WorldWideScience

Sample records for sediment transport pathways

  1. Sediment Connectivity and Transport Pathways in Tidal Inlets: a Conceptual Framework with Application to Ameland Inlet

    Science.gov (United States)

    Pearson, S.; van Prooijen, B. C.; Zheng Bing, W.; Bak, J.

    2017-12-01

    Predicting the response of tidal inlets and adjacent coastlines to sea level rise and anthropogenic interventions (e.g. sand nourishments) requires understanding of sediment transport pathways. These pathways are strongly dependent on hydrodynamic forcing, grain size, underlying morphology, and the timescale considered. To map and describe these pathways, we considered the concept of sediment connectivity, which quantifies the degree to which sediment transport pathways link sources to receptors. In this study we established a framework for understanding sediment transport pathways in coastal environments, using Ameland Inlet in the Dutch Wadden Sea as a basis. We used the Delft3D morphodynamic model to assess the fate of sediment as it moved between specific morphological units defined in the model domain. Simulation data was synthesized in a graphical network and then graph theory used to analyze connectivity at different space and time scales. At decadal time scales, fine and very fine sand (250μm) shows lower connectivity, even in more energetic areas. Greater sediment connectivity was found under the influence of wind and waves when compared to purely tidal forcing. Connectivity shows considerable spatial variation in cross shore and alongshore directions, depending on proximity to the inlet and dominant wave direction. Furthermore, connectivity generally increases at longer timescales. Asymmetries in connectivity (i.e. unidirectional transport) can be used to explain long-term erosional or depositional trends. As such, an understanding of sediment connectivity as a function of grain size could yield useful insights for resolving sediment transport pathways and the fate of a nourishment in coastal environments.

  2. Sediment Transport

    DEFF Research Database (Denmark)

    Liu, Zhou

    Flow and sediment transport are important in relation to several engineering topics, e.g. erosion around structures, backfilling of dredged channels and nearshore morphological change. The purpose of the present book is to describe both the basic hydrodynamics and the basic sediment transport...... mechanics. Chapter 1 deals with fundamentals in fluid mechanics with emphasis on bed shear stress by currents, while chapter 3 discusses wave boundary layer theory. They are both written with a view to sediment transport. Sediment transport in rivers, cross-shore and longshore are dealt with in chapters 2...

  3. Morphodynamics and Sediment Transport Pathways of the John's Pass-Blind Pass Dual Inlet System: Pinellas County, Florida

    Science.gov (United States)

    Horwitz, Mark H.

    The morphodynamics of an inlet channel draining an estuary or bay are governed by a complex system of temporally and spatially varying physical processes, including wind, waves, tides, sediment transport, and both tide and wave driven currents. In addition, sediment availability and characteristics in conjunction with underlying geologic framework bear on the morphology and morphologic behavior of an inlet system. This study examines the morphodynamics, sediment transport patterns and time-series morphologic change of John's Pass and Blind Pass, two structured tidal inlets that collectively make up a dual-inlet system sharing the tidal prism of northern Boca Ciega Bay, in Pinellas County, Florida. To quantify wave and tidal forcing and response mechanisms an array of hydrodynamic sensors were deployed over a 12 month period at both inshore and offshore locations. In order to capture morphologic changes and quantify volumetric changes within the inlets, bathymetric surveys of the inlets were conducted in 2010, 2011, 2012, and 2014. Similarly, bi-monthly beach survey data for the same range of time was acquired in order to quantify volumetric changes along adjacent stretches of beach. In addition to gaining insights into sediment pathways based on morphologic and volumetric variability, those data were also used to develop a regional sediment budget along the studied stretch of coast. To gain insights into the morphodynamics of the dual-inlet system, bathymetric and hydrodynamic data was used to develop a numerical model of the dual inlet system. Numerical model simulations based on existing or baseline conditions were compared with numerical simulations employing synthetic bathymetric and hydrodynamic conditions in order to examine inlet behavior under a range of different morphological and hydrodynamic conditions. John's Pass is the dominant of the two inlets. It exhibits mixed-energy straight morphology and captures ca 81% of the available tidal prism. The inlet

  4. Aeolian Sediment Availability and Transport

    NARCIS (Netherlands)

    Hoonhout, B.M.

    2017-01-01

    This thesis explores the nature of aeolian sediment availability and its influence on aeolian sediment transport. The aim is to improve large scale and long term aeolian sediment transport estimates in (nourished) coastal environments. The generally poor performance of aeolian sediment transport

  5. Sediment transport mechanics

    Science.gov (United States)

    Ballio, Francesco; Tait, Simon

    2012-12-01

    The Editor of Acta Geophysica and the Guest Editors wish to dedicate this Topical Issue on Sediment Transport Mechanics to the memory of Stephen Coleman, who died recently. During his career, Stephen had made an outstanding scientific contribution to the topic of Sediment Transport. The level of his contribution is demonstrated in the paper by Aberle, Coleman, and Nikora included in this issue, on which he started working before becoming aware of the illness that led to his untimely death. For scholars and colleagues Stephen remains an example of intellectual honesty and scientific insight.

  6. Contaminated sediment transport during floods

    International Nuclear Information System (INIS)

    Fontaine, T.A.

    1992-01-01

    Over the past 48 years, operations and waste disposal activities at Oak Ridge National Laboratory have resulted in the contamination of parts of the White Oak Creek catchment. The contaminants presenting the highest risk to human health and the environment are particle reactive and are associated with the soils and sediments in the White Oak Creek drainage system. The erosion of these sediments during floods can result in the transport of contaminants both within the catchment and off-site into the Clinch River. A data collection program and a modeling investigation are being used to evaluate the probability of contaminated sediment transport during floods and to develop strategies for controlling off-site transport under present and future conditions

  7. Sediment transport under breaking waves

    DEFF Research Database (Denmark)

    Christensen, Erik Damgaard; Hjelmager Jensen, Jacob; Mayer, Stefan

    2000-01-01

    generated at the surface where the wave breaks as well as the turbulence generated near the bed due to the wave-motion and the undertow. In general, the levels of turbulent kinetic energy are found to be higher than experiments show. This results in an over prediction of the sediment transport. Nevertheless...

  8. Longshore sediment transport along the Indian coast

    Digital Repository Service at National Institute of Oceanography (India)

    Chandramohan, P.; Nayak, B.U.

    An empirical sediment transport model has been developed based on longshore energy flux equation. Ship reported waves, published in Indian Daily Weather Reports, are compiled for 19 y and used for estimation of sediment transport. Annual gross...

  9. 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

  10. Mass balance, bedload extraction, surface morphology, and Holocene stratigraphic architecture along distinct sediment transport pathways of the Brahmaputra River in Bengal Basin

    Science.gov (United States)

    Sincavage, R.; Goodbred, S. L., Jr.; Wilson, C.; Pickering, J.; Paola, C.

    2015-12-01

    The Brahmaputra River has followed three preferred pathways within the Ganges-Brahmaputra-Meghna delta during the Holocene: the principal course along the modern Jamuna braidbelt and two subsidiary routes through the tectonically deforming Sylhet Basin. The Jamuna braidbelt follows a relatively straight and tectonically stable (subsidence rates generally Basin traverse an actively subsiding basin (typically 3-4 mm/yr, with rates as high as 7 mm/year near the adjacent Dauki foredeep). In spite of differential subsidence, the Brahmaputra has only episodically occupied Sylhet Basin for brief periods during most of the Holocene. We compare downstream rates of mass extraction via selective deposition along multiple sediment delivery pathways using quantitative grain size data from a network of over 400 closely-spaced (3-5 km) boreholes (up to 90 m deep). An exponential function to describe downstream fining was fitted to the data, with the exponent alpha taken to be the rate of downstream fining. Our data indicate 1.) the upper and lower reaches (~100 km) of all pathways exhibit limited to no fining, 2.) once fining begins it proceeds rapidly in a downstream direction until the coarse fraction has been extracted, and 3.) the fining rate in Sylhet Basin (α = 0.005) is considerably higher than that for the modern braidbelt (α = 0.001), likely due to a steeper slope down the fan delta. When converted to a scale-independent chi space, preserved stratigraphy along both courses show declining sand:mud ratios and sand body thickness at a chi distance of about 0.7, consistent with previous studies in other depositional settings. This downstream distance also generally coincides with a decrease in slope from the fan delta to the lower fluvial-tidal delta, as well as the cessation of downstream fining. Furthermore, this transition corresponds with the backwater length as calculated by a number of different methods. These initial results suggest that complete extraction of the

  11. Mesoscale eddies transport deep-sea sediments.

    Science.gov (United States)

    Zhang, Yanwei; Liu, Zhifei; Zhao, Yulong; Wang, Wenguang; Li, Jianru; Xu, Jingping

    2014-08-04

    Mesoscale eddies, which contribute to long-distance water mass transport and biogeochemical budget in the upper ocean, have recently been taken into assessment of the deep-sea hydrodynamic variability. However, how such eddies influence sediment movement in the deepwater environment has not been explored. Here for the first time we observed deep-sea sediment transport processes driven by mesoscale eddies in the northern South China Sea via a full-water column mooring system located at 2100 m water depth. Two southwestward propagating, deep-reaching anticyclonic eddies passed by the study site during January to March 2012 and November 2012 to January 2013, respectively. Our multiple moored instruments recorded simultaneous or lagging enhancement of suspended sediment concentration with full-water column velocity and temperature anomalies. We interpret these suspended sediments to have been trapped and transported from the southwest of Taiwan by the mesoscale eddies. The net near-bottom southwestward sediment transport by the two events is estimated up to one million tons. Our study highlights the significance of surface-generated mesoscale eddies on the deepwater sedimentary dynamic process.

  12. 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…

  13. A Sediment Transport Model for Sewers

    DEFF Research Database (Denmark)

    Mark, Ole; Larsson, Johan; Larsen, Torben

    1993-01-01

    This paper describes a mathematical model for transport processes in sewers. The model consists of three sub models, a surface model for the description of the buildup and the washoff of sediment particles from the surface area, a morphological model and an advection-dispersion model. The model...

  14. Sediment transport in an active erodible channel bend of ...

    Indian Academy of Sciences (India)

    Vertical distribution of suspended sediment concentration follows a power function with normalized depth. Average bed-material concentration at the reach level is computed from observed sediment profiles, and is compared against various sediment transport functions. Results show that the sediment transport function ...

  15. Longshore sediment transport model for the Indian west coast

    Digital Repository Service at National Institute of Oceanography (India)

    Chandramohan, P.; Nayak, B

    Longshore sediment transport rates for the Indian west coast from Cochin to Porbandar are estimated from ship observed wave data (1968 to 1986). The sediment transport rate is relatively high during the southwest monsoon period from June...

  16. Sediment transport in two mediterranean regulated rivers.

    Science.gov (United States)

    Lobera, G; Batalla, R J; Vericat, D; López-Tarazón, J A; Tena, A

    2016-01-01

    Mediterranean climate is characterized by highly irregular rainfall patterns with marked differences between wet and dry seasons which lead to highly variable hydrological fluvial regimes. As a result, and in order to ensure water availability and reduce its temporal variability, a high number of large dams were built during the 20th century (more than 3500 located in Mediterranean rivers). Dams modify the flow regime but also interrupt the continuity of sediment transfer along the river network, thereby changing its functioning as an ecosystem. Within this context, the present paper aims to assess the suspended sediment loads and dynamics of two climatically contrasting Mediterranean regulated rivers (i.e. the Ésera and Siurana) during a 2-yr period. Key findings indicate that floods were responsible for 92% of the total suspended sediment load in the River Siurana, while this percentage falls to 70% for the Ésera, indicating the importance of baseflows on sediment transport in this river. This fact is related to the high sediment availability, with the Ésera acting as a non-supply-limited catchment due to the high productivity of the sources (i.e. badlands). In contrast, the Siurana can be considered a supply-limited system due to its low geomorphic activity and reduced sediment availability, with suspended sediment concentration remaining low even for high magnitude flood events. Reservoirs in both rivers reduce sediment load up to 90%, although total runoff is only reduced in the case of the River Ésera. A remarkable fact is the change of the hydrological character of the River Ésera downstream for the dam, shifting from a humid mountainous river regime to a quasi-invariable pattern, whereas the Siurana experiences the opposite effect, changing from a flashy Mediterranean river to a more constant flow regime below the dam. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Longshore sediment transport at Golden Sands (Bulgaria

    Directory of Open Access Journals (Sweden)

    Hristo Nikolov

    2006-09-01

    Full Text Available The paper presents the results of studies on the qualitative and quantitative features of the littoral drift at Golden Sands (Bulgaria, carried out jointly by Polish and Bulgarian researchers. The mathematical modelling of physical coastal processes took wave transformation (wave diffraction and refraction; the effects of shoaling and wave breaking and longshore sediment transport into account. The computations were carried out for the mean statistical annual wave climate, determined on the basis of IO BAS wave data, simulated using the WAM method from long-term Black Sea wind data. The results of sediment transport computations clearly show that its direction off the Golden Sands shore is from north to south.

  18. Sediment transport drives tidewater glacier periodicity.

    Science.gov (United States)

    Brinkerhoff, Douglas; Truffer, Martin; Aschwanden, Andy

    2017-07-21

    Most of Earth's glaciers are retreating, but some tidewater glaciers are advancing despite increasing temperatures and contrary to their neighbors. This can be explained by the coupling of ice and sediment dynamics: a shoal forms at the glacier terminus, reducing ice discharge and causing advance towards an unstable configuration followed by abrupt retreat, in a process known as the tidewater glacier cycle. Here we use a numerical model calibrated with observations to show that interactions between ice flow, glacial erosion, and sediment transport drive these cycles, which occur independent of climate variations. Water availability controls cycle period and amplitude, and enhanced melt from future warming could trigger advance even in glaciers that are steady or retreating, complicating interpretations of glacier response to climate change. The resulting shifts in sediment and meltwater delivery from changes in glacier configuration may impact interpretations of marine sediments, fjord geochemistry, and marine ecosystems.The reason some of the Earth's tidewater glaciers are advancing despite increasing temperatures is not entirely clear. Here, using a numerical model that simulates both ice and sediment dynamics, the authors show that internal dynamics drive glacier variability independent of climate.

  19. Modelling of sediment transport at Muria peninsula coastal, Jepara

    International Nuclear Information System (INIS)

    Heni Susiati; Yarianto SBS; Wahyu Pandoe; Eko Kusratmoko; Aris Poniman

    2010-01-01

    Modelling of transport sediment modelling at Muria Peninsula have been done. In this study we had been used mathematical model that consist of hydrodynamics and sediment transport . Data input for modelling has been used tidal, monsoon wind, and river debit. Simulation result of sediment transport modelling showed that tides pattern and seasonal variations are the main causes of variations in the suspended sediment distribution in Muria Peninsula. (author)

  20. Sedimentation and transportation of mud rock material

    Science.gov (United States)

    Lin, J.; Ochiai, S.

    2008-12-01

    This research focuses on the transportation and sedimentation of mud rock slope at Niupu, southern Taiwan. The main purpose of this research is trying to identify the mechanism of erosion and sedimentation rate of the mud rock from the slope into the lake. By using regular sonar surveying and rainfall data, it is possible to identify a high erosion rate on mud rock area. The cementation of Miocene mud rock is loose and slope at 40-45 degree which is highly sensitive to the rainfall. It is also vulnerable to the erosion processes. There are some interesting characters related to the observation and surveying. The erosion processes are highly related to amounts of rainfall. When there is typhoon, tropical storm, there is high erosion. The erosion could occur when there is rainfall more than 10 mm/event and the surface of the mud rock could be incised up to 3 cm after 30 mm rainfall. The sedimentation rate could also as high as 0.5 m when there are two typhoons which attacked to this area within three months. This research also demonstrates that the high erosion on mud rock area will generate high sedimentation and high denudation rate. However the comparison of the rate of erosion and deposition is identified in this presentation. For hazard mitigation purpose, it is necessary to reduce the bared mud rock slope area to prevent the further erosion.

  1. Mathematical simulation of sediment and radionuclide transport in estuaries

    International Nuclear Information System (INIS)

    Onishi, Y.; Trent, D.S.

    1982-11-01

    The finite element model LFESCOT (Flow, Energy, Salinity, Sediment and Contaminant Transport Model) was synthesized under this study to simulate radionuclide transport in estuaries to obtain accurate radionuclide distributions which are affected by these factors: time variance, three-dimensional flow, temperature, salinity, and sediments. Because sediment transport and radionuclide adsorption/desorption depend strongly on sizes or types of sediments, FLESCOT simulates sediment and a sediment-sorbed radionuclide for the total of three sediment-size fractions (or sediment types) of both cohesive and noncohesive sediments. It also calculates changes of estuarine bed conditions, including bed elevation changes due to sediment erosion/deposition, and three-dimensional distributions of three bed sediment sizes and sediment-sorbed radionuclides within the bed. Although the model was synthesized for radionuclide transport, it is general enough to also handle other contaminants such as heavy metals, pesticides, or toxic chemicals. The model was checked for its capability for flow, water surface elevation change, salinity, sediment and radionuclide transport under various simple conditions first, confirming the general validity of the model's computational schemes. These tests also revealed that FLESCOT can use large aspect ratios of computational cells, which are necessary in handling long estuarine study areas. After these simple tests, FLESCOT was applied to the Hudson River estuary between Chelsea and the mouth of the river to examine how well the model can predict radionuclide transport through simulating tidally influenced three-dimensional flow, salinity, sediment and radionuclide movements with their interactions

  2. Modelling sediment clasts transport during landscape evolution

    Science.gov (United States)

    Carretier, Sébastien; Martinod, Pierre; Reich, Martin; Godderis, Yves

    2016-03-01

    Over thousands to millions of years, the landscape evolution is predicted by models based on fluxes of eroded, transported and deposited material. The laws describing these fluxes, corresponding to averages over many years, are difficult to prove with the available data. On the other hand, sediment dynamics are often tackled by studying the distribution of certain grain properties in the field (e.g. heavy metals, detrital zircons, 10Be in gravel, magnetic tracers). There is a gap between landscape evolution models based on fluxes and these field data on individual clasts, which prevent the latter from being used to calibrate the former. Here we propose an algorithm coupling the landscape evolution with mobile clasts. Our landscape evolution model predicts local erosion, deposition and transfer fluxes resulting from hillslope and river processes. Clasts of any size are initially spread in the basement and are detached, moved and deposited according to probabilities using these fluxes. Several river and hillslope laws are studied. Although the resulting mean transport rate of the clasts does not depend on the time step or the model cell size, our approach is limited by the fact that their scattering rate is cell-size-dependent. Nevertheless, both their mean transport rate and the shape of the scattering-time curves fit the predictions. Different erosion-transport laws generate different clast movements. These differences show that studying the tracers in the field may provide a way to establish these laws on the hillslopes and in the rivers. Possible applications include the interpretation of cosmogenic nuclides in individual gravel deposits, provenance analyses, placers, sediment coarsening or fining, the relationship between magnetic tracers in rivers and the river planform, and the tracing of weathered sediment.

