prior to, and during catchment-wide hydrological events. Analysis indicates that suspended sediment is delivered to the fluvial system predominantly via rapidly responding pathways driven by event hydrology. However, evidence of complex, figure-of-eight hysteresis is observed following periods of hydrological quiescence, highlighting the importance of preparatory processes. Sediment delivery via a slow moving, probably sub-surface pathway does occur, albeit infrequently and during low magnitude events at the catchment outlet. Phosphorus is revealed to have a distinct hysteretic response to that of suspended sediment, with sub-surface pathways dominating. However, high magnitude events were observed to exhibit threshold-like behaviour, whereby activation and connection of usually disconnected depositional zones to the fluvial networks results in the movement of vast phosphorus fluxes. Multiple pathways are observed for particulate and soluble constituents, highlighting the

Toward the Validation of Depth-Averaged Three Dimensional, Rans Steady-State Simulations of Fluvial Flows at Natural Scale

Science.gov (United States)

Mateo Villanueva, P. A.; Hradisky, M.

2010-12-01

Simulations of fluvial flows are strongly influenced by geometric complexity and overall uncertainty on measured flow variables, including those assumed to be well known boundary conditions. Often, 2D steady-state models are used for computational simulations of flows at the scale of natural rivers. Such models have been successfully incorporated in iRIC (formerly MD_SWMS), one of the widely used quasi-3D CFD solvers to perform studies of environmental flows. iRIC aids in estimating such quantities as surface roughness and shear stress, which, in turn, can be used to estimate sediment transport. However, the computational results are inherently limited in accuracy because of restricting the computations to 2D, or quasi-3D, space, which can affect the values of these predictions. In the present work we perform computer-based simulations of fluvial flows using OpenFOAM, a free, open source fully 3D CFD software package, and compare our results to predictions obtained from iRIC. First, we study the suitability of OpenFOAM as the main CFD solver to analyze fluvial flows and validate our results for two well documented rectangular channel configurations: the first case consists of a large aspect-ratio channel (ratio of depth over width 0.017, ratio of depth over length 0.0019) with a rectangular obstacle mounted at the bottom wall; the second case involves a large aspect-ratio channel (ratio of depth over width 0.1, ratio of depth over length 0.0025) with cubic obstacles mounted at the lower wall (one obstacle) and upper wall (two obstacles). Secondly, we apply our model to simulation or river at natural scale and compare our results to the output obtained from iRIC to quantify the differences in velocity profiles and other flow parameters when comparable solution techniques are used. Steady-state, RANS k-epsilon models are employed for all simulations.

Characterization of a fluvial aquifer at a range of depths and scales: the Triassic St Bees Sandstone Formation, Cumbria, UK

Science.gov (United States)

Medici, Giacomo; West, L. J.; Mountney, N. P.

2018-03-01

Fluvial sedimentary successions represent porous media that host groundwater and geothermal resources. Additionally, they overlie crystalline rocks hosting nuclear waste repositories in rift settings. The permeability characteristics of an arenaceous fluvial succession, the Triassic St Bees Sandstone Formation in England (UK), are described, from core-plug to well-test scale up to 1 km depth. Within such lithified successions, dissolution associated with the circulation of meteoric water results in increased permeability ( K 10-1-100 m/day) to depths of at least 150 m below ground level (BGL) in aquifer systems that are subject to rapid groundwater circulation. Thus, contaminant transport is likely to occur at relatively high rates. In a deeper investigation (> 150 m depth), where the aquifer has not been subjected to rapid groundwater circulation, well-test-scale hydraulic conductivity is lower, decreasing from K 10-2 m/day at 150-400 m BGL to 10-3 m/day down-dip at 1 km BGL, where the pore fluid is hypersaline. Here, pore-scale permeability becomes progressively dominant with increasing lithostatic load. Notably, this work investigates a sandstone aquifer of fluvial origin at investigation depths consistent with highly enthalpy geothermal reservoirs ( 0.7-1.1 km). At such depths, intergranular flow dominates in unfaulted areas with only minor contribution by bedding plane fractures. However, extensional faults represent preferential flow pathways, due to presence of high connective open fractures. Therefore, such faults may (1) drive nuclear waste contaminants towards the highly permeable shallow (< 150 m BGL) zone of the aquifer, and (2) influence fluid recovery in geothermal fields.

Fluvial sediments characterization of Hornád river in its chosen parts (preliminary study

Directory of Open Access Journals (Sweden)

Stela Hanigovská

2008-12-01

Full Text Available Knowledge of main river sedimentary characteristics is very important source of information for next study or potentialcommercial usage of fluvial sediments. In paper is shown characterization of sediment distribution in chosen part of the river Hornád.Three main facial types were studied and described – gravel, sand and clay. Model created in this study shows that Hornád is a riverwith predominant gravel transport. This model also shows a sufficient amount of gravel for commercial use in some parts of the river.

Controls on fluvial metamorphosis during global warming at the Paleocene-Eocene boundary (56 Ma) in Spain: extreme droughts, extreme floods or both?

Science.gov (United States)

Castelltort, Sebastien; Chen, Chen; Guerit, Laure; Foreman, Brady; Paola, Chris; Adatte, Thierry

2017-04-01

How does global warming change the frequency and intensity of extreme weather events? The response to this question is partly preserved in the geological record. 56 Ma ago, global temperatures increased during the Paleocene-Eocene Thermal Maximum (PETM), leading to a major biotic turnover, but how this event affected the nature of extreme events remains unknown. On several continents, fluvial systems with sinuous channels within fine-grained floodplains suddenly transformed at the P-E boundary into apparently coarser-grained braid plains with frequent lateral migrations, washing their muddy floodplains to the seas. This landscape transformation has been related to aridification and intensification of precipitation allowing transport of coarser material as a result of P-E global warming, with important implications for predicting the consequences of current global change. Here we test this hypothesis by quantifying the magnitude of grain size change and flow depth at a representative P-E locality in Northern Spain. We find that the size of pebbles in transport and flow depth remained similar to, or even smaller than, pre-PETM conditions. This suggests that, if more seasonal and extreme precipitation occurred, they are not necessarily borne out in the predicted deeper flow depths and coarser grain sizes, but rather trigger a shift to multiple active channels. However, an alternative or complementary explanation may rest in pollen data found in coeval marine records and which document a dramatic vegetation shift from permanent conifer forests prior to the crisis into periodic vegetation in brief periods of rain during the hyperthermal episode. Such change induced by long periods of intense droughts, could have enhanced erodibility of channel banks by decreasing root-controlled cohesion of fine-grained floodplains and interfluves, promoting their lateral mobility and the observed fluvial metamorphosis. Thus, although water is regarded as the main agent sculpting

Produção científica e redes de colaboração dos docentes vinculados aos programas de pós-graduação em Economia no Brasil

Directory of Open Access Journals (Sweden)

Eduardo A. Haddad

Full Text Available Resumo Este artigo apresenta os resultados de um estudo sobre as potencialidades da utilização dos dados curriculares derivados das informações da Plataforma Lattes como ferramentas para avaliação do desempenho científico de pesquisadores. Um novo indicador, denominado "Índice Multidimensional de Desempenho Científico" (IMDC, é proposto considerando um amplo conjunto de indicadores bibliométricos que buscam captar diferentes formas da produção acadêmica dos atuais pesquisadores vinculados à pós-graduação em Economia no Brasil. Os resultados permitem evidenciar uma tipologia de pesquisadores considerando suas diferentes estratégias de atuação. Economistas com maior impacto na profissão adotam uma estratégia caracterizada por um equilíbrio entre qualidade, quantidade e colaboração científica.

Post Waterflood CO2 Miscible Flood in Light Oil, Fluvial-Dominated Deltaic Reservoir, Class I

Energy Technology Data Exchange (ETDEWEB)

Bou-Mikael, Sami

2002-02-05

This report demonstrates the effectiveness of the CO2 miscible process in Fluvial Dominated Deltaic reservoirs. It also evaluated the use of horizontal CO2 injection wells to improve the overall sweep efficiency. A database of FDD reservoirs for the gulf coast region was developed by LSU, using a screening model developed by Texaco Research Center in Houston. The results of the information gained in this project is disseminated throughout the oil industry via a series of SPE papers and industry open forums.

Fluvial fluxes of natural radium isotopes and dissolved barium for Ubatuba embayments, Sao Paulo

International Nuclear Information System (INIS)

Sousa, Keila Cristina Pinheiro Marchini de

2008-01-01

Radium isotopes are among the most important isotopes in the environment from both radioprotection and geo-hydrological points of view. They are also a powerful tool for studying geohydrological processes and have been used intensively as tracers of groundwater sources that discharge into the coastal ocean.The complex exchange of fluvial, subsurface and seawater within a coastal area directly affects global biogeochemical cycles. Environmental scientists have few tools to accurately quantify such processes and must therefore rely on various tracer techniques. Radium isotopes have been frequently applied as tracers of submarine groundwater discharge (SGD). The unique radium signature of SGD is acquired within the subterranean estuary, a mixing zone between fresh groundwater and seawater in coastal aquifers. In this study we determined the fluvial fluxes of the radium isotopes and dissolved barium for Ubatuba embayments, northernmost part of Sao Paulo Bight. The research work was carried out from April/ 2007 to August/ 2007 and covered 17 small rivers sources that belong to the major surface draining system of such coastal area. During this period of investigation, groundwater samples were also collected from 10 sources available in this coastal region. Activity concentrations of 223 Ra in riverine waters discharging to Ubatuba and Caraguatatuba embayments varied from -1 to 335 mBq 1000L -1 (in Cocanha River), while 224 Ra concentrations ranged from 17 mBq 100L -1 to 7270 mBq 100L -1 . Activity concentrations up to 1424 mBq 100L -1 were observed for 226 Ra in riverine waters, while 228 Ra concentrations varied from 1412 mBq 100L -1 to 4058 mBq 100L -1 . Groundwater activity concentrations of 223 Ra varied from 1 mBq 100L -1 to 126 mBq 100L -1 , while 224 Ra ranged from 118 mBq 100L -1 to 3701 mBq 100L -1 . 223 Ra/ 224 Ra activity ratios up to 0.7x10 -1 and 0.2 were observed in riverine and groundwater, respectively. For 226 Ra groundwater activity concentrations

Year-round variations in the fluvial transport load of particulate 137Cs in a forested catchment affected by the Fukushima Daiichi Nuclear Power Plant accident

International Nuclear Information System (INIS)

Takeshi Matsunaga; Takahiro Nakanishi; Mariko Atarashi-Andoh; Erina Takeuchi; Kotomi Muto; Katsunori Tsuduki; Syusaku Nishimura; Jun Koarashi; Shigeyoshi Otosaka; Tsutomu Sato

2016-01-01

Particulate 137 Cs was collected from stream water for 2 years to assess the long-term trend of 137 Cs discharge from a forest after the Fukushima Nuclear Power Plant accident. A seasonal increase in the fluvial transport load of particulate 137 Cs in suspended solids (SS) was observed in July-October when rainfall was abundant. The 137 Cs load was controlled by the SS load. This control was attributed to cesium affinity for phyllosilicate clay minerals as verified by the low extractability of particulate 137 Cs. These findings indicate the fluvial particulate 137 Cs load is significantly related to the climate and geomorphological features of Japan. (author)

Human impacts on fluvial systems - A small-catchment case study

Science.gov (United States)

Pöppl, Ronald E.; Glade, Thomas; Keiler, Margreth

2010-05-01

Regulations of nearly two-thirds of the rivers worldwide have considerable influences on fluvial systems. In Austria, nearly any river (or) catchment is affected by humans, e.g. due to changing land-use conditions and river engineering structures. Recent studies of human impacts on rivers show that morphologic channel changes play a major role regarding channelization and leveeing, land-use conversions, dams, mining, urbanization and alterations of natural habitats (ecomorphology). Thus 'natural (fluvial) systems' are scarce and humans are almost always inseparably interwoven with them playing a major role in altering them coincidentally. The main objective of this study is to identify human effects (i.e. different land use conditions and river engineering structures) on river bed sediment composition and to delineate its possible implications for limnic habitats. The study area watersheds of the 'Fugnitz' River (~ 140km²) and the 'Kaja' River (~ 20km²) are located in the Eastern part of the Bohemian Massif in Austria (Europe) and drain into the 'Thaya' River which is the border river to the Czech Republic in the north of Lower Austria. Furthermore the 'Thaya' River is eponymous for the local National Park 'Nationalpark Thayatal'. In order to survey river bed sediment composition and river engineering structures facies mapping techniques, i.e. river bed surface mapping and ecomorphological mapping have been applied. Additionally aerial photograph and airborne laserscan interpretation has been used to create land use maps. These maps have been integrated to a numerical DEM-based spatial model in order to get an impression of the variability of sediment input rates to the river system. It is hypothesized that this variability is primarily caused by different land use conditions. Finally river bed sites affected by river engineering structures have been probed and grain size distributions have been analyzed. With these data sedimentological and ecological

What can we learn from fluvial incision in high mountains?

Science.gov (United States)

Fuchs, Margret; Gloaguen, Richard; Krbetschek, Matthias

2013-04-01

High and actively deforming mountain ranges attract the attention of geoscientists as they provide natural laboratories of fast evolving process-response systems. Tectonic compressional settings, often linked to perpendicular extension, control the topographic growth and hence, erosion, transport pathways and sedimentation. High altitude differences within short horizontal distances promote material re-organisation and high rates of surface processes. Furthermore, high mountains constitute orographic barriers that affect atmospheric circulations as well as host different climate regimes similar to those of widely separated latitudinal belts. Both cause a high sensitivity of surface processes to changes in climatic conditions. However, feedbacks between climatic and tectonic forcing are complex. Additionally, the dominance of one or the other varies in space and also over time, inheriting various traces of the paleo-morphodynamic conditions to the subsequent process regimes. To unravel the forces driving the evolution of relief in active mountains, numerous studies employ the drainage network of the corresponding mountains as a proxy of landscape evolution. Especially the rates of river incision provide a powerful tool to characterize the surface response and infer causes behind it. Several parameters of river incision are available to describe the fluvial incision at individual sites (e.g. terrace incision rates), along the river course (e.g. longitudinal river profiles, Hack index) and in its perpendicular dimension (e.g. valley cross sections, valley shape ratios). But they require careful interpretation. They are sensitive to both, climatic and tectonic forcing. Therefore, the synopsis of such indices for fluvial incision is essential to evaluate the role of climatic versus tectonic forcing. Here, we use the Panj river system, the major river draining the Pamir mountains of Central Asia, as an example. The Panj experiences high altitude changes of more than 4000

Significance of Thermal Fluvial Incision and Bedrock Transfer due to Ice Advection on Greenland Ice Sheet Topography

Science.gov (United States)

Crozier, J. A.; Karlstrom, L.; Yang, K.

2017-12-01

Ice sheet surface topography reflects a complicated combination of processes that act directly upon the surface and that are products of ice advection. Using recently-available high resolution ice velocity, imagery, ice surface elevation, and bedrock elevation data sets, we seek to determine the domain of significance of two important processes - thermal fluvial incision and transfer of bedrock topography through the ice sheet - on controlling surface topography in the ablation zone. Evaluating such controls is important for understanding how melting of the GIS surface during the melt season may be directly imprinted in topography through supraglacial drainage networks, and indirectly imprinted through its contribution to basal sliding that affects bedrock transfer. We use methods developed by (Karlstrom and Yang, 2016) to identify supraglacial stream networks on the GIS, and use high resolution surface digital elevation models as well as gridded ice velocity and melt rate models to quantify surface processes. We implement a numerically efficient Fourier domain bedrock transfer function (Gudmundsson, 2003) to predict surface topography due to ice advection over bedrock topography obtained from radar. Despite a number of simplifying assumptions, the bedrock transfer function predicts the observed ice sheet surface in most regions of the GIS with ˜90% accuracy, regardless of the presence or absence of supraglacial drainage networks. This supports the hypothesis that bedrock is the most significant driver of ice surface topography on wavelengths similar to ice thickness. Ice surface topographic asymmetry on the GIS is common, with slopes in the direction of ice flow steeper than those faced opposite to ice flow, consistent with bedrock transfer theory. At smaller wavelengths, topography consistent with fluvial erosion by surface hydrologic features is evident. We quantify the effect of ice advection versus fluvial thermal erosion on supraglacial longitudinal stream

Del turismo “cultural” al “rural”: un caso de la Pampa bonaerense (Argentina

Directory of Open Access Journals (Sweden)

Cecilia Pérez Winter

2017-07-01

Full Text Available En este artículo se examina el proceso de turistificación del partido de Exaltación de la Cruz (Argentina, promovido por el gobierno municipal. El interés es analizar cómo los procesos locales y globales inciden en la configuración de modalidades turísticas, a partir de la selección y mercantilización de elementos “naturales” (rurales e históricos-culturales. La investigación aquí expuesta se construyó a través del trabajo de campo realizado en el periodo 2011-2015 en la ciudad cabecera, Capilla del Señor. Allí se observó que los criterios establecidos en los procesos de patrimonialización fueron implementados para construir, en una primera etapa, un turismo “cultural” que permitió consolidar determinados discursos y representaciones de la ciudad. A su vez, se constata que la práctica turística utiliza pautas más flexibles, al adecuarse a las demandas del mercado turístico global, llevando a incluir, en una segunda etapa, elementos vinculados con la ruralidad del partido, los cuales eran desestimados anteriormente.

Rapid fluvial aggradation in response to climate change in northwestern Argentina

Science.gov (United States)

Wickert, Andrew; Schildgen, Taylor; Strecker, Manfred

2015-04-01

River channels near the edge of the northwestern Argentine Andes are rapidly aggrading at present, with preliminary estimates suggesting rates of ~20 cm yr-1. This mirrors cycles of extensive aggradation over the past 100,000 years that formed pronounced fill terraces along regional valley networks and record periods in which in which climate-driven sediment supply overcame uplift-driven river incision (Robinson et al, 2005). Here we use the new SedFlow model (Heimann et al., 2014) to help us understand the causes and spread of aggradation across these basins in the modern system, with the additional eventual goal to better interpret the geologic record. We provide field-derived grain-size distributions, field-measured and remotely-sensed channel widths and valley slopes, and a variety of possible sediment source locations and amounts as inputs to SedFlow, which routes sediment through the fluvial channel network to produce time-evolving predictions of aggradation and incision. We compare these predictions against changes in topography measured by IceSAT (Zwally et al., 2014) and field surveys. We initially test the system response to a series of isolated sediment inputs to observe interactions between tributary systems and the mainstem river. Recent observations indicate that debris-flow induced landslides are important contributors to aggradation in these rivers (Cencetti and Rivelli, 2011). These and other sediment production and transport processes are likely driven by variations in the El Niño Southern Oscillation (ENSO) (Bookhagen and Strecker, 2009). Therefore, we then run SedFlow with sediment inputs distributed across the landscape based on locations where ENSO influences may trigger enhanced landsliding. These model experiments help us towards our end goal of providing a more quantitative basis to interpret field observations of landscape response to changing patterns of precipitation. References: Bookhagen, B. and Strecker, M.: Amazonia: Landscape and

Fluvial sediment supply to a mega-delta reduced by shifting tropical-cyclone activity.

Science.gov (United States)

Darby, Stephen E; Hackney, Christopher R; Leyland, Julian; Kummu, Matti; Lauri, Hannu; Parsons, Daniel R; Best, James L; Nicholas, Andrew P; Aalto, Rolf

2016-11-10

The world's rivers deliver 19 billion tonnes of sediment to the coastal zone annually, with a considerable fraction being sequestered in large deltas, home to over 500 million people. Most (more than 70 per cent) large deltas are under threat from a combination of rising sea levels, ground surface subsidence and anthropogenic sediment trapping, and a sustainable supply of fluvial sediment is therefore critical to prevent deltas being 'drowned' by rising relative sea levels. Here we combine suspended sediment load data from the Mekong River with hydrological model simulations to isolate the role of tropical cyclones in transmitting suspended sediment to one of the world's great deltas. We demonstrate that spatial variations in the Mekong's suspended sediment load are correlated (r = 0.765, P sediment load reaching the delta is delivered by runoff generated by rainfall associated with tropical cyclones. Furthermore, we estimate that the suspended load to the delta has declined by 52.6 ± 10.2 megatonnes over recent years (1981-2005), of which 33.0 ± 7.1 megatonnes is due to a shift in tropical-cyclone climatology. Consequently, tropical cyclones have a key role in controlling the magnitude of, and variability in, transmission of suspended sediment to the coast. It is likely that anthropogenic sediment trapping in upstream reservoirs is a dominant factor in explaining past, and anticipating future, declines in suspended sediment loads reaching the world's major deltas. However, our study shows that changes in tropical-cyclone climatology affect trends in fluvial suspended sediment loads and thus are also key to fully assessing the risk posed to vulnerable coastal systems.

Investigating the use of the dual-polarized and large incident angle of SAR data for mapping the fluvial and aeolian deposits

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Ahmed Gaber

2017-12-01

Full Text Available Mapping the spatial distributions of the fluvial deposits in terms of particles size as well as imaging the near-surface features along the non-vegetated aeolian sand-sheets, provides valuable geological information. Thus this work aims at investigating the contribution of the dual-polarization SAR data in classifying and mapping the surface sediments as well as investigating the effect of the radar incident-angle on improving the images of the hidden features under the desert sand cover. For mapping the fluvial deposits, the covariance matrix ([C2] using four dual-polarized ALOS/PALSAR-1 scenes cover the Wadi El Matulla, East Qena, Egypt were generated. This [C2] matrix was used to generate a supervised classification map with three main classes (gravel, gravel/sand and sand. The polarimetric scattering response, spectral reflectance and temperatures brightness of these 3 classes were extracted. However for the aeolian deposits investigation, two Radarsat-1 and three full-polarimetric ALOS/PALSAR-1 images, which cover the northwestern sandy part of Sinai, Egypt were calibrated, filtered, geocoded and ingested in a GIS database to image the near-surface features. The fluvial mapping results show that the values of the radar backscattered coefficient (σ° and the degree of randomness of the obtained three classes are increasing respectively by increasing their grain size. Moreover, the large incident angle (θi = 39.7 of the Radarsat-1 image has revealed a meandering buried stream under the sand sheet of the northwestern part of Sinai. Such buried stream does not appear in the other optical, SRTM and SAR dataset. The main reason is the enhanced contrast between the low backscattered return from the revealed meandering stream and the surroundings as a result of the increased backscattering intensity, which is related to the relatively large incident angle along the undulated surface of the study area. All archaeological

METODOLOGÍA PARA UN A CARTOGRAFÍA DE VULNERABILIDAD DEL TERRITORIO FRENTE AL RIESGO DE INUNDACIÓN RELACIONADO CON LOS SISTEMAS DE SOCORRO Y ASISTENCIA. APLICACIÓN AL ÁREA INUNDABLE DEL BAJO GUADALHORCE (2016

Directory of Open Access Journals (Sweden)

Juan Francisco Sortino Barrionuevo

2017-01-01

Full Text Available El objetivo principal de esta comunicación es desarrollar una cartografía de evaluación de vulnerabilidad de los elementos expuesto frente al peligro de inundación, en concreto lo referente a los sistemas de socorro y asistencia con los que se cuenta, para que todos los organismos y entidades competente puedan contar con esta herramienta para la toma de decisiones y el desarrollo de sus Plane s de Actuación de Ámbito Local. La metodología de trabajo se basa en un análisis de redes que permite elaborar mapas de isócrona s de tiempo s de respuestas, para los diferentes agentes implicados en las labores de socorro y asistencia, bajo dos escenarios (sin episodios de inundación y con episodios de inundación, y establece una comparativa entre las diferentes situaciones. Los resultados obt enidos son una serie de cartografías vinculadas al análisis de los sistemas de socorro y asistencia que permiten analizar su eficacia durante la catástrofe. Los documentos cartográficos son útiles como herramienta de apoyo a la decisión en la fase de gesti ón de emergencias, y permiten sugerencias de mejora en la gestión del riesgo de inundación, a través del tratamiento aplicado de diferentes aspectos vinculados a la vulnerabilidad

Efectos del material particulado (PM) sobre la salud y el medioambiente

Science.gov (United States)

El tamaño de las partículas se encuentra directamente vinculado con el potencial para provocar problemas de salud. La exposición a estas partículas puede afectar tanto a los pulmones como al corazón. También afectan el medioambiente.

Zeroing of the TL signal of sediment undergoing fluvial transportation: a laboratory experiment

International Nuclear Information System (INIS)

Gemmell, A.M.D.

1985-01-01

Rates of bleaching of suspended sediment undergoing fluvial transportation in a closed laboratory flume beneath a u.v. lamp were measured. It was found that the speed of zeroing is inversely related to the speed of flow. This is attributed to the effects of flow turbulence in keeping sediment in suspension, thereby reducing the penetration of u.v. radiation, and to the re-entrainment of partially bleached or unbleached sediment into the flow. The time required to reduce TL to the residual levels indicated by sunlamp bleaching experiments are such as to suggest that at faster flows sediments in a heavily-laden stream may never attain a complete bleaching. (author)

Evolution of Subaerial Coastal Fluvial Delta Island Topography into Multiple Stable States Under Influence of Vegetation and Stochastic Hydrology

Science.gov (United States)

Moffett, K. B.; Smith, B. C.; O'Connor, M.; Mohrig, D. C.

2014-12-01

Coastal fluvial delta morphodynamics are prominently controlled by external fluvial sediment and water supplies; however, internal sediment-water-vegetation feedbacks are now being proposed as potentially equally significant in organizing and maintaining the progradation and aggradation of such systems. The time scales of fluvial and climate influences on these feedbacks, and of their responses, are also open questions. Historical remote sensing study of the Wax Lake Delta model system (Louisiana, USA) revealed trends in the evolution of the subaerial island surfaces from a non-systematic arrangement of elevations to a discrete set of levees and intra-island platforms with distinct vegetation types, designated as high marsh, low marsh, and mudflat habitat. We propose that this elevation zonation is consistent with multiple stable state theory, e.g. as applied to tidal salt marsh systems but not previously to deltas. According to zonally-distributed sediment core analyses, differentiation of island elevations was not due to organic matter accumulation as in salt marshes, but rather by differential mineral sediment accumulation with some organic contributions. Mineral sediment accumulation rates suggested that elevation growth was accelerating or holding steady over time, at least to date in this young delta, in contrast to theory suggesting rates should slow as elevation increases above mean water level. Hydrological analysis of island flooding suggested a prominent role of stochastic local storm events in raising island water levels and supplying mineral sediment to the subaerial island surfaces at short time scales; over longer time scales, the relative influences of local storms and inland/regional floods on the coupled sediment-water-vegetation system of the subaerial delta island surfaces remain the subject of ongoing study. These results help provide an empirical foundation for the next generation of coupled sediment-water-vegetation modeling and theory.

Distinguishing regional and local sources of pollution by trace metals and magnetic particles in fluvial sediments of the Morava River, Czech Republic

Czech Academy of Sciences Publication Activity Database

Nováková, Tereza; Matys Grygar, Tomáš; Bábek, O.; Famera, M.; Mihaljevič, M.; Strnad, L.

2013-01-01

Roč. 13, č. 2 (2013), s. 460-473 ISSN 1439-0108 Institutional support: RVO:61388980 Keywords : Enrichment factors * Fluvial sediments * Heavy metals * Local sources * Normalisation * Regional contamination Subject RIV: DD - Geochemistry Impact factor: 2.107, year: 2013

Fluvial Export Variability Of Limiting Nutrient Fluxes To The Indian Ocean From Kelani, Kalu and Gin Rivers Of Sri Lanka

Science.gov (United States)

Ranasinghage, P. N.; Silva, A. N.; Vlahos, P.

2016-12-01

Inorganic `reactive' nutrients hold the highest importance in understanding the role of limiting nutrients in the ocean since they facilitate marine biological productivity and carbon sequestration that would eventually pave the way to regulate the biogeochemical climate feedbacks. Significant inorganic fractions are expected to be exported episodically to the ocean from fluvial fluxes though this is poorly understood. Thus, no considerable amounts of published work regarding the fluxes from Sri Lankan freshwater streams have ever been recorded. A study was carried out to quantify the contribution of Kelani, Kalu and Gin Rivers, three major rivers in the wet zone of Sri Lanka, in exporting major limiting nutrient fluxes to the Indian Ocean; to understand the significance of their variability patterns with rainfall and understand differences in their inputs. The study was conducted during the summer monsoonal period from late August to early November at two-three week intervals where water samples were collected for ammonia, nitrite, nitrate, orthophosphate, silica, sulfate and iron analysis by Colorimetric Spectroscopy. Discharge and rainfall data were retrieved from the Department of Irrigation and Department of Meteorology, Sri Lanka respectively. According to Two Way ANOVA, none of the individual fluxes showed significant differences (p>0.1) both in their temporal and spatial variability suggesting that studied rivers respond similarly in fluvial transportation owing to the similar rainfall intensities observed during the study period in the wet zone. Linear Regression Analysis indicates that only PO43- (p<0.01), SO42- (p<0.01) and NO2-(p<0.01 for Kelani and Kalu; 0.0.1Key words; nutrients, fluvial, fluxes, Redfield ratios

Trends in publications in fluvial geomorphology over two decades: A truly new era in the discipline owing to recent technological revolution?