  3. Simulation of suspended sediment transport initialized with satellite ...

    Indian Academy of Sciences (India)

    have described the effective use of satellite remote sensing data in modelling sediment transport. Quillon et al. (2004) have coupled remote sens- ing data with in situ measurements to simulate suspended sediment transport in New Caledonia. Lagoon. Initial distribution of sediment concentrations are of critical importance ...

  4. Mathematical simulation of sediment and contaminant transport in surface waters. Annual report, October 1977--September 1978

    International Nuclear Information System (INIS)

    Onishi, Y.; Arnold, E.M.; Serne, R.J.; Cowan, C.E.; Thompson, F.L.; Mayer, D.W.

    1979-01-01

    Various pathways exist for exposure of humans and biota to radioactive materials released from nuclear facilities. Hydrologic transport (liquid pathway) is one element in the evaluation of the total radiation dose to man. Mathematical models supported by well-planned field data collection programs can be useful tools in assessing the hydrologic transport and ultimate fate of radionuclides. Radionuclides with high distribution coefficients or radionuclides in surface waters with high suspended sediment concentrations are, to a great extent, adsorbed by river and marine sediments. Thus, otherwise dilute contaminants are concentrated. Contaminated sediments may be deposited on the river and ocean beds creating a significant pathway to man. Contaminated bed sediment in turn may become a long-term source of pollution through desorption and resuspension. In order to assess migration and accumulation of radionuclides in surface waters, mathematical models must correctly simulate essential mechanisms of radionuclide transport. The objectives of this study were: (1) to conduct a critical review of (a) radionuclide transport models as well as sediment transport and representative water quality models in rivers, estuaries, oceans, lakes, and reservoirs, and (b) adsorption and desorption mechanisms of radionuclides with sediments in surface waters; (2) to synthesize a mathematical model capable of predicting short- and long-term transport and accumulation of radionuclides in marine environments

  5. Moisture and solute flux along preferred pathways characterized by fissured sediments in desert soils

    Science.gov (United States)

    Scanlon, Bridget R.

    1992-06-01

    Evaluation of preferred flow pathways is critical for waste disposal. These pathways reduce the effectiveness of thick desert soils in attenuating contaminants by short-circuiting flow through the unsaturated zone. Unsaturated flow in fissured sediments in the Chihuahuan Desert of Texas, U.S.A., was examined to determine if these sediments act as preferred pathways for water and solute transport. Fissures are surface features, or gulleys, that are underlain by fractures filled with loose sediment washed in from surrounding areas. Hydraulic and chemical approaches were used to investigate unsaturated flow processes beneath and adjacent to fissures, and the results were compared with data from surrounding geomorphic systems such as arroyos, ephemeral streams and interstreams. Typically, high water potentials in surficial sediments result from infiltration of recent precipitation. Below this surficial zone of high water potentials lies a zone of low water potentials that is much thinner beneath the fissure than in adjacent sediments or in sediments beneath ephemeral streams and interstreams. Maximum chloride concentrations in profiles in the fissured sediments (80-105 gm -3) were much lower than those measured in all other geomorphic systems (2000-6000 gm -3) because chloride is leached in the vicinity of the fissures. Minimum estimates of the moisture flux from chloride data ranged from 1 to 8 mm yr -1 in the fissured sediments and were up to 350 times greater than those calculated for ephemeral stream and interstream settings. The corresponding moisture velocities in the fissured sediments ranged from 10 to 70 mm yr -1. A tracer experiment demonstrated higher downward water and solute transport in the fracture fill beneath the fissure relative to adjacent sediments. Numerical simulations of the tracer experiment with the computer code TRACR3D reproduced the overall shape of the tracer plume. Sensitivity analyses demonstrated that the tracer plume is most sensitive

  6. Methane Bubbles Transport Particles From Contaminated Sediment to a Lake Surface

    Science.gov (United States)

    Delwiche, K.; Hemond, H.

    2017-12-01

    Methane bubbling from aquatic sediments has long been known to transport carbon to the atmosphere, but new evidence presented here suggests that methane bubbles also transport particulate matter to a lake surface. This transport pathway is of particular importance in lakes with contaminated sediments, as bubble transport could increase human exposure to toxic metals. The Upper Mystic Lake in Arlington, MA has a documented history of methane bubbling and sediment contamination by arsenic and other heavy metals, and we have conducted laboratory and field studies demonstrating that methane bubbles are capable of transporting sediment particles over depths as great as 15 m in Upper Mystic Lake. Methane bubble traps were used in-situ to capture particles adhered to bubble interfaces, and to relate particle mass transport to bubble flux. Laboratory studies were conducted in a custom-made 15 m tall water column to quantify the relationship between water column height and the mass of particulate transport. We then couple this particle transport data with historical estimates of ebullition from Upper Mystic Lake to quantify the significance of bubble-mediated particle transport to heavy metal cycling within the lake. Results suggest that methane bubbles can represent a significant pathway for contaminated sediment to reach surface waters even in relatively deep water bodies. Given the frequent co-occurrence of contaminated sediments and high bubble flux rates, and the potential for human exposure to heavy metals, it will be critical to study the significance of this transport pathway for a range of sediment and contaminant types.

  7. Sediment transport along the Goa-north Karnataka Coast, western India

    Digital Repository Service at National Institute of Oceanography (India)

    Kunte, P.D.

    of sediment transport. Although sediment-transport direction is bi-directional, net major sediment transport is southward. The geomorphic study identified possible sediment sources and sinks. Contributions of sources and losses due to sinks are assessed...

  8. System Identification Theory Approach to Cohesive Sediment Transport Modelling

    OpenAIRE

    CHEN, HUIXIN

    1997-01-01

    Two aspects of the modelling sediment transport are investigated. One is the univariate time series modelling the current velocity dynamics. The other is the multivariate time series modelling the suspended sediment concentration dynamics. Cohesive sediment dynamics and numerical sediment transport model are reviewed and investigated. The system identification theory and time series analysis method are developed and applied to set up the time series model for current velocity a...

  9. Oscillatory infragravity wave contribution to surf zone sediment transport

    DEFF Research Database (Denmark)

    Aagaard, Troels; Greenwood, Brian

    2008-01-01

    Field measurements reported in the literature demonstrate that suspended sediment transport due to infragravity wave motions can sometimes be very large and dominate the net sediment transport at a given measurement location within the surf zone. At other times, however, this transport component...

  10. A combined model of sediment production, supply and transport

    Directory of Open Access Journals (Sweden)

    M. Fujita

    2015-03-01

    Full Text Available In previous sediment-runoff models, the sediment production rates of mountain slopes, and the sediment supply rates to streams typically have been developed using empirical methods. A process-based model for sediment production and supply is, however, required for more exact simulations of sediment runoff. In this study, we develop a method to calculate the sediment production rate due to both freeze-thaw action and the sediment supply rate (i.e. erosion rate of talus. These numerical models were then connected to an existing sediment transport model. The integrated model presented here was applied to a small mountainous watershed. We found that the calculated sediment production rate was within the range of values typically observed for this region. Additionally, the estimated annual sediment discharge using the model agreed with observational results. Lastly, we found that the model can be used to qualitatively characterize typical features of the actual sediment routine in mountainous watersheds.

  11. Sediment transport dynamics in steep, tropical volcanic catchments

    Science.gov (United States)

    Birkel, Christian; Solano Rivera, Vanessa; Granados Bolaños, Sebastian; Brenes Cambronero, Liz; Sánchez Murillo, Ricardo; Geris, Josie

    2017-04-01

    How volcanic landforms in tropical mountainous regions are eroded, and how eroded materials move through these mostly steep landscapes from the headwaters to affect sediment fluxes are critical to water resources management in their downstream rivers. Volcanic landscapes are of particular importance because of the short timescales (70%) and sediments to downstream rivers. At the catchment outlet (Figure 1C) of the San Lorencito stream, we established high temporal resolution (5min) water quantity and sediment monitoring (turbidity). We also surveyed the river network on various occasions to characterize fluvial geomorphology including material properties. We could show that the rainfall-runoff-sediment relationships and their characteristic hysteresis patterns are directly linked to variations in the climatic input (storm intensity and duration) and the size, form and mineralogy of the transported material. Such a relationship allowed us to gain the following insights: (i) periodic landslides contribute significant volumes of material (> 100m3 per year) to the stream network, (ii) rainfall events that exceed a threshold of around 30mm/h rain intensity activate superficial flow pathways with associated mobilization of sediments (laminar erosion). However, the erosion processes are spatially very heterogeneous and mostly linked to finer material properties of the soils that mostly developed on more highly weathered bedrock. (iii) extreme events (return period > 50 years) mainly erode the streambed and banks cutting deeper into the bedrock and re-distribute massive amounts of material in the form of removed old alluvial deposits and new deposits created elsewhere, (iv) recovery after such extreme events in the form of fine material transport even during low intensity rainfall towards pre-event rainfall intensity thresholds takes only about two to three months. We conclude that the study catchment geomorphologically represents a low-resistance, but highly resilient

  12. Sediment transport in an active erodible channel bend

    Indian Academy of Sciences (India)

    Local variation of sediment transport is primarily controlled by active bank erosion, land spur and sand bar formation. Vertical distribution of suspended sediment concentration follows a power function with normalized depth. Average bed-material concentration at the reach level is computed from observed sediment profiles, ...

  13. Simulation of suspended sediment transport initialized with satellite ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 121; Issue 5 ... Suspended sediment concentrations; OCM; sediment transport model; tide. ... Optimization of the model mud parameters, like settling velocity and critical shear stress for erosion are realized with respect to the sediment size distribution and the bottom ...

  14. "Smart pebble" designs for sediment transport monitoring

    Science.gov (United States)

    Valyrakis, Manousos; Alexakis, Athanasios; Pavlovskis, Edgars

    2015-04-01

    Sediment transport, due to primarily the action of water, wind and ice, is one of the most significant geomorphic processes responsible for shaping Earth's surface. It involves entrainment of sediment grains in rivers and estuaries due to the violently fluctuating hydrodynamic forces near the bed. Here an instrumented particle, namely a "smart pebble", is developed to investigate the exact flow conditions under which individual grains may be entrained from the surface of a gravel bed. This could lead in developing a better understanding of the processes involved, focusing on the response of the particle during a variety of flow entrainment events. The "smart pebble" is a particle instrumented with MEMS sensors appropriate for capturing the hydrodynamic forces a coarse particle might experience during its entrainment from the river bed. A 3-axial gyroscope and accelerometer registers data to a memory card via a microcontroller, embedded in a 3D-printed waterproof hollow spherical particle. The instrumented board is appropriately fit and centred into the shell of the pebble, so as to achieve a nearly uniform distribution of the mass which could otherwise bias its motion. The "smart pebble" is powered by an independent power to ensure autonomy and sufficiently long periods of operation appropriate for deployment in the field. Post-processing and analysis of the acquired data is currently performed offline, using scientific programming software. The performance of the instrumented particle is validated, conducting a series of calibration experiments under well-controlled laboratory conditions.

  15. Distribution and transportation of suspended sediment

    International Nuclear Information System (INIS)

    Schubel, J.R.

    1975-01-01

    A number of studies of the distribution and character of suspended matter in the waters of the Atlantic shelf have documented the variations in the concentration of total suspended matter in both time and space. Very little is known, however, about the ultimate sources of inorganic suspended matter, and even less is known about the routes and rates of suspended sediment transport in shelf waters. Suspended particulate matter constitutes a potential vehicle for the transfer of energy-associated contaminants, radionuclides and oil, back to the coast and therefore to man. The concentrations of total suspended matter in shelf waters are typically so low, however, that the mechanism is ineffective. Studies of suspended particulate matter have a high scientific priority, but in this investigator's opinion the state of knowledge is adequate for preparation of the environmental impact statements that would be required for siting of offshore nuclear power plants and for oil drilling on the Atlantic Continental Shelf

  16. A longshore sediment transport estimation for the Indian coast

    Digital Repository Service at National Institute of Oceanography (India)

    Nayak, B.U.; Chandramohan, P.

    An empirical sediment transport model has been developed based on longshore energy flux equation. Study indicates that annual gross sediment transport rate is high (1.5 x 10 super(6) m super(3) to 2.0 x 10 super(6) m super(3)) along the coasts...

  17. Sediment transport in an active erodible channel bend of ...

    Indian Academy of Sciences (India)

    Spatial variation of sediment transport in an alluvial sand-bed river bend needs to be understood with ... Local variation of sediment transport is primarily controlled by active bank erosion, land spur and sand bar ..... of Water, Environment, Energy and Society (WEES)-2009, New Delhi, India, 1670–1676. Karmaker T, Dutta S ...

  18. Wave Induced Mine Burial and Sediment Transport in Coastal Environment: Wave and Sediment Transport Modeling Studies

    Science.gov (United States)

    2007-01-01

    predicting ripple and dune formation and evolution (e.g., Voropayev et al., 1999). In a larger context, this work will yield an experimentally...Engng. (in revision). Voropayev, S.I., McEachern, G.B., Boyer, D.L. and Fernando, H.J.S. (1999). “Dynamics of sand ripples and burial/scouring of...changes, in coastal and estuarine environments of active sediment transport (e.g., ripple migration). OBJECTIVE In the past year, our objective

  19. Sediment Transport Model for a Surface Irrigation System

    OpenAIRE

    Mailapalli, Damodhara R.; Raghuwanshi, Narendra S.; Singh, Rajendra

    2013-01-01

    Controlling irrigation-induced soil erosion is one of the important issues of irrigation management and surface water impairment. Irrigation models are useful in managing the irrigation and the associated ill effects on agricultural environment. In this paper, a physically based surface irrigation model was developed to predict sediment transport in irrigated furrows by integrating an irrigation hydraulic model with a quasi-steady state sediment transport model to predict sediment load in fur...

  20. The algal lift: Buoyancy-mediated sediment transport

    Science.gov (United States)

    Mendoza-Lera, Clara; Federlein, Laura L.; Knie, Matthias; Mutz, Michael

    2016-01-01

    The role of benthic algae as biostabilizers of sediments is well-known, however, their potential to lift and transport sediments remains unclear. Under low-flow conditions, matured algal mats may detach from the bed and may lift up sediment, thereby causing disturbance to the uppermost streambed sediment. We tested the potential of algal mats to lift sediments in 12 indoor flumes filled with sand (0.2 - 0.8 mm), gravel (2 - 8 mm) or a sand-gravel mixture (25/75% mass). After four weeks, the algal mats covered about 50% of the flumes area. Due to the accumulation of oxygen gas bubbles in the mats, that developed from high primary production at 4.5 weeks, about half of the algal mats detached from the bed carrying entangled sediments. Both the area covered by algal mats and detached area were similar among sediment types, but the amount of sediment transported tended to be higher for sand and sand-gravel mixture compared to gravel. Our results reveal that biologically mediated sediment transport mainly depends on the development of a dense filamentous algal matrix, that traps gas bubbles, increasing the mats buoyancy. This novel mechanism of sediment transport will occur in shallow ecosystems during low-flow periods, with the highest impact for sandy sediments.

  1. Measurements of Sediment Erosion and Transport with the ASSET Flume

    Science.gov (United States)

    Jepsen, R. A.; Roberts, J. D.; James, S. C.

    2003-12-01

    Soil and sediments play an important role in water management and water quality. Issues such as water turbidity, associated contaminants, reservoir sedimentation, undesirable erosion and scour, and aquatic habitat are all linked to sediment properties and behaviors. In situ analysis is necessary to develop an understanding of the erosion and transport of sediments. Sandia National Laboratories has recently patented the ASSET Flume that quantifies in situ erosion of a sediment core with depth while affording simultaneous examination of transport modes (bedload vs. suspended load) of the eroded material. Core erosion rates and ratios of bedload to suspended load transport of quartz sediments were studied with the ASSET Flume. The erosion and transport of a fine-grained natural cohesive sediment were also observed. Experiments using quartz sands revealed that the ratio of suspended load to bedload sediment transport is a function of grain diameter and shear stress at the sediment surface. Data collected from the ASSET Flume were used to formulate a novel empirical relation for predicting the ratio of bedload to suspended load as a function of shear stress and grain diameter for non-cohesive sediments.

  2. 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

  3. Selective Ionic Transport Pathways in Phosphorene.

    Science.gov (United States)

    Nie, Anmin; Cheng, Yingchun; Ning, Shoucong; Foroozan, Tara; Yasaei, Poya; Li, Wen; Song, Boao; Yuan, Yifei; Chen, Lin; Salehi-Khojin, Amin; Mashayek, Farzad; Shahbazian-Yassar, Reza

    2016-04-13

    Despite many theoretical predictions indicating exceptionally low energy barriers of ionic transport in phosphorene, the ionic transport pathways in this two-dimensional (2D) material has not been experimentally demonstrated. Here, using in situ aberration-corrected transmission electron microscopy (TEM) and density functional theory, we studied sodium ion transport in phosphorene. Our high-resolution TEM imaging complemented by electron energy loss spectroscopy demonstrates a precise description of anisotropic sodium ions migration along the [100] direction in phosphorene. This work also provides new insight into the effect of surface and the edge sites on the transport properties of phosphorene. According to our observation, the sodium ion transport is preferred in zigzag edge rather than the armchair edge. The use of this highly selective ionic transport property may endow phosphorene with new functionalities for novel chemical device applications.

  4. Sediment Transport Over Run-of-River Dams

    Science.gov (United States)

    O'Brien, M.; Magilligan, F. J.; Renshaw, C. E.

    2016-12-01

    Dams have numerous documented effects that can degrade river habitat downstream. One significant effect of large dams is their ability to trap sediment delivered from upstream. This trapping can alter sediment transport and grain size downstream - effects that often motivate dam removal decisions. However, recent indirect observations and modeling studies indicate that small, run-of-river (ROR) dams, which do not impede discharge, may actually leak sediment downstream. However, there are no direct measurements of sediment flux over ROR dams. This study investigates flow and sediment transport over four to six different New England ROR dams over a summer-fall field season. Sediment flux was measured using turbidity meters and tracer (RFID) cobbles. Sediment transport was also monitored through an undammed control site and through a river where two ROR dams were recently removed. These data were used to predict the conditions that contribute to sediment transport and trapping. Year 1 data show that tracer rocks of up to 61 mm were transported over a 3 m ROR dam in peak flows of 84% of bankfull stage. These tracer rocks were transported over and 10 m beyond the dam and continue to move downstream. During the same event, comparable suspended sediment fluxes of up to 81 g/s were recorded both upstream and downstream of the dam at near-synchronous timestamps. These results demonstrate the potential for sediment transport through dammed rivers, even in discharge events that do not exceed bankfull. This research elucidates the effects of ROR dams and the controls on sediment transport and trapping, contributions that may aid in dam management decisions.

  5. Transport and distribution of bottom sediments at Pirita Beach

    Directory of Open Access Journals (Sweden)

    Soomere, Tarmo

    2007-12-01

    Full Text Available The basic factors affecting sediment supply for and transport processes at Pirita Beach, a sandy section of the south­eastern coast of Tallinn Bay, are analysed. Observations of bathymetry, sediment properties and sources, sediment transport processes and their changes arising from coastal engineering activities are reported. The mean grain size is about 0.12 mm, with the fine sand fraction (0.063–0.125 mm accounting for about 77% of the sediments. Coarse sand dominates only along the waterline. The content of coarser sediments is greater in the northern part of the beach. A number of coastal engineering structures have blocked natural sediment supplies. The beach suffers from sediment deficit now and has lost about 400 m3 of sand annually from the dry beach between 1997 and 2005.

  6. Sediment Transport Model for a Surface Irrigation System

    Directory of Open Access Journals (Sweden)

    Damodhara R. Mailapalli

    2013-01-01

    Full Text Available Controlling irrigation-induced soil erosion is one of the important issues of irrigation management and surface water impairment. Irrigation models are useful in managing the irrigation and the associated ill effects on agricultural environment. In this paper, a physically based surface irrigation model was developed to predict sediment transport in irrigated furrows by integrating an irrigation hydraulic model with a quasi-steady state sediment transport model to predict sediment load in furrow irrigation. The irrigation hydraulic model simulates flow in a furrow irrigation system using the analytically solved zero-inertial overland flow equations and 1D-Green-Ampt, 2D-Fok, and Kostiakov-Lewis infiltration equations. Performance of the sediment transport model was evaluated for bare and cropped furrow fields. The results indicated that the sediment transport model can predict the initial sediment rate adequately, but the simulated sediment rate was less accurate for the later part of the irrigation event. Sensitivity analysis of the parameters of the sediment module showed that the soil erodibility coefficient was the most influential parameter for determining sediment load in furrow irrigation. The developed modeling tool can be used as a water management tool for mitigating sediment loss from the surface irrigated fields.

  7. Input-variable sensitivity assessment for sediment transport relations

    Science.gov (United States)

    Fernández, Roberto; Garcia, Marcelo H.

    2017-09-01

    A methodology to assess input-variable sensitivity for sediment transport relations is presented. The Mean Value First Order Second Moment Method (MVFOSM) is applied to two bed load transport equations showing that it may be used to rank all input variables in terms of how their specific variance affects the overall variance of the sediment transport estimation. In sites where data are scarce or nonexistent, the results obtained may be used to (i) determine what variables would have the largest impact when estimating sediment loads in the absence of field observations and (ii) design field campaigns to specifically measure those variables for which a given transport equation is most sensitive; in sites where data are readily available, the results would allow quantifying the effect that the variance associated with each input variable has on the variance of the sediment transport estimates. An application of the method to two transport relations using data from a tropical mountain river in Costa Rica is implemented to exemplify the potential of the method in places where input data are limited. Results are compared against Monte Carlo simulations to assess the reliability of the method and validate its results. For both of the sediment transport relations used in the sensitivity analysis, accurate knowledge of sediment size was found to have more impact on sediment transport predictions than precise knowledge of other input variables such as channel slope and flow discharge.

  8. Rainfall, runoff and sediment transport in a Mediterranean mountainous catchment.

    Science.gov (United States)

    Tuset, J; Vericat, D; Batalla, R J

    2016-01-01

    The relation between rainfall, runoff, erosion and sediment transport is highly variable in Mediterranean catchments. Their relation can be modified by land use changes and climate oscillations that, ultimately, will control water and sediment yields. This paper analyses rainfall, runoff and sediment transport relations in a meso-scale Mediterranean mountain catchment, the Ribera Salada (NE Iberian Peninsula). A total of 73 floods recorded between November 2005 and November 2008 at the Inglabaga Sediment Transport Station (114.5 km(2)) have been analysed. Suspended sediment transport and flow discharge were measured continuously. Rainfall data was obtained by means of direct rain gauges and daily rainfall reconstructions from radar information. Results indicate that the annual sediment yield (2.3 t km(-1) y(-1) on average) and the flood-based runoff coefficients (4.1% on average) are low. The Ribera Salada presents a low geomorphological and hydrological activity compared with other Mediterranean mountain catchments. Pearson correlations between rainfall, runoff and sediment transport variables were obtained. The hydrological response of the catchment is controlled by the base flows. The magnitude of suspended sediment concentrations is largely correlated with flood magnitude, while sediment load is correlated with the amount of direct runoff. Multivariate analysis shows that total suspended load can be predicted by integrating rainfall and runoff variables. The total direct runoff is the variable with more weight in the equation. Finally, three main hydro-sedimentary phases within the hydrological year are defined in this catchment: (a) Winter, where the catchment produces only water and very little sediment; (b) Spring, where the majority of water and sediment is produced; and (c) Summer-Autumn, when little runoff is produced but significant amount of sediments is exported out of the catchment. Results show as land use and climate change may have an important

  9. Sediment transport patterns at Kuala Sungai Kemaman, Terengganu

    International Nuclear Information System (INIS)

    Abdul Kadir Ishak

    2004-01-01

    The objective of this study is to determine the transport rate and transport direction of the offshore sand of Kg Kuala Kema man and Kg Geliga coastline using both hydraulic data and radioactive tracers. the result would demonstrate if the offshore sand contributes to the sedimentation at the Kuala Kemaman LKIM jetty. It will also be used to assist coastal engineering Division, Jabatan Pengairan dan Saliran Malaysia in calibrating their mathematical model for sediment transport. (Author)

  10. Pathways of organic carbon oxidation in three continental margin sediments

    DEFF Research Database (Denmark)

    Canfield, Donald Eugene; Jørgensen, Bo Barker; Fossing, Henrik

    1993-01-01

    that O2 respiration accounted for only between 3.6-17.4% of the total organic carbon oxidation. Dentrification was limited to a narrow zone just below the depth of O2 penetration, and was not a major carbon oxidation pathway. The processes of Fe reduction, Mn reduction and sulfate reduction dominated...... organic carbon mineralization, but their relative significance varied depending on the sediment. Where high concentrations of Mn-oxide were found (3-4 wt% Mn), only Mn reduction occurred. With lower Mn oxide concentrations more typical of coastal sediments, Fe reduction and sulfate reduction were most...

  11. Shifting sources and transport paths for the late Quaternary Escanaba Trough sediment fill (northeast Pacific)

    Science.gov (United States)

    Zuffa, G.G.; De Rosa, R.; Normark, W.R.

    1997-01-01

    Escanaba Trough, which forms the southernmost part of the axial valley of the actively spreading Gorda Ridge, is filled with several hundred meters of sediment of presumed late Quaternary age. Surficial sediment samples from gravity cores, deeper samples (as much as 390 m) from Site 35 of the Deep Sea Drilling Program (Leg 5), and the acoustic character of the sediment fill observed on seismic-reflection profiles indicate that much of the sediment fill is of turbidite origin. Gross composition and heavy- mineral analyses of sand samples show that two distinct petrofacies comprise the sediment fill. The lower part of the fill was derived primarily from the Klamath River source of northern California while the younger fill, including the surficial sand beds, are from the Columbia River drainage much farther north. The Escanaba Trough sediment provides an opportunity to evaluate concepts for paleogeographic and paleotectonic reconstructions that are based on facies analysis and compositional and textural data for the volcanic components because both intrabasinal and extrabasinal sources are present as well as coeval (neovolcanic) and non coeval (paleovolcanic) sourcre This study of a modern basin shows, that although the sediment sources could be identified, it was useful to have some knowledge of the sediment pathway(s), the effects of diagenesis, and the possible effects of sediment sorting as a result of long transport distances from the source area for some components. Application of these same techniques to ancient deposits without benefit of the additional parameters will face limitations.

  12. Contemporary sediment-transport processes in submarine canyons.

    Science.gov (United States)

    Puig, Pere; Palanques, Albert; Martín, Jacobo

    2014-01-01

    Submarine canyons are morphological incisions into continental margins that act as major conduits of sediment from shallow- to deep-sea regions. However, the exact mechanisms involved in sediment transfer within submarine canyons are still a subject of investigation. Several studies have provided direct information about contemporary sedimentary processes in submarine canyons that suggests different modes of transport and various triggering mechanisms. Storm-induced turbidity currents and enhanced off-shelf advection, hyperpycnal flows and failures of recently deposited fluvial sediments, dense shelf-water cascading, canyon-flank failures, and trawling-induced resuspension largely dominate present-day sediment transfer through canyons. Additionally, internal waves periodically resuspend ephemeral deposits within canyons and contribute to dispersing particles or retaining and accumulating them in specific regions. These transport processes commonly deposit sediments in the upper- and middle-canyon reaches for decades or centuries before being completely or partially flushed farther down-canyon by large sediment failures.

  13. Modeling transport and deposition of the Mekong River sediment

    Science.gov (United States)

    Xue, Zuo; He, Ruoying; Liu, J. Paul; Warner, John C.

    2012-01-01

    A Coupled Wave–Ocean–SedimentTransport Model was used to hindcast coastal circulation and fine sedimenttransport on the Mekong shelf in southeastern Asian in 2005. Comparisons with limited observations showed that the model simulation captured the regional patterns and temporal variability of surface wave, sea level, and suspended sediment concentration reasonably well. Significant seasonality in sedimenttransport was revealed. In summer, a large amount of fluvial sediments was delivered and deposited near the MekongRiver mouth. In the following winter, strong ocean mixing, and coastal current lead to resuspension and southwestward dispersal of a small fraction of previously deposited sediments. Model sensitivity experiments (with reduced physics) were performed to investigate the impact of tides, waves, and remotely forced ambient currents on the transport and dispersal of the fluvial sediment. Strong wave mixing and downwelling-favorable coastal current associated with the more energetic northeast monsoon in the winter season are the main factors controlling the southwestward along-shelf transport.

  14. On extracting sediment transport information from measurements of luminescence in river sediment

    Science.gov (United States)

    Gray, Harrison J.; Tucker, Gregory E.; Mahan, Shannon; McGuire, Chris; Rhodes, Edward J.

    2017-01-01

    Accurately quantifying sediment transport rates in rivers remains an important goal for geomorphologists, hydraulic engineers, and environmental scientists. However, current techniques for measuring long-time scale (102–106 years) transport rates are laborious, and formulae to predict transport are notoriously inaccurate. Here we attempt to estimate sediment transport rates by using luminescence, a property of common sedimentary minerals that is used by the geoscience community for geochronology. This method is advantageous because of the ease of measurement on ubiquitous quartz and feldspar sand. We develop a model from first principles by using conservation of energy and sediment mass to explain the downstream pattern of luminescence in river channel sediment. We show that the model can accurately reproduce the luminescence observed in previously published field measurements from two rivers with very different sediment transport styles. The model demonstrates that the downstream pattern of river sand luminescence should show exponential-like decay in the headwaters which asymptotes to a constant value with further downstream distance. The parameters from the model can then be used to estimate the time-averaged virtual velocity, characteristic transport lengthscale, storage time scale, and floodplain exchange rate of fine sand-sized sediment in a fluvial system. The sediment transport values predicted from the luminescence method show a broader range than those reported in the literature, but the results are nonetheless encouraging and suggest that luminescence demonstrates potential as a sediment transport indicator. However, caution is warranted when applying the model as the complex nature of sediment transport can sometimes invalidate underlying simplifications.

  15. Impact of bacterial NO3- transport on sediment biogeochemistry

    DEFF Research Database (Denmark)

    Sayama, Mikio; Risgaard-Petersen, Nils; Nielsen, Lars Peter

    2005-01-01

    Experiments demonstrated that Beggiatoa could induce a H2S-depleted suboxic zone of more than 10 mm in marine sediments and cause a divergence in sediment NO3– reduction from denitrification to dissimilatory NO3– reduction to ammonium. pH, O2, and H2S profiles indicated that the bacteria oxidized......2S with NO3– and transported S0 to the sediment surface for aerobic oxidation....

  16. Impact of Bacterial NO3- Transport on Sediment Biogeochemistry

    DEFF Research Database (Denmark)

    Nielsen, Lars Peter

    2005-01-01

    Experiments demonstrated that Beggiatoa could induce a H2S-depleted suboxic zone of more than 10 mm in marine sediments and cause a divergence in sediment NO3- reduction from denitrification to dissimilatory NO3- reduction to ammonium. pH, O2, and H2S profiles indicated that the bacteria oxidized......2S with NO3- and transported S0 to the sediment surface for aerobic oxidation....

  17. Fluvial sediments a summary of source, transportation, deposition, and measurement of sediment discharge

    Science.gov (United States)

    Colby, B.R.

    1963-01-01

    This paper presents a broad but undetailed picture of fluvial sediments in streams, reservoirs, and lakes and includes a discussion of the processes involved in the movement of sediment by flowing water. Sediment is fragmental material that originates from the chemical or physical disintegration of rocks. The disintegration products may have many different shapes and may range in size from large boulders to colloidal particles. In general, they retain about the same mineral composition as the parent rocks. Rock fragments become fluvial sediment when they are entrained in a stream of water. The entrainment may occur as sheet erosion from land surfaces, particularly for the fine particles, or as channel erosion after the surface runoff has accumulated in streams. Fluvial sediments move in streams as bedload (particles moving within a few particle diameters of the streambed) or as suspended sediment in the turbulent flow. The discharge of bedload varies with several factors, which may include particle size and a type of effective shear on the surface of the streambed. The discharge of suspended sediment depends partly on concentration of moving sediment near the streambed and hence on discharge of bedload. However, the concentration of fine sediment near the streambed varies widely, even for equal flows, and, therefore, the discharge of fine sediment normally cannot be computed theoretically. The discharge of suspended sediment also depends on velocity, turbulence, depth of flow, and fall velocity of the particles. In general, the coarse sediment transported by a stream moves intermittently and is discharged at a rate that depends on properties of the flow and of the sediment. If an ample supply of coarse sediment is available at the surface of the streambed, the discharge of the coarse sediment, such as sand, can be roughly computed from properties of the available sediment and of the flow. On the other hand, much of the fine sediment in a stream usually moves nearly

  18. Sediment transport in the area of the Sopot pier

    Science.gov (United States)

    Przyborska, Anna; Jakacki, Jaromir; Andrzejewski, Jan

    2017-04-01

    Coastal sediment transport is a natural process that appears when energy of waves is sufficient for moving solid particles from the bottom. Sediment transport rate depends on the median diameter of local sand and it is compatible with the direction of wave propagation. Also it is natural, that any protruded from the beach construction disturbs continuity of beach transport caused by waves. The Sopot pier has been built over 100 years ago and it is the longest wooden pier on the Baltic Sea coast, it is about half kilometre long. The pier is located at the end of the Monte Casino street and it is one of the biggest attractions of the city as well as in the country. In the past and now we have observed the disturbed sediment transport in the area of the Sopot pier. But during recent years, this process has gained greater momentum. The beach at the Sopot pier has been growing by several meters. All indicates that the cause of the observed phenomenon is the marina. The marina structure which is in some distance from the shore, has been acting as a powerful, emerged breakwater boundary. As a tool the sediment transport model was implemented for Sopot pier area. The implemented numerical forecasting sediment transport model in the area of the Sopot pier reflects well the deposit growth rate for the archived data from 2010 to 2015. On the basis of differences in bathymetry data provided by the Maritime office and the analysis the model results the average deposits in accumulation in the pear area was determined to be about 16,000 m3 / year for the assumed area of analysis, the model have shown similar result. The analysis suggests that strong winds generating significant waves as well as meaningful sediment transport dominate in the autumn and winter. You cannot, however, rule out strong waves in summer. Under moderate waves the sediment transport is insignificant. The most intense movement of the sediment is observed in the vicinity of the shoreline, it disappears with

  19. Cellular arsenic transport pathways in mammals.

    Science.gov (United States)

    Roggenbeck, Barbara A; Banerjee, Mayukh; Leslie, Elaine M

    2016-11-01

    Natural contamination of drinking water with arsenic results in the exposure of millions of people world-wide to unacceptable levels of this metalloid. This is a serious global health problem because arsenic is a Group 1 (proven) human carcinogen and chronic exposure is known to cause skin, lung, and bladder tumors. Furthermore, arsenic exposure can result in a myriad of other adverse health effects including diseases of the cardiovascular, respiratory, neurological, reproductive, and endocrine systems. In addition to chronic environmental exposure to arsenic, arsenic trioxide is approved for the clinical treatment of acute promyelocytic leukemia, and is in clinical trials for other hematological malignancies as well as solid tumors. Considerable inter-individual variability in susceptibility to arsenic-induced disease and toxicity exists, and the reasons for such differences are incompletely understood. Transport pathways that influence the cellular uptake and export of arsenic contribute to regulating its cellular, tissue, and ultimately body levels. In the current review, membrane proteins (including phosphate transporters, aquaglyceroporin channels, solute carrier proteins, and ATP-binding cassette transporters) shown experimentally to contribute to the passage of inorganic, methylated, and/or glutathionylated arsenic species across cellular membranes are discussed. Furthermore, what is known about arsenic transporters in organs involved in absorption, distribution, and metabolism and how transport pathways contribute to arsenic elimination are described. Copyright © 2016. Published by Elsevier B.V.