Science.gov (United States)

Piégay, Hervé; Kondolf, G. Mathias; Minear, J. Toby; Vaudor, Lise

2015-01-01

Trends in the field of fluvial geomorphology have been reviewed by a number of authors, who have emphasized the dramatic change occuring in the field in the last two decades of the twentieth century, largely as a result of technological advances. Nevertheless, no prior authors have systematically compiled data on publications in fluvial geomorphology over a long period and statistically analyzed the resulting data set. In this contribution we present a quantitative analysis of fluvial geomorphology papers published in the twenty-two-year period 1987–2009 in five journals of the discipline with a more specific focus on Geomorphology and Earth Surface Processes and Landforms (ESPL), identifying authorships, geographic origin of authors, and spatial and temporal scales covered. We also documented the tools employed, demonstrating the transformation of the field with the emergence of new tools over this period, and conducted a cluster to highlight links between tools and a set of factors (country of author's origin, journals, time, and spatial and temporal scales). Of the 1717 papers published in the five journals during this period, the results showed an increased diversity in the nationality of the first author, mainly when dealing with present time scale, and channel feature. Our data show a significant change in methods used in the field as a result of the increase in data availability and new sources of information from remote sensing (ground, airborne and, satellite). Clearly, a new era in knowledge production is observed since 2000, showing the emergence of a second period of active quantification and an internationalization of the fields.

Factores psicosociales y sociodemográficos vinculados al uso de sustancias psicoactivas en mujeres durante el embarazo. Una revisión narrativa

Directory of Open Access Journals (Sweden)

Lourdes María López-Granados

2017-12-01

Full Text Available Introducción: el consumo de sustancias durante el embarazo, sus efectos y consecuencias son un problema social y de salud pública grave y poco visible. Debido a los riesgos y consecuencias, se vuelve importante visibilizar los factores de riesgo del consumo de drogas en este grupo poblacional. Objetivo: identificar factores psicosociales y sociodemográficos del consumo de drogas lícitas e ilícitas en mujeres durante el embarazo. Método: se realizó una búsqueda de artículos de investigación, publicados entre 2010 y 2016, que trataran sobre estos factores en relación con el uso de drogas legales e ilegales durante el embarazo. Resultados: se encontraron 86 artículos, de los cuales se eliminaron los relacionados con efectos y consecuencias médicas y los realizados en animales. Después de la depuración, se concentraron 30 artículos, en los que se identificaron factores como edad, condiciones educativas, familiares, sociales, económicas, características del embarazo y antecedentes del mismo, así como la autopercepción de vulnerabilidad y la actitud favorable hacia el consumo de sustancias durante la gestación. Conclusiones y discusión: es necesario dedicar más esfuerzo al conocimiento de esta problemática y direccionar la búsqueda de raíces sociales complejas, sobre todo en el embarazo de adolescentes y otras poblaciones vulnerables.

Revitalizing a mature oil play: Strategies for finding and producing unrecovered oil in frio fluvial-deltaic sandstone reservoirs at South Texas. Annual report, October 1994--October 1995

Energy Technology Data Exchange (ETDEWEB)

Holtz, M.; Knox, P.; McRae, L. [and others

1996-02-01

The Frio Fluvial-Deltaic Sandstone oil play of South Texas has produced nearly 1 billion barrels of oil, yet it still contains about 1.6 billion barrels of unrecovered mobile oil and nearly the same amount of residual oil resources. Interwell-scale geologic facise models of Frio Fluvial-deltaic reservoirs are being combined with engineering assessments and geophysical evaluations in order to determine the controls that these characteristics exert on the location and volume or unrecovered mobile and residual oil. Progress in the third year centered on technology transfer. An overview of project tasks is presented.

Análisis del capital humano proveedor de la asistencia técnica pecuaria en Sinaloa

OpenAIRE

Venancio Cuevas Reyes; Julio Baca del Moral; Fernando Cervantes Escoto; Jorge Aguilar Ávila; José Antonio Espinosa García

2014-01-01

El objetivo de este artículo es analizar al agente proveedor de la asistencia técnica pecuaria en Sinaloa, a través de variables asociadas al capital humano, para identificar factores críticos y hacer propuestas para mejorar este servicio. Para examinar variables categóricas se utilizó muestreo estratificado, análisis de componentes principales y la prueba ji-cuadrada. Para caracterizar al técnico pecuario se identificaron cinco componentes vinculados con los atributos, habilidades, conocimie...

Transiciones en contexto: hallazgos vinculados a migración rural-urbana y enfermedades no transmisibles en Perú Transitions in context: findings related to rural-to-urban migration and chronic non-communicable diseases in Peru

Directory of Open Access Journals (Sweden)

J. Jaime Miranda

2012-09-01

Full Text Available El presente artículo busca describir, en contexto, los distintos procesos de cambio por el que transcurren, en la actualidad, nuestras sociedades y poblaciones a fin de comprender mejor la emergencia de las enfermedades crónicas no transmisibles en países de ingresos medios y bajos. Se describen aquellos factores relevantes para contextos específicos como el Perú, entre ellos migración interna, urbanización y los perfiles de adversidad en etapas tempranas de la vida, todos vinculados con enfermedades crónicas no transmisibles, incluyendo el sobrepeso y la obesidad. Se describe el modelo de “capacidad y carga”, el cual considera al riesgo de adquirir una enfermedad crónica no transmisible en la etapa adulta como una función de dos rasgos genéticos: capacidad metabólica y carga metabólica. Se presenta también la contribución de la migración rural-urbana a esta problemática en nuestro medio. Finalmente, se mencionan los retos pendientes en este tema para la salud pública del PerúIn order to better understand the emergence of chronic non-communicable diseases in low- and middle-income countries this article seeks to present, in context, different transitional processes which societies and populations are currently undergoing. Relevant factors for specific contexts such as Peru are described, including internal migration, urbanization and profiles of adversity in early life, all of them linked to chronic non-communicable diseases, including obesity and overweight. The capacity-load model, which considers chronic disease risk in adulthood as a function of two generic traits, metabolic capacity and metabolic load, is described. The contribution of rural-to-urban migration to this problem is also presented. Finally, these topics are framed within pending challenges for public health in Peru

Contrasting vulnerability of drained tropical and high-latitude peatlands to fluvial loss of stored carbon

Science.gov (United States)

Evans, Chris D.; Page, Susan E.; Jones, Tim; Moore, Sam; Gauci, Vincent; Laiho, Raija; Hruška, Jakub; Allott, Tim E. H.; Billett, Michael F.; Tipping, Ed; Freeman, Chris; Garnett, Mark H.

2014-11-01

Carbon sequestration and storage in peatlands rely on consistently high water tables. Anthropogenic pressures including drainage, burning, land conversion for agriculture, timber, and biofuel production, cause loss of pressures including drainage, burning, land conversion for agriculture, timber, and biofuel production, cause loss of peat-forming vegetation and exposure of previously anaerobic peat to aerobic decomposition. This can shift peatlands from net CO2 sinks to large CO2 sources, releasing carbon held for millennia. Peatlands also export significant quantities of carbon via fluvial pathways, mainly as dissolved organic carbon (DOC). We analyzed radiocarbon (14C) levels of DOC in drainage water from multiple peatlands in Europe and Southeast Asia, to infer differences in the age of carbon lost from intact and drained systems. In most cases, drainage led to increased release of older carbon from the peat profile but with marked differences related to peat type. Very low DOC-14C levels in runoff from drained tropical peatlands indicate loss of very old (centuries to millennia) stored peat carbon. High-latitude peatlands appear more resilient to drainage; 14C measurements from UK blanket bogs suggest that exported DOC remains young (use changes in the tropics. Data from the UK Peak District, an area where air pollution and intensive land management have triggered Sphagnum loss and peat erosion, suggest that additional anthropogenic pressures may trigger fluvial loss of much older (>500 year) carbon in high-latitude systems. Rewetting at least partially offsets drainage effects on DOC age.

Asociación entre los niveles de estrés y depresión y la adhesión al tratamiento en personas seropositivas al VIH en Hermosillo, México Association between stress and depression levels and treatment adherence among HIV-positive individuals in Hermosillo, México

Directory of Open Access Journals (Sweden)

Julio Alfonso Piña López

2008-06-01

Full Text Available OBJETIVOS: Evaluar la asociación entre las variables relacionadas con el estrés, los motivos y la depresión en personas seropositivas al VIH y la adhesión al tratamiento, y analizar su consistencia según un modelo psicológico teórico. MÉTODOS: Estudio transversal con la participación de 25 mujeres y 39 hombres seropositivos al VIH atendidos en el Centro Ambulatorio para la Prevención y Atención a VIH/Sida e Infecciones de Transmisión Sexual, en Hermosillo, Sonora, México. Se exploraron las variables psicológicas y el grado de adhesión al tratamiento, las situaciones vinculadas con el estrés y el grado de depresión. Se elaboraron índices de las variables de interés asociadas con el estrés, los motivos y la depresión. La asociación entre las variables se determinó mediante regresión múltiple. RESULTADOS: En el mes previo al estudio, 65,6% de los 64 participantes informó haber seguido fielmente el tratamiento indicado, mientras 34,4% incumplieron el tratamiento en alguna medida (χ2 = 6,250; P = 0,012. Según el análisis de regresión se encontró que solamente la combinación de niveles intermedios de estrés vinculado con la tolerancia a la ambigüedad y niveles bajos de depresión presentó una asociación significativa (F [3,58] = 3,298; P = 0,027 con la adhesión al tratamiento; la combinación de ambas variables explicó 38,2% de la varianza total encontrada. CONCLUSIONES: La combinación de los niveles de estrés vinculado con la tolerancia a la ambigüedad y de depresión podría emplearse como factor de predicción del fiel cumplimiento de las indicaciones médicas prescritas. Se deben tener en cuenta estos resultados al diseñar intervenciones y programas dirigidos a promover la adhesión al tratamiento en personas seropositivas al VIH.OBJECTIVES: To evaluate the association between variables related to stress, reasons, and depression, and adherence to treatment in HIV-positive individuals, and to analyze the

Multi-residues analysis of pre-emergence herbicides in fluvial sediments: application to the mid-Garonne River.

Science.gov (United States)

Devault, Damien A; Merlina, Georges; Lim, Puy; Probst, Jean-Luc; Pinelli, Eric

2007-09-01

Contamination of man and ecosystems by pesticides has become a major environmental concern. Whereas many studies exist on contamination from agriculture, the effects of urban sources are usually omitted. Fluvial sediment is a complex matrix of pollutants but little is known of its recent herbicide content. This study proposes a method for a fast and reliable analysis of herbicides by employing the accelerated solvent extractor (ASE). The aim of the study is to show the impact of a major town (Toulouse) on the herbicide content in the river. In this study, three herbicide families (i.e.s-triazine, substituted ureas and anilides) were analysed in fluvial sediment fractions at 11 sampling sites along the mid-Garonne River and its tributaries. River water contamination by herbicides is minor, except for at three sites located in urban areas. Among the herbicidal families studied, urban and suburban areas are distinguished from rural areas and were found to be the most contaminated sites during the study period, a winter low-water event. The herbicide content of the coarse sediment fractions is about one third of that found in the fine fractions and usually ignored. The distribution of pesticide concentrations across the whole range of particle sizes was investigated to clarify the role of plant remains on the significant accumulation in the coarse fractions.

Modelamiento geoestadístico de los depósitos fluviales de la zona c-formación mugrosa en el área la Cira-Este del Campo La Cira

OpenAIRE

Rojas Suárez, César Augusto

2011-01-01

Mediante algoritmos geoestadísticos se realizo el modelo tridimensional de los yacimientos fluviales de la Zona-C de la Formación Mugrosa en el área Cira-Este del Campo La Cira. Este modelo permitió calcular el aceite original en sitio e identificar las reservas que aun no han sido drenadas en el yacimiento. / Abstract. Geostatistical algorithms were used for making the three-dimensional model for the fluvial deposits of Zona-C of Mugrosa Formation in the Cira-Este area of the Cira Field. Thi...

Changing fluvial styles in volcaniclastic successions: A cretaceous example from the Cerro Barcino Formation, Patagonia

Science.gov (United States)

Umazano, A. Martín; Krause, J. Marcelo; Bellosi, Eduardo S.; Perez, Mariano; Visconti, Graciela; Melchor, Ricardo N.

2017-08-01

The Cretaceous Puesto La Paloma (PLPM) and Cerro Castaño (CCM) members (Cerro Barcino Formation, Chubut Group) are pyroclastic-rich, alluvial successions deposited in the Somuncurá-Cañadón Asfalto Basin during sag and endorheic conditions. The PLPM comprises sheet-like tuffaceous sandstone strata, whereas the overlying CCM includes sheet-to ribbon-channel sandstone bodies intercalated within tuffaceous and fine-grained sediments. In this context, the goals of this contribution were: i) to make a detailed documentation of the contrasting sedimentary palaeonvironments; and ii) to infer the allocyclic controls that governed the sedimentation of both units. The study area is located in the western sector of the basin, where six localities, which were studied. Six facies associations were defined including ash-falls, sheet-floods, shallow lakes, aeolian, fluvial channel-belts, and reworked debris-flows. We defined four stratigraphic intervals for the studied sections, denominated 1 to 4 in chronological order of deposition, which increase their thicknesses toward the Puesto Mesa-Cerro León site. The interval 1 (18-42 m thick) corresponds to the PLPM and includes numerous pedogenized sheet-flood deposits, carbonate-rich lacustrine, aeolian sandy facies, and ash-fall beds. The interval 1 is interpreted as an ephemeral and unconfined alluvial system that interacted with aeolian dunes and dry interdune zones. The interval 2 (20-47 m thick) represents the lower part of the CCM. It shows an alternation of fluvial channel-belt deposits and vegetated floodplain facies with sediments originated from sheet-floods, lakes, and few ash-falls and debris-flows. The mean palaeoflow was toward E-SE, except in the northernmost locality where the drainage was towards SW. Proportion of channel-belt bodies ranges from 10 to 36%, reaching higher values in the northern part of the study area, where they are also thicker. The interval 2 represents a permanent, meandering or locally low

Petrology and provenance of the Neogene fluvial succession in Pishin Belt (Katawaz Basin) western Pakistan: Implications for sedimentation in peripheral forelands basins

DEFF Research Database (Denmark)

Kasi, Aimal Khan; Kassi, Aktar Muhammad; Friis, Henrik

2017-01-01

Sandstones and conglomerates of the Neogene fluvial succession in Pishin Belt (Katawaz Basin), Pakistan were studied for the first time to understand the composition, provenance and tectonic settings of the source areas. Sandstones of the Miocene Dasht Murgha Group and Pliocene Malthanai Formatio...

Historia a medias e historias medias: imaginarios de lo pueblerino en el contexto de juicios al terrorismo de Estado

Directory of Open Access Journals (Sweden)

Ariel Gravano

2016-01-01

Full Text Available El propósito de este trabajo antropológico es presentar una situación en que la Historia «llega» a ciudades medias del centro de la provincia de Buenos Aires, Argentina. Se toman como caso juicios al terrorismo de Estado y hechos de relevancia nacional vinculados con la defensa de los derechos humanos. Lo hacemos desde el concepto de imaginarios identitarios urbanos, por los cuales adquiere importancia el análisis de cómo «la ciudad toda» vive esos acontecimientos, en los que se contrasta la Historia centralizada en la metrópolis y la historia local, en la que parece preponderar una imagen de «quietud», «donde nunca pasa (ni pasó nada». Avanzamos en la postulación de «lo pueblerino» como eje dentro de la dialéctica entre lo rural y lo urbano y la implicancia de actores y analistas «nativos», ante la posibilidad de problematizar tanto la Historia a medias cuanto sus propias historias medias.

Post Waterflood CO2 Miscible Flood in Light Oil, Fluvial-Dominated Deltaic Reservoir (Pre-Work and Project Proposal - Appendix)

Energy Technology Data Exchange (ETDEWEB)

Bou-Mikael, Sami

2002-02-05

The main objective of the Port Neches Project was to determine the feasibility and producibility of CO2 miscible flooding techniques enhanced with horizontal drilling applied to a Fluvial Dominated Deltaic reservoir. The second was to disseminate the knowledge gained through established Technology Transfer mechanisms to support DOE's programmatic objectives of increasing domestic oil production and reducing abandonment of oil fields.

Glacial lake outburst floods and fluvial erosion in the Himalaya - insights from the 2016 Bhote Koshi GLOF

Science.gov (United States)

Cook, K. L.; Gimbert, F.; Andermann, C.; Hovius, N.; Adhikari, B. R.

2017-12-01

The Himalaya is a region of rapid erosion where fluvial processes are assumed to be driven by precipitation delivered during the annual Indian Summer Monsoon. However, the rivers in this region are also subject to catastrophic floods caused by the failure of glacial lake and landslide dams. Because these floods are rarely observed, it has been difficult to isolate their impact on the rivers and adjacent hillslopes, and their importance for the long-term evolution of Himalayan valleys is largely unknown. In July 2016, the Bhotekoshi/Sunkoshi River in central Nepal was hit by a glacial lake outburst flood (GLOF) that caused substantial changes to the channel bed, banks, and adjacent hillslopes, causing at least 26 landslides and an average of 11 m of channel widening. The flood passed through a seismic and hydrological observatory installed along the river in June 2015, and we have used the resulting data to constrain the timing, duration, and bedload transport properties of the outburst flood. The impact of the flood on the river can be further observed with hourly time-lapse photographs, daily measurements of suspended sediment load, repeat lidar surveys, and satellite imagery. The outburst flood affected the river on several timescales. In the short term, it transported large amounts of coarse sediment and restructured the river bed during the hours of the flood pulse itself. Over intermediate timescales it resulted in elevated bedload and suspended load transport for several weeks following the flood. Over longer timescales the flood undercut and destabilized the river banks and hillslopes in a number of locations, leading to bank collapses, slumps, and landslides. Our data indicate that impacts of the GLOF far exceed those driven by the annual summer monsoon, likely due to extremely coarse sediment that armors much of the channel. The relatively frequent occurrence of GLOFs and the extremely high discharges relative to monsoon floods suggest that GLOFs may

Downstream mixing of sediment and tracers in agricultural catchments: Evidence of changing sediment sources and fluvial processes?

Science.gov (United States)

Ralph, Timothy; Wethered, Adam; Smith, Hugh; Heijnis, Henk

2014-05-01

Land clearance, soil tillage and grazing in agricultural catchments have liberated sediment and altered hydrological connectivity between hillslopes and channels, leading to increased sediment availability, mobilisation and delivery to rivers. The type and amount of sediment supplied to rivers is critical for fluvial geomorphology and aquatic ecosystem health. Contemporary sediment dynamics are routinely investigated using environmental radionuclides such as caesium-137 (Cs-137) and excess lead-210 (Pb-210ex), which can provide information regarding sediment source types and fluvial processes if sediment sources can be distinguished from one another and mixing models applied to representative samples. However, downstream transport, mixing and dilution of radionuclide-labelled sediment (especially from sources with low initial concentrations) can obliterate the tracer signal; sometimes before anything of geomorphological importance happens in the catchment. Can these findings be used as evidence of sediment source variations and fluvial processes when the limits of detection (of Cs-137 in particular) are being exceeded so rapidly downstream? Sediment sources and downstream sediment dynamics were investigated in Coolbaggie Creek, a major supplier of sediment to the Macquarie River in an agricultural catchment with temperate to semi-arid climate in Australia. Radionuclides were used to discriminate between the banks and gullies (Cs-137 1.45 +/- 0.47 Bq/kg; Pb-210ex 4.67 +/- 1.93 Bq/kg). Within the trunk stream, suspended sediment, organic matter and Cs-137 and Pb-210ex concentrations declined downstream. Results from a mixing model suggest that agricultural topsoils account for 95% of fine sediment entering the channel in the upper reach (200 m2) downstream, with channel expansion and gullies contributing fine sediment to the system. A lack of topsoil being supplied to the channel suggests minimal lateral connectivity between the catchment and the trunk stream in all

Judaísmo y la cuestión de la Guerra al final del segundo templo

Directory of Open Access Journals (Sweden)

César Vidal Manzanares

1994-01-01

Full Text Available En buena medida puede decirse que el período que, convencionalmente, se conoce como Segundo Templo se halla enmarcado entre dos guerras. Su punto de arranque lo constituye el final del destierro babilónico vinculado al conflicto bélico contra Nabucodonosor II; su punto de conclusión se encuentra en la guerra contra Roma iniciada en el 66 d. de C. En el curso de esta última, Israel desaparecería como entidad política semi-independiente, el Templo de Jerusalén sería arrasado y la nación se vería sumida en un marasmo de consecuencias difícilmente exagerables. Lejos, por lo tanto, de tratarse de un fenómeno abordable desde una perspectiva meramente especulativa, la guerra constituyó una realidad palpable y una referencia constante en este marco cronológico, especialmente en su tramo final. No sólo eso. De las respuestas que se dieron a esta coyuntura dependió, de manera directa, no sólo el desarrollo ulterior de la política en Eretz Israel, sino, muy especialmente, el futuro del judaismo y del cristianismo.

Post Waterflood CO2 Miscible Flood in Light Oil, Fluvial-Dominated Deltaic Reservoir (Pre-Work and Project Proposal), Class I

Energy Technology Data Exchange (ETDEWEB)

Bou-Mikael, Sami

2002-02-05

This project outlines a proposal to improve the recovery of light oil from waterflooded fluvial dominated deltaic (FDD) reservoir through a miscible carbon dioxide (CO2) flood. The site is the Port Neches Field in Orange County, Texas. The field is well explored and well exploited. The project area is 270 acres within the Port Neches Field.

An optical age chronology of late Quaternary extreme fluvial events recorded in Ugandan dambo soils

Science.gov (United States)

Mahan, S.A.; Brown, D.J.

2007-01-01

There is little geochonological data on sedimentation in dambos (seasonally saturated, channel-less valley floors) found throughout Central and Southern Africa. Radiocarbon dating is problematic for dambos due to (i) oxidation of organic materials during dry seasons; and (ii) the potential for contemporary biological contamination of near-surface sediments. However, for luminescence dating the equatorial site and semi-arid climate facilitate grain bleaching, while the gentle terrain ensures shallow water columns, low turbidity, and relatively long surface exposures for transported grains prior to deposition and burial. For this study, we focused on dating sandy strata (indicative of high-energy fluvial events) at various positions and depths within a second-order dambo in central Uganda. Blue-light quartz optically stimulated luminescences (OSL) ages were compared with infrared stimulated luminescence (IRSL) and thermoluminescence (TL) ages from finer grains in the same sample. A total of 8 samples were dated, with 6 intervals obtained at ???35, 33, 16, 10.4, 8.4, and 5.9 ka. In general, luminescence ages were stratigraphically, geomorphically and ordinally consistent and most blue-light OSL ages could be correlated with well-dated climatic events registered either in Greenland ice cores or Lake Victoria sediments. Based upon OSL age correlations, we theorize that extreme fluvial dambo events occur primarily during relatively wet periods, often preceding humid-to-arid transitions. The optical ages reported in this study provide the first detailed chronology of dambo sedimentation, and we anticipate that further dambo work could provide a wealth of information on the paleohydrology of Central and Southern Africa. ?? 2006 Elsevier Ltd. All rights reserved.

Late quaternary evolution of the Meuse fluvial system and its sediment composition : a reconstruction based on bulk sample geochemistry and forward modelling

NARCIS (Netherlands)

Tebbens, L.A.

1999-01-01

All fluvial systems ultimately drain into alluvial basins, where the weathering products of their upstream drainage areas accumulate over a time-span varying from 10 ⁰to 10 ⁶years. Most silted-up alluvial basins are low-gradient deltas that are

Valley-scale morphology drives differences in fluvial sediment budgets and incision rates during contrasting flow regimes

Science.gov (United States)

Weber, M. D.; Pasternack, G. B.

2017-07-01

High-resolution topographic surveys using LiDAR and multibeam sonar can be used to characterize and quantify fluvial change. This study used repeat surveys to explore how topographic change, fluvial processes, sediment budgets, and aggradation and incision rates vary across spatial scales and across two contrasting decadal flow regimes in a regulated gravel/cobble river. A novel method for quantifying digital elevation model uncertainty was developed and applied to a topographic change detection analysis from 2006/2008 to 2014. During this period, which had four modest 3-5 year floods, most sediment was laterally redistributed through bank erosion and channel migration. Erosion primarily occurred in the floodplain (97,000 m3), terraces (80,000 m3), and lateral bars (58,000 m3); while deposition occurred in the adjacent pools (73,000 m3), fast glides (48,000 m3), and runs (36,000 m3). In contrast, significantly higher magnitude and longer duration floods from 1999 to 2006/2008 caused sediment to be displaced longitudinally, with the upstream reaches exporting sediment and the downstream reaches aggrading. The river maintained floodplain connectivity during both periods, despite different processes dominating the type of connectivity. Larger floods promoted overbank scour and avulsion, while smaller floods promoted bank erosion and lateral migration. This study explores and illustrates how the geomorphic response to contrasting flood regimes in a nonuniform river is highly dependent on which landforms are controlling hydraulics.

Reply to the comment on "Geochemistry of buried river sediments from Ghaggar Plains, NW India: Multi-proxy records of variations in provenance, paleoclimate, and paleovegetation patterns in the Late Quaternary" by Singh et al. (2016), Palaeogeography, Palaeoclimatology, Palaeoecology 449 (2016) 85-100

DEFF Research Database (Denmark)

Singh, Ajit; Paul, Debajyoti; Sinha, Rajiv

2016-01-01

In the comment on our paper (this issue), Clift et al. (2016) compared our recently reported radiogenic Nd-isotopic record in two drill cores (Singh et al., 2016) with those from the Hakra floodplain sediments and Indus Delta sediments. While they agree with the concept of erosion patterns...... of these sediments. Moreover, we note that whereas our paper considers a similar to 75 ka fluvial depositional record, their comment is only based on the post-Last Glacial Maximum (LGM) record. When considering the longer record, their arguments do not negate the main conclusions of our original paper. (c) 2016...

Fluvial signatures of modern and paleo orographic rainfall gradients

Science.gov (United States)

Schildgen, Taylor; Strecker, Manfred

2016-04-01

The morphology of river profiles is intimately linked to both climate and tectonic forcing. While much interest recently has focused on how river profiles can be inverted to derive uplift histories, here we show how in regions of strong orographic rainfall gradients, rivers may primarily record spatial patterns of precipitation. As a case study, we examine the eastern margin of the Andean plateau in NW Argentina, where the outward (eastward) growth of a broken foreland has led to a eastward shift in the main orographic rainfall gradient over the last several million years. Rivers influenced by the modern rainfall gradient are characterized by normalized river steepness values in tributary valleys that closely track spatial variations in rainfall, with higher steepness values in drier areas and lower steepness values in wetter areas. The same river steepness pattern has been predicted in landscape evolution models that apply a spatial gradient in rainfall to a region of uniform erosivity and uplift rate (e.g., Han et al., 2015). Also, chi plots from river networks on individual ranges affected by the modern orographic rainfall reveal patterns consistent with assymmetric precipitation across the range: the largest channels on the windward slopes are characterized by capture, while the longest channels on the leeward slopes are dominated by beheadings. Because basins on the windward side both lengthen and widen, tributary channels in the lengthening basins are characterized by capture, while tributary channels from neighboring basins on the windward side are dominated by beheadings. These patterns from the rivers influenced by the modern orographic rainfall gradient provide a guide for identifying river morphometric signatures of paleo orographic rainfall gradients. Mountain ranges to the west of the modern orographic rainfall have been interpreted to mark the location of orographic rainfall in the past, but these ranges are now in spatially near-uniform semi-arid to

A chemometric approach to the evaluation of atmospheric and fluvial pollutant inputs in aquatic systems: The Guadalquivir River estuary as a case study

International Nuclear Information System (INIS)

Lopez-Lopez, Jose A.; Garcia-Vargas, Manuel; Moreno, Carlos

2011-01-01

To establish the quality of waters it is necessary to identify both point and non-point pollution sources. In this work, we propose the combination of clean analytical methodologies and chemometric tools to study discrete and diffuse pollution caused in a river by tributaries and precipitations, respectively. During a two-year period, water samples were taken in the Guadalquivir river (selected as a case study) and its main tributaries before and after precipitations. Samples were characterized by analysing nutrients, pH, dissolved oxygen, total and volatile suspended solids, carbon species, and heavy metals. Results were used to estimate fluvial and atmospheric inputs and as tracers for anthropic activities. Multivariate analysis was used to estimate the background pollution, and to identify pollution inputs. Principal Component Analysis and Cluster Analysis were used as data exploratory tools, while box-whiskers plots and Linear Discriminant Analysis were used to analyse and distinguish the different types of water samples. - Highlights: → Atmospheric and fluvial inputs of pollutants in Guadalquivir River were identified. → Point (tributary rivers) and non-point sources (rains) were studied. → Nature and extension of anthropogenic pollution in the river were established. - By combining trace environmental analysis and selected chemometric tools atmospheric and fluvial inputs of pollutants in rivers may be identified. The extension of the pollution originated by each anthropic activity developed along the River may be established, as well as the identification of the pollution introduced into the river by the tributary rivers (point sources) and by rains (non-point sources).

Post Waterflood CO2 Miscible Flood in Light Oil, Fluvial-Dominated Deltaic Reservoir (Pre-Work and Project Proposal - Appendix); FINAL

International Nuclear Information System (INIS)

Bou-Mikael, Sami

2002-01-01

The main objective of the Port Neches Project was to determine the feasibility and producibility of CO2 miscible flooding techniques enhanced with horizontal drilling applied to a Fluvial Dominated Deltaic reservoir. The second was to disseminate the knowledge gained through established Technology Transfer mechanisms to support DOE's programmatic objectives of increasing domestic oil production and reducing abandonment of oil fields

Fluvial terrace formation in the northern Upper Rhine Graben during the last 20 000 years as a result of allogenic controls and autogenic evolution

NARCIS (Netherlands)

Erkens, G.; Dambeck, R.; Volleberg, K.P.; Bouman, M.I.T.J.; Bos, J.A.A.; Cohen, K.M.; Hoek, W.Z.

2009-01-01

The northern Upper Rhine Graben hosts a well-preserved Late Weichselian and Holocene fluvial terrace sequence. Terraces differ in elevation, morphology, and overbank sediment characteristics. The purpose of this study was to determine the relative importance of allogenic controlling factors versus

Numerical analysis of palynological data from Neogene fluvial sediments as evidence for rainforest dynamics in western Amazonia

Science.gov (United States)

Salamanca, Sonia; van Manen, Milan; Hoorn, Carina

2014-05-01

Deep-time records that give an insight into the composition and dynamics of the ancestral Amazon rain forest are rare. Yet to understand the modern biodiversity patterns it is important to untangle the long-term evolution of this forest. Sampling Neogene strata requires drilling operations or complex fieldwork along the rivers where outcrops generally are small. In the nineties an exceptionally good exposure of fluvial sediments of early Miocene age (17.7-16.1 Ma) was documented near the island of Mariñame (Caquetá River, Colombian Amazonia) (Hoorn, 1994). This 60 m sediment succession consists of quartz-rich sands with a circa 10 m black, sandy clay intercalation. Palynomorphs are well preserved in these organic-rich clays and palynological analysis indicated high pollen diversity and changes in composition following changes in the sedimentary environment and water composition (see van Soelen et al., this session). A numerical analysis in R (2013) of the existing data, using a number of multivariate and other statistical techniques now shows a gradient of change in the composition of the Miocene palynological assemblages. Non-metric-multidimensional scaling using distance matrixes (Oksanen, 2012) and their visualizations in correlograms (Friendly, 2002) indicate that the regional (palm) swamp forests of Mauritiides franciscoi (Mauritia), frequently found together with other palms such as Psilamonocolpites amazonicus (Euterpe?) and Psilamonocolpites rinconii, were affected by a marine incursion. The latter is suggested by the change of composition and the presence of estuarine elements such as Zonocostites ramonae (Rhizophora), foraminifer linings and dinoflagellate cysts, which became common during the marine event. In the older part of the section, and at the top, Rhoipites guianensis (Sterculiaceae/Tiliaceae) is quite abundant, in contrast with the relatively low abundance of M. franciscoi. The numerical analysis allowed us to: a) group the pollen data into 3

Preliminary technical and economic viability for the implantation of fluvial transport of CNG (Compressed Natural Gas) for barges in Amazon Region; Avaliacao preliminar de viabilidade tecnico-economica para implantacao de transporte fluvial de GNC (Gas Natual Comprimido) por barcacas na Regiao Amazonica

Energy Technology Data Exchange (ETDEWEB)

Araujo, Marcos C.C. de; Porto, Paulo L. Lemgruber [Interocean Engenharia e Ship Management, Rio de janeiro, RJ (Brazil); Cunha, Rafael H. da [Metro Rio, RJ (Brazil); Garcia, Rafael M. [Pic Brasil (Brazil); Almeida, Marco A.R. de [Universidade Gama Filho (UGF), Rio de Janeiro, RJ (Brazil)

2004-07-01

The isolated regions of the Amazon present difficulties for integration with the electrical system which is creating some economic problems due to the consequent costs of electric generation of subsidies as a function of the fossil fuel use as oils diesel and fuel. A viable option is the use of Natural Gas - NG that is Also available in the region. Its modal of transport possible in the Region North they are for gas-lines or barges. The Compressed Natural Gas transport is distinguished that - CNG for barges was still not tested operationally in Brazil. Soon, to develop a Preliminary Study of Viability Technician - Economic - SVTE for the implantation of fluvial transport of CNG between the cities of Coari and Manaus is basic, therefore it is created strategical alternative for the electric generation in this region. The electric sector, the characteristics of the NG and the transport in this region had been analyzed to support to the work. The gas line and the fluvial transport of CNG for barges in this region are not conflicting, and they in a complementary form can act. The SVTE presented a Liquid Present Value and Internal Tax of very attractive Return justifying its implantation. (author)

Sediment Budget in the Taiwan Strait with High Fluvial Sediment Inputs from Mountainous Rivers: New Observations and Synthesis

Directory of Open Access Journals (Sweden)

Shuh-Ji Kao

2008-01-01

Full Text Available The shallow Taiwan Strait at the southern opening of the East China Sea (ECS receives abundant sediments from turbid mountainous rivers in Taiwan. The volume of sediment is among the highest sediment yields on the global surface. This large amount of sediment discharged from modern Taiwan (range: 175 - 380 Mt y-1 based on 50-yr data is comparable to that discharged from Changjaing (500 Mt y-1-decreasing in recent decades, underscoring the importance of sediment budget in the Taiwan Strait and sediment flux from Taiwan into the ECS.We documented fluvial mud and sand concentrations during flash flooding with our observations indicating that fluvial materials in Taiwan¡¦s rivers are chiefly composed of mud (> 70 and up to 98 . By contrast, sand fraction dominates (> 85 for most stations surface sediments in the Taiwan Strait. Super typhoon Herb alone delivered 130 Mt of sediments from Choshui, the largest river in Taiwan, yet only insignificant amounts of mud were found at the river mouth six months later. The actions of waves, tides, and currents apparently prevent the deposition of fine grained sediments. Assuming sand occupied 30 (the maximum of the 60 Mt y-1 total sediment input from major western Taiwanese rivers, our annual budget estimate shows that the amount of sand input (18 5 Mt y-1 is comparable to the burial output of sand (12 10 Mt y-1. However, mud burial (6 5 Mt y-1 in the strait is far below the estimated mud input (42 11 Mt y-1, resulting in a significant shortfall. Hydrodynamic conditions were synthesized to explain the distribution pattern of limited mud patches in the strait and to reveal potential pathways by which fine-grain sediment transportation takes place in the seas surrounding Taiwan. A significant shortfall in the mud budget in the Taiwan Strait suggests that ~85 of the fluvial mud left the strait. Alternatively, the 50-year modern sediment flux data used in this study reflects exacerbated sediment flux due to human

Post Waterflood CO2 Miscible Flood in Light Oil, Fluvial-Dominated Deltaic Reservoir (Pre-Work and Project Proposal), Class I; FINAL

International Nuclear Information System (INIS)

Bou-Mikael, Sami

2002-01-01

This project outlines a proposal to improve the recovery of light oil from waterflooded fluvial dominated deltaic (FDD) reservoir through a miscible carbon dioxide (CO2) flood. The site is the Port Neches Field in Orange County, Texas. The field is well explored and well exploited. The project area is 270 acres within the Port Neches Field

Visibilidad pública y tratamiento informativo del movimiento de cooperación al desarrollo (1992-2002 Visibilidad pública y tratamiento informativo del movimiento de cooperación al desarrollo (1992-2002

Directory of Open Access Journals (Sweden)

Ariel Jerez

2004-01-01

Full Text Available En España los años noventa ven aparecer el primer gran movimientos social vinculado a la problemática de la solidaridad y el desarrollo internacional, impulsando tres grandes campañas: la inicial (1994 está centrada principalmente en la reclamación simbólica de la cesión deL 0,7% del PIB para cooperación al desarrollo recomendado por Naciones Unidas en le década deL 70; La segunda (1998 busca presionar con un diversificado repertorio de acción colectiva sobre la elaboración parlamentaria de la ley marco de cooperación internacional como el objetivo de dotar de un mayor control sobre aquellos instrumentos de cooperación vinculados al comercio exterior y la tercera (2000 impulse una consulte social sobre ha deuda externa que se desarrolla de manera paralela a las elecciones generales ese año. Esta creciente politización de los objetivos del movimiento recibe un tratamiento informativo muy diferenciado en estos tres momentos, poniendo de manifiesto la relación entre la estructura de oportunidad mediática y las alianzas político mediática entre, en este caso, prensa escrita y partidos (en su posición relativa de gobierno y oposición. El análisis de esta relación entre partidos y medios da cuenta de las profundas transformaciones que está viviendo la esfera pública en las coordenadas de la sociedad de la información y, cómo pesa sobre el espacio público en el que trabaja la sociedad civil en las sociedades democráticas.During the 1990’s arises the biggest social movement linked to international solidarity and development in Spain. The activities involve three main campaignes. The initial one (1994 is focused on the symbolic demand of the 0,7% PIB budget, recommended by the UN in the 70’s. The second campaign (1988 displays a diversified repertoire of collective action pressing the parliamentary debates on the Law for International Cooperation in order no exert civil control on the foreign commercial relations. The

Deformed Fluvial Terraces of Little Rock Creek Capture Off-Fault Strain Adjacent to the Mojave Section of the San Andreas Fault

Science.gov (United States)

Moulin, A.; Scharer, K. M.; Cowgill, E.

2017-12-01

Examining discrepancies between geodetic and geomorphic slip-rates along major strike-slip faults is essential for understanding both fault behavior and seismic hazard. Recent work on major strike-slip faults has highlighted off-fault deformation and its potential impact on fault slip rates. However, the extent of off-fault deformation along the San Andreas Fault (SAF) remains largely uncharacterized. Along the Mojave section of the SAF, Little Rock Creek drains from south to north across the fault and has cut into alluvial terraces abandoned between 15 and 30 ka1. The surfaces offer a rare opportunity to both characterize how right-lateral slip has accumulated along the SAF over hundreds of seismic cycles, and investigate potential off-fault deformation along secondary structures, where strain accumulates at slower rates. Here we use both field observations and DEM analysis of B4 lidar data to map alluvial and tectonic features, including 9 terrace treads that stand up to 80 m above the modern channel. We interpret the abandonment and preservation of the fluvial terraces to result from episodic capture of Little Rock Creek through gaps in a shutter ridge north of the fault, followed by progressive right deflection of the river course during dextral slip along the SAF. Piercing lines defined by fluvial terrace risers suggest that the amount of right slip since riser formation ranges from 400m for the 15-ka-riser to 1200m for the 30-ka-riser. Where they are best-preserved NE of the SAF, terraces are also cut by NE-facing scarps that trend parallel to the SAF in a zone extending up to 2km from the main fault. Exposures indicate these are fault scarps, with both reverse and normal stratigraphic separation. Geomorphic mapping reveals deflections of both channel and terrace risers (up to 20m) along some of those faults suggesting they could have accommodated a component of right-lateral slip. We estimated the maximum total amount of strike-slip motion recorded by the

EL PLAN GLOBAL FRENTE AL RIESGO DE INUNDACIÓN EN LA RIBERA DEL JÚCAR

Directory of Open Access Journals (Sweden)

Gemma Barber Arlandis

2012-01-01

Full Text Available El Plan Global del Júcar frente al riesgo de inundación pretende minimizar los daños causados por las avenidas que periódicamente afectan a la Ribera del Júcar. En el presente artículo se describen y analizan las actuaciones de este Plan, la génesis del mismo, el proceso de elaboración y sus resultados. La problemática es compleja, ya que el riesgo de inundación abarca un territorio muy poblado, con un importante desarrollo industrial y agrícola. Además, la existencia de espacios naturales de elevado valor ambiental, hace que las intervenciones derivadas del Plan consideren al mismo nivel la defensa frente a avenidas y las demandas sociales y ambientales, tras el consenso alcanzado en un proceso de participación pública. El Plan incorpora aspectos innovadores en ingeniería hidráulica, cuyo resultado es una actuación integrada y sostenible, que compatibiliza la protección frente a avenidas con la recuperación y mejora del ámbito fluvial, y su función como corredor vertebrador del territorio.

Quaternary Morphodynamics of Fluvial Dispersal Systems Revealed: The Fly River, PNG, and the Sunda Shelf, SE Asia, simulated with the Massively Parallel GPU-based Model 'GULLEM'

Science.gov (United States)

Aalto, R. E.; Lauer, J. W.; Darby, S. E.; Best, J.; Dietrich, W. E.

2015-12-01

During glacial-marine transgressions vast volumes of sediment are deposited due to the infilling of lowland fluvial systems and shallow shelves, material that is removed during ensuing regressions. Modelling these processes would illuminate system morphodynamics, fluxes, and 'complexity' in response to base level change, yet such problems are computationally formidable. Environmental systems are characterized by strong interconnectivity, yet traditional supercomputers have slow inter-node communication -- whereas rapidly advancing Graphics Processing Unit (GPU) technology offers vastly higher (>100x) bandwidths. GULLEM (GpU-accelerated Lowland Landscape Evolution Model) employs massively parallel code to simulate coupled fluvial-landscape evolution for complex lowland river systems over large temporal and spatial scales. GULLEM models the accommodation space carved/infilled by representing a range of geomorphic processes, including: river & tributary incision within a multi-directional flow regime, non-linear diffusion, glacial-isostatic flexure, hydraulic geometry, tectonic deformation, sediment production, transport & deposition, and full 3D tracking of all resulting stratigraphy. Model results concur with the Holocene dynamics of the Fly River, PNG -- as documented with dated cores, sonar imaging of floodbasin stratigraphy, and the observations of topographic remnants from LGM conditions. Other supporting research was conducted along the Mekong River, the largest fluvial system of the Sunda Shelf. These and other field data provide tantalizing empirical glimpses into the lowland landscapes of large rivers during glacial-interglacial transitions, observations that can be explored with this powerful numerical model. GULLEM affords estimates for the timing and flux budgets within the Fly and Sunda Systems, illustrating complex internal system responses to the external forcing of sea level and climate. Furthermore, GULLEM can be applied to most ANY fluvial system to

Grain-size evolution in suspended sediment and deposits from the 2004 and 2008 controlled-flood experiments in Marble and Grand Canyons, Arizona

Science.gov (United States)

Draut, Amy E.; Topping, David J.; Rubin, David M.; Wright, Scott A.; Schmidt, John C.

2010-01-01

Since the closure of Glen Canyon Dam in 1963, the hydrology, sediment supply, and distribution and size of modern alluvial deposits in the Colorado River through Grand Canyon have changed substantially (e.g., Howard and Dolan, 1981; Johnson and Carothers, 1987; Webb et al., 1999; Rubin et al., 2002; Topping et al., 2000, 2003; Wright et al., 2005; Hazel et al., 2006). The dam has reduced the fluvial sediment supply at the upstream boundary of Grand Canyon National Park by about 95 percent. Regulation of river discharge by dam operations has important implications for the storage and redistribution of sediment in the Colorado River corridor. In the absence of natural floods, sediment is not deposited at elevations that regularly received sediment before dam closure. There has been a systemwide decrease in the size and number of subaerially exposed fluvial sand deposits since the 1960s, punctuated by episodic aggradation during the exceptional high-flow intervals in the early 1980s and by sediment input from occasional tributary floods (Beus and others, 1985; Schmidt and Graf, 1990; Kearsley et al., 1994; Schmidt et al., 2004; Wright et al., 2005; Hazel et al., 2006). Fluvial sandbars are an important component of riparian ecology that, among other functions, enclose eddy backwaters that form native-fish habitat, provide a source for eolian sand that protects some archaeological sites, and are used as campsites by thousands of river-runners annually (Rubin et al., 1990; Kearsley et al., 1994; Neal et al., 2000; Wright et al., 2005; Draut and Rubin, 2008).

Paleogeographic and Depositional Model for the Neogene fluvial succession, Pishin Belt Northwest Pakistan

DEFF Research Database (Denmark)

Kasi, Aimal Khan; Kassi, Akhtar Muhammad; Umar, Muhammad

2017-01-01

Miocene subaerial sedimentation started after the final closure of Katawaz Remnant Ocean. Based on detailed field data twelve facies were recognized in Neogene successions exposed in Pishin Belt. These facies were further organized into four facies associations i.e. channels, crevasse splay, natural levee...... and floodplain facies associations. Facies associations and variations provided ample evidences to recognize number of fluvial architectural components in the succession e.g., low-sinuosity sandy braided river, mixed-load meandering, high-sinuosity meandering channels, single-story sandstone and/or conglomerate...... channels, lateral accretion surfaces (point bars) and alluvial fans. Neogene sedimentation in the Pishin Belt was mainly controlled by active tectonism and thrusting in response to oblique collision of the Indian Plate with Afghan Block of the Eurasian Plate along the Chaman-Nushki Fault. Post Miocene...

Inputs and Fluvial Transport of Pharmaceutical Chemicals in An Urban Watershed

Science.gov (United States)

Foster, G. D.; Shala, L.

2006-05-01

Pharmaceuticals and personal care products (PPCPs) are classes of emerging chemical contaminants thought to enter the aquatic environment primarily through wastewater treatment plant (WTP) discharges. As the use of drugs is expected to rise with the aging demographics of the human population and with more river water being diverted to meet potable water demands, the presence of PPCPs in surface water is becoming an issue of public concern. The intent of our study was to quantify potential WTP inputs of PPCPs to rivers in the Wasington, DC (USA) region, and to investigate the fluvial transport of PPCPs in the Anacostia River (AR), the mainstem of a highly contaminated urban watershed in Washington, DC. The approach was to sample WTP water at various stages of treatment, and to measure seasonal concentrations of PPCPs in fluvial transport in the AR. Surface water from the AR was collected through the use of automated samplers during normal flow and storm flow regimes near the head of tide of the AR, just upstream from the confluence of the Northeast (NE) and Northwest (NW) Branches, the two prominent drainages in the watershed. The water samples were filtered to separate river particles from water, and the filtered water was extracted using solid phase extraction (SPE) cartridges. The filters were extracted by sonication in methanol. The SPE and filter extracts were analyzed for a group of widely distributed PPCPs as trimethylsilyl derivatives by using gas chromatography/mass spectrometry. The most frequently detected PPCPs at WTPs included ibuprofen, caffeine, naproxen and triclosan, which ranged from 45 μg/L (caffeine) to 5 μg/L (triclosan) in WTP influent and from 0.08 μg/L (triclosan) to 0.02 μg/L (ibuprofen) in effluent water. Similar PPCPs were detected in both the NE and NW Branches of the AR, but higher concentrations on average were observed in the NE Branch, which receives WTP effluent upstream from the sampling point. The incidence of PPCPs correlated

Which DEM is best for analyzing fluvial landscape development in mountainous terrains?

Science.gov (United States)

Boulton, Sarah J.; Stokes, Martin

2018-06-01

Regional studies of fluvial landforms and long-term (Quaternary) landscape development in remote mountain landscapes routinely use satellite-derived DEM data sets. The SRTM and ASTER DEMs are the most commonly utilised because of their longer availability, free cost, and ease of access. However, rapid technological developments mean that newer and higher resolution DEM data sets such as ALOS World 3D (AW3D) and TanDEM-X are being released to the scientific community. Geomorphologists are thus faced with an increasingly problematic challenge of selecting an appropriate DEM for their landscape analyses. Here, we test the application of four medium resolution DEM products (30 m = SRTM, ASTER, AW3D; 12 m = TanDEM-X) for qualitative and quantitative analysis of a fluvial mountain landscape using the Dades River catchment (High Atlas Mountains, Morocco). This landscape comprises significant DEM remote sensing challenges, notably a high mountain relief, steep slopes, and a deeply incised high sinuosity drainage network with narrow canyon/gorge reaches. Our goal was to see which DEM produced the most representative best fit drainage network and meaningful quantification. To achieve this, we used ArcGIS and Stream Profiler platforms to generate catchment hillshade and slope rasters and to extract drainage network, channel long profile and channel slope, and area data. TanDEM-X produces the clearest landscape representation but with channel routing errors in localised high relief areas. Thirty-metre DEMs are smoother and less detailed, but the AW3D shows the closest fit to the real drainage network configuration. The TanDEM-X elevation values are the closest to field-derived GPS measurements. Long profiles exhibit similar shapes but with minor differences in length, elevation, and the degree of noise/smoothing, with AW3D producing the best representation. Slope-area plots display similarly positioned slope-break knickpoints with modest differences in steepness and concavity

Contrasting styles of aeolian, fluvial and marine interaction in the Cutler Group of the Paradox Basin, SE Utah, USA

OpenAIRE

Wakefield, Oliver; Mountney, Nigel

2017-01-01

The Permian-Pennsylvanian Cutler Group of the Paradox foreland basin of southeast Utah is characterised by a variety of styles of interaction between coeval aeolian, fluvial and marine environments that have resulted in the generation and preservation of a complex suite of stratal architectures. Detailed 3D architectural element analysis has enabled the nature of these interactions to be interpreted in order to constrain both the spatial and temporal scale over which competing ...

Connectivity of Multi-Channel Fluvial Systems: A Comparison of Topology Metrics for Braided Rivers and Delta Networks

Science.gov (United States)

Tejedor, A.; Marra, W. A.; Addink, E. A.; Foufoula-Georgiou, E.; Kleinhans, M. G.

2016-12-01

Advancing quantitative understanding of the structure and dynamics of complex networks has transformed research in many fields as diverse as protein interactions in a cell to page connectivity in the World Wide Web and relationships in human societies. However, Geosciences have not benefited much from this new conceptual framework, although connectivity is at the center of many processes in hydro-geomorphology. One of the first efforts in this direction was the seminal work of Smart and Moruzzi (1971), proposing the use of graph theory for studying the intricate structure of delta channel networks. In recent years, this preliminary work has precipitated in a body of research that examines the connectivity of multiple-channel fluvial systems, such as delta networks and braided rivers. In this work, we compare two approaches recently introduced in the literature: (1) Marra et al. (2014) utilized network centrality measures to identify important channels in a braided section of the Jamuna River, and used the changes of bifurcations within the network over time to explain the overall river evolution; and (2) Tejedor et al. (2015a,b) developed a set of metrics to characterize the complexity of deltaic channel networks, as well as defined a vulnerability index that quantifies the relative change of sediment and water delivery to the shoreline outlets in response to upstream perturbations. Here we present a comparative analysis of metrics of centrality and vulnerability applied to both braided and deltaic channel networks to depict critical channels in those systems, i.e., channels where a change would contribute more substantially to overall system changes, and to understand what attributes of interest in a channel network are most succinctly depicted in what metrics. Marra, W. A., Kleinhans, M. G., & Addink, E. A. (2014). Earth Surface Processes and Landforms, doi:10.1002/esp.3482Smart, J. S., and V. L. Moruzzi (1971), Quantitative properties of delta channel networks

Fetiches de poder y muerte. Una mirada mexicana sobre la obra de Cecilia Noriega-Bozovich

NARCIS (Netherlands)

Aguiar, J.C.G.; Buntinx, G.

2016-01-01

El trabajo de Cecilia Noriega-Bozovich está vinculado de manera muy directa con la sociedad peruana, a la cual convierte al mismo tiempo en su tema principal. Esta mirada encaja en lo que pudiera ser una ‘escuela latinoamericana’, donde la producción artística va acompañada de un registro o

Percepción de los consumidores: Calidad, inocuidad y seguridad de productos alimenticios basados en la Ley de Protección al Consumidor

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Rodolfo Misael Mejía Dietrich

2016-06-01

Full Text Available En los últimos años la cultura del respeto a los derechos del consumidor salvadoreño ha sido promovida desde instituciones gubernamentales y no gubernamentales. El objetivo del estudio fue indagar las experiencias, inquietudes y expectativas de consumidores del departamento de San Miguel, en relación a su percepción sobre el cumplimiento o no de sus derechos, vinculados a la calidad, inocuidad y seguridad de productos alimenticios. Contrastando ésta opinión con la emitida por los empresarios a fin de establecer similitudes y diferencias respecto al tema. El tipo de estudio fue descriptivo y explicativo, se describieron y analizaron causas y efectos de la relación entre variables como cumplimiento de requisitos: calidad, inocuidad y seguridad de productos alimenticios con cumplimiento de leyes. Para el análisis de los datos se utilizaron las técnicas de la estadística básica: Tablas de frecuencias y gráficos. Se encontró que los consumidores son sensibles a los altos precios de la canasta básica alimenticia influyendo en sus decisiones de compra; que reciben productos alimenticios de mediana calidad y que estos productos no siempre son accesibles a sus presupuestos; asimismo, existe un alto porcentaje de consumidores que desconocen sus derechos y deberes otorgados por la Ley de Protección al Consumidor.

Sedimentary architecture and optical dating of Middle and Late Pleistocene Rhine-Meuse deposits - Fluvial response to climate change, sea-level fluctuation and glaciation

NARCIS (Netherlands)

Busschers, F.S.; Weerts, H.J.T.; Wallinga, J.; Cleveringa, P.; Kasse, C.; Wolf, H.de; Cohen, K.M.

2005-01-01

Eight continuous corings in the west-central Netherlands show a 15 to 25 m thick stacked sequence of sandy to gravelly channel-belt deposits of the Rhine-Meuse system. This succession of fluvial sediments was deposited under net subsiding conditions in the southern part of the North Sea Basin and

Sedimentary architecture and optical dating of Middle and Late Pleistocene Rhine-Meuse deposits fluvial response to climate change, sea-level fluctuation and glaciation

NARCIS (Netherlands)

Busschers, F.S.; Weerts, H.J.T.; Wallinga, J.; Kasse, C.; Cleveringa, P.; de Wolf, H.; Cohen, K.M.

2005-01-01

Eight continuous corings in the west-central Netherlands show a 15 to 25 m thick stacked sequence of sandy to gravelly channel-belt deposits of the Rhine-Meuse system. This succession of fluvial sediments was deposited under net subsiding conditions in the southern part of the North Sea Basin and

Multi-scale tectonic controls on fluvial terrace formation in a glacioeustatically-dominated river system: inference from the lower Min¿o terrace record

NARCIS (Netherlands)

Viveen, W.

2013-01-01

The general aim of this thesis is to untangle the interacting effects of climate, glacioeustacy, and regional, and local tectonics on fluvial terrace formation. The NW Iberian lower Miño River valley was chosen as a study site, because for this region, a very detailed, long-term,

The impact of reduction of doublet well spacing on the Net Present Value and the life time of fluvial Hot Sedimentary Aquifer doublets

NARCIS (Netherlands)

Willems, C.J.L.; Maghami Nick, Hamidreza M.; Bruhn, D.F.

This paper evaluates the impact of reduction of doublet well spacing, below the current West Netherlands Basin standard of 1000 to 1500 m, on the Net Present Value (NPV) and the life time of fluvial Hot Sedimentary Aquifer (HSA) doublets. First, a sensitivity analysis is used to show the possible

El delito de piratería y el principio de justicia universal

OpenAIRE

Ramos Koprivitza, Ulises Sandal

2014-01-01

[ES] El incremento internacional del delito de piratería en los albores del Siglo XXI coloca, nuevamente, a esta actividad ilícita como un problema de actualidad para el Derecho penal, concomitantemente, al estudio del principio de justicia universal que se encuentra históricamente vinculado con este delito y que obliga al examen profundo de ambas figuras jurídicas para establecer la naturaleza y fundamento del principio de justicia universal; así como, los mecanismos adecuados para la repres...

El nuevo espacio rural en El Salvador. An??lisis de un programa educativo de participaci??n comunitaria

OpenAIRE

Ramo Garzar??n, Rosario Marta

2011-01-01

El actual concepto de Derecho a la Educaci??n como Educaci??n para Todos, est?? vinculado al desarrollo social, econ??mico, pol??tico y cultural de los pa??ses en desarrollo y especialmente al de sus contextos rurales. Desde este enfoque, este estudio analiza la efectividad de algunas pol??ticas educativas llevadas a cabo en las dos ??ltimas d??cadas en el Salvador, EDUCO. Estas decisiones pol??ticas en materia educativa han tenido como objetivo la protecci??n, promoci??n y r...

Evolution of Early Pleistocene fluvial systems in central Poland prior to the first ice sheet advance – a case study from the Bełchatów lignite mine

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Goździk Jan

2017-06-01

Full Text Available Deposits formed between the Neogene/Pleistocene transition and into the Early Pleistocene have been studied, mainly on the basis of drillings and at rare, small outcrops in the lowland part of Polish territory. At the Bełchatów lignite mine (Kleszczów Graben, central Poland, one of the largest opencast pits in Europe, strata of this age have long been exposed in extensive outcrops. The present paper is based on our field studies and laboratory analyses, as well as on research data presented by other authors. For that reason, it can be seen as an overview of current knowledge of lowermost Pleistocene deposits at Bełchatów, where exploitation of the Quaternary overburden has just been completed. The results of cartographic work, sedimentological, mineralogical and palynological analyses as well as assessment of sand grain morphology have been considered. All of these studies have allowed the distinction of three Lower Pleistocene series, i.e., the Łękińsko, Faustynów and Krzaki series. These were laid down in fluvial environments between the end of the Pliocene up to the advance of the first Scandinavian ice sheet on central Poland. The following environmental features have been interpreted: phases of river incision and aggradation, changes of river channel patterns, source sediments for alluvia, rates of aeolian supply to rivers and roles of fluvial systems in morphological and geological development of the area. The two older series studied, i.e., Łękińsko and Faustynów, share common characteristics. They were formed by sinuous rivers in boreal forest and open forest environments. The Neogene substratum was the source of the alluvium. The younger series (Krzaki formed mainly in a braided river setting, under conditions of progressive climatic cooling. Over time, a gradual increase of aeolian supply to the fluvial system can be noted; initially, silt and sand were laid down, followed by sand only during cold desert conditions. These

SEDIMENTAÇÃO FLUVIAL QUATERNÁRIA NO VALE DO ALTO CURSO DO RIO MACAÉ, ESTADO DO RIO DE JANEIRO, BRASIL.

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Mônica dos Santos Marçal

2015-09-01

Full Text Available O trabalho foi desenvolvido no vale do alto curso do rio Macaé, norte do estado do Rio de Janeiro, e tem como objetivo apresentar as análises geomorfológicas e estratigráficas, além das idades obtidas com o método da luminescência (LOE, realizadas em feições sedimentares de terraços fluviais. Foram selecionadas duas áreas de sedimentação denominadas AS-1, localizada mais a montante do vale, e AS-2 mais a jusante. As feições ocorrem em quatro níveis, sendo três níveis de terraço fluvial, denominados Nível Superior (T1, Nível Intermediário (T2 e Nível Inferior (T3, e um Nível de Planície de Inundação atual (PI. Estão distribuídos de forma descontínua, predominantemente na margem esquerda do rio Macaé, sendo que a planície de inundação (PI ocorre em níveis diferentes em cada margem do vale. Os resultados obtidos das datações por LOE para os sedimentos dos três níveis de terraços (T1, T2 e T3 apresentam boa correspondência às evidências geomorfológicas e estratigráficas utilizadas na definição dos níveis deposicionais aluviais.