  20. Simulation of suspended sediment transport initialized with satellite ...

    Indian Academy of Sciences (India)

    vations are inadequate to understand the sedi- ment dispersion by the alternating tidal currents in regions like Gulf of Kachchh, while numerical. Keywords. Suspended sediment concentrations; OCM; sediment transport model; tide. J. Earth Syst. Sci. 121, No. 5, October 2012, pp. 1201–1213. cO Indian Academy of Sciences.

  1. Hydrodynamic Drivers of Sediment Transport Across a Fringing Reef

    NARCIS (Netherlands)

    Bodde, W.P.; Pomeroy, A.W.M.; Van Dongeren, A.R.; Lowe, R.; van Thiel de Vries, J.S.M.

    2014-01-01

    Coral reefs are highly valuable ecosystems, which are under an increasing number of environmental pressures. Sedimentation and sediment transport patterns are among key physical drivers of coral reefs, so it is important to improve our understanding of these poorly studied dynamics on reefs. To this

  2. Bankfull discharge and sediment transport in northwestern California

    Science.gov (United States)

    K. M. Nolan; T. E. Lisle; H. M. Kelsey

    1987-01-01

    Abstract - High-magnitude, low-frequency discharges are more responsible for transporting suspended sediment and forming channels in northwestern California than in previously studied areas. Bankfull discharge and the magnitude and frequency of suspended sediment discharge were determined at five gaging stations in northwestern California. Although discharges below...

  3. Neural network-genetic programming for sediment transport

    Digital Repository Service at National Institute of Oceanography (India)

    Singh, A.K.; Deo, M.C.; SanilKumar, V.

    The planning, operation, design and maintenance of almost all harbour and coastal engineering facilities call for an estimation of the longshore sediment transport rate. This is currently and popularly done with the help of empirical equations...

  4. Complexities in coastal sediment transport studies by numerical modelling

    Digital Repository Service at National Institute of Oceanography (India)

    Ilangovan, D.; ManiMurali, R.

    authors have tried to convey the complexities involved in accurate prediction of coastal sediment transport studies by numerical methods due to some unpredictable variations in the input parameters pertaining to the challenging coastal environments...

  5. Modelling of Sediment Transport in Beris Fishery Port

    Directory of Open Access Journals (Sweden)

    Samira Ardani

    2015-06-01

    Full Text Available In this paper, the large amount of sedimentation and the resultant shoreline advancements at the breakwaters of Beris Fishery Port are studied. A series of numerical modeling of waves, sediment transport, and shoreline changes were conducted to predict the complicated equilibrium shoreline. The outputs show that the nearshore directions of wave components are not perpendicular to the coast which reveals the existence of longshore currents and consequently sediment transport along the bay. Considering the dynamic equilibrium condition of the bay, the effect of the existing sediment resources in the studied area is also investigated. The study also shows that in spite of the change of the diffraction point of Beris Bay after the construction of the fishery port, the bay is approaching its dynamic equilibrium condition, and the shoreline advancement behind secondary breakwater will stop before blocking the entrance of the port. The probable solutions to overcome the sedimentation problem at the main breakwater are also discussed.

  6. Anthropogenic Impact on Sediment Transport in the Mississippi River

    Science.gov (United States)

    Gregory, Brittney; Herrmann, Achim; Clift, Peter

    2017-04-01

    Many of the most prominent deltas in the world are suffering from sediment starvation and subsidence due to human alteration of the upper catchments. The Mississippi River Delta is not immune to these problems which are accentuated by the addition of dams and artificial levees diverting sediment from the delta and coast throughout the last century. The Missouri, Ohio, and Arkansas Rivers have historically supplied most of the suspended sediment load to the Lower Mississippi over the last 60 years, with the Missouri being the largest single contributor. While suspended sediment load plays an important role in floodplain and delta construction, the transport of coarser sediment is also important to a healthy coastline. Very little data exists to constrain how coarser sediment is mixed and transported down the Mississippi despite its invaluable importance to the coastal beaches and barrier islands. Using traditional provenance tools it is possible to study both the coarse and fine load of the modern Mississippi River to quantify transportation and mixing models. This, in turn, will demonstrate human impact on both the suspended and bedload of the Mississippi and its tributaries. This study uses apatite rare earth element geochemistry and zircon U-Pb dating in conjunction with Sr-Nd isotope ratios and clay mineralogy to interpret the transportation of both fine and coarse sediment within the modern Mississippi and its tributaries. These data are preliminary and are part of a larger study that will determine anthropogenic impact on the aggradation of the modern delta floodplain over the last 1000 years.

  7. Radiotracer investigations for sediment transport in ports of India

    International Nuclear Information System (INIS)

    Pant, H.J.; Sharma, V.K.; Goswami, Sunil; Singh, Gursharan

    2013-01-01

    The knowledge of mixing and transport of sediments in coastal region is of vital importance for evaluating suitability of dumping site for dredged sediments produced during maintenance of shipping channels, expansion of existing projects and construction of new projects. Gamma-emitting radiotracers are commonly used for investigation of movement of sediments on seabed using Scandium-46 (scandium glass powder) as radiotracer. The radiotracer is injected on seabed at a desired location and its movement followed over a period of time using waterproof NaI(Tl) scintillation detectors. The recorded data is analyzed to obtain transport parameters and utilized for assessing the suitability of the dumping sites and optimization of the dredging operations. About 70 large-scale investigations have been carried out in different ports in India leading to significant economical benefits to the Ports. Present paper discusses various aspects of the radiotracer technique for sediment transport, methodology of data analysis and a specific case study. (author)

  8. Incorporation of Fine-Grained Sediment Erodibility Measurements into Sediment Transport Modeling, Capitol Lake, Washington

    Science.gov (United States)

    Stevens, Andrew W.; Gelfenbaum, Guy; Elias, Edwin; Jones, Craig

    2008-01-01

    Capitol Lake was created in 1951 with the construction of a concrete dam and control gate that prevented salt-water intrusion into the newly formed lake and regulated flow of the Deschutes River into southern Puget Sound. Physical processes associated with the former tidally dominated estuary were altered, and the dam structure itself likely caused an increase in retention of sediment flowing into the lake from the Deschutes River. Several efforts to manage sediment accumulation in the lake, including dredging and the construction of sediment traps upriver, failed to stop the lake from filling with sediment. The Deschutes Estuary Feasibility Study (DEFS) was carried out to evaluate the possibility of removing the dam and restoring estuarine processes as an alternative ongoing lake management. An important component of DEFS was the creation of a hydrodynamic and sediment transport model of the restored Deschutes Estuary. Results from model simulations indicated that estuarine processes would be restored under each of four restoration alternatives, and that over time, the restored estuary would have morphological features similar to the predam estuary. The model also predicted that after dam-removal, a large portion of the sediment eroded from the lake bottom would be deposited near the Port of Olympia and a marina located in lower Budd Inlet seaward of the present dam. The volume of sediment transported downstream was a critical piece of information that managers needed to estimate the total cost of the proposed restoration project. However, the ability of the model to predict the magnitude of sediment transport in general and, in particular, the volume of sediment deposition in the port and marina was limited by a lack of information on the erodibility of fine-grained sediments in Capitol Lake. Cores at several sites throughout Capitol Lake were collected between October 31 and November 1, 2007. The erodibility of sediments in the cores was later determined in the

  9. Effects of Hydrograph Shape on Sediment Transport and Size

    Science.gov (United States)

    Feehan, S.; Hempel, L. A.; Grant, G.

    2017-12-01

    Very few studies have investigated the effects of differently shaped hydrographs on sediment transport and size, and those that have, largely focused on sediment transport dynamics in fixed-width flumes with armored streambeds. To better understand how hydrograph shape controls transport dynamics in a more complex channel, we conducted a set of Froude-scaled physical experiments in an adjustable width flume with an un-armored bed that developed a meandering planform pattern with pool-riffle morphology. Experiments were conducted in a 12.2m long, 1.5m wide stream table at the University of British Columbia. Sediment size range from fine sand to small gravel, with a median grain size of 1.5mm. While hydrographs had different shapes, magnitudes, and durations, we kept total equilibrium feed mass equivalent among experiments. Sediment was fed at a constant rate at the inlet and, due to the adjustable boundary design, was continuously recruited from channel banks so that the channel was never supply limited. Sediment was collected at the outlet; sediment mass was measured every 10-15 minutes and grain size was sampled every 30 minutes. We found that sediment transport pattern reflects the rate of channel evolution and excavation over the course of the hydrograph. We introduce a new metric, cumulative sediment concentration, to evaluate temporal trends in sediment transport rate. Cumulative sediment concentration increased during rates of rapid channel excavation, particularly during the rising limb of the hydrograph as curvature developed, and decreased during periods of slow or no morphologic change. Slowly rising hydrographs had multiple peaks in the cumulative sediment concentration curve that reflected rapid channel excavation, then stability, following an increase in flow, whereas quickly rising hydrographs had cumulative sediment concentration curves that continuously increased. The latter suggests that during quickly rising hydrographs, the flow rises faster than

  10. Sediment transport on the Palos Verdes shelf, California

    Science.gov (United States)

    Ferre, B.; Sherwood, C.R.; Wiberg, P.L.

    2010-01-01

    Sediment transport and the potential for erosion or deposition have been investigated on the Palos Verdes (PV) and San Pedro shelves in southern California to help assess the fate of an effluent-affected deposit contaminated with DDT and PCBs. Bottom boundary layer measurements at two 60-m sites in spring 2004 were used to set model parameters and evaluate a one-dimensional (vertical) model of local, steady-state resuspension, and suspended-sediment transport. The model demonstrated skill (Brier scores up to 0.75) reproducing the magnitudes of bottom shear stress, current speeds, and suspended-sediment concentrations measured during an April transport event, but the model tended to underpredict observed rotation in the bottom-boundary layer, possibly because the model did not account for the effects of temperature-salinity stratification. The model was run with wave input estimated from a nearby buoy and current input from four to six years of measurements at thirteen sites on the 35- and 65-m isobaths on the PV and San Pedro shelves. Sediment characteristics and erodibility were based on gentle wet-sieve analysis and erosion-chamber measurements. Modeled flow and sediment transport were mostly alongshelf toward the northwest on the PV shelf with a significant offshore component. The 95th percentile of bottom shear stresses ranged from 0.09 to 0.16 Pa at the 65-m sites, and the lowest values were in the middle of the PV shelf, near the Whites Point sewage outfalls where the effluent-affected layer is thickest. Long-term mean transport rates varied from 0.9 to 4.8 metric tons m-1 yr-1 along the 65-m isobaths on the PV shelf, and were much higher at the 35-m sites. Gradients in modeled alongshore transport rates suggest that, in the absence of a supply of sediment from the outfalls or PV coast, erosion at rates of ???0.2 mm yr-1 might occur in the region southeast of the outfalls. These rates are small compared to some estimates of background natural sedimentation

  11. Simulation of contaminated sediment transport in White Oak Creek basin

    International Nuclear Information System (INIS)

    Bao, Y.; Clapp, R.B.; Brenkert, A.L.; Moore, T.D.; Fontaine, T.A.

    1995-01-01

    This paper presents a systematic approach to management of the contaminated sediments in the White Oak Creek watershed at Oak Ridge National Laboratory near Oak Ridge, Tennessee. The primary contaminant of concern is radioactive cesium-137 ( 137 Cs), which binds to soil and sediment particles. The key components in the approach include an intensive sampling and monitoring system for flood events; modeling of hydrological processes, sediment transport, and contaminant flux movement; and a decision framework with a detailed human health risk analysis. Emphasis is placed on modeling of watershed rainfall-runoff and contaminated sediment transport during flooding periods using the Hydrologic Simulation Program- Fortran (HSPF) model. Because a large number of parameters are required in HSPF modeling, the major effort in the modeling process is the calibration of model parameters to make simulation results and measured values agree as closely as possible. An optimization model incorporating the concepts of an expert system was developed to improve calibration results and efficiency. Over a five-year simulation period, the simulated flows match the observed values well. Simulated total amount of sediment loads at various locations during storms match with the observed values within a factor of 1.5. Simulated annual releases of 137 Cs off-site locations match the data within a factor of 2 for the five-year period. The comprehensive modeling approach can provide a valuable tool for decision makers to quantitatively analyze sediment erosion, deposition, and transport; exposure risk related to radionuclides in contaminated sediment; and various management strategies

  12. Sediment supply versus local hydraulic controls on sediment transport and storage in a river with large sediment loads

    Science.gov (United States)

    Dean, David J.; Topping, David J.; Schmidt, John C.; Griffiths, Ronald E.; Sabol, Thomas A.

    2016-01-01

    The Rio Grande in the Big Bend region of Texas, USA, and Chihuahua and Coahuila, Mexico, undergoes rapid geomorphic changes as a result of its large sediment supply and variable hydrology; thus, it is a useful natural laboratory to investigate the relative importance of flow strength and sediment supply in controlling alluvial channel change. We analyzed a suite of sediment transport and geomorphic data to determine the cumulative influence of different flood types on changing channel form. In this study, physically based analyses suggest that channel change in the Rio Grande is controlled by both changes in flow strength and sediment supply over different spatial and temporal scales. Channel narrowing is primarily caused by substantial deposition of sediment supplied to the Rio Grande during tributary-sourced flash floods. Tributary floods have large suspended-sediment concentrations, occur for short durations, and attenuate rapidly downstream in the Rio Grande, depositing much of their sediment in downstream reaches. Long-duration floods on the mainstem have the capacity to enlarge the Rio Grande, and these floods, released from upstream dams, can either erode or deposit sediment in the Rio Grande depending upon the antecedent in-channel sediment supply and the magnitude and duration of the flood. Geomorphic and sediment transport analyses show that the locations and rates of sand erosion and deposition during long-duration floods are most strongly controlled by spatial changes in flow strength, largely through changes in channel slope. However, spatial differences in the in-channel sediment supply regulate sediment evacuation or accumulation over time in long reaches (greater than a kilometer).

  13. Sediment Transport and Vegetative Controls on Delta Channel Networks

    Science.gov (United States)

    Lauzon, R.; Murray, A. B.; Piliouras, A.; Kim, W.

    2016-02-01

    As they are governed by complex interactions between coastal, wetland, and fluvial processes, many of the controls on delta evolution are not well understood. The interactions between sediment transport processes and vegetative controls which shape the flow of water on a delta is one such poorly understood process. On deltas dominated by sediment transport, flow is characterized by rapid lateral migration and frequent switching of active channels and resembles a braided stream system. On the other hand, vegetation can reduce channel migration rates and strengthen existing channel banks, resulting in well-developed, localized flow patterns like dendritic or distributary channel networks. Previous work has shown through modeling (i.e. Murray and Paola 1994, 1997) and flume experiments (i.e. Gran and Paola 2001) that interactions between vegetation and sediment which allow or prohibit lateral transport of sediment is fundamental in explaining the morphology of fluvial systems, but many delta modeling efforts assume conditions like those of a vegetated delta. In fact, deltas introduce additional variables like sea level rise, subsidence, the creation of new land, and variable deposition rates, all of which will influence vegetation growth and sediment transport. Here we present a new numerical model designed to generate basic understanding of the processes controlling delta channel formation by examining the factors influencing whether sediment transport or vegetative controls dominate. Model development is informed by laboratory flume experiment at U T Austin. A novel synthesis building on past approaches to modeling braided-stream systems (the Murray and Paola model) and vegetated deltas (DeltaRCM; Liang et al 2015), the new model explores the effects of sea level rise, subsidence, sediment and water discharge, vegetation growth, and sediment properties (including here effects of vegetation) on delta channel morphology.