3-D Characterization of Detrital Zircon Grains and its Implications for Fluvial Transport, Mixing, and Preservation Bias

Science.gov (United States)

Markwitz, V.; Kirkland, C. L.; Mehnert, A.; Gessner, K.; Shaw, J.

2017-12-01

Detrital zircon studies can suffer from selective loss of provenance information due to U-Pb age discordance, metamictization, metamorphic overprinting and fluviatile transport processes. The relationship between isotopic composition and zircon grain shape, and how grain shape is modified during transport, is largely unknown. We combine X-ray tomography with U-Pb geochronology to quantify how fluvial transport affects 3-D zircon shape, detrital age signature, and grain density along the Murchison River, whose catchment comprises Eoarchean to Early Paleozoic source rocks in Western Australia. We acquired tomographic volumes and isotopic data from 373 detrital zircons to document changes in size, shape and density in transport direction, and explore how grain shape, age spectra and the proportion of discordant material vary along the channel. Results show that shape characteristics are sensitive to transport distance, stream gradient, proximity to source material, and whether the source consists of primary or recycled zircons. With increasing transport distance, grain lengths decrease more than their widths. Furthermore, the loss of metamict grains occurs at a near constant rate, resulting in a linear increase of mean calculated zircon density by ca. 0.03 g/cm3 per 100 km transport distance. 3-D grain shape is therefore strongly linked to detrital age signature, and mean grain density is a function of the absolute transport distance. 3-D shape characteristics provide valuable information on detrital zircon populations, including the interaction between source materials with fluvial transport processes, which significantly affects preservation bias and, by inference, the representativeness of the sampled data.

The Spatial Distribution of Bed Sediment on Fluvial System: A Mini Review of the Aceh Meandering River

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Muhammad Irham

2016-08-01

Full Text Available Dynamic interactions of hydrological and geomorphological processes in the fluvial system result in accumulated deposit on the bed because the capacity to carry sediment has been exceeded. The bed load of the Aceh fluvial system is primarily generated by mechanical weathering resulting in boulders, pebbles, and sand, which roll or bounce along the river bed forming temporary deposits as bars on the insides of meander bends, as a result of a loss of transport energy in the system. This dynamic controls the style and range of deposits in the Aceh River. This study focuses on the spatial distribution of bed-load transport of the Aceh River. Understanding the spatial distribution of deposits facilitates the reconstruction of the changes in controlling factors during accumulation of deposits. One of the methods can be done by sieve analysis of sediment, where the method illuminates the distribution of sediment changes associated with channel morphology under different flow regimes. Hence, the purpose of this mini review is to investigate how the sediment along the river meander spatially dispersed. The results demonstrate that channel deposits in the Aceh River are formed from four different type of materials: pebble deposited along upstream left bank; sand located on the upstream, downstream, and along meander belts; and silt and clay located along the cut bank of meander bends. Because of different depositional pattern, the distribution of the sediment along the river can be used as a surrogate to identify bank stability, as well as to predict critical geometry for meander bend initiation

Architectural elements and bounding surfaces in fluvial deposits: anatomy of the Kayenta formation (lower jurassic), Southwest Colorado

Science.gov (United States)

Miall, Andrew D.

1988-03-01

Three well-exposed outcrops in the Kayenta Formation (Lower Jurassic), near Dove Creek in southwestern Colorado, were studied using lateral profiles, in order to test recent regarding architectural-element analysis and the classification and interpretation of internal bounding surfaces. Examination of bounding surfaces within and between elements in the Kayenta outcrops raises problems in applying the three-fold classification of Allen (1983). Enlarging this classification to a six-fold hierarchy permits the discrimination of surfaces intermediate between Allen's second- and third-order types, corresponding to the upper bounding surfaces of macroforms, and internal erosional "reactivation" surfaces within the macroforms. Examples of the first five types of surface occur in the Kayenta outcrops at Dove Creek. The new classifications is offered as a general solution to the problem of description of complex, three-dimensional fluvial sandstone bodies. The Kayenta Formation at Dove Creek consists of a multistorey sandstone body, including the deposits of lateral- and downstream-accreted macroforms. The storeys show no internal cyclicity, neither within individual elements nor through the overall vertical thickness of the formation. Low paleocurrent variance indicates low sinuosity flow, whereas macroform geometry and orientation suggest low to moderate sinuosity. The many internal minor erosion surfaces draped with mud and followed by intraclast breccias imply frequent rapid stage fluctuation, consistent with variable (seasonal? monsonal? ephemmeral?) flow. The results suggest a fluvial architecture similar to that of the South Saskatchewan River, through with a three-dimensional geometry unlike that interpreted from surface studies of that river.

The legacy of lead (Pb) in fluvial bed sediments of an urban drainage basin, Oahu, Hawaii.

Science.gov (United States)

Hotton, Veronica K; Sutherland, Ross A

2016-03-01

The study of fluvial bed sediments is essential for deciphering the impact of anthropogenic activities on water quality and drainage basin integrity. In this study, a systematic sampling design was employed to characterize the spatial variation of lead (Pb) concentrations in bed sediment of urban streams in the Palolo drainage basin, southeastern Oahu, Hawaii. Potentially bioavailable Pb was assessed with a dilute 0.5 N HCl extraction of the  Pukele (19) > Waiomao (8). Comparisons to sediment quality guidelines and potential toxicity estimates using a logistic regression model (LRM) indicated a significant potential risk of Palolo Stream bed sediments to bottom-dwelling organisms.

Sedimentary architecture and optical dating of Middle and Late Pleistocene Rhine-Meuse deposits – fluvial response to climate change, sea-level fluctuation and glaciation

NARCIS (Netherlands)

Busschers, F.S.; Weerts, H.J.T.; Wallinga, J.; Cleveringa, P.; Kasse, C.; Wolf, H. de; Cohen, K.M.

2005-01-01

Eight continuous corings in the west-central Netherlands show a 15 to 25 m thick stacked sequence of sandy to gravelly channel-belt deposits of the Rhine-Meuse system. This succession of fluvial sediments was deposited under net subsiding conditions in the southern part of the North Sea Basin and

Fluvial River Regime in Disturbed River Systems: A Case Study of Evolution of the Middle Yangtze River in Post-TGD (Three Gorges Dam), China

NARCIS (Netherlands)

Zhao, G.; Lu, J; Visser, P.J.

2015-01-01

The fluvial river is a kind of open system that can interact with its outside environments and give response to disturbance from outside on the earth. It can adjust itself to the disturbances outside the system and reflects new characteristics in the process of reaching a new equilibrium. The TGD

Fluvial-Deltaic Strata as a High-Resolution Recorder of Fold Growth and Fault Slip

Science.gov (United States)

Anastasio, D. J.; Kodama, K. P.; Pazzaglia, F. P.

2008-12-01

Fluvial-deltaic systems characterize the depositional record of most wedge-top and foreland basins, where the synorogenic stratigraphy responds to interactions between sediment supply driven by tectonic uplift, climate modulated sea level change and erosion rate variability, and fold growth patterns driven by unsteady fault slip. We integrate kinematic models of fault-related folds with growth strata and fluvial terrace records to determine incremental rates of shortening, rock uplift, limb tilting, and fault slip with 104-105 year temporal resolution in the Pyrenees and Apennines. At Pico del Aguila anticline, a transverse dècollement fold along the south Pyrenean mountain front, formation-scale synorogenic deposition and clastic facies patterns in prodeltaic and slope facies reflect tectonic forcing of sediment supply, sea level variability controlling delta front position, and climate modulated changes in terrestrial runoff. Growth geometries record a pinned anticline and migrating syncline hinges during folding above the emerging Guarga thrust sheet. Lithologic and anhysteretic remanent magnetization (ARM) data series from the Eocene Arguis Fm. show cyclicity at Milankovitch frequencies allowing detailed reconstruction of unsteady fold growth. Multiple variations in limb tilting rates from roof ramp and basal dècollement. Along the northern Apennine mountain front, the age and geometry of strath terraces preserved across the Salsomaggiore anticline records the Pleistocene-Recent kinematics of the underlying fault-propagation fold as occurring with a fixed anticline hinge, a rolling syncline hinge, and along-strike variations in uplift and forelimb tilting. The uplifted intersection of terrace deposits documents syncline axial surface migration and underlying fault-tip propagation at a rate of ~1.4 cm/yr since the Middle Pleistocene. Because this record of fault slip coincides with the well-known large amplitude oscillations in global climate that contribute

Obtaining isochrones from pollution signals in a fluvial sediment record: A case study in a uranium-polluted floodplain of the Ploučnice River, Czech Republic

International Nuclear Information System (INIS)

Matys Grygar, T.; Elznicová, J.; Bábek, O.; Hošek, M.; Engel, Z.; Kiss, T.

2014-01-01

Highlights: • Integrated approach to assess pollutant distribution in floodplain. • Natural background concentration is a function and not a value. • Concept of local enrichment factors based on local background functions. • Secondary pollution from transient fluvial deposits. - Abstract: Uranium mining and processing in the watershed of the Ploučnice River in the Czech Republic during a well-defined time interval (1969–1989) allowed for a study of pollutant fates in sediments of a meandering river that is otherwise in a nearly natural state. A considerable part of the primary pollution is present in hotspots in the floodplain 10–15 km downstream from the mining district. One of the hotspots was characterised using geoinformatic, geophysical and geochemical means. The floodplain geomorphology and architecture and river channel dynamics were studied to develop an understanding of the formation of the hotspot and evaluate further movement of pollutants in the river system. Local background functions (with Rb or Ti as a predictor) and local enrichment factors (LEFs) were obtained for Ba, Ni, Pb, U and Zn concentrations in unpolluted sediments from the deeper strata of the active floodplain, an abandoned floodplain and an ancient terrace. The most recent (2013) overbank fines in the study area are still considerably enriched in Ni, U and Zn (LEF 3, 6 and 8, respectively), and thus pollution by heavy metals several km downstream of the hotspots continuously increases even though the primary source of pollution was terminated more than 20 years ago. The onset of the primary pollution (the base of the polluted strata) is hence clearly identified in the distal floodplain sediments as persistent and a potentially isochronous pollution signal in the fluvial record, whereas a secondary pollution signal overwrites the expected “primary pollution climax” and “pollution improvement” signals. That inertia of the fluvial system can also be expected in other

Metodología alternativa para la aplicación del aprendizaje servicio en la Educación Básica

OpenAIRE

Escudero, Alexandro; Ochoa, Azucena

2016-01-01

Las experiencias de aprendizaje servicio son estrategias educativas que permiten al alumnado salir de los salones de clase y colaborar en la solución de un problema sentido de la comunidad. Este servicio a la comunidad siempre está vinculado al aprendizaje de un contenido formal del currículum, pero sus resultados generalmente exceden esas expectativas de aprendizaje. Esta investigación en proceso encontró que la aplicación de la metodología habitual del aprendizaje servicio encuentra varias ...

La relación entre las dicotomías cultura-naturaleza, hombre-mujer y humano-animal en el pensamiento feminista

OpenAIRE

Rodríguez Carreño, Jimena

2016-01-01

Gran parte del pensamiento feminista ha combatido el dualismo hombre/mujer al tiempo que ha tolerado el que enfrenta a la naturaleza con la cultura y a los humanos con los animales. Lo cierto es, sin embargo, que estos tres dualismos se encuentran tan vinculados que, para combatir uno de ellos, hay que combatirlos todos. Mostrar esta relación esencial entre dichas dicotomías es el objetivo fundamental de este trabajo. Al analizar tales dualismos, surgen otros también de gran importan...

Fuentes del crecimiento económico en Argentina 1990-2004: ¿otro caso de la tiranía de los números?

OpenAIRE

Coremberg, Ariel

2007-01-01

Se investigan las principales fuentes del crecimiento económico en Argentina durante el período 1990-2004, con el fin de identificar cuál fue su perfil de crecimiento prevaleciente: extensivo, asociado al dinamismo de los factores productivos, o intensivo, vinculado con las ganancias de productividad. Fil: Coremberg, Ariel. Universidad Nacional de La Plata. La Plata. Argentina

PERCEPCIONES DE LOS CIUDADANOS DE BARRANQUILLA (COLOMBIA FRENTE AL GOBIERNO ELECTRÓNICO

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Carlos Arcila Calderón

2014-01-01

Full Text Available El Gobierno Electrónico ( GE es un instrumento de cambio social importante en la sociedad actual. El objetivo del presente estudio es conocer cuáles son las percepciones (expectativas y experiencias de los ciudadanos de Barranquilla frente al GE . Se utilizó la encuesta como técnica de recolección de datos y la investigación se desarrolló en dos etapas: una exploratoria con una muestra aleatoria de ciudadanos de Barranquilla (n= 345 y otra descriptiva con una muestra focalizada de jóvenes estudiantes (n=180 de la Universidad del Norte. Los resultados de ambas encuestas muestran un bajo conocimiento de las plataformas de GE y que quienes la conocían tenían dificultades en definirlas. Encontramos que el GE está más vinculado a la bús - queda de información, para la que se tiene una percepción positiva del diseño e interface, que a la participación e interacción efectiva. Adicionalmente, encontramos que existe una relación significativa entre la edad y el uso y confianza del GE : los mayores tienden más a usarla, pero los menores las valoran mejor. La investigación concluye y recomienda que la investigación futura sobre el tema ahonde sobre los aspectos sociales y esté centrada en los ciudadanos, más que en los aspectos meramente técnicos.

Deformaciones neotectónicas en el relieve fluvial de la Llanura Sur de Pinar del Río, Cuba

OpenAIRE

Estévez Cruz, Elmidio; Ordaz Hernández, Alexis; Hernández Santana, José Ramón

2017-01-01

Resumen: Las investigaciones neotectónicas se enfocan a la determinación de los movimientos tectónicos más recientes de la corteza terrestre y poseen un gran significado en el análisis geomorfológico de la estructura del relieve moderno. En las regiones relativamente llanas no siempre resulta fácil el reconocimiento de evidencias de las deformaciones neotectónicas en el relieve fluvial. Desde el punto de vista metodológico, quedó demostrada la eficiencia del empleo de los métodos geológicos, ...

Relación entre el proceso evolutivo del ser humano y su predisposición al cáncer

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Armando Ernesto Pérez Cala

2018-02-01

Full Text Available El cáncer se ha convertido en la primera causa de morbimortalidad en numerosos países. En las últimas décadas se ha asistido a un cambio en el paradigma conceptual de las enfermedades neoplásicas, que ahora se enfoca hacia la perspectiva ecológica-evolutiva de estas. Con el objetivo de analizar, con elementos actualizados, la relación entre el proceso evolutivo del ser humano y su predisposición al cáncer, se realizó una revisión sistemática de la literatura, a partir de tres bases de datos, Medline, Scopus, y SciELO. Se tuvieron en cuenta atributos de consistencia de los artículos revisados, se excluyeron los estudios con niveles IV y V de evidencia y los de calidad insuficiente. Las búsquedas acumuladas actuales sugieren la necesidad de ver a las diversas neoplasias desde la perspectiva de la dinámica de sistemas complejos y sus implicaciones evolutivas. El proceso evolutivo humano posee particularidades biosociales que le predisponen a sufrir tumores malignos. La postura bípeda incrementó vulnerabilidad al efecto oncogénico de las radiaciones ultravioletas. La conducta sexual incrementó el riesgo de contraer infecciones por virus oncogénicos. El paso a una predominantemente cárnica y la introducción de la cocción, se tradujo en la incorporación de agentes xenobióticos cuyo metabolismo deriva agentes carcinógenos. La postergación del envejecimiento humano devino en un mayor tiempo para el acúmulo de mutaciones. Las modificaciones en el patrón sexual y reproductivo en la mujer han influido en su predisposición al cáncer de mama. En la génesis poblacional del cáncer subyacen fundamentos biosociales vinculados al proceso evolutivo de la especie.

Características sedimentares fluviais associadas ao grau de reservação da mata Ciliar - Rio Urumajó, Nordeste Paraense Fluvial sedimentology associated with the degree of preservation of the riparian vegetation, Urumajó River, PA / Brazil

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Roney Nonato Reis de Brito

2009-03-01

Full Text Available Os rios são os agentes mais importantes no transporte dos sedimentos para as áreas mais baixas dos continentes e para o mar. Além dos efeitos diretos do clima local, a cobertura vegetal atua no controle da descarga e no suprimento de sedimentos. Sendo assim, o presente trabalho enfoca o padrão de distribuição granulométrica do rio Urumajó (nordeste paraense em relação ao estado de preservação da mata ciliar. Cinco estações (A-E foram estabelecidas de forma a registrar um transecto da nascente à foz do rio. Nessas estações, procedeu-se com a caracterização da mata ciliar, bem como do seu grau de preservação. Além disto, elaborou-se um perfil transversal ao canal para cada estação, com coleta de cinco amostras de sedimentos em cada perfil. Estes foram submetidos à análise granulométrica, que resultou na obtenção de valores da média, mediana, seleção, assimetria e curtose. Com os resultados foi possível reconhecer as características sedimentares normais do rio, onde areia média é a principal classe granulométrica transportada. Foram observadas nas estações A e C a clara tendência das amostras serem moderadamente bem selecionadas e aproximadamente simétricas, com dominância absoluta de areia média, o que está diretamente relacionado ao seu bom estado de preservação. Significativas variações granulométricas nas estações B, D e E foram associadas com o processo erosivo das margens do rio, conseqüência da degradação da mata ciliar. Além disso, foi constatada a influência das correntes de maré na sedimentologia da estação E, subsidiando também a delimitação do ambiente estuarino que se encontra associado ao canal fluvial.Rivers are the main ways of sediment transport from inland to the coastal zone and oceans. Despite direct influence of climate, the vegetation coverage plays a central role in liquid and solid fluvial discharge. In this context, the present work aimed to study the fluvial

Implications of the fluvial history of the Wacheqsa River for hydrologic engineering and water use at Chavín de Húntar, Peru

Science.gov (United States)

Contreras, Daniel A.; Keefer, David K.

2009-01-01

Channeling of water through a variety of architectural features represents a significant engineering investment at the first millennium B.C. ceremonial center of Chavín de Huántar in the Peruvian Central Andes. The site contains extensive evidence of the manipulation of water, apparently for diverse purposes. The present configuration of the two local rivers, however, keeps available water approximately 9m below the highest level of water-bearing infrastructure in the site. Geomorphic and archaeological investigation of the fluvial history of the Wacheqsa River has revealed evidence that the Chavín-era configuration of the Wacheqsa River was different. A substantially higher water level, likely the result of a local impoundment of river water caused by a landslide dam, made the provision of water for the hydrologic system within the site a more readily practical possibility. We review what is known of that system and argue that the fluvial history of the Wacheqsa River is critical to understanding this aspect of hydrologic engineering and ritual practice at Chavín. This study demonstrates the relative rapidity and archaeological relevance of landscape change in a dynamic environment.

A consistent magnetic polarity stratigraphy of Plio-Pleistocene fluvial sediments from the Heidelberg Basin (Germany)

Science.gov (United States)

Scheidt, Stephanie; Hambach, Ulrich; Rolf, Christian

2014-05-01

Deep drillings in the Heidelberg Basins provide access to one of the thickest and most complete successions of Quaternary and Upper Pliocene continental sediments in Central-Europe [1]. In absence of any comprehensive chronostratigraphic model, these sediments are so far classified by lithological and hydrogeological criteria. Therefore the age of this sequence is still controversially discussed ([1], [2]). In spite of the fact that fluvial sediments are a fundamental challenge for the application of magnetic polarity stratigraphy we performed a thorough study on four drilling cores (from Heidelberg, Ludwigshafen and nearby Viernheim). Here, we present the results from the analyses of these cores, which yield to a consistent chronostratigraphic framework. The components of natural remanent magnetisation (NRM) were separated by alternating field and thermal demagnetisation techniques and the characteristic remanent magnetisations (ChRM) were isolated by principle component analysis [3]. Due to the coring technique solely inclination data of the ChRM is used for the determination of the magnetic polarity stratigraphy. Rock magnetic proxies were applied to identify the carriers of the remanent magnetisation. The investigations prove the NRM as a stable, largely primary magnetisation acquired shortly after deposition (PDRM). The Matuyama-Gauss boundary is clearly defined by a polarity change in each core, as suggested in previous work [4]. These findings are in good agreement with the biostratigraphic definition of the base of the Quaternary ([5], [6], [7]). The Brunhes-Matuyama boundary could be identified in core Heidelberg UniNord 1 and 2 only. Consequently, the position of the Jaramillo and Olduvai subchron can be inferred from the lithostratigraphy and the development of fluvial facies architecture in the Rhine system. The continuation of the magnetic polarity stratigraphy into the Gilbert chron (Upper Pliocene) allows alternative correlation schemes for the cores

Fluvial reservoir characterization using topological descriptors based on spectral analysis of graphs

Science.gov (United States)

Viseur, Sophie; Chiaberge, Christophe; Rhomer, Jérémy; Audigane, Pascal

2015-04-01

Fluvial systems generate highly heterogeneous reservoir. These heterogeneities have major impact on fluid flow behaviors. However, the modelling of such reservoirs is mainly performed in under-constrained contexts as they include complex features, though only sparse and indirect data are available. Stochastic modeling is the common strategy to solve such problems. Multiple 3D models are generated from the available subsurface dataset. The generated models represent a sampling of plausible subsurface structure representations. From this model sampling, statistical analysis on targeted parameters (e.g.: reserve estimations, flow behaviors, etc.) and a posteriori uncertainties are performed to assess risks. However, on one hand, uncertainties may be huge, which requires many models to be generated for scanning the space of possibilities. On the other hand, some computations performed on the generated models are time consuming and cannot, in practice, be applied on all of them. This issue is particularly critical in: 1) geological modeling from outcrop data only, as these data types are generally sparse and mainly distributed in 2D at large scale but they may locally include high-resolution descriptions (e.g.: facies, strata local variability, etc.); 2) CO2 storage studies as many scales of investigations are required, from meter to regional ones, to estimate storage capacities and associated risks. Recent approaches propose to define distances between models to allow sophisticated multivariate statistics to be applied on the space of uncertainties so that only sub-samples, representative of initial set, are investigated for dynamic time-consuming studies. This work focuses on defining distances between models that characterize the topology of the reservoir rock network, i.e. its compactness or connectivity degree. The proposed strategy relies on the study of the reservoir rock skeleton. The skeleton of an object corresponds to its median feature. A skeleton is

Sandstone-body and shale-body dimensions in a braided fluvial system: Salt wash sandstone member (Morrison formation), Garfield County, Utah

Science.gov (United States)

Robinson, J.W.; McCabea, P.J.

1997-01-01

Excellent three-dimensional exposures of the Upper Jurassic Salt Wash Sandstone Member of the Morrison Formation in the Henry Mountains area of southern Utah allow measurement of the thickness and width of fluvial sandstone and shale bodies from extensive photomosaics. The Salt Wash Sandstone Member is composed of fluvial channel fill, abandoned channel fill, and overbank/flood-plain strata that were deposited on a broad alluvial plain of low-sinuosity, sandy, braided streams flowing northeast. A hierarchy of sandstone and shale bodies in the Salt Wash Sandstone Member includes, in ascending order, trough cross-bedding, fining-upward units/mudstone intraclast conglomerates, singlestory sandstone bodies/basal conglomerate, abandoned channel fill, multistory sandstone bodies, and overbank/flood-plain heterolithic strata. Trough cross-beds have an average width:thickness ratio (W:T) of 8.5:1 in the lower interval of the Salt Wash Sandstone Member and 10.4:1 in the upper interval. Fining-upward units are 0.5-3.0 m thick and 3-11 m wide. Single-story sandstone bodies in the upper interval are wider and thicker than their counterparts in the lower interval, based on average W:T, linear regression analysis, and cumulative relative frequency graphs. Multistory sandstone bodies are composed of two to eight stories, range up to 30 m thick and over 1500 m wide (W:T > 50:1), and are also larger in the upper interval. Heterolithic units between sandstone bodies include abandoned channel fill (W:T = 33:1) and overbank/flood-plain deposits (W:T = 70:1). Understanding W:T ratios from the component parts of an ancient, sandy, braided stream deposit can be applied in several ways to similar strata in other basins; for example, to (1) determine the width of a unit when only the thickness is known, (2) create correlation guidelines and maximum correlation lengths, (3) aid in interpreting the controls on fluvial architecture, and (4) place additional constraints on input variables to

Plio-Quaternary river incision rates inferred from burial dating (Al-26/Be-10) of in cave-deposited alluvium in the Meuse catchment (E Belgium): new insights into the uplift history of the Ardennes massif

Science.gov (United States)

Rixhon, Gilles; Bourlès, Didier; Braucher, Régis; Peeters, Alexandre; Demoulin, Alain

2017-04-01

Although the Late Cenozoic uplift of the intraplate Variscan Ardennes/Rhenish massif (N Europe) has been long studied, its causes, shape and timing are still under debate (Demoulin & Hallot, 2009). This is mainly due to the scarcity of reliable ages for uplift markers, such as Quaternary terrace staircases along the deeply-incised valleys or Late Tertiary planation surfaces. In parallel, multi-level cave systems in limestone rocks, wherein abandoned phreatic passages filled with alluvium represent former phases of fluvial base-level stability, record the history of regional river incision (Anthony & Granger, 2007). Here, we present new burial ages (Al-26/Be-10) from fluvial gravels washed in a multi-level cave system developed in Devonian limestones of the lower Ourthe valley (main Ardennian tributary of the Meuse). Our results highlight a significant increase of incision rates from the Middle Pleistocene on, and allow reconstructing the incision history in the northern part of the Ardennes over the last 3.4 Ma. These long-term incision rates derived from burial ages are then discussed in relation to the existing studies dealing with river incision and/or tectonic uplift of the Ardennes/Rhenish massif (e.g. Demoulin & Hallot, 2009; Rixhon et al., 2011). Our cosmogenic nuclide ages thus enlarge the data pool required to explore the spatio-temporal characteristics of the drainage system's incision response to combined tectonic and climatic signals. References Anthony, D., Granger, D.E., 2007. A new chronology for the age of Appalachian erosional surfaces determined by cosmogenic nuclides in cave sediments. Earth Surf. Process. Landforms 32, 874-887 Demoulin, A., Hallot, E., 2009. Shape and amount of the Quaternary uplift of the western Rhenish shield and the Ardennes (western Europe). Tectonophysics 474, 696-708. Rixhon, G., et al., 2011. Quaternary river incision in NE Ardennes (Belgium): Insights from Be-10/Al-26 dating of rive terraces. Quaternary Geochronology 6

Assessing the role of detrital zircon sorting on provenance interpretations in an ancient fluvial system using paleohydraulics - Permian Cutler Group, Paradox Basin, Utah and Colorado

Science.gov (United States)

Findlay, C. P., III; Ewing, R. C.; Perez, N. D.

2017-12-01

Detrital zircon age signatures used in provenance studies are assumed to be representative of entire catchments from which the sediment was derived, but the extent to which hydraulic sorting can bias provenance interpretations is poorly constrained. Sediment and mineral sorting occurs with changes in hydraulic conditions driven by both allogenic and autogenic processes. Zircon is sorted from less dense minerals due to the difference in density, and any age dependence on zircon size could potentially bias provenance interpretations. In this study, a coupled paleohydraulic and geochemical provenance approach is used to identify changes in paleohydraulic conditions and relate them to spatial variations in provenance signatures from samples collected along an approximately time-correlative source-to-sink pathway in the Permian Cutler Group of the Paradox Basin. Samples proximal to the uplift have a paleoflow direction to the southwest. In the medial basin, paleocurrent direction indicates salt movement caused fluvial pathways divert to the north and northwest on the flanks of anticlines. Channel depth, flow velocity, and discharge calculations were derived from field measurements of grain size and dune and bar cross-stratification indicate that competency of the fluvial system decreased from proximal to the medial basin by up to a factor of 12. Based upon the paleohydraulic calculations, zircon size fractionation would occur along the transect such that the larger zircons are removed from the system prior to reaching the medial basin. Analysis of the size and age distribution of zircons from the proximal and distal fluvial system of the Cutler Group tests if this hydraulic sorting affects the expected Uncompahgre Uplift age distribution.

Fluvial modulation of hydrodynamics and salt transport in a highly stratified estuary

Directory of Open Access Journals (Sweden)

Carla de Abreu D'Aquino

2010-06-01

de descarga fluvial. Séries temporais de nível da água, correntes e salinidade foram registradas durante 50 horas, em um local aproximadamente 7 km da desembocadura. Dois levantamentos longitudinais de salinidade também foram realizados. Os dados hidrográficos foram utilizados para calcular o fluxo advectivo de sal visando investigar os termos do transporte em função da mudança da descarga fluvial. Os resultados mostram que a estrutura estuarina foi fortemente modulada pela vazão fluvial. O nível da água baixou em torno de 0,5 m durante as primeiras 25 horas em relação direta com o decaimento da enchente do rio. Embora a coluna de água fosse altamente estratificada durante todo o período, e a estratificação aumentou durante as últimas 25 horas. As correntes foram mais intensas, de vazante e uni-direcionais no início, tornando mais fracas bidirecionais à medida que o nível da água baixou, adquirindo um padrão de maré. O transporte total de sal nas primeiras 25 horas foi de -13,6 Kg.m-1.s-1 (sentido do mar, mudando para 3 Kg.m-1.s-1 nas últimas 25 horas (sentido de terra. Foi também notável que o pH no estuário, registrado junto com a salinidade, em torno de 5, indicando que a qualidade da água ficou afetada pela atividade de mineração de carvão que ocorre na bacia hidrográfica.