  14. Cadmium absorption and transportation pathways in plants.

    Science.gov (United States)

    Song, Yu; Jin, Liang; Wang, Xiaojuan

    2017-02-01

    Controlling the uptake, transport, translocation, and accumulation of excessive amounts of cadmium from polluted environments is critical for plants and, consequently, humans with regard to food safety. Plants adopt various cellular and molecular mechanisms to minimize Cd toxicity. Upon exposure to Cd, plants initially implement avoidance strategies, such as production of organic acids, chelation, and sequestration, to prevent metal access to root cells. Nevertheless, Cd can be transported through the roots, stems, and leaves via apoplastic and symplastic pathways. These processes have been controlled by specific sites at the root surface and root cortex, in cells responsible for loading the root xylem, at the transition between the vascular systems of the root and the shoot, and in connecting tissues and cells at the stem. Although resistance to heavy metal cadmium can be achieved by either avoidance or tolerance, genetic basis to tolerance is therefore implied, in that these mechanisms are heritable attributes of tolerant mutants or genotypes.

  15. Sediment transport and morphodynamics of the Douro River estuary

    Science.gov (United States)

    Portela, Luís Ivens

    2008-04-01

    A combination of dredging data, hydrographic surveys and numerical modelling has been used to assess morphological change and sediment transport in the Douro River estuary. The system is dominated by sand- and gravel-sized sediments and confined by resistant rock types. The evolution of the bed in the last 20 years has been strongly influenced by the opening of a navigation channel. According to the data available to date, the average maintenance dredging volume has been of the order of 0.4 × 106 m3 year-1. Comparisons of hydrographic surveys reveal a rate of volume loss of the same magnitude. Apparently, maintenance dredging mainly involves local material, transported into the channel from shallower areas of the estuary. The results of numerical modelling indicate that the sediment transport capacity due to tidal currents is very limited. River flood events increase the transport capacity by several orders of magnitude, thus playing a critical role in sediment redistribution and supply to the coast. The average sediment transport capacity is estimated to be of the order of 0.1 × 106 m3 year-1 in most of the estuary and 0.5 × 106 m3 year-1 at the inlet, with a large uncertainty. It is concluded that, if morphological stability is set as an environmental objective, the dredged material should not be removed from the system but rather be used to nourish the estuarine beaches and the barrier spit.

  16. Distribution of biologic, anthropogenic, and volcanic constituents as a proxy for sediment transport in the San Francisco Bay Coastal System

    Science.gov (United States)

    McGann, Mary; Erikson, Li H.; Wan, Elmira; Powell, Charles; Maddocks, Rosalie F.; Barnard, P.L.; Jaffee, B.E.; Schoellhamer, D.H.

    2013-01-01

    Although conventional sediment parameters (mean grain size, sorting, and skewness) and provenance have typically been used to infer sediment transport pathways, most freshwater, brackish, and marine environments are also characterized by abundant sediment constituents of biological, and possibly anthropogenic and volcanic, origin that can provide additional insight into local sedimentary processes. The biota will be spatially distributed according to its response to environmental parameters such as water temperature, salinity, dissolved oxygen, organic carbon content, grain size, and intensity of currents and tidal flow, whereas the presence of anthropogenic and volcanic constituents will reflect proximity to source areas and whether they are fluvially- or aerially-transported. Because each of these constituents have a unique environmental signature, they are a more precise proxy for that source area than the conventional sedimentary process indicators. This San Francisco Bay Coastal System study demonstrates that by applying a multi-proxy approach, the primary sites of sediment transport can be identified. Many of these sites are far from where the constituents originated, showing that sediment transport is widespread in the region. Although not often used, identifying and interpreting the distribution of naturally-occurring and allochthonous biologic, anthropogenic, and volcanic sediment constituents is a powerful tool to aid in the investigation of sediment transport pathways in other coastal systems.

  17. Consistency between 2D-3D Sediment Transport models

    Science.gov (United States)

    Villaret, Catherine; Jodeau, Magali

    2017-04-01

    Sediment transport models have been developed and applied by the engineering community to estimate transport rates and morphodynamic bed evolutions in river flows, coastal and estuarine conditions. Environmental modelling systems like the open-source Telemac modelling system include a hierarchy of models from 1D (Mascaret), 2D (Telemac-2D/Sisyphe) and 3D (Telemac-3D/Sedi-3D) and include a wide range of processes to represent sediment flow interactions under more and more complex situations (cohesive, non-cohesive and mixed sediment). Despite some tremendous progresses in the numerical techniques and computing resources, the quality/accuracy of model results mainly depend on the numerous choices and skills of the modeler. In complex situations involving stratification effects, complex geometry, recirculating flows… 2D model assumptions are no longer valid. A full 3D turbulent flow model is then required in order to capture the vertical mixing processes and to represent accurately the coupled flow/sediment distribution. However a number of theoretical and numerical difficulties arise when dealing with sediment transport modelling in 3D which will be high-lighted : (1) Dependency of model results to the vertical grid refinement and choice of boundary conditions and numerical scheme (2) The choice of turbulence model determines also the sediment vertical distribution which is governed by a balance between the downward settling term and upward turbulent diffusion. (3) The use of different numerical schemes for both hydrodynamics (mean and turbulent flow) and sediment transport modelling can lead to some inconsistency including a mismatch in the definition of numerical cells and definition of boundary conditions. We discuss here those present issues and present some detailed comparison between 2D and 3D simulations on a set of validation test cases which are available in the Telemac 7.2 release using both cohesive and non-cohesive sediments.

  18. Life cycle analysis of transportation fuel pathways

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-02-24

    The purpose of this work is to improve the understanding of the concept of life cycle analysis (LCA) of transportation fuels and some of its pertinent issues among non-technical people, senior managers, and policy makers. This work should provide some guidance to nations considering LCA-based policies and to people who are affected by existing policies or those being developed. While the concept of employing LCA to evaluate fuel options is simple and straightforward, the act of putting the concept into practice is complex and fraught with issues. Policy makers need to understand the limitations inherent in carrying out LCA work for transportation fuel systems. For many systems, even those that have been employed for a 100 years, there is a lack of sound data on the performance of those systems. Comparisons between systems should ideally be made using the same tool, so that differences caused by system boundaries, allocation processes, and temporal issues can be minimized (although probably not eliminated). Comparing the results for fuel pathway 1 from tool A to those of fuel system 2 from tool B introduces significant uncertainty into the results. There is also the question of the scale of system changes. LCA will give more reliable estimates when it is used to examine small changes in transportation fuel pathways than when used to estimate large scale changes that replace current pathways with completely new pathways. Some LCA tools have been developed recently primarily for regulatory purposes. These tools may deviate from ISO principles in order to facilitate simplicity and ease of use. In a regulatory environment, simplicity and ease of use are worthy objectives and in most cases there is nothing inherently wrong with this approach, particularly for assessing relative performance. However, the results of these tools should not be confused with, or compared to, the results that are obtained from a more complex and rigorous ISO compliant LCA. It should be

  19. Harmonize input selection for sediment transport prediction

    Science.gov (United States)

    Afan, Haitham Abdulmohsin; Keshtegar, Behrooz; Mohtar, Wan Hanna Melini Wan; El-Shafie, Ahmed

    2017-09-01

    In this paper, three modeling approaches using a Neural Network (NN), Response Surface Method (RSM) and response surface method basis Global Harmony Search (GHS) are applied to predict the daily time series suspended sediment load. Generally, the input variables for forecasting the suspended sediment load are manually selected based on the maximum correlations of input variables in the modeling approaches based on NN and RSM. The RSM is improved to select the input variables by using the errors terms of training data based on the GHS, namely as response surface method and global harmony search (RSM-GHS) modeling method. The second-order polynomial function with cross terms is applied to calibrate the time series suspended sediment load with three, four and five input variables in the proposed RSM-GHS. The linear, square and cross corrections of twenty input variables of antecedent values of suspended sediment load and water discharge are investigated to achieve the best predictions of the RSM based on the GHS method. The performances of the NN, RSM and proposed RSM-GHS including both accuracy and simplicity are compared through several comparative predicted and error statistics. The results illustrated that the proposed RSM-GHS is as uncomplicated as the RSM but performed better, where fewer errors and better correlation was observed (R = 0.95, MAE = 18.09 (ton/day), RMSE = 25.16 (ton/day)) compared to the ANN (R = 0.91, MAE = 20.17 (ton/day), RMSE = 33.09 (ton/day)) and RSM (R = 0.91, MAE = 20.06 (ton/day), RMSE = 31.92 (ton/day)) for all types of input variables.

  20. Sediment transport simulation in an armoured stream

    Science.gov (United States)

    Milhous, Robert T.; Bradley, Jeffrey B.; Loeffler, Cindy L.

    1986-01-01

    Improved methods of calculating bed material stability and transport must be developed for a gravel bed stream having an armoured surface in order to use the HEC-6 model to examine channel change. Good possibilities exist for use of a two layer model based on the Schoklitsch and the Einstein-Brown transport equations. In Einstein-Brown the D35 of the armour is used for stabilities and the D50 of the bed (sub-surface) is used for transport. Data on the armour and sub-surface size distribution needs to be obtained as part of a bed material study in a gravel bed river; a "shovel" sample is not adequate. The Meyer-Peter, Muller equation should not be applied to a gravel bed stream with an armoured surface to estimate the initiation of transport or for calculation of transport at low effective bed shear stress.

  1. Sediment transport via needle ice: a new method for diffusive transport on laboratory-scale hillslopes

    Science.gov (United States)

    Sweeney, K. E.; Roering, J. J.; Rempel, A. W.

    2012-12-01

    Convex hilltops formed by diffusive sediment transport are a fundamental feature of soil-mantled landscapes worldwide. Additionally, the competition and interaction between hillslopes and valleys control basic topographic metrics, such as relief, drainage density, and breaks in slope-area scaling. Despite recent progress in erosive landscape experiments, no published work has explored the competition of hillslope diffusion and channel advection experimentally. Here, we present preliminary findings on the plausibility of needle ice driven frost creep as a mechanism for laboratory hillslope transport of wet sediment. In nature, needle ice is a diurnal form of ice segregation, whereby liquid water held in sediment pore space is driven upward toward a near-surface freezing front by a temperature-controlled liquid pressure gradient. As needles grow perpendicular to the surface, sediment is incorporated in the growing needle ice by temperature perturbations and associated downward shifts in the freezing front. Sediment then moves downslope due to melting or sublimation of the ice needles. We constructed a slope of saturated sediment in a freezer to constrain the temperature, grain size, and soil moisture limits on laboratory needle ice growth and sediment transport. Surficial sediment transport is measured during experimentation by tracking the movement of colored grains. Additionally, at the end of each run we measure depth-dependent sediment transport by taking slices of the experimental slope and observing the displacement of buried columns of colored grains. In agreement with past work, we find that with temperatures just below freezing, soil moisture above 35%, and silt-sized sediment, the moisture migration induced by freezing releases enough latent heat to maintain the location of the freezing front and encourage needle ice growth. Our experiments demonstrate that the amount of sediment incorporated during needle growth, i.e., the transport efficiency, can be

  2. Numerical modeling of episodic sediment supply events to headwater channels and subsequent fluvial sediment transport

    Science.gov (United States)

    Müller, T.; Hassan, M. A.

    2014-12-01

    In steep headwater catchments episodic events can rapidly contribute large amounts of sediment to the channel network. The fluvial system may react to this input in different ways, ranging from a swift evacuation of the contributed material to a long term morphological adjustment of the channel. How this response affects fluvial sediment transport is poorly understood and is scope of our study. We set up a numerical model to investigate how different magnitudes, frequencies and grain size distributions (GSD) of sediment supply events influence the sediment dynamics in the fluvial system. We used a randomized time series of disturbances and simulated subsequent fluvial reworking using a bed load transport model. Besides tracking the volume of stored sediment, we investigate changes in the GSD of the channel. In our model, the GSD of the fluvial channel approaches the GSD of the sediment input under high supply conditions, in which large quantities of material are supplied by a high frequency of events. This results in an exceedance of the ability of the fluvial system to significantly evacuate the supply. On the other hand, if the fluvial system is given enough time to rework the input material, the GSD of the channel gets coarser with time, as the smaller grain sizes are transported away. We further analyze the conditions under which the system is stable or more sensitive to changes in the magnitude or frequency of sediment supply. Our model shows how the combination of episodic time scales of disturbances and constant time scales of fluvial reworking results in temporal patterns of fluvial sediment transport.

  3. Preliminary Results on Sediment Sorting Under Intense Bedload Transport

    Science.gov (United States)

    Hernandez Moreira, R. R.; Vautin, D.; Mathews, S. L.; Kuprenas, R.; Viparelli, E.

    2014-12-01

    Previous experiments show that parallel-laminated deposits are emplaced under upper plane bed regime by the migration of small-amplitude, long-wavelength bedforms. The present research focuses on how sediment is sorted under upper plane bed and sheet flow transport regimes, and whether parallel-lamination is inhibited during sheet flow transport. The problem of studying the sorting of sediment under so intense transport conditions is plagued by the uncertainties related to flow resistances and bedload transport rates. We simplify the problem by first running the experiments with uniform sediment, to establish a baseline that will aid in the design of the experiments with poorly sorted material. We are running experiments at the Hydraulics Laboratory of the Department of Civil and Environmental Engineering at the University of South Carolina in Columbia, in a unidirectional sediment-feed flume, 9 meters long by 0.2 meters wide, of which 7 meters are used as test section. During the experiments, water surface and bed elevations are periodically measured to characterize the global parameters of the flow, e.g. mean flow velocity and bed shear stress. When the flow and the sediment transport reach conditions of mobile bed equilibrium, bed elevation fluctuations are measured with ultrasonic transducer systems at six fixed locations. Channel bed aggradation is then induced by slowly raising the tail gate of the flume such that there is no change in transport regime, as confirmed by additional measurements of water surface and bed elevation and bed elevation fluctuations. Preliminary observations under upper plane bed regime show the formation of the small-amplitude and long-wavelength bedforms, as well as hints of parallel lamination in the deposits. In the near future we aim to achieve sheet flow transport conditions with both uniform and non-uniform grain size distributions to look at the internal structure of the emplaced deposit.

  4. Radiotracer and Sealed Source Applications in Sediment Transport Studies

    International Nuclear Information System (INIS)

    2014-01-01

    The investigation of sediment transport in seas and rivers is crucial for civil engineering and littoral protection and management. Coastlines and seabeds are dynamic regions, with sediments undergoing periods of erosion, transport, sedimentation and consolidation. The main causes for erosion in beaches include storms and human actions such as the construction of seawalls, jetties and the dredging of stream mouths. Each of these human actions disrupts the natural flow of sand. Current policies and practices are accelerating the beach erosion process. However, there are viable options available to mitigate this damage and to provide for sustainable coastlines. Radioactive methods can help in investigating sediment dynamics, providing important parameters for better designing, maintaining and optimizing civil engineering structures. Radioisotopes as tracers and sealed sources have been useful and often irreplaceable tools for sediment transport studies. The training course material is based on lecture notes and practical works delivered by many experts in IAEA supported activities. Lectures and case studies were reviewed by a number of specialists in this field

  5. Ion transport in deep-sea sediments

    International Nuclear Information System (INIS)

    Heath, G.R.

    1979-01-01

    Initial assessment of the ability of deep-sea clays to contain nuclear waste is optimistic. Yet, the investigators have no delusions about the complexity of the natural geochemical system and the perturbations that may result from emplacement of thermally-hot waste cannisters. Even though they may never be able to predict the exact nature of all these perturbations, containment of the nuclides by the waste form/cannister system until most of the heat has decayed, and burial of the waste to a sufficient depth that the altered zone can be treated as a black box source of dissolved nuclides to the enclosing unperturbed sediment, encourage them to believe that ion migration in the deep seabed can be modeled accurately and that our preliminary estimates of migration rates are likely to be reasonably realistic

  6. Quantifying postfire aeolian sediment transport using rare earth element tracers

    Science.gov (United States)

    Dukes, David; Gonzales, Howell B.; Ravi, Sujith; Grandstaff, David E.; Van Pelt, R. Scott; Li, Junran; Wang, Guan; Sankey, Joel B.

    2018-01-01

    Grasslands, which provide fundamental ecosystem services in many arid and semiarid regions of the world, are undergoing rapid increases in fire activity and are highly susceptible to postfire-accelerated soil erosion by wind. A quantitative assessment of physical processes that integrates fire-wind erosion feedbacks is therefore needed relative to vegetation change, soil biogeochemical cycling, air quality, and landscape evolution. We investigated the applicability of a novel tracer technique—the use of multiple rare earth elements (REE)—to quantify soil transport by wind and to identify sources and sinks of wind-blown sediments in both burned and unburned shrub-grass transition zone in the Chihuahuan Desert, NM, USA. Results indicate that the horizontal mass flux of wind-borne sediment increased approximately threefold following the fire. The REE tracer analysis of wind-borne sediments shows that the source of the horizontal mass flux in the unburned site was derived from bare microsites (88.5%), while in the burned site it was primarily sourced from shrub (42.3%) and bare (39.1%) microsites. Vegetated microsites which were predominantly sinks of aeolian sediments in the unburned areas became sediment sources following the fire. The burned areas showed a spatial homogenization of sediment tracers, highlighting a potential negative feedback on landscape heterogeneity induced by shrub encroachment into grasslands. Though fires are known to increase aeolian sediment transport, accompanying changes in the sources and sinks of wind-borne sediments may influence biogeochemical cycling and land degradation dynamics. Furthermore, our experiment demonstrated that REEs can be used as reliable tracers for field-scale aeolian studies.