Between the River and the City. Resilience VS Vulnerability in Settlement Systems of Fluvial Environment

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Filippo Angelucci

2014-05-01

Full Text Available In the presence of increasingly frequent extreme weather phenomena, water management in complex settlement areas, such as those located in a fluvial environment, involves not only the reduction of that area’s fragility but, more importantly, the regeneration of the lost interactions between the physical, economic and social dimensions of the area. Research conducted along the Pescara river has taken up this challenge, reinterpreting the critical environmental situation of the case study areas as the chance to oversee a more ample “water project” which could tackle the vulnerability of the territory by identifying new means of resilience and responsiveness to adverse natural events and by carrying out proactive coexistence scenarios between cities, inhabitants, institutions and natural resources.

Fault-sourced alluvial fans and their interaction with axial fluvial drainage: An example from the Plio-Pleistocene Upper Valdarno Basin (Tuscany, Italy)

Science.gov (United States)

Fidolini, Francesco; Ghinassi, Massimiliano; Aldinucci, Mauro; Billi, Paolo; Boaga, Jacopo; Deiana, Rita; Brivio, Lara

2013-05-01

The present study deals with the fault-sourced, alluvial-fan deposits of the Plio-Pleistocene Upper Valdarno Basin (Northern Apennines, Italy). Different phases of alluvial fan aggradation, progradation and backstep are discussed as possible effects of the interaction among fault-generated accommodation space, sediment supply and discharge variations affecting the axial fluvial drainage. The Upper Valdarno Basin, located about 35 km SE of Florence, is filled with 550 m palustrine, lacustrine and alluvial deposits forming four main unconformity-bounded units (i.e. synthems). The study alluvial-fan deposits belong to the two uppermost synthems (Montevarchi and Torrente Ciuffenna synthems) and are Early to Middle Pleistocene in age. These deposits are sourced from the fault-bounded, NE margin of the basin and interfinger with axial fluvial deposits. Alluvial fan deposits of the Montevarchi Synthem consist of three main intervals: i) a lower interval, which lacks any evidence of a depositional trend and testify balance between the subsidence rate (i.e. fault activity) and the amount of sediment provided from the margin; ii) a coarsening-upward middle interval, pointing to a decrease in subsidence rate associated with an augment in sediment supply; iii) a fining-upward, upper interval (locally preserved), documenting a phase of tectonic quiescence associated with a progressive re-equilibration of the tectonically-induced morphological profile. The basin-scale unconformity, which separates the Montevarchi and Torrente Ciuffenna synthems was due to the entrance of the Arno River into the basin as consequence of a piracy. This event caused a dramatic increase in water discharge of the axial fluvial system, and its consequent embanking. Such an erosional surface started to develop in the axial areas, and propagated along the main tributaries, triggering erosion of the alluvial fan deposits. Alluvial-fan deposits of the Torrente Ciuffenna Synthem accumulated above the

Fluvial Connectivity and Sediment Dispersal within Continental Extensional Basins; Assessment of Controlling Factors using Numerical Modelling

Science.gov (United States)

Geurts, A., Jr.; Cowie, P. A.; Gawthorpe, R.; Huismans, R. S.; Pedersen, V. K.

2017-12-01

Progressive integration of drainage networks has been documented in many regional-scale studies of extensional continental systems. While endorheic drainage and lake sedimentation are common features observed in basin stratigraphy, they often disappear from the record due to the development of a through-going river network. Because changes in the fluvial connectivity of extensional basins have profound impact on erosion and sediment dispersal, and thus the feedback between surface processes and tectonics, it is of great importance to understand what controls them. Headward erosion (also called headward capture or river piracy) is often suggested to be the main mechanism causing basins to become interconnected over time with one another and with the regional/coastal drainage network. We show that overspill mechanisms (basin over-filling or lake over-spilling) play a key role in the actively extending central Italian Apennines, even though this area is theoretically favorable for headward erosion (short distances to the coast in combination with rapid surface uplift). In other tectonic settings (e.g. contractional basins and high plateaux) the role of headward erosion in transverse drainage development and integrating endorheic basins has also been increasingly questioned. These two mechanisms predict very different spatio-temporal patterns of sediment dispersal and thus timing of sediment loading (or erosional unloading) along active normal faults, which in turn may influence the locus of subsequent extensional deformation. By means of surface process modelling we develop a process-based understanding of the controls on fluvial connectivity between extensional basins in the central Italian Apennines. We focus on which conditions (tectonic and erosional) favour headward erosion versus overspill and compare our model results with published field evidence for drainage integration and the timing of basin sedimentation/incision.

Interactions between fluvial forces and vegetation size, density and morphology influence plant mortality during experimental floods

Science.gov (United States)

Stella, J. C.; Kui, L.; Manners, R.; Wilcox, A. C.; Lightbody, A.; Sklar, L. S.

2015-12-01

Introduction and methods Fluvial disturbance is a key driver of riparian vegetation dynamics in river corridors. Despite an increasing understanding of ecohydraulic interactions between plants and fluvial forces, the interactive influences of plant morphology and sediment supply on plant mortality, a key demographic factor, are largely unknown. To better understand these processes, we designed and conducted a series of flume experiments to: (1) quantify effects of plant traits that interact with flow and sediment transport on plant loss to scour during floods; and (2) predict plant dislodgement for different species across a range of plant sizes, patch densities, and sediment condition (equilibrium transport versus sediment deficit). We ran ten experimental floods in a 28 m long × 0.6 m wide × 0.71 m tall flume, using live, 1-3 year-old tamarisk and cottonwood seedlings with contrasting morphologies with varied combinations of size and density. Results and discussion Both sediment supply and plant traits (morphology and composition) have significant impacts on plant vulnerability during floods. Sediment deficit resulted in bed degradation and a 35% greater risk of plant loss compared to equilibrium sediment conditions. The probability of plant dislodgement in sparse patches was 4.5 times greater than in dense patches. Tamarisk plants and patches had greater frontal area, basal diameter and longer roots compared to cottonwood across all seedling heights. These traits, as well as its lower crown position reduced tamarisk's vulnerability to scour by 75%. Compared with cottonwood, tamarisk exhibits better resistance to floods, due to its greater root biomass and longer roots that stabilize soil, and its greater frontal area and lower crown that effectively trap sediment. These traits likely contribute to riverscape-scale changes in channel morphology that are evident where tamarisk has invaded native riparian communities, and explain the persistence of tamarisk

Evidences of Paleoearthquakes in Palaeolithic settlements within fluvial sequences of the Tagus Basin (Madrid, Central Spain).

Science.gov (United States)

Silva, Pablo G.; Rodríguez Pascua, M. A.; Pérez López, R.; Giner Robles, J. L.; Roquero, E.; Tapias, F.; López Recio, M.; Rus, I.; Morin, J.

2010-05-01

Multiple evidences of soft-sediment to brittle deformation within the Pleistocene fluvial terraces of the Tagus, Jarama, Tajuña and Manzanares river valleys have been described since the middle 20th Century. Cryoturbation, hydroplastic deformations due to underlying karstic collapses or halokinesis on the substratum of neogene gypsums, and seismic shaking have been proposed to interpret these structures. These deformations are typically concentrated in the +18-20 m terrace levels, and closely linked to well-known Palaeolithic sites, in some cases overlaying and/or affecting true prehistoric settlements (i.e. Arganda, Arriaga and Tafesa sites) within the Jarama and Manzanares valleys. The affected settlements typically display acheulian lithic industry linked to the scavenging of large Pleistocene mammals (i.e. Elephas antiquus). Commonly, deformational structures are concentrated in relatively thin horizons (10-50 cm thick) bracketed by undeformed fluvial sands and gravels. The soft-sediment deformations usually consist on medium to fine sized sands injected and protruded in overlaying flood-plain clayey silts, showing a wide variety of convolutes, injections, sand-dikes, dish and pillar structures, mud volcanoes, faults and folds, some times it is possible to undertake their 3D geometrical analysis due to the exceptional conservation of the structures (Tafesa). Recent geo-archaeological prospecting on the for the Palaeolithic Site of Arriaga (South Madrid City) conducted during the year 2009, let to find out an exceptional horizon of deformation of about 1.20 m thick. It consisted on highly disturbed and pervasively liquefacted sands, which hardly can be attributed to no-seismic processes. The acheulian lithic industry of the Madrid Region have been classically attributed the Late Middle Pleistocene (Comunidad de Madrid, AUDEMA S.A. (Proyecto Arriaga-2009). This is a contribution of GQM-AEQUA.

Fluvial export of radionuclides: impact on sediment storages of the Rhone River and fluxes towards the Mediterranean Sea; Transfert des radionucleides artificiels par voie fluviale: consequences sur les stocks sedimentaires rhodaniens et les exports vers la Mediterranee

Energy Technology Data Exchange (ETDEWEB)

Rolland, B

2006-02-15

This study deals with the behaviour of trace contaminants originating from chronic liquid releases within fluvial aquatic systems. It focuses on some particle reactive artificial radionuclides that were released by the Marcoule nuclear fuel reprocessing plant during several years mainly prior the end of the nineties and that are still detected in the lower Rhone river. It underlines the decrease of {sup 137}Cs, {sup 238}Pu and {sup 239+240}Pu fluxes to the Mediterranean Sea in relation with the variations in the chronic liquid releases from Marcoule. The role of flood events on radionuclides exports processes is particularly considered. Over the years 2002 to 2004, floods contributed for 67%, 55%, 68%, 49% and 56% of the mean annual fluxes of {sup 137}Cs, {sup 238}Pu and {sup 239+240}Pu and natural {sup 7}Be et {sup 210}Pbxs, although these events only represented 5% of time. The removal, during floods, of sediments contaminated by the Marcoule releases contributes on the average for 19%, 44% and 22% of the annual exports of {sup 137}Cs, {sup 238}Pu and {sup 239+240}Pu towards the Sea. Thus, such sedimentary stocks act as a delayed source term of artificial radioactivity that is currently significant. Determination of the sediments residence times before removal allows to evaluate the Rhone capacity to clear its contaminated stocks. Residence times of 200 years, 100 years and 900 years are estimated to be necessary to totally remove the accumulated {sup 137}Cs, {sup 238}Pu and {sup 239+240}Pu, respectively. The location typologies of sediment storages within fluvial systems are also specified. These location are represented on one hand by dams, and on the other hand by river banks and oxbow lakes. Stocks accumulated in dams seem to be removed more easily than those trapped in banks. (author)

Análisis del comportamiento de la demanda de importaciones de limón persa (Citrus latifolia tanaka) y mexicano (Citrus aurantifolia swingle) en los Estados Unidos

OpenAIRE

Sánchez Torres, Yolanda

2011-01-01

La agricultura mexicana en la década de los setentas inicia un proceso de expansión en la producción de frutas y hortalizas; y con ello la relevancia de frutas de clima tropical en el mercado mundial. Para 2008 México ocupaba el segundo lugar como productor mundial (14.94%) de limones y el primero como exportador (20.5%), teniendo dos variedades altamente competitivas: el limón mexicano, orientado al mercado nacional (96.2%) y el limón persa vinculado al mercado internacional (50.3%). El obj...

Mundos utópicos y distópicos: El progreso y la ciencia como síntomas modernos en el cine mexicano de ciencias ficción (2002-2012)

OpenAIRE

González Garza, Alejandro; Zavala Scherer, Diego

2013-01-01

El presente artículo aborda, de manera monográfica, la producción de largometrajes mexicanos asociados al género de ciencia ficción, en el periodo del 2002 al 2012. El texto parte de entender este género como un producto cultural vinculado profundamente con la sociedad que lo imagina. Esta forma de proposición de mundos posibles, futuros o paralelos, es la clave de análisis de los deseos y peligros que, en este caso la sociedad mexicana, vislumbra sobre su propio devenir histórico...

Ayotzinapa en el contexto de la restauración autoritaria en México

OpenAIRE

Velázquez Ramírez, Adrián

2015-01-01

El objetivo de estas líneas es ofrecer algunas coordenadas que le permitan al lector ubicar la desaparición de 43 estudiantes en septiembre de 2014 dentro del proceso político mexicano de las últimas décadas. En efecto, lo ocurrido en Ayotzinapa –Guerrerono es un caso aislado sino una tragedia que, con actores, escalas y magnitudes diferentes, se ha repetido a lo largo de los últimos años en el escenario mexicano. Cuaderno vinculado al vol. 5, no. 10 Facultad de Humanidades y Ciencias d...

a Review of Late Holocene Fluvial Systems in the Karst Maya Lowlands with Focus on the Rio Bravo, Belize

Science.gov (United States)

Beach, T.; Luzzadder-Beach, S.; Krause, S.; Doyle, C.

2015-12-01

The Maya Lowlands is mostly an internally draining karst region with about 400 m of regional relief. Fluvial and fluviokarst systems drain the edges of this landscape either from low limestone uplands or igneous and metamorphic complexes. Thus far most fluvial research has focused around archaeology projects, and here we review the extant research conducted across the region and new research on the transboundary Rio Bravo watershed of Belize and Guatemala. The Rio Bravo drains a largely old growth tropical forest today, but was partly deforested around ancient Maya cities and farms from 3,000 to 1000 BP. Several studies estimate that 30 to 40 percent of forest survived through the Maya period. Work here has focused on soils and sediment movement along slope catenas, in floodplain sites, and on contributions from groundwater with high dissolved loads of sulfate and calcium. We review radiocarbon dates and present new dates and soil stratigraphy from these sequences to date slope and floodplain movement, and we estimate ancient land use from carbon isotopic and pollen evidence. Aggradation in this watershed occurred by flooding, gypsum precipitation, upland erosion, and ancient Maya canal building and filling for wetland farming. Soil erosion and aggradation started at least by 3,000 BP and continued through the ancient Maya period, though reduced locally by soil conservation, post urban construction, and source reduction, especially in Maya Classic period from 1700 to 1000 BP.

Correlation of fluvial sequences in the Mediterranean basin over the last 200 ka and their relationship to climate change

Science.gov (United States)

Macklin, M. G.; Fuller, I. C.; Lewin, J.; Maas, G. S.; Passmore, D. G.; Rose, J.; Woodward, J. C.; Black, S.; Hamlin, R. H. B.; Rowan, J. S.

2002-08-01

This paper presents a new correlation of Late and Middle Pleistocene fluvial sedimentary sequences in Greek, Libyan and Spanish river basins and evaluates river response to climate change over the Last Interglacial-Glacial Cycle. Over the past 200,000 years there have been at least 13 major alluviation episodes in the Mediterranean, although the amplitude, frequency and possibly, duration of these events varied significantly across the region. Parts of Oxygen Isotope Stage (OIS) 5 appears to have been periods of pronounced landscape change in many Mediterranean catchments with major river aggradation occurring at ˜109-111 ka (during OIS 5d) and most notably at ˜88 ka (OIS 5b/5a boundary). Other parts of OIS 5 appear to have been periods of relative fluvial inactivity. OIS 2 and 3 were both characterised by an apparent increase in the number of alluviation events, and this record of river behaviour parallels many other palaeoenvironmental records in the region which also show more frequent climate fluctuations between ˜12 and 65 ka. There is evidence for a high degree of synchrony in major river aggradation events across the Mediterranean in catchments with very different sizes, tectonic regimes and histories. Climate-related changes in catchment hydrology and vegetation cover over the last 200 ka would appear to be the primary control of large-scale (catchment wide) sedimentation over time periods of between 10 3 and 10 4 years.

Quantifying Quaternary Deformation in the Eastern Cordillera of the Colombian Andes Using Cosmogenic Nuclide Geochronology and Fluvial Geomorphology

Science.gov (United States)

Dalman, E.; Taylor, M. H.; Veloza-fajardo, G.; Mora, A.

2014-12-01

Northwest South America is actively deforming through the interaction between the Nazca, South American, and Caribbean plates. Though the Colombian Andes are well studied, much uncertainty remains in the rate of Quaternary deformation along the east directed frontal thrust faults hundreds of kilometers in board from the subduction zones. The eastern foothills of the Eastern Cordillera (EC) preserve deformed landforms, allowing us to quantify incision rates. Using 10Be in-situ terrestrial cosmogenic nuclide (TCN) geochronology, we dated 2 deformed fluvial terraces in the hanging wall of the Guaicaramo thrust fault. From the 10Be concentration and terrace profile relative to local base level, we calculated incision rates. We present a reconstructed slip history of the Guaicaramo thrust fault and its Quaternary slip rate. Furthermore, to quantify the regional Quaternary deformation, we look at the fluvial response to tectonic uplift. Approximately 20 streams along the eastern foothills of the Eastern Cordillera (EC) were studied using a digital elevation model (DEM). From the DEM, longitudinal profiles were created and normalized channel steepness (Ksn) values calculated from plots of drainage area vs. slope. Knickpoints in the longitudinal profiles can record transient perturbations or differential uplift. Calculated Ksn values indicate that the EC is experiencing high rates of uplift, with the highest mean Ksn values occurring in the Cocuy region. Mean channel steepness values along strike of the foothills are related to increasing uplift rates from south to north. In contrast, we suggest that high channel steepness values in the south appear to be controlled by high rates of annual precipitation.

A Middle-Upper Miocene fluvial-lacustrine rift sequence in the Song Ba Rift, Vietnam

DEFF Research Database (Denmark)

Lars H., Nielsen; Henrik I., Petersen; Nguyen D., Dau

2007-01-01

The small Neogene Krong Pa graben is situated within the continental Song Ba Rift, which is bounded by strike-slip faults that were reactivated as extensional faults in Middle Miocene time. The 500 m thick graben-fill shows an overall depositional development reflecting the structural evolution...... subsidence rate and possibly a higher influx of water from the axial river systems the general water level in the graben rose and deep lakes formed. High organic preservation in the lakes prompted the formation of two excellent oil-prone lacustrine source-rock units. In the late phase of the graben...... as carrier beds, whereas the braided fluvial sandstones and conglomerates along the graben margins may form reservoirs. The Krong Pa graben thus contains oil-prone lacustrine source rocks, effective conduits for generated hydrocarbons and reservoir sandstones side-sealed by the graben faults toward...

The effects of peat mining on fluvial fish and their environment

International Nuclear Information System (INIS)

Laine, A.; Sutela, T.; Heikkinen, K.; Karvonen, K.; Huhta, A.; Mutka, T.; Lappalainen, A.

1996-01-01

The effects of peat mining on the quality of the stream bed, benthic fauna and fluvial fish were studied at rifles of the Rivers Iijoki and Kiiminkijoki in 1991-94. The amount of organic matter that accumulated on the bottom increased below peat mining areas. Some shifts were seen also in the composition and density of the benthic fauna. In spite of the increase in the total density of the benthic fauna, the growth of the young salmonids was weaker in the riffles that were affected by peat production. Especially large-sized caddish fly larvae were eaten less and also the stomachs of one- year-old salmon were on the average less full there than in the reference areas. Fish densities varied a lot, and no statistical differences were observed between the loaded and the reference areas. The survival of the stocked 0+ salmon fry, however, decreased along with increasing load from peat mining areas. Below the peat mining areas, also the mortality of the incubated brown trout roe was higher than in the reference areas, most probably because of the siltage of the river bottom

FLUVIAL PROCESSES IN ATTACHMENT BARS IN THE UPPER PARANÁ RIVER, BRAZIL

Directory of Open Access Journals (Sweden)

Vanessa Cristina Dos Santos

2017-08-01

Full Text Available Bars are semi-submerged fluvial forms associated with the availability of sediments and a temporal dynamic, whose dimensions are controlled by the flow and depth of the channel.  Attachment bars are very common in large anabranching river systems and play an important role in island formation and ecology. The Upper Paraná River exhibits an anabranching pattern characterized by channels of different sizes, separated by islands and bars. The objective of this work is to present the processes involved in the formation and development of attachment bars in Santa Rosa Island, situated in Porto Rico, State of Parana, Southern Brazil. Acquisition campaigns were performed to obtain data on channel hydraulics (ADCP equipment, morphometry (Echo-sound profiles and textural parameters (grain-size analyses at high and medium water levels. Santa Rosa Island divides the flow into two channels of distinct hydraulic and sedimentary dynamics. Flow diversion produces a decrease in flow velocity and consequent sediment deposition near the upstream end of Santa Rosa Island. The formation and maintenance of attachment bars in Santa Rosa Island is related to flow competence reduction and the occurrence of divergent currents. Vegetation cover and flow regime control its permanence. 

Percepciones de los ciudadanos de Barranquilla (Colombia frente al gobierno electrónico

Directory of Open Access Journals (Sweden)

Carlos Arcila Calderón

2013-11-01

Full Text Available El Gobierno Electrónico (GE es un instrumento de cambio social importante en la sociedad actual. El objetivo del presente estudio es conocer cuáles son las percepciones (expectativas y experiencias de los ciudadanos de Barranquilla frente al GE. Se utilizó la encuesta como técnica de recolección de datos y la investigación se desarrolló en dos etapas: una exploratoria con una muestra aleatoria de ciudadanos de Barranquilla (n= 345 y otra descriptiva con una muestra focalizada de jóvenes estudiantes (n=180 de la Universidad del Norte. Los resultados de ambas encuestas muestran un bajo conocimiento de las plataformas de GE y que quienes la conocían tenían dificultades en definirlas. Encontramos que el GE está más vinculado a la búsqueda de información, para la que se tiene una percepción positiva del diseño e interface, que a la participación e interacción efectiva. Adicionalmente, encontramos que existe una relación significativa entre la edad y el uso y confianza del GE: los mayores tienden más a usarla, pero los menores las valoran mejor. La investigación concluye y recomienda que la investigación futura sobre el tema ahonde sobre los aspectos sociales y esté centrada en los ciudadanos, más que en los aspectos meramente técnicos.

Signos Vitales de los CDC–El cáncer y el consumo de tabaco (Cancer and Tobacco Use)

Centers for Disease Control (CDC) Podcasts

Este podcast se basa en la edición de noviembre del 2016 del informe Signos Vitales de los CDC. Hay una larga lista de cánceres vinculados al consumo de tabaco, que es la principal causa prevenible de cáncer y de muertes por cáncer. Infórmese más aquí.

Compound simulation of fluvial floods and storm surges in a global coupled river-coast flood model : Model development and its application to 2007 Cyclone Sidr in Bangladesh

NARCIS (Netherlands)

Ikeuchi, Hiroaki; Hirabayashi, Yukiko; Yamazaki, Dai; Muis, Sanne; Ward, Philip J.; Winsemius, Hessel C.; Verlaan, Martin; Kanae, Shinjiro

2017-01-01

Water-related disasters, such as fluvial floods and cyclonic storm surges, are a major concern in the world's mega-delta regions. Furthermore, the simultaneous occurrence of extreme discharges from rivers and storm surges could exacerbate flood risk, compared to when they occur separately. Hence, it

Fluvial dispersion of radioactive mill tailings in the seasonally-wet tropics, northern Australia

International Nuclear Information System (INIS)

East, T.J.; Cull, R.F.; Murray, A.S.; Duggan, K.

1988-01-01

Erosion of tailings at the Northern Herculaes mine at Moline, abandoned in 1972 has resulted in large present-day input (up to 90g L -1 ) of radioactive sediments into local watercourses after the failure of containment bunds. This has been used as an analogue for predicting the possible fluvial dispersion of mine sediments at existing and future uranium mines in this region, e.g. it is helping to formulate rehabilitation policies at Ranger. The downstream dispersal patterns of radioactive tailings is controlled by the nature of sedimentary environments, the properties of tailing sediments which affect transport and the dilution of flow and sediment from incoming tributaries. A generally consistent relationship exist between the type of sedimentary floodplain environment and the surface gamma dose rates. While dose rates are shown to decrease with distance downstream from the source, there is a tendency for fine particles to be more radioactive. 28 refs., 2 tabs., 9 figs

Investigations of contaminated fluvial sediment deposits: merging of statistical and geomorphic approaches.

Science.gov (United States)

Ryti, Randall T; Reneau, Steven L; Katzman, Danny

2005-05-01

Concentrations of contaminants in sediment deposits can have large spatial variability resulting from geomorphic processes acting over long time periods. Thus, systematic (e.g., regularly spaced sample locations) or random sampling approaches might be inefficient and/or lead to highly biased results. We demonstrate the bias associated with systematic sampling and compare these results to those achieved by methods that merge a geomorphic approach to evaluating the physical system and stratified random sampling concepts. By combining these approaches, we achieve a more efficient and less biased characterization of sediment contamination in fluvial systems. These methods are applied using a phased sampling approach to characterize radiological contamination in sediment deposits in two semiarid canyons that have received historical releases from the Los Alamos National Laboratory. Uncertainty in contaminant inventory was used as a metric to evaluate the adequacy of sampling during these phased investigations. Simple, one-dimensional Monte Carlo simulations were used to estimate uncertainty in contaminant inventory. We also show how one can use stratified random sampling theory to help estimate uncertainty in mean contaminant concentrations.

Reservoir Characterization, Production Characteristics, and Research Needs for Fluvial/Alluvial Reservoirs in the United States

Energy Technology Data Exchange (ETDEWEB)

Cole, E.L.; Fowler, M.L.; Jackson, S.R.; Madden, M.P.; Raw-Schatzinger, V.; Salamy, S.P.; Sarathi, P.; Young, M.A.

1999-04-28

The Department of Energy's (DOE's) Oil Recovery Field Demonstration Program was initiated in 1992 to maximize the economically and environmentally sound recovery of oil from known domestic reservoirs and to preserve access to this resource. Cost-shared field demonstration projects are being initiated in geology defined reservoir classes which have been prioritized by their potential for incremental recovery and their risk of abandonment. This document defines the characteristics of the fifth geological reservoir class in the series, fluvial/alluvial reservoirs. The reservoirs of Class 5 include deposits of alluvial fans, braided streams, and meandering streams. Deposit morphologies vary as a complex function of climate and tectonics and are characterized by a high degree of heterogeneity to fluid flow as a result of extreme variations in water energy as the deposits formed.

Effects of livestock exclusion on density, survival and biomass of the perennial sagebrush grass Hymenachne pernambucense (Poaceae) from a temperate fluvial wetland

Science.gov (United States)

Magnano, Andrea L.; Nanni, Analía S.; Krug, Pamela; Astrada, Elizabeth; Vicari, Ricardo; Quintana, Rubén D.

2018-01-01

In Argentina, the intensification of soybean production has displaced a substantial proportion of cattle ranching to fluvial wetlands such as those in the Delta of the Paraná River. Cattle grazing affects structure and dynamics of native forage plants but there is little information on this impact in populations from fluvial wetlands. This study addresses the effect of cattle ranching on density, survival, mean life-span and aerial biomass of Hymenachne pernambucense (Poaceae), an important forage species in the region. The study was carried out monthly for one year in permanents plots subject to continuous grazing and plots excluded from grazing in the Middle Delta of the Paraná River. In plots excluded from grazing, tillers showed significantly higher population density and survival, and a two-fold increase in mean life-span, while continuous grazing decreased survival of cohorts. The largest contribution to tiller density in ungrazed and grazed populations was made by spring and summer cohorts, respectively. Total and green biomass were significantly higher in the ungrazed population, with highest differences in late spring-early summer. Cattle grazing affected the relationship between tiller density and green biomass suggesting that cattle prefer sprouts because they are more palatable and nutritious than older tissue.

Evaluación de requerimientos ecológicos para el diseño de regímenes ambientales de caudales fluviales

Directory of Open Access Journals (Sweden)

Juan Manuel Diez-Hernández

2008-11-01

Full Text Available Las sociedades avanzadas medioambientalmente están reclamando progresivamente una gestión fluvial auténticamente integral, que implemente Planes de Manejo de Cuencas Hidrográficas fundamentados en el paradigma del Régimen Ambiental de Caudales (RAC. Este trabajo sugiere una metodología genérica para establecer RAC confiables, que posibiliten el aprovechamiento hídrico a un coste ecológico admisible. Adicionalmente, plantea los criterios y técnicas preferentes para la evaluación de los requerimientos ecosistémicos de caudal, los cuales componen el RAC mediante el Régimen de Caudales Ecológicos (RCE. La adaptación de estos procedimientos para los ríos de Colombia favorecerá la conservación de su valiosa biodiversidad. / The environmentally advanced societies are claiming progressively an authentically integral fluvial management, that implements Watershed Management Programs based on the paradigm of the Environmental Flows Regime (EFR. This work suggests a generic methodology for the reliable EFR setting, that facilitate the water use with an environmental acceptable cost. Additionally, it outlines the approaches and outstanding techniques for the evaluation of instream flow requirements, which constitute the EFR by means of the Instream Flow Regime (IFR. The adaptation of these approaches to the Colombian rivers will contribute to the conservation of their valuable biodiversity.

A Pleistocene coastal alluvial fan complex produced by Middle Pleistocene glacio-fluvial processes

Science.gov (United States)

Adamson, Kathryn; Woodward, Jamie; Hughes, Philip; Giglio, Federico; Del Bianco, Fabrizio

2014-05-01

A coarse-grained alluvial fan sequence at Lipci, Kotor Bay, in western Montenegro, provides a sedimentary record of meltwater streams draining from the Orjen Massif (1,894 m a.s.l.) to the coastal zone. At Lipci sedimentary evidence and U-series ages have been used alongside offshore bathymetric imagery and seismic profiles to establish the size of the fan and constrain the nature and timing of its formation. Establishing the depositional history of such coastal fans is important for our understanding of cold stage sediment flux from glaciated uplands to the offshore zone, and for exploring the impact of sea level change on fan reworking. There is evidence of at least four phases of Pleistocene glaciation on the Orjen massif, which have been U-series dated and correlated to MIS 12, MIS 6, MIS 5d-2 and the Younger Dryas. A series of meltwater channels delivered large volumes of coarse- and fine-grained limestone sediment from the glaciated uplands into the Bay of Kotor. At the southern margin of the Orjen massif, a series of large (>700 m long) alluvial fans has developed. Some of these extend offshore for up to 600 m. Lipci fan lies downstream of end moraines in the valley immediately above, which were formed by an extensive outlet glacier of the Orjen ice cap during MIS 12. The terrestrial deposits are part of the fan apex (50 m a.s.l.) that lies at the foot of a steep bedrock channel, but the majority of the fan is now more than 25 m below sea level. The terrestrial fan sediments are strongly cemented by multiple generations of calcite precipitates: the oldest U-series ages are infinite indicating that the fan is >350 ka in age. These ages are in agreement with alluvial sedimentary evidence and U-series ages from other fluvial units on Mount Orjen. The terrestrial portion of the Lipci fan surface contains several channels. These are well preserved due to cementation with calcium carbonate. Submarine imagery indicates that the now submerged portion of the fan also

Costa Oriental Maya: una acercamiento al comercio y navegación

Directory of Open Access Journals (Sweden)

Iván Renato Zúñiga Carrasco

2014-01-01

Full Text Available La costa oriental de la Península de Yucatán ofreció un medio ideal para navegantes y mercaderes por la geografía costera peninsular cruzada por extensas redes fluviales que se extienden a lo largo de sus costas y se remontan lejanamente en el interior. E l intercambio de productos a través de largas distancias fue un factor básico en la homogeneidad cultural del mundo maya, jugando un papel crítico en el desarrollo de esta antigua civilización. El comercio marítimo maya se remonta al periodo Preclásico Ta rdío (300 a.C. - 300 d.C. Muchos puertos estaban ubicados en lugares estratégicos para el comercio, como islas, promontorios o a la entrada de ríos y en la mayoría de las veces se ubicaban en lugares protegidos del mar abierto. Las canoas utilizadas por los nativos no se trataba de simples troncos ahuecados; el uso de velas además y remos como puede verse en representaciones en murales y códices.

Una revisión de inundaciones fluviales en Chile, período 1574-2012: causas, recurrencia y efectos geográficos

OpenAIRE

Rojas,Octavio; Mardones,María; Arumí,José Luis; Aguayo,Mauricio

2014-01-01

Una revisión bibliográfica de inundaciones fluviales históricas en el período 15742012 a través de diferentes publicaciones, permite analizar, explicar y sistematizar causas o factores detonantes, periodos de recurrencia, distribución y efectos geográficos de las inundaciones acaecidas en Chile continental. Según el factor detonante se identifican 5 tipos principales de inundaciones asociadas a: procesos volcánicos, procesos nivoglaciares, deslizamientos, intervenciones antrópicas y precipita...

The impact of reduction of doublet well spacing on the Net Present Value and the life time of fluvial Hot Sedimentary Aquifer doublets

DEFF Research Database (Denmark)

Willems, C. J. L.; Nick, H. M.; Goense, T.

2017-01-01

This paper evaluates the impact of reduction of doublet well spacing, below the current West Netherlands Basin standard of 1000 - 1500 m, on the Net Present Value (NPV) and the life time of fluvial Hot Sedimentary Aquifer (HSA) doublets. First, a sensitivity analysis is used to show the possible ...... the potential and risks of HSA doublets. This factor significantly affects doublet life time and net energy production of the doublet....

Geological and Petrophysical Characterization of the Ferron Sandstone for 3-D Simulation of a Fluvial-Deltaic Reservoir

Energy Technology Data Exchange (ETDEWEB)

Chidsey, Jr, Thomas C.

2001-10-31

The objective of the Ferron Sandstone project was to develop a comprehensive, interdisciplinary, quantitative characterization f fluvial-deltaic reservoir to allow realistic interwell and reservoir-scale models to be developed for improved oil-field development in similar reservoirs world-wide. Quantitative geological and petrophysical information on the Cretaceous Ferron Sandstone in east-central Utah was collected. Both new and existing data was integrated into a three-dimensional model of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Simulation results could improve reservoir management through proper infill and extension drilling strategies, reduction of economic risks, increased recovery from existing oil fields, and more reliable reserve calculations.

Dating of river terraces along Lefthand Creek, western High Plains, Colorado, reveals punctuated incision

Science.gov (United States)

Foster, Melissa A.; Anderson, Robert S.; Gray, Harrison J.; Mahan, Shannon A.

2017-10-01

The response of erosional landscapes to Quaternary climate oscillations is recorded in fluvial terraces whose quantitative interpretation requires numerical ages. We investigate gravel-capped strath terraces along the western edge of Colorado's High Plains to constrain the incision history of this shale-dominated landscape. We use 10Be and 26Al cosmogenic radionuclides (CRNs), optically stimulated luminescence (OSL), and thermally transferred OSL (TT-OSL) to date three strath terraces, all beveled in shale bedrock and then deposited upon by Lefthand Creek, which drains the crystalline core of the Front Range. Our study reveals: (i) a long history (hundreds of thousands of years) of fluvial occupation of the second highest terrace, T2 (Table Mountain), with fluvial abandonment at 92 ± 3 ka; (ii) a brief occupation of a narrow and spatially confined terrace, T3, at 98 ± 7 ka; and (iii) a 10-25 thousand year period of cutting and fluvial occupation of a lower terrace, T4, marked by the deposition of a lower alluvial unit between 59 and 68 ka, followed by deposition of an upper alluvial package at 40 ± 3 ka. In conjunction with other recent CRN studies of strath terraces along the Colorado Front Range (Riihimaki et al., 2006; Dühnforth et al., 2012), our data reveal that long periods of lateral planation and fluvial occupation of strath terraces, sometimes lasting several glacial-interglacial cycles, are punctuated by brief episodes of rapid vertical bedrock incision. These data call into question what a singular terrace age represents, as the strath may be cut at one time (its cutting-age) and the terrace surface may be abandoned at a much later time (its abandonment age), and challenge models of strath terraces that appeal to simple pacing by the glacial-interglacial cycles.

Geoarchaeological investigation at Al-Khiday (central Sudan): late Quaternary palaeoenvironment and site formation

Science.gov (United States)

Zerboni, Andrea; Usai, Donatella; Salvatori, Sandro

2010-05-01

The micromorphological investigation on several pluristratified archaeological sites in central Sudan (Al-Khiday, left bank of the White Nile, Khartoum region, Sudan) permitted to elucidate depositional and post-depositional processes playing a role in the formation and preservation of the archaeological record. At Al-Khiday sites are located at the top of small mounds, representing the remains of Pleistocene sandy fluvial bars, and were attended since the beginning of the Holocene. The first occupation of the area corresponds to a pre-Mesolithic cemetery; than Mesolithic groups lived upon the mounds and their occupation is testified by several archaeological features: pits filled by ash and bones and living floors. Preserved Neolithic features are scarce and limited to few graves (V millennium BC). After this phase, a long gap in human attendance is registered, during which wind continued to dismantling the mounds and the sites; at ca. 2000 years BP Meroitic/Post-Meroitic groups built their tombs at the top of the archaeological sequences and altered most of the stratigraphic record. Thanks to micromorphology, it was possible to distinguish between archaeological strata still in situ and those disturbed by natural and anthropic processes; furthermore, this approach allowed to interpret the significance of several archaeological features (living floors, fireplaces, and garbage pits). In this case micromorphology of archaeological deposits was a key tool to reconstruct the depositional and post-depositional processes that contributed to the formation and preservation of the archaeological record.

Efectos de las presas en la dinàmica fluvial del curso bajo del río Ebro

OpenAIRE

Vericat Querol, Damià; Batalla, Ramon J.

2004-01-01

La morfología fluvial del cauce del río Ebro aguas abajo de las presas de Mequinenza y Ribarroja ha experimentado una serie de cambios a lo largo de la segunda mitad del siglo XX, entre los que cabe destacar: a) erosión lateral, b) colonización de zonas activas por vegetación de ribera, y c) disminución de la anchura. Dichos cambios se han producido después de la construcción y cierre de las presas en la década de los setenta. Las presas alteran la magnitud y frecuencia de las cre...

La evolución del paisaje fluvial en la confluencia de los ríos Tajo y Jarama

OpenAIRE

Berrocal Menárguez, Ana Belén

2013-01-01

La tesis doctoral que se presenta realiza un análisis de la evolución del paisaje fluvial de las riberas de los ríos Tajo y Jarama en el entorno de Aranjuez desde una perspectiva múltiple. Contempla y conjuga aspectos naturales, tales como los hidrológicos, geomorfológicos y ecológicos; también culturales, como la regulación hidrológica y la gestión del agua, las intervenciones en cauce y márgenes, la evolución de la propiedad y los cambios de usos del suelo, fundamentalmente. Este análisis h...

Effects of ZnO nanoparticles and Zn"2"+ on fluvial biofilms and the related toxicity mechanisms

International Nuclear Information System (INIS)

Xu, Yi; Wang, Chao; Hou, Jun; Dai, Shanshan; Wang, Peifang; Miao, Lingzhan; Lv, Bowen; Yang, Yangyang; You, Guoxiang

2016-01-01

Zinc oxide nanoparticles (ZnO NPs) used in consumer products are largely released into the environment through the wastewater stream. The health hazard of ZnO NPs and the contribution of dissolved Zn"2"+ in toxicity of ZnO NPs has attracted extensive worldwide attention. In this study, the toxic effects of ZnO nanoparticles (ZnO NPs) and the effects of dissolved Zn"2"+ on fluvial biofilms were investigated. At the end of the exposure time (21 days), scanning electron microscopy (SEM) images and bioaccumulation experiments revealed that large quantities of ZnO NPs were adsorbed on the biofilm. The algal biomasses were significantly decreased by six- and eleven-fold compared with the control (1.43 μg/L) by exposure to concentrations of 100 mg/L ZnO NPs and 7.85 mg/L Zn"2"+, respectively. Moreover, under the same exposure conditions, the quantum yields presented contents of 53.33 and 33.33% relative to the control, and a shift in the community composition that manifested as a strong reduction in diatoms was observed from 7 days and reached 15.63 and 6.25% of the control after 21 days of exposure, respectively. The reductions in bacteria viability and reactive oxygen species (ROS) production were noticeably enhanced following exposure to 100 mg/L ZnO NPs and 7.85 mg/L Zn"2"+, respectively. Additionally, the acute and rapid toxicity of Zn"2"+ and the increasing toxicity of the ZnO NPs with increased bioaccumulation were noted in the exposure experiment. - Highlights: • Fluvial biofilm was exposed to ZnO NPs and the dissolved Zn"2"+. • Chl-a and Φ_M decreased at high doses (100 and 7.85 mg/L of ZnO NPs and Zn"2"+). • A shift in the algae community composition was observed at high dosage levels. • The enhanced production of ROS declined the bacteria viability. • Zn"2"+ was more toxic than that of the ZnO-NPs.

Determination of Distribution and Properties of Soil Formed on Different Fluvial Deposit

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Orhan DENGİZ

2014-03-01

Full Text Available Alluvial land, formed on accumulated sediment depositions by time, show large variety in their properties at short distances. Therefore, different soils can be form on these lands. The objective of this research was to determine, mapping and classify different soils formed on fluvial land used for intensive cultivation in Örencik village of Samsun Bafra district. Total study area is approximately 407.9 ha. Average annual temperature and precipitation are 13.6 oC and 764.3 mm, respectively. After examination of topographic, land use, geologic and geomorphologic maps and land observation, 9 profile places were excavated in study area. Detailed land observations were done with grid method and auger examinations. The soil samples were taken from each profile and their analyses were done in the laboratory. By assessing the results of analyses and field studies, 7 different soil series were determined and described. Three of them were classified as Entisol due to their young age, three of them were classified as Inceptisol and one is as Vertisol. Whereas Cevizlik series has the largest area (24.7%, Elmacıdede series has the smallest area in the study area (7.8%.

The environmental project of the enhancement of the fluvial area: L’Aquila and the Aterno River

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Luciana Mastrolonardo

2016-06-01

Full Text Available Il contributo si colloca in un programma interdisciplinare volto alla valorizzazione e la tutela del fiume, attraverso il controllo dei flussi e l’attivazione di simbiosi. Si integrano, con un approccio che parte dalla progettazione ambientale, le tematiche urbane, paesaggistiche, tecnologiche ed ecologiche, per orientare lo sviluppo del territorio in termini di tutela e valorizzazione delle risorse, e per recuperare le discontinuità rappresentata oggi dal fiume, in alcuni contesti urbani, conferendole maggiore riconoscibilità e potenzialità. Nello specifico si indaga il rapporto tra L’Aquila e il fiume Aterno per individuare, a livello locale, le strategie perseguibili per il recupero delle connessioni tra l’ambito fluviale e urbano, per la valorizzazione del territorio e il ripristino della funzionalità dell’acqua nel suo ciclo vitale. 

Mundos utópicos y distópicos: el progreso y la ciencia como síntomas modernos en el cine mexicano de ciencias ficción / Utopian and Dystopian Worlds: Science and Progress as Modern Symptoms in Mexican Sci-Fi Films (2002-2012)

OpenAIRE

Alejandro González Garza; Diego Zavala Scherer

2016-01-01

El presente artículo aborda, de manera monográfica, la producción de largometrajes mexicanos asociados al género de ciencia ficción, en el periodo del 2002 al 2012. El texto parte de entender este género como un producto cultural vinculado profundamente con la sociedad que lo imagina. Esta forma de proposición de mundos posibles, futuros o paralelos, es la clave de análisis de los deseos y peligros que, en este caso la sociedad mexicana, vislumbra sobre su propio devenir histórico. A partir d...

El nuevo espacio rural en El Salvador. Análisis de un programa educativo de participación comunitaria

OpenAIRE

R. Marta Ramo Garzarán

2011-01-01

El actual concepto de Derecho a la Educación como Educación para Todos, está vinculado al desarrollo social, económico, político y cultural de los países en desarrollo y especialmente al de sus contextos rurales. Desde este enfoque, este estudio analiza la efectividad de algunas políticas educativas llevadas a cabo en las dos últimas décadas en el Salvador, EDUCO. Estas decisiones políticas en materia educativa han tenido como objetivo la protección, promoción y realización progresiva del cit...

Presentación y relatoría : Eje temático: Estudios sociales del deporte

OpenAIRE

Cachorro, Gabriel

2015-01-01

En la mesa de trabajo “Estudios sociales del Deporte”, se buscó promover la reflexión y el intercambio de miradas en torno a diferentes tópicos vinculados al abordaje de los eventos deportivos y la articulación con el periodismo deportivo. A su vez, se buscó disparar la reflexión acerca del Deporte como espacio de socialidad e identidad y formación subjetiva. Se miró el mercado, el Estado y las políticas deportivas: educacionales, salud, económicas. Se ubicó al deporte como derecho social: co...

Algunos pa(isajes oscuros en la historia del arte costarricense

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Pablo Bonilla Elizondo

2013-07-01

Full Text Available El presente artículo busca iluminar una serie de manifestaciones artísticas normalmente ignoradas por la historia del arte costarricense. Ubicadas fuera de lo que comúnmente se considera como la experiencia estética (autónoma, sublime, bella, noble, estos objetos de estudio han sido menospreciados y excluidos de los relatos dominantes. No es de extrañar, que ese desprecio esté vinculado a los peligros propios de la crítica, más cuando se enlaza el pensamiento político al pensamiento simbólico y al imaginario cultural de los pueblos.

The eolic fluvial succession and paleoclimatic evolution of Rio Conlara, San Luis, Argentina

International Nuclear Information System (INIS)

Chiesa, J.

2004-01-01

The outcroping deposits in the ravines of the Conlara River are dominated by silt with subordinated and variable percentages of sand and clays. In the section that is described, at the south of the town of Santa Rosa del Conlara, these materials have been deposited responding generally climatic changing conditions. The base of the profile, assigned to the late Pleistocene, contains extint fauna of the Lujanense and a datation of 8950 B.P., and it is represented by fluvial sandy gravels. The overlaying succession, assigned to the Holocene, shows an intercalation of horizons generated by eolic-loessic deposits and deposits with development of pedogenetic processes. The whole succession shows characteristic of corresponding to a vegetated plain, next to the river flood plain. The discriminated horizons are the result of a detailed sampling and the representation of range parameters of the same ones, in function of the depth, this last one oscillates between 6 and 8 meters. The quaternary deposits of the region, support indistinctly as on the crystalline basement of San Luis range, as on the calcretes assigned to the Neogene [es

Impact of super-distal ash fallout on tropical hydrology and landscape: a case study from the YTT deposits of the Perak river, Malaysia

Science.gov (United States)

Gatti, E.; Saidin, M.; Gibbard, P.; Oppenheimer, C.

2011-12-01

The Younger Toba Tuff eruption, approximately 73 ka ago, is the largest known for the Quaternary and its climate, environmental and human consequences are keenly debated (Oppenheimer, 2011).While the distribution (Rose and Chesner, 1987; Rose and Chesner, 1990; Chesner et al., 1991; Schulz et al., 2002; Von Rad et al., 2002) , geochemical properties (Shane et al., 1995; Westgate et al., 1998) and volcanic significance (Rampino and Self, 1982; Rampino and Self, 1993; Rampino and Ambrose, 2000; Oppenheimer, 2002; Mason et al., 2004)of the YTT have been widely studied, few attention has been given to the significance of the distal volcanic ash deposits within their receiving basin context. Although several studies exist on the impact of pyroclastic flows on proximal rivers and lakes (Collins and Dunne, 1986; Thompson et al., 1986; Hayes et al., 2002; Németh and Cronin, 2007), only few address the issues of the dynamic of preservation of super-distal fine ash deposits in rivers (also due to the lack of direct data on super-eruptions). It has also been demonstrated that models of the styles and timing of distal volcanoclastic re-sedimentation are more complicated than those developed for proximal settings of stratovolcanoes (Kataoka et al., 2009). We present an analysis of the taphonomy (intended as accumulation and preservation) of distal volcanic ash in fluvial and lacustrian contexts in newly discovered Toungest Toba Tuff sites in the Lenggong valley, western Peninsular Malaysia. The paper aims to characterise the nature of distal tephras in fluvial environments towards a stratigraphic distinction between primary ash and secondary ash, characterisation of the pre-ash fall receiving environment in term of fluvial dynamic and landscape morphology, and assessment of the time of recovery.

La transversalidad en la política turístico-cultural del pueblo mágico de Metepec, México

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David Hernández Díaz

2017-01-01

Full Text Available El tema de la política turístico-cultural se ha convertido en un aspecto prioritario para la administración pública en el desarrollo de proyectos vinculados al turismo y la cultura y, más aún, cuando se alude a la transversalidad como acción renovadora en la política pública. En este sentido, el presente trabajo efectúa una reflexión crítica en torno a este tipo de política en el municipio de Metepec, denominado Pueblo Mágico. Para ello, se analiza la aparición de la transversalidad en la política pública turístico-cultural, se revisan diversos programas de organismos que fomentan y promueven el turismo y la cultura en Metepec y trabajan en favor de la transversalidad e interacción de sus dependencias, así como entrevistas a diversos actores sociales para conocer su opinión en torno a esta temática. El estudio rescata la perspectiva crítica del turismo y la cultura con el fin de proponer un enfoque que revalore la transversalidad en sus políticas y la interacción entre los organismos vinculados al tema.

MODELOS DE LIDERAZGO POSITIVO: MARCO TEÓRICO Y LÍNEAS DE INVESTIGACIÓN

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Javier Blanch, Francisco Gil

2016-09-01

Full Text Available El objetivo de este artículo es doble, en primer lugar, se define el marco teórico del liderazgo positivo así como las razones de su aparición. Este surge vinculado al paradigma de la psicología organizacional positiva, en cuyo ámbito, se han desarrollado las diferentes formas de liderazgo que lo integran (i.e. transformacional, de servicio, espiritual, auténtico y positivo. Aunque el constructo no parece unívocamente delimitado, los diferentes tipos que se incluyen bajo esta denominaciónpresentan una gran afinidad y elementos comunes. En segundo lugar, se revisan aspectos prácticos vinculados a la investigación empírica que constatan el impacto de este tipo de liderazgo en las organizaciones y se subraya la relación entre estas formas de liderazgo y variables organizacionales positivas. Finalmente, se analizan futuras líneas de investigación para el desarrollo de este marco conceptual.

A Conceptual Framework and Classification for the Fluvial-Backwater-Marine Transition in Coastal Rivers Globally

Science.gov (United States)

Howes, N. C.; Georgiou, I. Y.; Hughes, Z. J.; Wolinsky, M. A.

2012-12-01

Channels in fluvio-deltaic and coastal plain settings undergo a progressive series of downstream transitions in hydrodynamics and sediment transport, which is consequently reflected in their morphology and stratigraphic architecture. Conditions progress from uniform fluvial flow to backwater conditions with non-uniform flow, and finally to bi-directional tidal flow or estuarine circulation at the ocean boundary. While significant attention has been given to geomorphic scaling relationships in purely fluvial settings, there have been far fewer studies on the backwater and tidal reaches, and no systematic comparisons. Our study addresses these gaps by analyzing geometric scaling relationships independently in each of the above hydrodynamic regimes and establishes a comparison. To accomplish this goal we have constructed a database of planform geometries including more than 150 channels. In terms of hydrodynamics studies, much of the work on backwater dynamics has concentrated on the Mississippi River, which has very limited tidal influence. We will extend this analysis to include systems with appreciable offshore tidal range, using a numerical hydrodynamic model to study the interaction between backwater dynamics and tides. The database is comprised of systems with a wide range of tectonic, climatic, and oceanic forcings. The scale of these systems, as measured by bankfull width, ranges over three orders of magnitude from the Amazon River in Brazil to the Palix River in Washington. Channel centerlines are extracted from processed imagery, enabling continuous planform measurements of bankfull width, meander wavelength, and sinuosity. Digital terrain and surface models are used to estimate floodplain slopes. Downstream tidal boundary conditions are obtained from the TOPEX 7.1 global tidal model, while upstream boundary conditions such as basin area, relief, and discharge are obtained by linking the databases of Milliman and Meade (2011) and Syvitski (2005). Backwater

Open-water and under-ice seasonal variations in trace element content and physicochemical associations in fluvial bed sediment.

Science.gov (United States)

Doig, Lorne E; Carr, Meghan K; Meissner, Anna G N; Jardine, Tim D; Jones, Paul D; Bharadwaj, Lalita; Lindenschmidt, Karl-Erich

2017-11-01

Across the circumpolar world, intensive anthropogenic activities in the southern reaches of many large, northward-flowing rivers can cause sediment contamination in the downstream depositional environment. The influence of ice cover on concentrations of inorganic contaminants in bed sediment (i.e., sediment quality) is unknown in these rivers, where winter is the dominant season. A geomorphic response unit approach was used to select hydraulically diverse sampling sites across a northern test-case system, the Slave River and delta (Northwest Territories, Canada). Surface sediment samples (top 1 cm) were collected from 6 predefined geomorphic response units (12 sites) to assess the relationships between bed sediment physicochemistry (particle size distribution and total organic carbon content) and trace element content (mercury and 18 other trace elements) during open-water conditions. A subset of sites was resampled under-ice to assess the influence of season on these relationships and on total trace element content. Concentrations of the majority of trace elements were strongly correlated with percent fines and proxies for grain size (aluminum and iron), with similar trace element grain size/grain size proxy relationships between seasons. However, finer materials were deposited under ice with associated increases in sediment total organic carbon content and the concentrations of most trace elements investigated. The geomorphic response unit approach was effective at identifying diverse hydrological environments for sampling prior to field operations. Our data demonstrate the need for under-ice sampling to confirm year-round consistency in trace element-geochemical relationships in fluvial systems and to define the upper extremes of these relationships. Whether contaminated or not, under-ice bed sediment can represent a "worst-case" scenario in terms of trace element concentrations and exposure for sediment-associated organisms in northern fluvial systems

The igapó of the Negro River in central Amazonia: Linking late-successional inundation forest with fluvial geomorphology

Science.gov (United States)

Montero, Juan Carlos; Latrubesse, Edgardo M.

2013-10-01

Despite important progress on Amazonian floodplain research, the flooded forest of the Negro River "igapó" has been little investigated. In particular, no study has previously focused the linkage between fluvial geomorphology and the floristic variation across the course of the river. In this paper we describe and interpret relations between igapó forest, fluvial geomorphology and the spatial evolution of the igapó forest through the Holocene. Therefore, we investigate the effect of geomorphological units of the floodplain and channel patterns on tree diversity, composition and structural parameters of the late-successional igapó forest. Our results show that sites sharing almost identical flooding regime, exhibit variable tree assemblages, species richness and structural parameters such as basal area, tree density and tree heights, indicating a trend in which the geomorphologic styles seem to partially control the organization of igapó's tree communities. This can be also explained by the high variability of well-developed geomorphologic units in short distances and concentrated in small areas. In this dynamic the inputs from the species pool of tributary rivers play a crucial role, but also the depositional and erosional processes associated with the evolution of the floodplain during the Holocene may control floristic and structural components of the igapó forests. These results suggest that a comprehensive approach integrating floristic and geomorphologic methods is needed to understand the distribution of the complex vegetation patterns in complex floodplains such as the igapó of the Negro River. This combination of approaches may introduce a better comprehension of the temporal and spatial evolutionary analysis and a logic rationale to understand the vegetation distribution and variability in function of major landforms, soil distributions and hydrology. Thus, by integrating the past into macroecological analyses will sharpen our understanding of the

Fluvial export of radionuclides: impact on sediment storages of the Rhone River and fluxes towards the Mediterranean Sea

International Nuclear Information System (INIS)

Rolland, B.

2006-02-01

This study deals with the behaviour of trace contaminants originating from chronic liquid releases within fluvial aquatic systems. It focuses on some particle reactive artificial radionuclides that were released by the Marcoule nuclear fuel reprocessing plant during several years mainly prior the end of the nineties and that are still detected in the lower Rhone river. It underlines the decrease of 137 Cs, 238 Pu and 239+240 Pu fluxes to the Mediterranean Sea in relation with the variations in the chronic liquid releases from Marcoule. The role of flood events on radionuclides exports processes is particularly considered. Over the years 2002 to 2004, floods contributed for 67%, 55%, 68%, 49% and 56% of the mean annual fluxes of 137 Cs, 238 Pu and 239+240 Pu and natural 7 Be et 210 Pbxs, although these events only represented 5% of time. The removal, during floods, of sediments contaminated by the Marcoule releases contributes on the average for 19%, 44% and 22% of the annual exports of 137 Cs, 238 Pu and 239+240 Pu towards the Sea. Thus, such sedimentary stocks act as a delayed source term of artificial radioactivity that is currently significant. Determination of the sediments residence times before removal allows to evaluate the Rhone capacity to clear its contaminated stocks. Residence times of 200 years, 100 years and 900 years are estimated to be necessary to totally remove the accumulated 137 Cs, 238 Pu and 239+240 Pu, respectively. The location typologies of sediment storages within fluvial systems are also specified. These location are represented on one hand by dams, and on the other hand by river banks and oxbow lakes. Stocks accumulated in dams seem to be removed more easily than those trapped in banks. (author)

Fluvial response to climate variations and anthropogenic perturbations for the Ebro River, Spain in the last 4,000 years.

Science.gov (United States)

Xing, Fei; Kettner, Albert J; Ashton, Andrew; Giosan, Liviu; Ibáñez, Carles; Kaplan, Jed O

2014-03-01

Fluvial sediment discharge can vary in response to climate changes and human activities, which in return influences human settlements and ecosystems through coastline progradation and retreat. To understand the mechanisms controlling the variations of fluvial water and sediment discharge for the Ebro drainage basin, Spain, we apply a hydrological model HydroTrend. Comparison of model results with a 47-year observational record (AD 1953-1999) suggests that the model adequately captures annual average water discharge (simulated 408 m(3)s(-1) versus observed 425 m(3)s(-1)) and sediment load (simulated 0.3 Mt yr(-1) versus observed 0.28 ± 0.04 Mt yr(-1)) for the Ebro basin. A long-term (4000-year) simulation, driven by paleoclimate and anthropogenic land cover change scenarios, indicates that water discharge is controlled by the changes in precipitation, which has a high annual variability but no long-term trend. Modeled suspended sediment load, however, has an increasing trend over time, which is closely related to anthropogenic land cover variations with no significant correlation to climatic changes. The simulation suggests that 4,000 years ago the annual sediment load to the ocean was 30.5 Mt yr(-1), which increased over time to 47.2 Mt yr(-1) (AD 1860-1960). In the second half of the 20th century, the emplacement of large dams resulted in a dramatic decrease in suspended sediment discharge, eventually reducing the flux to the ocean by more than 99% (mean value changes from 38.1 Mt yr(-1) to 0.3 Mt yr(-1)). Copyright © 2013 Elsevier B.V. All rights reserved.