  7. Modelling of Cohesive Sediment Transport in the Maasmond Area

    NARCIS (Netherlands)

    Wang, L.

    2006-01-01

    In the Dutch coastal zone, where the marine environment is highly dynamic owing to tidal currents, wind-driven, wave-driven, and density-driven currents and waves, the cohesive sediment dynamics is always a great concern to transportation authority and coastal managers. So far, a lot research has

  8. Sediment transport in an active erodible channel bend of ...

    Indian Academy of Sciences (India)

    and sediment transport modelling in a curved channel (Chang 1988). ... spiral motion of the flow directed normal to the main flow and the super-elevation of the water surface. The secondary current, which develops upon entering a channel bend, will eventually ... from flume studies and calibrated using the river data.

  9. Annual variation in the net longshore sediment transport rate

    CSIR Research Space (South Africa)

    Schoonees, JS

    2000-05-01

    Full Text Available The annual variation in the net long shore sediment transport rates at three South African and at one North African site is investigated. The net rates at these sites, given in the first table, showed large variations. It was found that measurements...

  10. Jokulhlaups and sediment transport in Watson River, Kangerlussuaq, West Greenland

    DEFF Research Database (Denmark)

    Mikkelsen, A. B.; Hasholt, Bent; Knudsen, N. T.

    2013-01-01

    For 3 years, during a 4-year observation period (2007-2010), jokulhlaups were observed from a lake at the northern margin of Russells Gletscher. At a gauging station located on a bedrock sill near the outlet of Watson River into Sdr Stromfjord, discharge and sediment transport was monitored during...

  11. Hydrology, sediment transport dynamics and geomorphology of a ...

    African Journals Online (AJOL)

    ... a large catchment size, a seasonal climate of a dry winter and wet summer, evergreen vegetation in the catchment, variable precipitation and the occurrence of regionally pervasive climatic oscillations. This research aimed to address how streamflow variability impacted upon sediment transport and thus, geomorphology.

  12. Sediment transport and channel morphology of small, forested streams.

    Science.gov (United States)

    Marwan A. Hassan; Michael Church; Thomas E. Lisle; Francesco Brardinoni; Lee Benda; Gordon E. Grant

    2005-01-01

    This paper reviews sediment transport and channel morphology in small, forested streams in the Pacific Northwest region of North America to assess current knowledge of channel stability and morphology relevant to riparian management practices around small streams. Small channels are defined as ones in which morphology and hydraulics may be significantly influenced by...

  13. Interactive 4D Visualization of Sediment Transport Models

    Science.gov (United States)

    Butkiewicz, T.; Englert, C. M.

    2013-12-01

    Coastal sediment transport models simulate the effects that waves, currents, and tides have on near-shore bathymetry and features such as beaches and barrier islands. Understanding these dynamic processes is integral to the study of coastline stability, beach erosion, and environmental contamination. Furthermore, analyzing the results of these simulations is a critical task in the design, placement, and engineering of coastal structures such as seawalls, jetties, support pilings for wind turbines, etc. Despite the importance of these models, there is a lack of available visualization software that allows users to explore and perform analysis on these datasets in an intuitive and effective manner. Existing visualization interfaces for these datasets often present only one variable at a time, using two dimensional plan or cross-sectional views. These visual restrictions limit the ability to observe the contents in the proper overall context, both in spatial and multi-dimensional terms. To improve upon these limitations, we use 3D rendering and particle system based illustration techniques to show water column/flow data across all depths simultaneously. We can also encode multiple variables across different perceptual channels (color, texture, motion, etc.) to enrich surfaces with multi-dimensional information. Interactive tools are provided, which can be used to explore the dataset and find regions-of-interest for further investigation. Our visualization package provides an intuitive 4D (3D, time-varying) visualization of sediment transport model output. In addition, we are also integrating real world observations with the simulated data to support analysis of the impact from major sediment transport events. In particular, we have been focusing on the effects of Superstorm Sandy on the Redbird Artificial Reef Site, offshore of Delaware Bay. Based on our pre- and post-storm high-resolution sonar surveys, there has significant scour and bedform migration around the

  14. Impacts of Cropland Changes on Water Balance, Sediment and Nutrient Transport in Eden River, UK

    Science.gov (United States)

    Huang, Yumei; Quinn, Paul; Liang, Qiuhua; Adams, Russell

    2017-04-01

    Water is the key to food and human life. Farming is the main part of economic and society in Eden, with approximately 2000 farms which covers 95% of under crops. However, with the growth of farming practice and global climate changes, Eden has presented great challenges and bringing uncertainty in the water quality caused by the agricultural diffuse pollution. This expected to reduce negative impacts of the water diffuse pollution from agriculture in Eden. Therefore, there is a high need to ensure effective water resource management to enhance water quality, to address the flow pathways and sediment transport in different farming practice and cropland changes. Hence we need to understand nutrient and the hydrological flow pathways from soil to Hillslope to channel. The aim of this research is to evaluate the impacts of different cropland changes on water balance, sediment and nutrient transport. By using the hydrological models Soil and Water Assessment Tool (SWAT) and the Catchment Runoff Attenuation Flux Tool (CRAFT), it can show the sediment and nutrient export from the load for each flow pathways (overland flow, soil water flow and ground water flow). We will show results from a small research catchment (10km2) area to the whole of Eden (800km2) at a daily time step.

  15. Storm and tsunami induced sediment transport and morphology changes in vicinity of tidal inlets

    Digital Repository Service at National Institute of Oceanography (India)

    Jayakumar, S.; ManiMurali, R.

    . Satellite images before and after the storm were used to study the morphology changes. Sediment transport is estimated utilising available sediment transport formulae and the hydrodynamics forcing obtained from a depth averaged hydrodynamic model...

  16. Runoff and sediment transport in a degraded area

    Directory of Open Access Journals (Sweden)

    Edivaldo Lopes Thomaz

    2012-02-01

    Full Text Available Gully erosion occurs by the combined action of splash, sheetwash and rill-wash (interrill and rill erosion. These erosion processes have a great capacity for both sediment production and sediment transport. The objectives of this experiment were to evaluate hydrological and sediment transport in a degraded area, severely dissected by gullies; to assess the hydraulic flow characteristics and their aggregate transport capacity; and to measure the initial splash erosion rate. In the study area in Guarapuava, State of Paraná, Brazil (lat 25º 24' S; long 51º24' W; 1034 m asl, the soil was classified as Cambissolo Húmico alumínico, with the following particle-size composition: sand 0.116 kg kg-1; silt 0.180 kg kg-1; and clay 0.704 kg kg-1. The approach of this research was based on microcatchments formed in the ground, to study the hydrological response and sediment transport. A total of eight rill systems were simulated with dry and wet soil. An average rainfall of 33.7 ± 4.0 mm was produced for 35 to 54 min by a rainfall simulator. The equipment was installed, and a trough was placed at the end of the rill to collect sediments and water. During the simulation, the following variables were measured: time to runoff, time to ponding, time of recession, flow velocity, depth, ratio of the initial splash and grain size. The rainsplash of dry topsoil was more than twice as high as under moist conditions (5 g m-2 min-1 and 2 g m-2 min-1, respectively. The characteristics of the flow hydraulics indicate transition from laminar to turbulent flow [Re (Reynolds number 1000-2000]. In addition, it was observed that a flow velocity of 0.12 m s-1 was the threshold for turbulent flow (Re > 2000, especially at the end of the rainfall simulation. The rill flow tended to be subcritical [Fr (Froude Number < 1.0]. The variation in hydrological attributes (infiltration and runoff was lower, while the sediment yield was variable. The erosion in the rill systems was

  17. Sediment transport patterns in the San Francisco Bay Coastal System from cross-validation of bedform asymmetry and modeled residual flux

    Science.gov (United States)

    Barnard, Patrick L.; Erikson, Li H.; Elias, Edwin P.L.; Dartnell, Peter; Barnard, P.L.; Jaffee, B.E.; Schoellhamer, D.H.

    2013-01-01

    The morphology of ~ 45,000 bedforms from 13 multibeam bathymetry surveys was used as a proxy for identifying net bedload sediment transport directions and pathways throughout the San Francisco Bay estuary and adjacent outer coast. The spatially-averaged shape asymmetry of the bedforms reveals distinct pathways of ebb and flood transport. Additionally, the region-wide, ebb-oriented asymmetry of 5% suggests net seaward-directed transport within the estuarine-coastal system, with significant seaward asymmetry at the mouth of San Francisco Bay (11%), through the northern reaches of the Bay (7–8%), and among the largest bedforms (21% for λ > 50 m). This general indication for the net transport of sand to the open coast strongly suggests that anthropogenic removal of sediment from the estuary, particularly along clearly defined seaward transport pathways, will limit the supply of sand to chronically eroding, open-coast beaches. The bedform asymmetry measurements significantly agree (up to ~ 76%) with modeled annual residual transport directions derived from a hydrodynamically-calibrated numerical model, and the orientation of adjacent, flow-sculpted seafloor features such as mega-flute structures, providing a comprehensive validation of the technique. The methods described in this paper to determine well-defined, cross-validated sediment transport pathways can be applied to estuarine-coastal systems globally where bedforms are present. The results can inform and improve regional sediment management practices to more efficiently utilize often limited sediment resources and mitigate current and future sediment supply-related impacts.

  18. Sediment Transport Study in Haeundae Beach using Radioisotope Labelled Compound

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Seop; Kim, Jong Bum; Jung, Sung Hee [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of); Lee, Jong Sup [Pukyong National Univ., Busan (Korea, Republic of)

    2005-07-01

    Haeundae beach is one of the most famous resorts in Korea and plays an important role as a special tourism district. However, the length and width of the beach are being reduced continuously, which would have bad influence on the regional economy and be the financial burden to the local authority considering that a large amount of budget is spent in the beach nourishment annually. Hence, it is necessary to understand the dynamic behavior of sediments in the coast for the systematic preservation plan of coastal environment. Lately a monitoring system using radioactive isotope as tracers is considered as a novel technique in understanding the dynamic transport of sediments. The objective of this study is to investigate the possible variations in sedimentary distribution and quantify the characteristics of sediments using radiotracer.

  19. Sediment Transport Study in Haeundae Beach using Radioisotope Labelled Compound

    International Nuclear Information System (INIS)

    Kim, Jin Seop; Kim, Jong Bum; Jung, Sung Hee; Lee, Jong Sup

    2005-01-01

    Haeundae beach is one of the most famous resorts in Korea and plays an important role as a special tourism district. However, the length and width of the beach are being reduced continuously, which would have bad influence on the regional economy and be the financial burden to the local authority considering that a large amount of budget is spent in the beach nourishment annually. Hence, it is necessary to understand the dynamic behavior of sediments in the coast for the systematic preservation plan of coastal environment. Lately a monitoring system using radioactive isotope as tracers is considered as a novel technique in understanding the dynamic transport of sediments. The objective of this study is to investigate the possible variations in sedimentary distribution and quantify the characteristics of sediments using radiotracer

  20. Sediment and radionuclide transport in rivers: radionuclide transport modeling for Cattaraugus and Buttermilk Creeks, New York

    International Nuclear Information System (INIS)

    Onishi, Y.; Yabusaki, S.B.; Kincaid, C.T.; Skaggs, R.L.; Walters, W.H.

    1982-12-01

    SERATRA, a transient, two-dimensional (laterally-averaged) computer model of sediment-contaminant transport in rivers, satisfactorily resolved the distribution of sediment and radionuclide concentrations in the Cattaraugus Creek stream system in New York. By modeling the physical processes of advection, diffusion, erosion, deposition, and bed armoring, SERATRA routed three sediment size fractions, including cohesive soils, to simulate three dynamic flow events. In conjunction with the sediment transport, SERATRA computed radionuclide levels in dissolved, suspended sediment, and bed sediment forms for four radionuclides ( 137 Cs, 90 Sr, 239 240 Pu, and 3 H). By accounting for time-dependent sediment-radionuclide interaction in the water column and bed, SERATA is a physically explicit model of radionuclide fate and migration. Sediment and radionuclide concentrations calculated by SERATA in the Cattaraugus Creek stream system are in reasonable agreement with measured values. SERATRA is in the field performance phase of an extensive testing program designed to establish the utility of the model as a site assessment tool. The model handles not only radionuclides but other contaminants such as pesticides, heavy metals and other toxic chemicals. Now that the model has been applied to four field sites, including the latest study of the Cattaraugus Creek stream system, it is recommended that a final model be validated through comparison of predicted results with field data from a carefully controlled tracer test at a field site. It is also recommended that a detailed laboratory flume be tested to study cohesive sediment transport, deposition, and erosion characteristics. The lack of current understanding of these characteristics is one of the weakest areas hindering the accurate assessment of the migration of radionuclides sorbed by fine sediments of silt and clay

  1. Effect of Vegetation on Sediment Transport across Salt Marshes

    Science.gov (United States)

    Coleman, D. J.; Kirwan, M. L.; Guntenspergen, G. R.; Ganju, N. K.

    2016-12-01

    Salt marshes are a classic example of ecogeomorphology where interactions between plants and sediment transport govern the stability of a rapidly evolving ecosystem. In particular, plants slow water velocities which facilitates deposition of mineral sediment, and the resulting change in soil elevation influences the growth and species distribution of plants. The ability of a salt marsh to withstand sea level rise (SLR) is therefore dependent, among other factors, on the availability of mineral sediment. Here we measure suspended sediment concentrations (SSC) along a transect from tidal channel to marsh interior, exploring the role biomass plays in regulating the magnitude and spatial variability in vertical accretion. Our study was conducted in Spartina alterniflora dominated salt marshes along the Atlantic Coast from Massachusetts to Georgia. At each site, we deployed and calibrated optical back scatter turbidity probes to measure SSC in 15 minute intervals in a tidal channel, on the marsh edge, and in the marsh interior. We visited each site monthly to measure plant biomass via clip plots and vertical accretion via two types of sediment tiles. Preliminary results confirm classic observations that biomass is highest at the marsh edge, and that SSC and vertical accretion decrease across the marsh platform with distance from the channel. We expect that when biomass is higher, such as in southern sites like Georgia and months late in the growing season, SSC will decay more rapidly with distance into the marsh. Higher biomass will likely also correspond to increased vertical accretion, with the greatest effect at marsh edge locations. Our study will likely demonstrate how salt marsh plants interact with sediment transport dynamics to control marsh morphology and thus contribute to marsh resilience to SLR.

  2. Assessing Sediment Transport at Navy Facilities (User’s Guide)

    Science.gov (United States)

    2007-09-01

    move along the channel as a series of bedforms (for example, ripples , dunes , and antidunes). Direct measurement of bedload transport is so difficult...are particle sizes that make up the sediment beds of common aquatic systems, sands , and silts. Table 1 describes the typical ranges of particle (or...type. For example, a mixture of a small amount of sand with clay can be called a sandy clay, and a smaller amount of silt with sand might be called

  3. Glider observations and modeling of sediment transport in Hurricane Sandy

    Science.gov (United States)

    Miles, Travis; Seroka, Greg; Kohut, Josh; Schofield, Oscar; Glenn, Scott

    2015-03-01

    Regional sediment resuspension and transport are examined as Hurricane Sandy made landfall on the Mid-Atlantic Bight (MAB) in October 2012. A Teledyne-Webb Slocum glider, equipped with a Nortek Aquadopp current profiler, was deployed on the continental shelf ahead of the storm, and is used to validate sediment transport routines coupled to the Regional Ocean Modeling System (ROMS). The glider was deployed on 25 October, 5 days before Sandy made landfall in southern New Jersey (NJ) and flew along the 40 m isobath south of the Hudson Shelf Valley. We used optical and acoustic backscatter to compare with two modeled size classes along the glider track, 0.1 and 0.4 mm sand, respectively. Observations and modeling revealed full water column resuspension for both size classes for over 24 h during peak waves and currents, with transport oriented along-shelf toward the southwest. Regional model predictions showed over 3 cm of sediment eroded on the northern portion of the NJ shelf where waves and currents were the highest. As the storm passed and winds reversed from onshore to offshore on the southern portion of the domain waves and subsequently orbital velocities necessary for resuspension were reduced leading to over 3 cm of deposition across the entire shelf, just north of Delaware Bay. This study highlights the utility of gliders as a new asset in support of the development and verification of regional sediment resuspension and transport models, particularly during large tropical and extratropical cyclones when in situ data sets are not readily available.

  4. Miocene mass-transport sediments, Troodos Massif, Cyprus

    Science.gov (United States)

    Lord, A.R.; Harrison, R.W.; BouDagher-Fadel, M.; Stone, B.D.; Varol, O.

    2009-01-01

    Sediment mass-transport layers of submarine origin on the northern and southern flanks of the Troodos ophiolitic massif are dated biostratigraphically as early Miocene and late Miocene, respectively and therefore represent different seismogenic events in the uplift and erosional history of the Troodos terrane. Analysis of such events has potential for documenting Miocene seismic and uplift events regionally in the context of changing stress field directions and plate vectors through time. ?? 2009 The Geologists' Association.

  5. Capabilities of the Large-Scale Sediment Transport Facility

    Science.gov (United States)

    2016-04-01

    respectively). There were only minor changes in output voltage within a 9 0C (48 0F) temperature change and exhibited little short -term drift ±0.04% of range ...longshore sand transport rate generated under obliquely incident waves. The LSTF instrumentation includes acoustic Doppler velocimeters (ADVs), wave gauges...pump flow meters, sediment trap weigh tanks, and beach profiling lidar . A detailed discussion of the original LSTF features and capabilities can be

  6. Surficial sediment distribution and net sediment transport pattern in İzmir Bay, western Turkey

    Science.gov (United States)

    Duman, Muhammet; Avcı, Mert; Duman, Şükriye; Demirkurt, Erkan; Düzbastılar, Musa Kazım

    2004-06-01

    İzmir Bay, a microtidal bay in the eastern Aegean Sea, is an area of fine-grained sediment. The surficial sediments may be subdivided into seven zones based on their grain size. The western part of the outer bay is covered by silty and muddy sand, whilst the eastern part of the outer bay is covered with silt and mud. Most of the central bay is covered with sandy silt containing up to 50% carbonate and the area between the central and inner bay is floored by silt. Total organic carbon concentrations of the surface sediments vary between 0.40% and 3.12%, and increase in proportion to silt content. Accumulation of organic matter in the inner bay is probably produced by the inflow from raw sewage outfalls. The grain size trends are analyzed in conjunction with information on hydrodynamics, mineralogy and geochemistry, to derive sediment movement patterns. The pattern gives a preliminary idea of sediment transport directions together with the main areas of deposition and the possible dispersal patterns of contaminants in the İzmir Bay environment.

  7. Modeling sediment transport with an integrated view of the biofilm effects

    Science.gov (United States)

    Fang, H. W.; Lai, H. J.; Cheng, W.; Huang, L.; He, G. J.

    2017-09-01

    Most natural sediment is invariably covered by biofilms in reservoirs and lakes, which have significant influence on bed form dynamics and sediment transport, and also play a crucial role in natural river evolution, pollutant transport, and habitat changes. However, most models for sediment transport are based on experiments using clean sediments without biological materials. In this study, a three-dimensional mathematical model of hydrodynamics and sediment transport is presented with a comprehensive consideration of the biofilm effects. The changes of the bed resistance mainly due to the different bed form dynamics of the biofilm-coated sediment (biosediment), which affect the hydrodynamic characteristics, are considered. Moreover, the variations of parameters related to sediment transport after the biofilm growth are integrated, including the significant changes of the incipient velocity, settling velocity, reference concentration, and equilibrium bed load transport rate. The proposed model is applied to evaluate the effects of biofilms on the hydrodynamic characteristics and sediment transport in laboratory experiments. Results indicate that the mean velocity increases after the biofilm growth, and the turbulence intensity near the river bed decreases under the same flow condition. Meanwhile, biofilm inhibits sediment from moving independently. Thus, the moderate erosion is observed for biosediment resulting in smaller suspended sediment concentrations. The proposed model can reasonably reflect these sediment transport characteristics with biofilms, and the approach to integration of the biological impact could also be used in other modeling of sediment transport, which can be further applied to provide references for the integrated management of natural aqueous systems.

  8. Elemental compositions of sediments at Haiphong harbour area as determined by nuclear analytical techniques application in sediment transport studies and conservation of the environment

    International Nuclear Information System (INIS)

    Hien, P.D.; Hai, P.S.; Quang, N.H.; Chuong, P.N.; Xuang, N.N.

    1992-01-01

    Nuclear analytical techniques were applied to determine the elemental compositions of suspended and bottom sediments, collected at different sites in Haiphong harbor area (North Viet nam). The study was aimed at: 1/Understanding the origin of the sediment filling up the access channel and causing large expenditures for dredging operations. 2/Determining the background concentrations of trace elements in sediment. This would allow to detect in the future any pollution caused by the discharge of industrial wastes in the water due to the growing industrialization of the area. 3/Identifying the elements, which can be served as activatable tracers in sediment transport studies. The results obtained for the concentrations of nearly 30 elements show rather similar elemental compositions, reflecting a common origin of the sediments taken from different locations in the harbour area. The results could not allow to identify the pathway of the sediment transported to and deposited on the bottom of the access channel. Meanwhile, a considerable difference was found in the elemental compositions of the sediment and the soil taken at the nearby to the channel island bank. This would definitely exclude any hypothesis on the interrelationship between the sediment on the bottom of the channel with the soil abraded from the island. Among the tracer elements with concentrations in sediment at the ppm level, indium and selenium have been selected as the most suitable activatable tracers. Experiments on tracer preparation are in progress and some preliminary results have been obtained. The analysis also provides the background levels of the elements-pollutants, on the basis of which any industrial pollution in the future could be revealed.(Authors)(1 Table)

  9. Measuring hydrodynamics and sediment transport processes in the Dee Estuary

    Directory of Open Access Journals (Sweden)

    R. Bolaños

    2010-06-01

    Full Text Available The capability of monitoring and prediction in the marine environment provides information that may allow sustainable development of coastal and offshore regions. Therefore, the continuous measurement of environmental processes becomes an important source of information. The present paper shows data collected during 6 years, and in particular during 2008, in the Dee Estuary. The aim of the data collection is to improve the observations of the mobile sediments in coastal areas and its forcing hydrodynamics and turbulence. Data includes information from the deployment of instrumented rigs measuring sediment in suspension, currents, waves, sea level, sediment size and bedforms as well as cruise work including grab sampling, CTD profiles and side-scan sonar. The data cover flood and ebb tides during spring and neap periods with moderate and mild wave events, thus, having a good coverage of the processes needed to improve knowledge of sediment transport and the parameterizations used in numerical modelling. The data, in raw and treated, are being banked at BODC (British Oceanographic Data Centre, http://www.bodc.ac.uk/ which is the formal British organization for looking after and distributing data concerning the marine environment.

  10. Measuring hydrodynamics and sediment transport processes in the Dee Estuary

    Science.gov (United States)

    Bolaños, R.; Souza, A.

    2010-06-01

    The capability of monitoring and prediction in the marine environment provides information that may allow sustainable development of coastal and offshore regions. Therefore, the continuous measurement of environmental processes becomes an important source of information. The present paper shows data collected during 6 years, and in particular during 2008, in the Dee Estuary. The aim of the data collection is to improve the observations of the mobile sediments in coastal areas and its forcing hydrodynamics and turbulence. Data includes information from the deployment of instrumented rigs measuring sediment in suspension, currents, waves, sea level, sediment size and bedforms as well as cruise work including grab sampling, CTD profiles and side-scan sonar. The data cover flood and ebb tides during spring and neap periods with moderate and mild wave events, thus, having a good coverage of the processes needed to improve knowledge of sediment transport and the parameterizations used in numerical modelling. The data, in raw and treated, are being banked at BODC (British Oceanographic Data Centre, blank">http://www.bodc.ac.uk/) which is the formal British organization for looking after and distributing data concerning the marine environment.

  11. Suspended sediment transport in the Gulf of Lions (NW Mediterranean): Impact of extreme storms and floods

    NARCIS (Netherlands)

    Ulses, C.; Estournel, C.; Durrieu de Madron, X.; Palanques, A.

    2008-01-01

    In situ observations were combined with 3D modeling to gain understanding of and to quantify the suspended sediment transport in the Gulf of Lions (NW Mediterranean Sea). The outputs of a hydrodynamic–sediment transport coupled model were compared to near-bottom current and suspended sediment

  12. Formation and development of a breaker bar under regular waves. Part 2: Sediment transport and morphology

    DEFF Research Database (Denmark)

    Jacobsen, Niels Gjøl; Fredsøe, Jørgen

    2014-01-01

    In Part 2 of this work, the hydrodynamic model described in Part 1 is applied for the simulation of sediment transport and the associated morphological development of breaker bars. The sediment description is split into bed load and suspended load, and like the hydrodynamics the sediment transport...... is phase-resolved in order to get on- and offshore directed contributions to the sediment transport from phase lags between the suspended sediment and the hydrodynamics.First, the sediment transport over a morphologically fixed bed of a constant slope is considered, and the transport rates are discussed......) is discussed relative to the reference simulation.The coupling between sediment transport rate and morphology is analysed and discussed. © 2014 Elsevier B.V....

  13. Pathways of organic carbon oxidation in three continental margin sediments

    DEFF Research Database (Denmark)

    Canfield, Donald Eugene; Jørgensen, Bo Barker; Fossing, Henrik

    1993-01-01

    We have combined several different methodologies to quantify rates of organic carbon mineralization by the various electron acceptors in sediments from the coast of Denmark and Norway. Rates of NH4+ and Sigma CO2 liberation sediment incubations were used with O2 penetration depths to conclude tha...

  14. Pathways and Microbiology of Thiosulfate Transformations and Sulfate Reduction in a Marine Sediment (Kattegat, Denmark)

    DEFF Research Database (Denmark)

    JØRGENSEN, BB; BAK, F.

    1991-01-01

    Reductive and oxidative pathways of the sulfur cycle were studied in a marine sediment by parallel radiotracer experiments with (SO4(2-))-S-35, (H2S)-S-35, and (S2O3(2-))-S-35 injected into undisturbed sediment cores. The distributions of viable populations of sulfate- and thiosulfate-reducing ba...

  15. SEPAL – a simple GIS-based tool to estimate sediment pathways in lowland catchments

    Directory of Open Access Journals (Sweden)

    N. Fohrer

    2009-08-01

    Full Text Available Even though soil loss in the lowlands imposes not as much a restriction on land use and agricultural productivity as in erosion affected mountainous areas, the input of fine sediment into the rivers and streams is a concern due to water quality issues and substrate siltation. Drains, river banks and agricultural fields are the three main sources of fine sediment in lowland regions. For a successful implementation of measures to decrease sediment input a well-founded knowledge of the individual entry pathways is essential. To assess the importance of possible entry pathways, a GIS based methodology (SEPAL has been established combining the ABAG, a river bank erosion formula and a regression approach to include the contributions of drains. SEPAL has been applied on a study catchment in Northern Germany. The results show that 15% of the sediment input into the river comes from agricultural drains, 71% from river banks and 14% from adjacent fields. A comparison of the results with field-mapping and -sampling shows that the approach is plausible. The calculated total annual sediment input is 616 t yr−1, while the measured suspended sediment load is 636 t yr−1. It can be concluded that the methodology is suitable for estimating sediment entry pathways and annual sediment loads in lowland catchments as a base for modelling projects and further investigations. However, further work is necessary for gaining sound knowledge about uncertainties and especially about the processes forcing sediment input from drains.

  16. Check dams effects on sediment transport in steep slope flume

    Science.gov (United States)

    Piton, Guillaume; Recking, Alain

    2014-05-01

    Depending on many influences (geology, relief, hydrology, land use, etc.) some mountainous watershed are prone to cause casualties and facilities damages. Large amounts of sediments episodically released by torrents are often the biggest problem in torrent related hazard mitigation. Series of transversal structures as check dams and ground sills are often used in the panel of risk mitigation technics. A large literature exits on check dams and it mainly concerns engineering design, e.g. toe scouring, stability stress diagram, changes in upper and lower reaches equilibrium slopes. Check dams in steep slope rivers constitute fixed points in the bed profile and prevent general bed incision. However their influence on sediment transport once they are filled is not yet clear. Two flume test campaigns, synthetize in Table 1, were performed to investigate this question: Table 1 : experiment plan Run (duration) Ref1 (50h)CD1a (30h)CD1b (30h)Ref2 (92h)CD2 (18h) Solid feeding discharge (g.s^-1) 44 44 44 60 60 Number of check dams none 1 3 none 2 A nearly 5-m-long, 10-cm-wide and 12%-steep flume was used. The water discharge was set to 0,55 l/s in all runs. A mixture of poorly sorted natural sediments with diameters between 0.8 and 40 mm was used. An open solid-discharge-feeding circuit kept the inlet sediment flux constant during all experiments. As both feeding rates did not present variation, changes in outlet solid discharge were assumed to be due to bed variations in the bed storage. We observed strong fluctuations of solid flux and slope in each reaches of all runs between: (i) steep aggradating armoured bed and (ii) less steep and finer bed releasing bedload sheets during erosion events and inducing bedload pulses. All experiments showed consistent results: transported volume associated with erosion event decreased with the length between two subsequent check dams. Solid transversal structures shorten the upstream erosion-propagation and avoid downstream change in the

  17. Sediment transport primer: estimating bed-material transport in gravel-bed rivers

    Science.gov (United States)

    Peter Wilcock; John Pitlick; Yantao Cui

    2009-01-01

    This primer accompanies the release of BAGS, software developed to calculate sediment transport rate in gravel-bed rivers. BAGS and other programs facilitate calculation and can reduce some errors, but cannot ensure that calculations are accurate or relevant. This primer was written to help the software user define relevant and tractable problems, select appropriate...

  18. Tailings dam-break flow - Analysis of sediment transport

    Science.gov (United States)

    Aleixo, Rui; Altinakar, Mustafa

    2015-04-01

    A common solution to store mining debris is to build tailings dams near the mining site. These dams are usually built with local materials such as mining debris and are more vulnerable than concrete dams (Rico et al. 2008). of The tailings and the pond water generally contain heavy metals and various toxic chemicals used in ore extraction. Thus, the release of tailings due to a dam-break can have severe ecological consequences in the environment. A tailings dam-break has many similarities with a common dam-break flow. It is highly transient and can be severely descructive. However, a significant difference is that the released sediment-water mixture will behave as a non-Newtonian flow. Existing numerical models used to simulate dam-break flows do not represent correctly the non-Newtonian behavior of tailings under a dam-break flow and may lead to unrealistic and incorrect results. The need for experiments to extract both qualitative and quantitative information regarding these flows is therefore real and actual. The present paper explores an existing experimental data base presented in Aleixo et al. (2014a,b) to further characterize the sediment transport under conditions of a severe transient flow and to extract quantitative information regarding sediment flow rate, sediment velocity, sediment-sediment interactions a among others. Different features of the flow are also described and analyzed in detail. The analysis is made by means of imaging techniques such as Particle Image Velocimetry and Particle Tracking Velocimetry that allow extracting not only the velocity field but the Lagrangian description of the sediments as well. An analysis of the results is presented and the limitations of the presented experimental approach are discussed. References Rico, M., Benito, G., Salgueiro, AR, Diez-Herrero, A. and Pereira, H.G. (2008) Reported tailings dam failures: A review of the European incidents in the worldwide context , Journal of Hazardous Materials, 152, 846

  19. Sediment transport and depth variation study of the Gulf of Kutch using remote sensing

    Digital Repository Service at National Institute of Oceanography (India)

    Kunte, P.D.; Wagle, B.G.; Sugimori, Y.

    of actual data and principal components were generated to study sediment transport, depth variation and associated processes by mapping coastal and underwater geomorphic features and suspended sediment plumes. Submerged shoals, located as deep as 20 m below...

  20. Influence of turbulence on bed load sediment transport

    DEFF Research Database (Denmark)

    Sumer, B. Mutlu; Chua, L.; Cheng, N. S.

    2003-01-01

    -bed experiments and the ripple-covered-bed experiments. In the former case, the flow in the presence of the turbulence generator was adjusted so that the mean bed shear stress was the same as in the case without the turbulence generator in order to single out the effect of the external turbulence on the sediment...... transport. In the ripple-covered-bed case, the mean and turbulence quantities of the streamwise component of the velocity were measured, and the Shields parameter, due to skin friction, was determined. The Shields parameter, together with the r.m.s. value of the streamwise velocity fluctuations, were...

  1. Investigating transport pathways in the ocean

    Science.gov (United States)

    Griffa, Annalisa; Haza, Angelique; Özgökmen, Tamay M.; Molcard, Anne; Taillandier, Vincent; Schroeder, Katrin; Chang, Yeon; Poulain, P.-M.

    2013-01-01

    The ocean is a very complex medium with scales of motion that range from thousands of kilometers to the dissipation scales. Transport by ocean currents plays an important role in many practical applications ranging from climatic problems to coastal management and accident mitigation at sea. Understanding transport is challenging because of the chaotic nature of particle motion. In the last decade, new methods have been put forth to improve our understanding of transport. Powerful tools are provided by dynamical system theory, that allow the identification of the barriers to transport and their time variability for a given flow. A shortcoming of this approach, though, is that it is based on the assumption that the velocity field is known with good accuracy, which is not always the case in practical applications. Improving model performance in terms of transport can be addressed using another important methodology that has been recently developed, namely the assimilation of Lagrangian data provided by floating buoys. The two methodologies are technically different but in many ways complementary. In this paper, we review examples of applications of both methodologies performed by the authors in the last few years, considering flows at different scales and in various ocean basins. The results are among the very first examples of applications of the methodologies to the real ocean including testing with Lagrangian in-situ data. The results are discussed in the general framework of the extended fields related to these methodologies, pointing out to open questions and potential for improvements, with an outlook toward future strategies.

  2. Transport zonation limits coupled nitrification-denitrification in permeable sediments

    DEFF Research Database (Denmark)

    Kessler, Adam J.; Glud, Ronnie N.; Cardenas, M. Bayani

    2013-01-01

    into the coupling between ammonification, nitrification and denitrification in stationary sand ripples, we combined the diffusion equilibrium thin layer (DET) gel technique with a computational reactive transport biogeochemical model. The former approach provided high-resolution two-dimensional distributions of NO3......- and N-15-N-2 gas. The measured two-dimensional profiles correlate with computational model simulations, showing a deep pool of N-2 gas forming, and being advected to the surface below ripple peaks. Further isotope pairing calculations on these data indicate that coupled nitrification-denitrification......Measurement of biogeochemical processes in permeable sediments (including the hyporheic zone) is difficult because of complex multidimensional advective transport. This is especially the case for nitrogen cycling, which involves several coupled redox-sensitive reactions. To provide detailed insight...