Rasgos morfoestructurales de la llanura amazónica del Perú: efecto de la Neotectónica sobre los cambios fluviales y la delimitación de las provincias morfológicas

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1992-01-01

l’Ucayali respectivement vers le nord (50km et vers le sud-est (100km durant une période récente, probablement limitée à l’Holocène. L’environnement géodynamique de la dépression Ucamara suggère une relation étroite entre les sauts successifs et de direction constante des lits fluviaux et l’activité néotectonique. Les trois grandes zones de lacs et marécages de la dépression Ucamara, Concordia, Puinahua et Punga, sont présentées et leurs caractéristiques discutées en relation avec les structures du fond du bassin (failles et plis. Les données néotectoniques et sismotectoniques des régions environnantes sont comparées aux données morphostructurales, et discutées en terme d’évolution tectonique quaternaire. Se presentan las regiones de la Amazonia peruana en relación con la tectónica reciente andina y con la respuesta del drenaje fluvial. Las principales provincias morfoestructurales son: el piedemonte o Zona Subandina (antepaís que está bordeado hacia el este por grandes depresiones (antefosa en el noreste (Cuenca del Marañón y el sureste (Madre de Dios del Perú, y el Cratón Brasileño (Geoanticlinal de Iquitos más al este. Estructuralmente, la Zona Subandina comprende 2 subzonas: la faja escurrida y plegada subandina (Subandean thrust and fold belt, STFB, que aflora principalmente en el piedemonte superior y la Zona subandina de bloques basculados (Subandean tilted block zone, STBZ. Los principales ríos que atraviesan la STFB son antecedentes o sobreimpuestos, pero el drenaje secundario es conforme a las estructuras (subsecuente. En la STBZ las cuencas fluviales están canalizadas paralelamente al grano estructural. La Cuenca del Marañón comprende, al norte, una depresión a lo largo del río Pastaza, y al sur, la gran depresión de Ucamara con extensas llanuras de inundación y lagos controlados tectónicamente. Hacia el este, el Geoanticlinal de Iquitos representa una estructura epirogénica positiva en el borde occidental

A first look at the influence of anthropogenic climate change on the future delivery of fluvial sediment to the Ganges-Brahmaputra-Meghna delta.

Science.gov (United States)

Darby, Stephen E; Dunn, Frances E; Nicholls, Robert J; Rahman, Munsur; Riddy, Liam

2015-09-01

We employ a climate-driven hydrological water balance and sediment transport model (HydroTrend) to simulate future climate-driven sediment loads flowing into the Ganges-Brahmaputra-Meghna (GBM) mega-delta. The model was parameterised using high-quality topographic data and forced with daily temperature and precipitation data obtained from downscaled Regional Climate Model (RCM) simulations for the period 1971-2100. Three perturbed RCM model runs were selected to quantify the potential range of future climate conditions associated with the SRES A1B scenario. Fluvial sediment delivery rates to the GBM delta associated with these climate data sets are projected to increase under the influence of anthropogenic climate change, albeit with the magnitude of the increase varying across the two catchments. Of the two study basins, the Brahmaputra's fluvial sediment load is predicted to be more sensitive to future climate change. Specifically, by the middle part of the 21(st) century, our model results suggest that sediment loads increase (relative to the 1981-2000 baseline period) over a range of between 16% and 18% (depending on climate model run) for the Ganges, but by between 25% and 28% for the Brahmaputra. The simulated increase in sediment flux emanating from the two catchments further increases towards the end of the 21(st) century, reaching between 34% and 37% for the Ganges and between 52% and 60% for the Brahmaputra by the 2090s. The variability in these changes across the three climate change simulations is small compared to the changes, suggesting they represent a significant increase. The new data obtained in this study offer the first estimate of whether and how anthropogenic climate change may affect the delivery of fluvial sediment to the GBM delta, informing assessments of the future sustainability and resilience of one of the world's most vulnerable mega-deltas. Specifically, such significant increases in future sediment loads could increase the resilience

Marine intervals in Neogene fluvial deposits of western Amazonia

Science.gov (United States)

Boonstra, Melanie; Troelstra, Simon; Lammertsma, Emmy; Hoorn, Carina

2014-05-01

Amazonia is one of the most species rich areas on Earth, but this high diversity is not homogeneous over the entire region. Highest mammal and tree-alpha diversity is found in the fluvio-lacustrine Pebas system, a Neogene wetland associated with rapid radiation of species. The estuarine to marine origin of various modern Amazonian fish, plants, and invertebrates has been associated with past marine ingressions into this freshwater Pebas system. The exact nature and age of these invasions is, however, debated. Here we present new evidence from fluvial and fluvio-lacustrine deposits of Neogene age in southeast Colombia, that point to periods of widespread marine conditions in western Amazonia. Our evidence is based on an analysis of marine palynomorphs, such as organic linings of foraminifera and dinoflagellate cysts, present in dark sandy clay sediments that outcrop along the Caqueta and Amazon rivers. Characteristically, the foraminiferal linings can be assigned to three benthic morphotypes only, e.g. Ammonia, Elphidium and Trochammina. This low diversity assemblage is associated with estuarine/marginal marine conditions. No distinct marine elements such as shelf or planktonic species were encountered. The observed foraminiferal linings and dinocyst assemblages are typical for a (eutrophic) shallow marine environment, suggesting that the Pebas freshwater wetland system occasionally changed to (marginal) marine. Although some reworked elements are found, a typical Neogene dinocyst taxon is commonly found supporting in situ deposition. Sedimentological features typical for tidal conditions that are reported for sites in Peru and northeastern Brazil likely relate to these marine ingressions. Sea level changes as well as foreland basin development related to Andes formation may have facilitated the entry of marine water during the Neogene.

The volcaniclastic sequence of Aranzazu: Record of the impact of volcanism on Neogene fluvial system in the middle part of the Central Cordillera, Colombia

International Nuclear Information System (INIS)

Borrero Pena, Carlos Alberto; Rosero Cespedes, Juan Sebastian; Valencia M, Julian David; Pardo Trujillo, Andres

2008-01-01

The volcaniclastic sequence of Aranzazu (VSA, late Pliocene - early Pleistocene?) was sourced from the northernmost sector of the Machin - Cerro Bravo volcanic complex. The volcaniclastic accumulations filled the pre-existing fault-bend depressions in the surroundings of Aranzazu town (Caldas department, Colombia). A new classification of volcaniclastic deposits is proposed, in which the lahars are defined as volcaniclastic resedimented deposits, and differentiated from the primary volcaniclastic and epiclastic deposits. The updating the sedimentology and rheology of the deposits related with the laharic events is aimed. The VSA stratigraphy is based on the lithofacies identification and the definition of the architectural elements for syn- and inter-eruptive periods. The VSA lower member corresponds to the successive aggradation of syneruptive lahars (SV and SB elements) resulted from re-sedimentation of pumice-rich pyroclastic deposits and transported as debris and hyperconcentrated stream/flood flows. The VSA middle and upper members defined by coal contents were formed during the dominion of inter-eruptive (FF element) over the syn-eruptive (SV and SB elements) periods. They were formed during the reestablishment of the fluvial condition after the syn-eruptive laharic activity. Once the fluvial deposition was strengthened, the necessary conditions for the peat formation were propitious and the coal-bearing bed sets were developed.

DIABETES MELLITUS Y SU ASOCIACIÓN CON DETERIORO COGNITIVO Y DEMENCIA

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DR. Gonzalo Muñoz A.

2016-03-01

Se han descrito alteraciones en todos los dominios cognitivos, sin embargo velocidad psicomotora y atención son los más comúnmente vinculados a la diabetes. Concluimos que la diabetes tiene como órgano blanco el cerebro y enfatizamos la importancia del estudio neuropsicológico en pacientes con larga historia de la enfermedad y en aquellos donde pudiera existir un trastorno cognitivo que puede condicionar la adherencia al tratamiento.

Late Pleistocene sea-level changes recorded in tidal and fluvial deposits from Itaubal Formation, onshore portion of the Foz do Amazonas Basin, Brazil

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Isaac Salém Alves Azevedo Bezerra

Full Text Available ABSTRACTThe Pleistocene deposits exposed in the Amapá Coastal Plain (onshore portion of the Foz do Amazonas Basin, northeastern South America were previously interpreted as Miocene in age. In this work, they were named as "Itaubal Formation" and were included in the quaternary coastal history of Amazonia. The study, through facies and stratigraphic analyses in combination with optically stimulated luminescence (single and multiple aliquot regeneration, allowed interpreting this unit as Late Pleistocene tidal and fluvial deposits. The Itaubal Formation, which unconformably overlies strongly weathered basement rocks of the Guianas Shield, was subdivided into two progradational units, separated by an unconformity related to sea-level fall, here named as Lower and Upper Units. The Lower Unit yielded ages between 120,600 (± 12,000 and 70,850 (± 6,700 years BP and consists of subtidal flat, tide-influenced meandering stream and floodplain deposits, during highstand conditions. The Upper Unit spans between 69,150 (± 7,200 and 58,150 (± 6,800 years BP and is characterized by braided fluvial deposits incised in the Lower Unit, related to base-level fall; lowstand conditions remained until 23,500 (± 3,000 years BP. The studied region was likely exposed during the Last Glacial Maximum and then during Holocene, covered by tidal deposits influenced by the Amazon River.

Effects of ZnO nanoparticles and Zn{sup 2+} on fluvial biofilms and the related toxicity mechanisms

Energy Technology Data Exchange (ETDEWEB)

Xu, Yi; Wang, Chao [Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098 (China); College of Environment, Hohai University, Nanjing 210098 (China); Hou, Jun, E-mail: hhuhjyhj@126.com [Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098 (China); College of Environment, Hohai University, Nanjing 210098 (China); Dai, Shanshan [Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098 (China); College of Environment, Hohai University, Nanjing 210098 (China); Wang, Peifang, E-mail: pfwang2005@hhu.edu.cn [Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098 (China); College of Environment, Hohai University, Nanjing 210098 (China); Miao, Lingzhan; Lv, Bowen; Yang, Yangyang; You, Guoxiang [Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, Hohai University, Nanjing 210098 (China); College of Environment, Hohai University, Nanjing 210098 (China)

2016-02-15

Zinc oxide nanoparticles (ZnO NPs) used in consumer products are largely released into the environment through the wastewater stream. The health hazard of ZnO NPs and the contribution of dissolved Zn{sup 2+} in toxicity of ZnO NPs has attracted extensive worldwide attention. In this study, the toxic effects of ZnO nanoparticles (ZnO NPs) and the effects of dissolved Zn{sup 2+} on fluvial biofilms were investigated. At the end of the exposure time (21 days), scanning electron microscopy (SEM) images and bioaccumulation experiments revealed that large quantities of ZnO NPs were adsorbed on the biofilm. The algal biomasses were significantly decreased by six- and eleven-fold compared with the control (1.43 μg/L) by exposure to concentrations of 100 mg/L ZnO NPs and 7.85 mg/L Zn{sup 2+}, respectively. Moreover, under the same exposure conditions, the quantum yields presented contents of 53.33 and 33.33% relative to the control, and a shift in the community composition that manifested as a strong reduction in diatoms was observed from 7 days and reached 15.63 and 6.25% of the control after 21 days of exposure, respectively. The reductions in bacteria viability and reactive oxygen species (ROS) production were noticeably enhanced following exposure to 100 mg/L ZnO NPs and 7.85 mg/L Zn{sup 2+}, respectively. Additionally, the acute and rapid toxicity of Zn{sup 2+} and the increasing toxicity of the ZnO NPs with increased bioaccumulation were noted in the exposure experiment. - Highlights: • Fluvial biofilm was exposed to ZnO NPs and the dissolved Zn{sup 2+}. • Chl-a and Φ{sub M} decreased at high doses (100 and 7.85 mg/L of ZnO NPs and Zn{sup 2+}). • A shift in the algae community composition was observed at high dosage levels. • The enhanced production of ROS declined the bacteria viability. • Zn{sup 2+} was more toxic than that of the ZnO-NPs.

New data on the chronology of the Vale do Forno sedimentary sequence (Lower Tejo River terrace staircase) and its relevance as a fluvial archive of the Middle Pleistocene in western Iberia

DEFF Research Database (Denmark)

Cunha, Pedro; Martins, Antonio; Buylaert, Jan-Pieter

2017-01-01

The Vale do Forno archaeological sites (Alpiarça, central Portugal) document the earliest human occupation in the Lower Tejo River, well established in geomorphological and environmental terms, within the Middle Pleistocene. In a staircase of six fluvial terraces, the Palaeolithic sites were found...

The Atlas of Natural Hazards and Risks of Austria: first results for fluvial and pluvial floods

Science.gov (United States)

Mergili, Martin; Tader, Andreas; Glade, Thomas; Neuhold, Clemens; Stiefelmeyer, Heinz

2015-04-01

Incoherent societal adaptation to natural processes results in significant losses every year. A better knowledge of the spatial and temporal distribution of hazards and risks, and of particular hot spots in a given region or period, is essential for reducing adverse impacts. Commonly, different hazard and risk estimations are performed within individual approaches based on tailor-made concepts. This works well as long as specific cases are considered. The advantage of such a procedure is that each individual hazard and risk is addressed in the best possible manner. The drawback, however, consists in the fact that the results differ significantly in terms of quality and accuracy and therefore cannot be compared. Hence, there is a need to develop a strategy and concept which uses similar data sources of equivalent quality in order to adequately analyze the different natural hazards and risks at broader scales. The present study is aiming to develop such a platform. The project Risk:ATlas focuses on the design of an atlas visualizing the most relevant natural hazards and, in particular, possible consequences for the entire territory of Austria. Available as a web-based tool and as a printed atlas, it is seen as a key tool to improve the basis for risk reduction, risk adaptation and risk transfer. The atlas is founded on those data sets available for the entire territory of Austria at a consistent resolution and quality. A 1 m resolution DEM and the official cadastre and building register represent the core, further data sets are employed according to the requirements for each natural hazard and risk. In this contribution, the methodology and the preliminary results for fluvial and pluvial floods and their consequences to buildings for three selected test areas in different types of landscapes (rural, urban and mountainous) are presented. Flooding depths expected for annualities of 30, 100 and 300 are derived from existing data sets for fluvial floods and are computed

Probing the Gaps: A Synthesis of Well-known and Lesser-known Hydrological Feedbacks Influencing Vegetation Patterning and Long-term Geomorphic Change in Low-gradient Fluvial Landscapes

Science.gov (United States)

Larsen, L.; Christensen, A.; Harvey, J. W.; Ma, H.; Newman, S.; Saunders, C.; Twilley, R.

2017-12-01

Emergence of vegetation patterning in fluvial landscapes is a classic example of how autogenic processes can drive long term fluvial and geomorphic adjustments in aquatic ecosystems. Studies elucidating the physics of flow through vegetation patches have produced understanding of how patterning in topography and vegetation commonly emerges and what effect it has on long term geomorphic change. However, with regard to mechanisms underlying pattern existence and resilience, several knowledge gaps remain, including the role of landscape-scale flow-vegetation feedbacks, feedbacks that invoke additional biogeochemical or biological agents, and determination of the relative importance of autogenic processes relative to external drivers. Here we provide a synthesis of the processes over a range of scales known to drive vegetation patterning and sedimentation in low gradient fluvial landscapes, emphasizing recent field and modeling studies in the Everglades, FL and Wax Lake Delta, LA that address these gaps. In the Everglades, while flow routing and sediment redistribution at the patch scale is known to be a primary driver of vegetation pattern emergence, landscape-scale routing of flow, as driven by the landscape's connectivity, can set up positive feedbacks that influence the rate of pattern degradation. Recent flow release experiments reveal that an additional feedback, involving phosphorus concentrations, flow, and floating vegetation communities that are abundant under low phosphorus, low flow conditions further stabilizes the alternative landscape states established through local scale sediment redistribution. Biogeochemistry-vegetation-sediment feedbacks may also be important for geomorphic development of newly emerging landscapes such as the Wax Lake Delta. There, fine sediment deposition shapes hydrogeomorphic zones with vegetation patterns that stimulate the growth of biofilm, while biofilm characteristics override the physical characteristics of vegetation

Proyecto MOP: "Concesión de defensas fluviales y carretera Ribera Norte Río Bío-Bío, sector Chiguayante-Puente Viejo"

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Roberto Lira Olmo

2000-08-01

Full Text Available Como se indica en la Editorial, el tema central a tratar en esta edición es la perspectiva urbana en relación a los "frentes de agua" de la región y de la intercomuna Concepción-Talcahuano; y particularmente uno de los programas más emblemáticos que se están proyectando actualmente en la región: el de "Defensas Fluviales y Carretera Ribera Norte del río Bío-Bío, Chiguayante-Puente Viejo".

Sedimentology of the upper Karoo fluvial strata in the Tuli Basin, South Africa

Science.gov (United States)

Bordy, Emese M.; Catuneanu, Octavian

2001-08-01

The sedimentary rocks of the Karoo Supergroup in the Tuli Basin (South Africa) may be grouped in four stratigraphic units: the basal, middle and upper units, and the Clarens Formation. This paper presents the findings of the sedimentological investigation of the fluvial terrigenous clastic and chemical deposits of the upper unit. Evidence provided by primary sedimentary structures, palaeontological record, borehole data, palaeo-flow measurements and stratigraphic relations resulted in the palaeo-environmental reconstruction of the upper unit. The dominant facies assemblages are represented by sandstones and finer-grained sediments, which both can be interbedded with subordinate intraformational coarser facies. The facies assemblages of the upper unit are interpreted as deposits of a low-sinuosity, ephemeral stream system with calcretes and silcretes in the dinosaur-inhabited overbank area. During the deposition of the upper unit, the climate was semi-arid with sparse precipitation resulting in high-magnitude, low-frequency devastating flash floods. The current indicators of the palaeo-drainage system suggest flow direction from northwest to southeast, in a dominantly extensional tectonic setting. Based on sedimentologic and biostratigraphic evidence, the upper unit of the Tuli Basin correlates to the Elliot Formation in the main Karoo Basin to the south.

Enhancing the natural removal of As in a reactive fluvial confluence receiving acid drainage

Science.gov (United States)

Abarca, M. I.; Arce, G.; Montecinos, M.; Guerra, P. A.; Pasten, P.

2014-12-01

Fluvial confluences are natural reactors that can determine the fate of contaminants in watersheds receiving acid drainage. Hydrological, hydrodynamic and chemical factors determine distinct conditions for the formation of suspended particles of iron and aluminum oxyhydroxides. The chemical and physical properties of these particle assemblages (e.g. particle size, chemical composition) can vary according to inflow mixing ratios, hydrodynamic velocity profiles, and chemical composition of the flows mixing at the confluence. Due to their capacity to sorb metals, it is important to identify the optimal conditions for removing metals from the aqueous phase, particularly arsenic, a contaminant frequently found in acid drainage. We studied a river confluence in the Lluta watershed, located in the arid Chilean Altiplano. We performed field measurements and laboratory studies to find optimal mixing ratio for arsenic sorption onto oxyhydroxide particles at the confluence between the Azufre (pH=2, As=2 mg/L) and the Caracarani river (pH=8, Ascontaminants. An analogy between confluences and coagulation-flocculation-sedimentation drinking water plants could be used to engineer such intervention.Acknowledgements: Proyecto Fondecyt 1130936 and Proyecto CONICYT FONDAP 15110020

Fluvial responses to land-use changes and climatic variations within the Drury Creek watershed, southern Illinois

Science.gov (United States)

Miller, Suzanne Orbock; Ritter, Dale F.; Kochel, R. Craig; Miller, Jerry R.

1993-04-01

Fluvial responses to climatic variation and Anglo-American settlement were documented for the Drury Creek watershed, southern Illinois by examining stratigraphic, geomorphic, climatic, and historical data. Regional analyses of long-term precipitation records document a period of decreasing mean annual precipitation from 1904 to about 1945, and an increasing trend in annual precipitation from 1952 to the present. The period between 1945 and 1951 experienced a large number of intense storms that resulted in high annual precipitation totals. Statistical relationships illustrate that changes in precipitation totals are transferred to the hydrologic system as fluctuations in stream discharge. Historical records of southern Illinois show that a maximum period of settlement and deforestation occurred between the 1860s and 1920s. This era ended in the 1940s when large tracts of land were revegetated in an attempt to curtail erosion which had caused extensive upland degradation. In response to hillslope erosion at least two meters of fine-grained sediments were deposited on valley floors. Average sedimentation rates, determined using decdrochronologic techniques, are estimated to be 2.11 cm/yr for the period between 1890 and 1988; rates that are 1 to 2 orders of magnitude greater than pre-settlement values calculated for other areas of the midwest. However, botanical data suggest that aggradation was episodic, possibly occurring during three periods characterized by greater annual precipitation. Since the 1940s, sedimentation rates have declined. Reduced rates of sedimentation are related to an episode of channel entrenchment that reduced overbank flooding. Entrenchment coincided with a period of: (1) reduced sediment yields associated with watershed revegetation and the introduction of soil conservation practices, and (2) intense storm activity that resulted in long periods of high discharge. As a result of channel incision and hillslope erosion, newly exposed bedrock in

José María Rivas Groot

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Rafael Maya

1979-05-01

Full Text Available El nombre de este poeta se halla vinculado, principalmente, al recuerdo de su famosa poesía titulada "Las Constelaciones", una de las notas líricas más altas del Parnaso colombiano. Sin embargo la obra de Rivas Groot es copiosa, y abarca los más diversos géneros literarios. Fue poeta, crítico, novelista, autor de cuentos, historiador, polemista católico, tratadista de cuestiones internacionales, etc.

El rol de los ingresos tributarios en el manejo de la deuda pública y su incidencia en la estabilidad presupuestaria en Ecuador

OpenAIRE

Celi Masache, Maryuri Elizabeth

2016-01-01

El presente trabajo de investigación tiene como eje trascendental de su contenido los ingresos tributarios y su rol en las fases de la deuda pública, como componentes vinculados de la actividad financiera del Estado; la realidad financiera del Estado ecuatoriano introduce al estudio del presupuesto y la planificación nacional para vislumbrar el manejo de la deuda pública atendiendo muy especialmente a los principios de equilibrio, estabilidad presupuestaria y sostenibilidad financiera. El ...

Non-Fluvial Controls of Erosion, Sediment Transport and Fluvial Morphology in a mid-Atlantic Piedmont Watershed, White Clay Creek, Pennsylvania, U.S.A.

Science.gov (United States)

McCarthy, K.; Affinito, R. A.; Pizzuto, J. E.; Stotts, S.; Henry, T.; Krauthauser, M.; O'Neal, M. A.

2017-12-01

Quantifying contemporary sediment budgets is essential for restoration and ecosystem management of mid-Atlantic watersheds, but relevant processes and controls are poorly understood. In the 153 km2 White Clay Creek watershed in southeastern Pennsylvania, longitudinal profiles reflect migration of knickpoints though bedrock over Quaternary timescales. In bank exposures along stream valleys, saprolite, bedrock, and matrix-supported cobbly and bouldery diamicton (likely colluvial) commonly underlie finer-grained clay, silt, sand, and gravel deposits of valley floor depositional environments. Overbank sedimentation rates were quantified by measuring the thickness of sediment deposited over the roots of floodplain trees. The sampled trees range in age from 25-270 years with median sediment accumulation rates of approximately 2 mm/yr (range 0-10 mm/yr). Rates of bank retreat (measured from historical aerial imagery or root-exposure dendrochronology) vary from 6-36 cm/yr, with median rates of 10 cm/yr. While bank erosion rates are subject to a variety of controls, including channel curvature, the density of riparian trees, and freeze-thaw processes, the strongest influence appears to be the grain size and thickness of bouldery diamicton exposed along the toes of retreating banks. Cobbles and boulders supplied by eroding diamicton also mantle the bed of the channel, such that 33- 80% of the bed material remains immobile at bankfull stage. A conceptual model of fluvial processes and sediment budgets for these channels must account for the watershed's history of changing climate, tectonics, and land use, requiring mapping of bedrock, colluvium, former mill dam sediments, and other non-alluvial deposits and controls. Efforts to apply hydraulic geometry principles (requiring a precise adjustment to contemporary hydraulic and sediment regime) or to treat these channels as traditional "threshold" rivers are unlikely to be successful.

Al-Qurû’ fi Al-Qur’an ‘Inda Al-Anbary fi Al-Adhdâd

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Raushani Azza

2018-03-01

Full Text Available This study examines about the term al-Qurû in the Qur’an. Al-Qurû is one of the most popular discussions among muslim scholars and mufasir, both in terms of language and fiqh. However, there is a bate among muslim scholar and mufasir about the meaning of al-Qurû. It’s because al-Qurû is one of the sentence of al-Adhdâd wich has two meaning, especially in the Qur’an, namely haid (menstruation and thahr. One of the most popular muslim scholar who concern in Qur’an and Arabic is al-Anbari with his book al-Adhdâd. Al-Anbari explains that Qurû has two meanings, First, al-Qurû in etymology is the form of Jama’ from aqra and qurû. Second, al-Qurû has a meaning of menstruation, thahr, or the period of iddah as a sign of being allowed to remarry after certain period of time.

Recuerdo y presencia del profesor Calixto Torres Umaña

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Alberto Amaris Mora

1986-01-01

Full Text Available El 13 de Agosto de 1.985 se cumplió el primer centenario del nacimiento del Profesor Calixto Torres Umaña en la ilustre y señorial ciudad de Tunja, primero de los cuatro hijos que llegaron al hogar del matrimonio constituído por el médico Severo Torres Barreto y doña Ana Josefa Umaña Quijano. El mundo médico en general, pero particularmente el que se halla vinculado al área pediátrica de la Facultad de Medicina de la Universidad Nacional, recordó el hecho con especial solemnidad y devoción científica.

Estructura agraria y trabajo en un contexto de cambios: el caso de Uruguay

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Joaquín Cardeillac Gulla

2017-12-01

Full Text Available El artículo describe los cambios de la estructura agraria y la estructura social que ocurrieron en Uruguay entre 1980 y 2011. Mediante información censal, se muestra la disminución del número absoluto de asalariados agropecuarios, que se da junto al aumento de su importancia relativa frente a otros tipos sociales vinculados al sector, particularmente en relación a los productores familiares. Por otro lado, se observan modificaciones en las zonas de residencia de estos asalariados, que comienzan a cuestionar esa fuerte restricción a la elección del lugar de residencia, tradicional entre los trabajadores rurales.

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African Journals Online (AJOL)

USER

2016-11-01

Nov 1, 2016 ... fluvial dynamics of the stream due to impoundment. Asonye et al. (2007) reported that turbidity and conductivity were far above the acceptable limits recommended by WHO in some Nigeria streams and water ways. Pollution indicators in River Kaduna,. Kaduna state, Nigeria was determined by. Mahre et al.

Las faunas pleistocenas de Fuensanta del Júcar y El Provencio y su significado en la evolución del Cuaternario de la Llanura manchega.

OpenAIRE

Mazo Pérez, Ana Victoria; Pérez-González, Alfredo; Aguirre, Emiliano

1990-01-01

Las terrazas fluviales de +60 m de Fuensanta del Júcar (Sistema aluvial del río Júcar) y de +15-16 m de El Provencio, perteneciente al Sistema fluvial del Guadiana, han proporcionado restos de vertebrados del Pleistoceno. En la primera localidad, que se encuentra en Albacete, se han identificado: Mammuthus meridionalis NESTI, forma progresiva, Hippopotamus major CUVIER y Cervidae ind. En El Provencio (Cuenca): Mammuthus meridionalis NESTI y Bovidae ind. (Bos o Bison). El grado de evolución de...

Turismo Alternativo y Educación. Una propuesta para contribuir al desarrollo humano.

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César David Torres Fernández

2013-01-01

Full Text Available Este trabajo realiza una propuesta para contribuir al desarrollo humano, la problemática a tratar es la falta del mismo en este planeta. Por desarrollo humano se entiende la evolución integral del ser humano desde el punto de vista socioeconómico, político, cultural y espiritual (en armonía consigo mismo, con la naturaleza y con los demás seres humanos. En nuestro país existe pobreza, desempleo, corrupción, desigualdad, una pésima educación y cultura, así como problemas de alimentación que lo ubican entre los países con mayor obesidad adulta e infantil en el mundo, existiendo también en las zonas marginadas la desnutrición infantil. Por ello, debemos propiciar diversas opciones de desarrollo; se considera que el turismo alternativo, vinculado a la educación y a la cultura, puede contribuir de manera importante a contrarrestar la problemática antes planteada. En este sentido, nos interesa trabajar con las nuevas generaciones a manera de prevención, concientizándolas, que conozcan y practiquen los valores éticos, morales, familiares, espirituales, etcétera. En el aspecto metodológico, la investigación es de tipo bibliográfico, trabajo de campo, entrevistas y observaciones propias. Es un proyecto que surge como una alternativa dentro del desarrollo sustentable, con actividades de turismo de aventura y ecoturismo, asociado con talleres educativos relacionados con educación ambiental, valores, formación humana y social, educación para la paz, etcétera.

Al-Âyah al-Mutasyâbihât al-Lafzhiyyah fi Sûrah al-An’âm ‘Inda al-Kirmâny

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Hikmatiar Pasya

2017-07-01

Full Text Available This paper discusses about the verses of mutasyâbihât in the Quran. The debate of this verses caused various opinions. The meaning of the mutasyâbihât in this paper is the similarity and difference of the words in the Qur'an. Mufasir have different opinion about the meaning of the verse of mutasyâbihât al-lafdzi. In addition, many Hufadz of the Quran who are confused from one verse to another, or one chapter to another. It’s because similarity of verses in the Qur'an with other verses. So the writer wants to explain the verses mutasyâbihât al-lafdzi in the perspective of Hamzh al-Karmani in Surah al-An'âm. In this discussion the author discovers some passages in mutasyâbihât al-lafdzi, namely Asrâru al-balaghah fi mutasyabih al-lafdzi, Asrar al-balaghah fi mutasyabih al-hurf, and murâ'ah al-ikhtilâfmurâd bi al-lafdzi al-mukarrar.

Lineamientos estratégicos para el desarrollo competitivo del sector turístico en Venezuela

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Milagros Gutiérrez

2015-01-01

Full Text Available El desarrollo competitivo del sector turístico de un país, se fundamenta en su capacidad para generar prosperidad económica sostenida, incluyendo aspectos como la calidad de vida de los ciudadanos y la sustentabilidad ambiental, sobre la base del uso de los atractivos naturales y del patrimonio histórico cultural. En tal sentido, este artículo tiene por objetivo proponer algunos lineamientos estratégicos para el desarrollo competitivo del sector turístico en Venezuela como país con importantes potencialidades turísticas. Para ello, se realizó una investigación de tipo documental, sustentada en la evaluación de los contenidos teóricos relacionados con los principales modelos de competitividad vinculados al turismo. De la información analizada se desprende que la competitividad puede ser promovida concertando estrategias dirigidas al posicionamiento del país, en las que se involucren los actores vinculados al sector turístico y entes gubernamentales. Se concluye que, en el caso concreto de Venezuela, estas estrategias deben incluir, acciones orientadas a la creación de redes de cooperación entre las empresas turísticas, capacitación de los trabajadores del sector y la promoción de la cultura turística en comunidades receptoras. Adicionalmente, es primordial superar deficiencias y limitaciones del macroentorno económico, social y ambiental que condicionan el desarrollo competitivo del país, y consecuencialmente, del turismo.

Operation disturbance by wind turbines of fixed radars from civil aviation, national defense, Meteo-France, and maritime and fluvial harbors and navigation (PNM)

International Nuclear Information System (INIS)

2008-01-01

Wind turbines and the movement of their blades can have penalizing effects on the processing of radars data. These disturbances can have a strong impact on the air, maritime and fluvial safety, on the protection of the territory and on the prevention of natural hazards. Reports made by the national agency of frequencies (ANFR) have established recommendations for the definition of protection areas (5 km) and coordination areas (5 to 30 km) which have to be taken into consideration prior to any project of wind turbine. (J.S.)

Espacio público informal. Apreciaciones sobre la infraestructura y los espacios de uso colectivo en el campamento de Pudeto Bajo de Ancud

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Cristian Silva

2011-08-01

Full Text Available Una dimensión de los espacios públicos poco abordada, es la presente en los asentamientos urbanos informales, campamentos o barriadas. Aquí, el espacio público se presenta como un lugar socialmente compartido pero además, como una infraestructura funcional a los mecanismos de sobrevivencia. En el caso del campamento de Pudeto Bajo en Ancud se puede apreciar claramente la dimensión operativa de estos espacios públicos vinculados a las actividades laborales u oficios, tales como la pesca artesanal, accesos compartidos a las viviendas, lugares de acopio de materias primas o herramientas de pesca o como simples patios de juego o traspaso. Al mismo tiempo los espacios públicos de mayor escala se presentan en los bordes, como fronteras entre el campamento y la ciudad actuando como amortiguadores de una relación urbana muchas veces compleja e incluso conflictiva. El rol de estas categorías espaciales es fundamental para el desarrollo del asentamiento: por una parte los espacios públicos interiores vinculados al trabajo evita la generación de espacios en desuso y abandono, y por otra parte los espacios públicos de frontera median la tensión inherente entre las formas de producción urbana informal y la ciudad formal o planificada.

Hacia directrices y conceptos de diseño de vialidad sustentable: el caso del corredor fluvial del río Mapocho ─sección occidental─ y su entorno. / Guidelines and concepts to design sustainable transportation: the western section of the corridor of the Mapocho River and its environment.

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María Patricia Henríquez Orellana

2010-12-01

Full Text Available Se explora un polígono donde existe un potencial de desarrollo sostenible conteniendo el tramo poniente del río Mapocho, posible de constituirse en un corredor fluvial recreacional y de transporte como uno de los elementos estructuradores metropolitanos. Se trata del uso del espacio corredor del río Mapocho y su entorno inmediato para la integración urbana-regional. La investigación FONDECYT 1090199 – 2009/2010 planteó que resolver la conformación de éste corredor requiere un fortalecimiento integral de la vialidad que mejore la accesibilidad, conectividad y conexidad del corredor, potenciando un sistema vial asociado al río, pero no perturbador del río; diversificado y articulador de actividades pertinentes junto y eventualmente sobre el territorio de la movilidad fluvial; que conecte los asentamientos de borde, contribuya a la producción de espacio público para la recreación y esparcimiento tranquilo de los habitantes, y conjuntamente en las áreas rurales facilite la coexistencia con la actividad agraria y campesina. Esto permitiría la integración plena del río a la vida metropolitana y periurbana de Santiago. Dicha acción requiere ser abordada desde un ordenamiento territorial ambientalmente sustentable y no sólo desde la ingeniería./The western section of the Mapocho river is an especial area for a future sustainable development. The author essay the possibility of this section as a recreational and transportation corridor that could be also a integration node for de city and the region.

Recorridos y trayectorias de trabajadores y militantes vinculados a una cooperativa de trabajo del Movimiento Evita

OpenAIRE

Gusmerotti, Lucrecia

2012-01-01

Sobre la transitada avenida Mitre, al lado de una concesionaria de vehículos, estaba el lavadero de autos que tenía un espacioso bar. Ahí solían reunirse habitualmente militantes del Movimiento Evita de Avellaneda porque estaba a media cuadra de la Factoría, era tranquilo, se podía tomar un buen café y contaba con televisión por cable donde pasaban los canales de noticias. En ese lugar me citaron diferentes activistas del Movimiento Evita durante mi investigación, para la realización de entre...

Concentrations of selected metals in Quaternary-age fluvial deposits along the lower Cheyenne and middle Belle Fourche Rivers, western South Dakota, 2009-10

Science.gov (United States)

Stamm, John F.; Hoogestraat, Galen K.

2012-01-01

The headwaters of the Cheyenne and Belle Fourche Rivers drain the Black Hills of South Dakota and Wyoming, an area that has been affected by mining and ore-milling operations since the discovery of gold in 1875. A tributary to the Belle Fourche River is Whitewood Creek, which drains the area of the Homestake Mine, a gold mine that operated from 1876 to 2001. Tailings discharged into Whitewood Creek contained arsenopyrite, an arsenic-rich variety of pyrite associated with gold ore, and mercury used as an amalgam during the gold-extraction process. Approximately 18 percent of the tailings that were discharged remain in fluvial deposits on the flood plain along Whitewood Creek, and approximately 25 percent remain in fluvial deposits on the flood plain along the Belle Fourche River, downstream from Whitewood Creek. In 1983, a 29-kilometer (18-mile) reach of Whitewood Creek and the adjacent flood plain was included in the U.S. Environmental Protection Agency's National Priority List of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, commonly referred to as a "Superfund site." Listing of this reach of Whitewood Creek was primarily in response to arsenic toxicity of fluvial deposits on the flood plain. Lands along the lower Cheyenne River were transferred to adjoining States and Tribes in response to the Water Resources Development Act (WRDA) of 1999. An amendment in 2000 to WRDA required a study of sediment contamination of the Cheyenne River. In response to the WRDA amendment, the U.S. Geological Survey completed field sampling of reference sites (not affected by mine-tailing disposal) along the lower Belle Fourche and lower Cheyenne Rivers. Reference sites were located on stream terraces that were elevated well above historical stream stages to ensure no contamination from historical mining activity. Sampling of potentially contaminated sites was performed on transects of the active flood plain and adjacent terraces that could

Efecto del drenaje ácido de minas sobre el agua y el sedimento del estuario de los ríos Tinto y Odiel

OpenAIRE

Carro Flores, Berta

2016-01-01

Son numerosos los estudios realizados con respecto al efecto del drenaje ácido de minas en los sistemas fluviales que desembocan en el estuario de los ríos Tinto y Odiel (Aroba et at., 2007; Cánovas et al., (2008); De la Torre et al (2009, 2010, 2014); Grande et al., (2000, 2003, 2005, 2010, 2011, 2013, 2014); Olías et al., (2004); Sáinz et al., (2000, 2002, 2003, 2004, 2005); Sarmiento et al., (2009)), la contaminación asociada a la actividad minera de la zona (Nelson y Lamoth...

Seguridad ciudadana y respuesta penal

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Beatriz Scapusio Minvielle

2015-10-01

Full Text Available El concepto de seguridad ciudadana será empleado en esta comunicación en su sentido restringido, vinculado al sentimiento de confianza de la población de no verse expuesta a hechos de violencia física, tengan origen éstos en actos individuales o sociales.  (...Contenido: Diferentes expresiones de la seguridad ciudadana. La respuesta penal. Evaluación global del problema. El desafío dogmático. Conclusiones

Cursos INDEM de verano: aprendiendo a interpretar las claves del mundo financiero

OpenAIRE

Mayoral, Silvia; Gómez Jorge, Fabiola; Alonso Ferreiro, Ignacio

2015-01-01

El Instituto para el Desarrollo Empresarial (INDEM), vinculado al Departamento de Economía de la Empresa de la Universidad Carlos III de Madrid ha organizado varios cursos y talleres, orientados a estudiantes de grado y profesionales del sector económico y financiero. Dichos cursos han sido dirigidos por expertos en finanzas, marketing, contabilidad y management. Contiene: Entrevista a Silvia Mayoral Blaya, Profesora titular en el Departamento de Economía de la Empresa de la UC3M y vicedec...

El libre desarrollo de la personalidad (Un bien jurídico digno del Estado constitucional)

OpenAIRE

Migu Ontiveros Alonso

2006-01-01

Con fundamento en la dignidad humana, en su calidad de valor fundamental plasmado en toda Constitución moderna, el autor propone incorporar, en calidad de bien jurídicamente protegido, al libre desarrollo de la personalidad, con el objeto de proteger a los grupos especialmente vulnerables ante los delitos vinculados a la explotación humana. el libre desarrollo de la personalidad, se afirma en este breve artículo, puede ser equiparado a la vida humana como valor supero del se...

Trayectorias, redes migratorias y procesos identitarios, en la conformación del mercado de trabajo agrícola destinado a bolivianos : estudio en dos municipios del este salteño 1960 - 2013.

OpenAIRE

Ataide, Soraya

2015-01-01

La presente tesis pretende aportar a los estudios sobre la segmentación étnica de los mercados laborales en general y de aquellos vinculados a los migrantes bolivianos en Salta (Argentina), en particular. Partimos de la existencia de un mercado de trabajo agrícola segmentado por la pertenencia de los trabajadores al colectivo nacional: bolivianos, en dos municipios de la provincia de Salta, Apolinario Saravia y Gral. Pizarro. En este caso, la migración boliviana conforma un destino temprano, ...

El concepto de "Autorrealización" como identidad personal: una revisión crítica

OpenAIRE

Bernal Guerrero, Antonio

2002-01-01

En este artículo, hacemos una revisión crítica del concepto de autorrealización, vinculado a la identidad personal. Reconociendo el valor de las aportaciones de las teorías humanistas que se han preocupado por el sentido y alcance del concepto de autorrealización, consideramos que su contribución al ámbito pedagógico ha sido limitada. Sugerimos, finalmente, la posibilidad de reorganizar conceptualmente la identidad personal, desde las nuevas investigaciones de la persona.

Diffusion-induced quadrupole relaxation of 27Al nuclei in dilute Al-Ti, Al-Cr, Al-Mn, and Al-Cu alloys at high temperatures

International Nuclear Information System (INIS)

Bottyan, L.; Beke, D.L.; Tompa, K.

1983-01-01

The temperature dependence of the laboratory frame spin-lattice relaxation time of 27 Al nuclei is measured in 5N Al and in dilute Al-Ti, Al-Cr, Al-Mn, and Al-Cu alloys at 5.7 and 9.7 MHz resonance frequencies. The relaxation in pure aluminium is found to be purely due to the conduction electrons. An excess T 1 -relaxation contribution is detected in all Al-3d alloys investigated above 670 K. The excess relaxation rate is proportional to the impurity content and the temperature dependence of the excess contribution is of Arrhenius-type with an activation energy of (1.3 +- 0.3) eV for all of the investigated alloys. The relaxation contribution is found to be quadrupolar in origin and is caused by the relative diffusional jumps of solute atoms and Al atoms relatively far from the impurity. (author)

Interfacial phenomena in the reactions of Al-B, Al-Ti-B, and Al-Zr-B alloys with KF-AlF3 and NaF-AlF3 melts

International Nuclear Information System (INIS)

Lee, M.S.; Terry, B.S.; Grieveson, P.

1993-01-01

The interfacial phenomena occurring during the contacting of liquid Al-B, Al-Ti-B, and Al-Zr-B melts with KF-AlF 3 liquid fluxes have been investigated by optical examination of quenched metal drops previously immersed in the liquid fluxes. Reactions in the Al-B/KF-AlF 3 system involve the formation of metastable AlB 12 at the metal/flux interface. At high KBF 4 levels in the flux, the AlB 12 is dispersed in the flux and also at low KBF 4 levels in the metal. Reactions in the Al-Ti-B/KF-AlF 3 system involve the formation of TiB 2 , which may be dispersed in either the metal or the flux depending upon the composition of the flux. The results obtained for the Al-Ti-B/NaF-AlF 3 and Al-Zr-B/KF-AlF 3 systems were similar to those observed for the Al-Ti-B/KF-AlF 3 system

Operation disturbance by wind turbines of fixed radars from civil aviation, national defense, Meteo-France, and maritime and fluvial harbors and navigation (PNM); Perturbations par les aerogenerateurs du fonctionnement des radars fixes de l'Aviation civile, de la Defense nationale, de Meteo-France et des ports et navigation maritime et fluviale (PNM)

Energy Technology Data Exchange (ETDEWEB)

NONE

2008-07-01

Wind turbines and the movement of their blades can have penalizing effects on the processing of radars data. These disturbances can have a strong impact on the air, maritime and fluvial safety, on the protection of the territory and on the prevention of natural hazards. Reports made by the national agency of frequencies (ANFR) have established recommendations for the definition of protection areas (5 km) and coordination areas (5 to 30 km) which have to be taken into consideration prior to any project of wind turbine. (J.S.)

Inverse modelling of fluvial sediment connectivity identifies characteristics and spatial distribution of sediment sources in a large river network.

Science.gov (United States)

Schmitt, R. J. P.; Bizzi, S.; Kondolf, G. M.; Rubin, Z.; Castelletti, A.

2016-12-01

Field and laboratory evidence indicates that the spatial distribution of transport in both alluvial and bedrock rivers is an adaptation to sediment supply. Sediment supply, in turn, depends on spatial distribution and properties (e.g., grain sizes and supply rates) of individual sediment sources. Analyzing the distribution of transport capacity in a river network could hence clarify the spatial distribution and properties of sediment sources. Yet, challenges include a) identifying magnitude and spatial distribution of transport capacity for each of multiple grain sizes being simultaneously transported, and b) estimating source grain sizes and supply rates, both at network scales. Herein, we approach the problem of identifying the spatial distribution of sediment sources and the resulting network sediment fluxes in a major, poorly monitored tributary (80,000 km2) of the Mekong. Therefore, we apply the CASCADE modeling framework (Schmitt et al. (2016)). CASCADE calculates transport capacities and sediment fluxes for multiple grainsizes on the network scale based on remotely-sensed morphology and modelled hydrology. CASCADE is run in an inverse Monte Carlo approach for 7500 random initializations of source grain sizes. In all runs, supply of each source is inferred from the minimum downstream transport capacity for the source grain size. Results for each realization are compared to sparse available sedimentary records. Only 1 % of initializations reproduced the sedimentary record. Results for these realizations revealed a spatial pattern in source supply rates, grain sizes, and network sediment fluxes that correlated well with map-derived patterns in lithology and river-morphology. Hence, we propose that observable river hydro-morphology contains information on upstream source properties that can be back-calculated using an inverse modeling approach. Such an approach could be coupled to more detailed models of hillslope processes in future to derive integrated models

Synthesizing (ZrAl3 + AlN)/Mg-Al composites by a 'matrix exchange' method

Science.gov (United States)

Gao, Tong; Li, Zengqiang; Hu, Kaiqi; Han, Mengxia; Liu, Xiangfa

2018-06-01

A method named 'matrix exchange' to synthesize ZrAl3 and AlN reinforced Mg-Al composite was developed in this paper. By inserting Al-10ZrN master alloy into Mg matrix and reheating the cooled ingot to 550 °C, Al and Mg atoms diffuse to the opposite side. As a result, liquid melt occurs once the interface areas reach to proper compositions. Then dissolved Al atoms react with ZrN, leading to the in-situ formation of ZrAl3 and AlN particles, while the Al matrix is finally replaced by Mg. This study provides a new insight for preparing Mg composites.

Coupled growth of Al-Al2Cu eutectics in Al-Cu-Ag alloys

International Nuclear Information System (INIS)

Hecht, U; Witusiewicz, V; Drevermann, A

2012-01-01

Coupled eutectic growth of Al and Al 2 Cu was investigated in univariant Al-Cu-Ag alloys during solidification with planar and cellular morphology. Experiments reveal the dynamic selection of small spacings, below the minimum undercooling spacing and show that distinct morphological features pertain to nearly isotropic or anisotropic Al-Al 2 Cu interfaces.

AL ITTIJAHAT AL MUNHARIFAH FI AT TAFSIR LI BADLI ASHAB AL MADZAHIB AL NAHWIYYAH WA BADL MAN YAJHALUNA QAWAID AL LUGHAH AL ARABIYYAH FI NADHAR MUHAMMAD HUSAIN AL DZAHABIY

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Misbakhudin Misbakhudin

2017-06-01

Full Text Available One of the most precious achievement in qur’anic studies was the book of Al-Ittijâhât al-Munharifah fî al-Tafsîr: Dawâfi’uha wa Daf’uha written by A great Islamic scholar, Muhammad Husein al-Dzahabî. He was succeeded in discussing several issues of corruptions of the exegesis of the holy Qur’an. This article is aimed to explain and to describe his analysis toward several corrupted linguist interpretations in their originations and such corrupted linguistic interpretations of the holy Qur’an which are ignoring Arabic structures and grammers

Salud reproductiva e interculturalidad

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Adriana A. Feltri

2006-01-01

Full Text Available Este artículo de opinión ha sido realizado por varios autores en base a un texto que relata el conflicto suscitado entre la comunidad mapuche y una médica del sistema de salud de la provincia del Neuquén, al incorporarse a las mujeres de la comunidad al programa de salud sexual y reproductiva. Los participantes expresan sus opiniones en dos rondas: en la primera se refieren específicamente al texto y en la segunda comentan las exposiciones de la primera. Entre los tópicos analizados con mayor profundidad se destacan los vinculados con la normatividad en las intervenciones de los sistemas de salud y con las relaciones de poder que se producen entre ambos géneros y entre las diferentes culturas.

Flood hazards analysis based on changes of hydrodynamic processes in fluvial systems of Sao Paulo, Brazil.

Science.gov (United States)

Simas, Iury; Rodrigues, Cleide

2016-04-01

The metropolis of Sao Paulo, with its 7940 Km² and over 20 million inhabitants, is increasingly being consolidated with disregard for the dynamics of its fluvial systems and natural limitations imposed by fluvial terraces, floodplains and slopes. Events such as floods and flash floods became particularly persistent mainly in socially and environmentally vulnerable areas. The Aricanduva River basin was selected as the ideal area for the development of the flood hazard analysis since it presents the main geological and geomorphological features found in the urban site. According to studies carried out by Anthropic Geomorphology approach in São Paulo, to study this phenomenon is necessary to take into account the original hydromorphological systems and its functional conditions, as well as in which dimensions the Anthropic factor changes the balance between the main variables of surface processes. Considering those principles, an alternative model of geographical data was proposed and enabled to identify the role of different driving forces in terms of spatial conditioning of certain flood events. Spatial relationships between different variables, such as anthropogenic and original morphology, were analyzed for that purpose in addition to climate data. The surface hydrodynamic tendency spatial model conceived for this study takes as key variables: 1- The land use present at the observed date combined with the predominant lithological group, represented by a value ranging 0-100, based on indexes of the National Soil Conservation Service (NSCS-USA) and the Hydraulic Technology Center Foundation (FCTH-Brazil) to determine the resulting balance of runoff/infiltration. 2- The original slope, applying thresholds from which it's possible to determine greater tendency for runoff (in percents). 3- The minimal features of relief, combining the curvature of surface in plant and profile. Those three key variables were combined in a Geographic Information System in a series of

Tipping points in Anthropocene fluvial dynamics

Science.gov (United States)

Notebaert, Bastiaan; Broothaerts, Nils; Verstraeten, Gert; Berger, Jean-François; Houbrechts, Geoffrey

2016-04-01

the river partially maintains its braided pattern. The Amblève River in the Belgian Ardennes uplands underwent less dramatic changes. Large parts of the catchment are deforested during the last 700 years, leading to an increase in floodplain sedimentation. Despite this major sediment pulse, change in floodplain morphology remained limited to an increase in bank height. We argue that a combination of floodplain and channel morphology, the fine texture of supplied sediment and the high stream power of channel forming events result is a system that is less sensitive to change. Also the relative short time of impact may play a role. These three examples demonstrate the varying impact of human deforestation on floodplain geomorphology. For the Dijle and Valdaine region this lead to dramatic changes once a certain tipping point is reached. In contrast the Amblève river is more resilient to human impact due to its specific morphological setting. The morphology of the catchments and the nature of supplied sediments plays a major role in the sensitivity of fluvial systems to environmental impact. Once the tipping points are reached, it is difficult for the river to revert to its original state and floodplains remain highly impacted.

Del “mar es de todos” al mar reservado: turistas, poblaciones de pescadores y reservas marinas en Canarias

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José J. Pascual

2003-01-01

Full Text Available Los patrones de desarrollo de las últimas décadas en Canarias y en otras zonas del Estado han originado nuevos usos del espacio marítimo y litoral. Frente a los tradicionales vinculados a la pesca, ahora dominan frecuentemente los turísticos y recreativos. La naturaleza, construida o recreada, se convierte especialmente en los últimos años en un atractivo clave para muchos destinos. En este contexto, las reservas marinas intentan preservar ciertas zonas de especial valor biológico de los excesos de la pesca, a la vez que deberían conjugar los usos turísticos y recreativos a realizar en tales espacios con la conservación de sus valores naturales. En Canarias han constituido uno de los instrumentos claves de la política de conservación y gestión de pesquerías en las áreas costeras de las Islas. Actualmente hay tres en funcionamiento, siguiendo una tendencia cada vez más general en todo el mundo. Pero a la vez que con ellas se controla la extracción de recursos por los profesionales, se impulsan una serie de usos vinculados a determinadas formas de turismo que han generado importantes transformaciones en las poblaciones vinculadas a estas zonas protegidas. Otros impactos inducidos por el turismo o la acuicultura han alterado también sus estrategias económicas o el uso de los espacios tanto en tierra como en el mar

Mercury methylation and demethylation by periphyton biofilms and their host in a fluvial wetland of the St. Lawrence River (QC, Canada)

International Nuclear Information System (INIS)

Hamelin, Stéphanie; Planas, Dolors; Amyot, Marc

2015-01-01

Wetlands in large rivers are important sites of production of the neurotoxin methylmercury (MeHg), and the periphyton growing on wetland macrophytes are increasingly recognized as key players in this production and transfer in food webs. Information is lacking about mercury methylation (K m ) and demethylation (K d ) rates in periphytic biofilms from the Northern Hemisphere, as well as about the drivers of net MeHg production, hampering ecosystem modeling of Hg cycling. Mercury methylation and demethylation rates were measured in periphytic biofilms growing on submerged plants in a shallow fluvial lake located in a temperate cold region (St. Lawrence River, Quebec, Canada). Incubations were performed in situ within macrophyte beds using low-level spikes of 199 HgO and Me 200 Hg stable isotopes as tracers. A direct relationship was observed between K m (0.002 to 0.137 d −1 ) and [MeHg] in periphyton. A similar relationship was found between K d (0.096 to 0.334 d −1 ) and [inorganic Hg]. Periphyton of Lake St. Pierre reached high levels of net MeHg production that were two orders of magnitude higher than those found in local sediment. This production varied through the plant growing season and was mainly driven by environmental variables such as depth of growth, available light, dissolved oxygen, temperature, plant community structure, and productivity of the habitat. - Highlights: • Periphyton Hg methylation and demethylation were studied in a large fluvial lake. • Addition of stable Hg isotopes was used to obtain in situ rates for these processes. • Net methylation was higher in periphyton than in local sediments. • Methylation and demethylation rates fluctuated during the summer. • Key drivers of rates were depth, light, temperature, and community structure

Mercury methylation and demethylation by periphyton biofilms and their host in a fluvial wetland of the St. Lawrence River (QC, Canada)

Energy Technology Data Exchange (ETDEWEB)

Hamelin, Stéphanie; Planas, Dolors [GRIL, Département de sciences biologiques, Université du Québec à Montréal, C.P. 8888, Succursale Centre-Ville, Montreal, Quebec H3C 3P8 (Canada); Amyot, Marc [GRIL, Département de sciences biologiques, Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montréal, Quebec H3C 3J7 (Canada)

2015-04-15

Wetlands in large rivers are important sites of production of the neurotoxin methylmercury (MeHg), and the periphyton growing on wetland macrophytes are increasingly recognized as key players in this production and transfer in food webs. Information is lacking about mercury methylation (K{sub m}) and demethylation (K{sub d}) rates in periphytic biofilms from the Northern Hemisphere, as well as about the drivers of net MeHg production, hampering ecosystem modeling of Hg cycling. Mercury methylation and demethylation rates were measured in periphytic biofilms growing on submerged plants in a shallow fluvial lake located in a temperate cold region (St. Lawrence River, Quebec, Canada). Incubations were performed in situ within macrophyte beds using low-level spikes of {sup 199}HgO and Me{sup 200}Hg stable isotopes as tracers. A direct relationship was observed between K{sub m} (0.002 to 0.137 d{sup −1}) and [MeHg] in periphyton. A similar relationship was found between K{sub d} (0.096 to 0.334 d{sup −1}) and [inorganic Hg]. Periphyton of Lake St. Pierre reached high levels of net MeHg production that were two orders of magnitude higher than those found in local sediment. This production varied through the plant growing season and was mainly driven by environmental variables such as depth of growth, available light, dissolved oxygen, temperature, plant community structure, and productivity of the habitat. - Highlights: • Periphyton Hg methylation and demethylation were studied in a large fluvial lake. • Addition of stable Hg isotopes was used to obtain in situ rates for these processes. • Net methylation was higher in periphyton than in local sediments. • Methylation and demethylation rates fluctuated during the summer. • Key drivers of rates were depth, light, temperature, and community structure.

Anatomy and dimensions of fluvial crevasse-splay deposits: Examples from the Cretaceous Castlegate Sandstone and Neslen Formation, Utah, U.S.A.

Science.gov (United States)

Burns, C. E.; Mountney, N. P.; Hodgson, D. M.; Colombera, L.

2017-04-01

Crevasse-splay deposits form a volumetrically significant component of many fluvial overbank successions (up to 90% in some successions).Yet the relationships between the morphological form of accumulated splay bodies and their internal facies composition remains poorly documented from ancient successions. This work quantifies lithofacies distributions and dimensions of exhumed crevasse-splay architectural elements in the Campanian Castlegate Sandstone and Neslen Formation, Mesaverde Group, Utah, USA, to develop a depositional model. Fluvial crevasse-splay bodies thin from 2.1 m (average) to 0.8 m (average) and fine from a coarsest recorded grain size of lower-fine sand to fine silt away from major trunk channel bodies. Internally, the preserved deposits of splays comprise laterally and vertically variable sandstone and siltstone facies associations: proximal parts are dominated by sharp and erosional-based sandstone-prone units, which may be structureless or may comprise primary current lineation on beds and erosional gutter casts; medial parts comprise sets of climbing-ripple strata and small scale deformed beds; distal parts comprise sets of lower-stage plane beds and complex styles of lateral grading into fine-grained floodbasin siltstones and coals. Lithofacies arrangements are used to establish the following: (i) recognition criteria for crevasse-splay elements; (ii) criteria for the differentiation between distal parts of crevasse-splay bodies and floodplain fines; and (iii) empirical relationships with which to establish the extent (ca. 500 m long by 1000 m wide) and overall semi-elliptical planform shape of crevasse-splay bodies. These relationships have been established by high-resolution stratigraphic correlation and palaeocurrent analysis to identify outcrop orientation with respect to splay orientation. This permits lateral changes in crevasse-splay facies architecture to be resolved. Facies models describing the sedimentology and architecture of

A History of Pebbles and Silt – Fluvial Sediment Transport, Hydropower and Technical Expertise at the Austrian Danube and its Tributaries

Directory of Open Access Journals (Sweden)

Schoder Angelika

2016-08-01

Full Text Available The paper investigates experts’ perceptions of hydropower, sediment regime, and their interaction in the 20th century with an environmental historical approach, based on various case studies at both the Danube River and one of its tributaries, and on a review of contemporary literature authored by engineers. Results show that questions of sediment continuity have engaged planners of hydropower plants since the advent of this technology, and decisions were at any time influenced by multiple interests (navigation, electricity demand, nature conservation. In such an intricate fluvial landscape, phenomena like reservoir sedimentation and riverbed incision can be approached as “legacies” of past technical interventions, which limit the options of current and future river management.

Sources of 137Cs fluvial export from a forest catchment evaluated by stable carbon and nitrogen isotopic characterization of organic matter

International Nuclear Information System (INIS)

Kotomi Muto; Mariko Atarashi-Andoh; Jun Koarashi; Erina Takeuchi; Syusaku Nishimura; Katsunori Tsuduki; Takeshi Matsunaga

2017-01-01

Fluvial export of particulate and dissolved 137 Cs was investigated to reveal its sources and transfer mechanisms in a broadleaved forest catchment using a continuous collection system. The finest size fraction (<75 µm), consisting of decomposed litter and surface mineral soil, was the dominant fraction in the particulate 137 Cs load, although the contribution of coarser size fractions increased during high water discharge in 2014. The dissolved 137 Cs originated from the decomposition of 137 Cs-contaminated litter. Temporal changes in 137 Cs distribution in the litter-mineral soil system indicated that the dissolved 137 Cs load will be moderated in several years, while particulate 137 Cs load has the potential to continue for a long time. (author)