  3. Photosynthetic, respiratory and extracellular electron transport pathways in cyanobacteria.

    Science.gov (United States)

    Lea-Smith, David J; Bombelli, Paolo; Vasudevan, Ravendran; Howe, Christopher J

    2016-03-01

    Cyanobacteria have evolved elaborate electron transport pathways to carry out photosynthesis and respiration, and to dissipate excess energy in order to limit cellular damage. Our understanding of the complexity of these systems and their role in allowing cyanobacteria to cope with varying environmental conditions is rapidly improving, but many questions remain. We summarize current knowledge of cyanobacterial electron transport pathways, including the possible roles of alternative pathways in photoprotection. We describe extracellular electron transport, which is as yet poorly understood. Biological photovoltaic devices, which measure electron output from cells, and which have been proposed as possible means of renewable energy generation, may be valuable tools in understanding cyanobacterial electron transfer pathways, and enhanced understanding of electron transfer may allow improvements in the efficiency of power output. This article is part of a Special Issue entitled Organization and dynamics of bioenergetic systems in bacteria, edited by Conrad Mullineaux. Copyright © 2015. Published by Elsevier B.V.

  4. On the influence of suspended sediment transport on the generation of offshore sand waves

    NARCIS (Netherlands)

    Sterlini-Van der Meer, Fenneke; Hulscher, Suzanne J.M.H.; van den Berg, J.; Geurts, Bernardus J.; Clercx, H.J.H.; Uijttewaal, Wim

    2007-01-01

    Sand waves are bed-forms occurring in shallow seas. Although their characteristics are mainly affected by bed load transport, during rough weather suspended sediment transport can influence their characteristics. As a first step to model these influences, we added suspended sediment transport to a

  5. A combined model of sediment production, supply and transport

    OpenAIRE

    M. Fujita; K. Yamanoi; H. Izumiyama

    2015-01-01

    In previous sediment-runoff models, the sediment production rates of mountain slopes, and the sediment supply rates to streams typically have been developed using empirical methods. A process-based model for sediment production and supply is, however, required for more exact simulations of sediment runoff. In this study, we develop a method to calculate the sediment production rate due to both freeze-thaw action and the sediment supply rate (i.e. erosion rate of talus). These numerical models...

  6. Multispecies reactive transport modelling of electrokinetic remediation of harbour sediments.

    Science.gov (United States)

    Masi, Matteo; Ceccarini, Alessio; Iannelli, Renato

    2017-03-15

    We implemented a numerical model to simulate transport of multiple species and geochemical reactions occurring during electrokinetic remediation of metal-contaminated porous media. The main phenomena described by the model were: (1) species transport by diffusion, electromigration and electroosmosis, (2) pH-dependent buffering of H + , (3) adsorption of metals onto particle surfaces, (4) aqueous speciation, (5) formation and dissolution of solid precipitates. The model was applied to simulate the electrokinetic extraction of heavy metals (Pb, Zn and Ni) from marine harbour sediments, characterized by a heterogeneous solid matrix, high buffering capacity and aged pollution. A good agreement was found between simulations of pH, electroosmotic flow and experimental results. The predicted residual metal concentrations in the sediment were also close to experimental profiles for all of the investigated metals. Some removal overestimation was observed in the regions close to the anode, possibly due to the significant metal content bound to residual fraction. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. Defining Lipid Transport Pathways in Animal Cells

    Science.gov (United States)

    Pagano, Richard E.; Sleight, Richard G.

    1985-09-01

    A new technique for studying the metabolism and intracellular transport of lipid molecules in living cells based on the use of fluorescent lipid analogs is described. The cellular processing of various intermediates (phosphatidic acid and ceramide) and end products (phosphatidylcholine and phosphatidylethanolamine) in lipid biosynthesis is reviewed and a working model for compartmentalization during lipid biosynthesis is presented.

  8. Tracing contaminant pathways in sandy heterogeneous glaciofluvial sediments using a sedimentary depositional model

    International Nuclear Information System (INIS)

    Webb, E.K.; Anderson, M.P.

    1990-01-01

    Heterogeneous sedimentary deposits present complications for tracking contaminant movement by causing a complex advective flow field. Connected areas of high conductivity produce so-called fast paths that control movement of solutes. Identifying potential fast paths and describing the variation in hydraulic properties was attempted through simulating the deposition of a glaciofluvial deposit (outwash). Glaciofluvial deposits usually consist of several depositional facies, each of which has different physical characteristics, depositional structures and hydraulic properties. Therefore, it is unlikely that the property of stationarity (a constant mean hydraulic conductivity and a mono-modal probability distribution) holds for an entire glaciofluvial sequence. However, the process of dividing an outwash sequence into geologic facies presumably identifies units of material with similar physical characteristics. It is proposed that patterns of geologic facies determined by field observation can be quantified by mathematical simulation of sediment deposition. Subsequently, the simulated sediment distributions can be used to define the distribution of hydrogeologic parameters and locate possible fast paths. To test this hypothesis, a hypothetical glacial outwash deposit based on geologic facies descriptions contained in the literature was simulated using a sedimentary depositional model, SEDSIM, to produce a three-dimensional description of sediment grain size distributions. Grain size distributions were then used to estimate the spatial distribution of hydraulic conductivity. Subsequently a finite-difference flow model and linked particle tracking algorithm were used to trace conservative transport pathways. This represents a first step in describing the spatial heterogeneity of hydrogeologic characteristics for glaciofluvial and other braided stream environments. (Author) (39 refs., 7 figs.)

  9. Sediment Transport and erosion modeling at Heaundae Beach in Korea.

    Science.gov (United States)

    Do, K.; Yoo, J.; McCall, R. T.

    2016-12-01

    The sand pocket beaches with two headlands are global features, but it's not easy to predict berm and dune erosion due to alongshore variation of water depth. This study investigates the sediment transport and morphological change using available wave and beach profile data, as well as to assess the applicability of the XBeach morphological model (Roelvink et al., 2009). The Haeundae is small pocket beach, 1.4 km long, located in the southern corner of the Korean Peninsula. The Korea Institute of Ocean Science and Technology (KIOST) measured beach profile along 27 survey lines. The beach profiles were surveyed five times from 17 June 2014 to 10 October 2014. For this duration, a wave gauge (AWAC) was installed at a depth about 23 m off the coast of Haeundae Beach. Severe four storms attacked Haeundae Beach for this duration and these storms lasted about 1 2 days with a peak significant wave height of 2.5 4.0 m. The placed sand is fairly sorted and its median diameter is 0.23 mm. 2DH coastal morphological model, XBeach developed to simulate dune erosion due to storm impacts. The model is based on the nonlinear shallow water equation and resolves nearshore hydrodynamics by employing a 2DH description of wave groups and infragravity motions. In this study, the numerical model XBeach was compared with the field data and used to estimate the sediment transport pattern on the sand pocket beach. The numerical model resulted in a comparable prediction in the west-part, but the east-part cannot reproduce the erosion and accretion of the sand, partly due to complex bathymetry and the lack of sediment. This limitation needs to be improved to use measured sand thickness data in future study

  10. Distribution of clay minerals in marine sediments off Chennai, Bay of Bengal, India: Indicators of sediment sources and transport processes .

    Digital Repository Service at National Institute of Oceanography (India)

    Veerasingam, S.; Venkatachalapathy, R.; Ramkumar, T.

    . Due to the presence of man-made breakwaters and the naturally formed offshore shoals along the Chennai coast with a series of alternating zones of erosion and deposition caused. Rangarao et al. (2009) estimated the sediment transport along Ennore...

  11. Transport of Sr 2+ and SrEDTA 2- in partially-saturated and heterogeneous sediments

    Science.gov (United States)

    Pace, M. N.; Mayes, M. A.; Jardine, P. M.; McKay, L. D.; Yin, X. L.; Mehlhorn, T. L.; Liu, Q.; Gürleyük, H.

    2007-05-01

    Strontium-90 has migrated deep into the unsaturated subsurface beneath leaking storage tanks in the Waste Management Areas (WMA) at the U.S. Department of Energy's (DOE) Hanford Reservation. Faster than expected transport of contaminants in the vadose zone is typically attributed to either physical hydrologic processes such as development of preferential flow pathways, or to geochemical processes such as the formation of stable, anionic complexes with organic chelates, e.g., ethylenediaminetetraacetic acid (EDTA). The goal of this paper is to determine whether hydrological processes in the Hanford sediments can influence the geochemistry of the system and hence control transport of Sr 2+ and SrEDTA 2-. The study used batch isotherms, saturated packed column experiments, and an unsaturated transport experiment in an undisturbed core. Isotherms and repacked column experiments suggested that the SrEDTA 2- complex was unstable in the presence of Hanford sediments, resulting in dissociation and transport of Sr 2+ as a divalent cation. A decrease in sorption with increasing solid:solution ratio for Sr 2+ and SrEDTA 2- suggested mineral dissolution resulted in competition for sorption sites and the formation of stable aqueous complexes. This was confirmed by detection of MgEDTA 2-, MnEDTA 2-, PbEDTA 2-, and unidentified Sr and Ca complexes. Displacement of Sr 2+ through a partially-saturated undisturbed core resulted in less retardation and more irreversible sorption than was observed in the saturated repacked columns, and model results suggested a significant reservoir (49%) of immobile water was present during transport through the heterogeneous layered sediments. The undisturbed core was subsequently disassembled along distinct bedding planes and subjected to sequential extractions. Strontium was unequally distributed between carbonates (49%), ion exchange sites (37%), and the oxide (14%) fraction. An inverse relationship between mass wetness and Sr suggested that

  12. Bead-Based Microfluidic Sediment Analogues: Fabrication and Colloid Transport.

    Science.gov (United States)

    Guo, Yang; Huang, Jingwei; Xiao, Feng; Yin, Xiaolong; Chun, Jaehun; Um, Wooyong; Neeves, Keith B; Wu, Ning

    2016-09-13

    Mobile colloids can act as carriers for low-solubility contaminants in the environment. However, the dominant mechanism for this colloid-facilitated transport of chemicals is unclear. Therefore, we developed a bead-based microfluidic platform of sediment analogues and measured both single and population transport of model colloids. The porous medium is assembled through a bead-by-bead injection method. This approach has the versatility to build both electrostatically homogeneous and heterogeneous media at the pore scale. A T-junction at the exit also allowed for encapsulation and enumeration of colloids effluent at single particle resolution to give population dynamics. Tortuosity calculated from pore-scale trajectory analysis and its comparison with lattice Boltzmann simulations revealed that transport of colloids was influenced by the size exclusion effect. The porous media packed by positively and negatively charged beads into two layers showed distinctive colloidal particle retention and significant remobilization and re-adsorption of particles during water flushing. We demonstrated the potential of our method to fabricate porous media with surface heterogeneities at the pore scale. With both single and population dynamics measurement, our platform has the potential to connect pore-scale and macroscale colloid transport on a lab scale and to quantify the impact of grain surface heterogeneities that are natural in the subsurface environment.

  13. Mg/Ca and Sr/Ca as novel geochemical proxies for understanding sediment transport processes within coral reefs

    Science.gov (United States)

    Gacutan, J.; Vila-Concejo, A.; Nothdurft, L. D.; Fellowes, T. E.; Cathey, H. E.; Opdyke, B. N.; Harris, D. L.; Hamylton, S.; Carvalho, R. C.; Byrne, M.; Webster, J. M.

    2017-10-01

    Sediment transport is a key driver of reef zonation and biodiversity, where an understanding of sediment dynamics gives insights into past reef processes and allows the prediction of geomorphic responses to changing environmental conditions. However, modal conditions within the back-reef seldom promote sediment transport, hence direct observation is inherently difficult. Large benthic foraminifera (LBF) have previously been employed as 'tracers' to infer sediment transport pathways on coral reefs, as their habitat is largely restricted to the algal flat and post-mortem, their calcium carbonate test is susceptible to sediment transport forces into the back-reef. Foraminiferal test abundance and post-depositional test alteration have been used as proxies for sediment transport, although the resolution of these measures becomes limited by low test abundance and the lack of variation within test alteration. Here we propose the novel use of elemental ratios as a proxy for sediment transport. Two species, Baculogypsina sphaerulata and Calcarina capricornia, were analysed using a taphonomic index within One Tree and Lady Musgrave reefs, Great Barrier Reef (Australia). Inductively coupled plasma-atomic emission spectrometry (ICP-AES) was used to determine Mg/Ca and Sr/Ca and these ratios were compared with taphonomic data. Decreases in test Mg/Ca accompany increases in Sr/Ca in specimens from algal-flat to lagoonal samples in both species, mirroring trends indicated by taphonomic values, therefore indicating a relationship with test alteration. To delineate mechanisms driving changes in elemental ratios, back-scattered electron (BSE) images, elemental mapping and in situ quantitative spot analyses by electron microprobe microanalysis (EPMA) using wavelength dispersive X-ray spectrometers (WDS) were performed on un-altered algal flat and heavily abraded tests for both species. EPMA analyses reveal heterogeneity in Mg/Ca between spines and the test wall, implying the loss of

  14. Bengal Fan sediment transport activity and response to climate forcing inferred from sediment physical properties

    Science.gov (United States)

    Weber, M. E.; Wiedicke-Hombach, M.; Kudrass, H. R.; Erlenkeuser, H.

    2003-02-01

    We obtained sediment physical properties and geochemical data from 47 piston and gravity cores located in the Bay of Bengal, to study the complex history of the Late Pleistocene run-off from the Ganges and Brahmaputra rivers and its imprint on the Bengal Fan. Grain-size parameters were predicted from core logs of density and velocity to infer sediment transport energy and to distinguish different environments along the 3000-km-long transport path from the delta platform to the lower fan. On the shelf, 27 cores indicate rapidly prograding delta foresets today that contain primarily mud, whereas outer shelf sediment has 25% higher silt contents, indicative of stronger and more stable transport regime, which prevent deposition and expose a Late Pleistocene relic surface. Deposition is currently directed towards the shelf canyon 'Swatch of No Ground', where turbidites are released to the only channel-levee system that is active on the fan during the Holocene. Active growth of the channel-levee system occurred throughout sea-level rise and highstand with a distinct growth phase at the end of the Younger Dryas. Coarse-grained material bypasses the upper fan and upper parts of the middle fan, where particle flow is enhanced as a result of flow-restriction in well-defined channels. Sandier material is deposited mainly as sheet-flow deposits on turbidite-dominated plains at the lower fan. The currently most active part of the fan with 10-40-cm-thick turbidites is documented for the central channel including inner levees (e.g., site 40). Site 47 from the lower fan far to the east of the active channel-levee system indicates the end of turbidite sedimentation at 300 ka for that location. That time corresponds to the sea-level lowering during late isotopic stage 9 when sediment supply to the fan increased and led to channel avulsion farther upstream, probably indicating a close relation of climate variability and fan activity. Pelagic deep-sea sites 22 and 28 contain a 630

  15. Experimental and numerical investigation of the coupling of turbulence and sediment transport over dunes

    Science.gov (United States)

    Schmeeckle, M. W.; Leary, K. P.

    2016-12-01

    We investigate the spatiotemporal coupling of sediment transport over dunes using a turbulence- and particle-resolving numerical model and high-speed video in a laboratory flume. The model utilizes the Large Eddy Simulation (LES) for the fluid turbulence and a Discrete Element Method (DEM) simulation for the sediment. Previous experiments assessing the effects of flow separation on downstream fluid turbulent structures and bedload transport suggest that localized, intermittent, high-magnitude transport events, called permeable splat events, play an important role in both downstream and cross-stream transport near flow reattachment. The flume was lined with 17 concrete ripples that had a 2 cm high crest and were 30 cm long. A high-speed camera observed sediment transport along the entirety of the bedform at 250 Hz. Downstream and vertical fluid velocity was observed at 1mm and 3 mm above the bed using Laser Doppler Velocitmetry (LDV) at 15 distances along bedform profile. As observed in our previous backward-facing step experiments and simulations, mean downstream fluid velocity increases nonlinearly with increasing distance along the ripple. Observed sediment transport, however, increases linearly with increasing distance along the ripple with an exception at the crest of the bedform, where both mean downstream fluid velocity and sediment transport decrease significantly. Previous experiments assessing only the effect of flow separation showed that calculating sediment transport as a function of boundary shear stress using a Meyer-Peter Müller type equation, produced a zone of underestimated transport near flow reattachment. Results reported here show that calculating sediment transport in this way underestimates observed sediment transport along the entire profile of the bedform, not just near flow reattachment. Preliminary sediment transport time-series data show a zone of high-magnitude cross-stream transport near flow reattachment, suggesting that permeable

  16. Compositon of sediments transported by the wind at different heights

    Science.gov (United States)

    Iturri, Antonela; Funk, Roger; Leue, Martin; Sommer, Michael; Buschiazzo, Daniel

    2017-04-01

    Wind erosion (WE) is one of the most important degradation process of soils in arid- and semiarid environments in the world, affecting soil properties and adjacent ecosystems, including human health. Estimations about the amount of eroded soil are available in Argentina and in the world, but the quality of the eroded sediments, particularly the sorting effects in agricultural soils, has been scarcely studied. The trend of the different mineral and organic soil compounds, which enrich in different size classes, can define height distribution profiles. Therefore, the uppermost 2.5 cm of four agricultural loess soils that differ in granulometric composition were used for WE simulations in a wind tunnel. Particles with a diameter smaller than 10 µm (PM10) were collected with a laboratory dust generator. The bulk soil and all the sediment samples were characterized by the granulometric composition, the soil organic carbon (SOC) content and the mineral and organic functional groups. Despite different texture, the soils were subjected to similar sorting processes in height, but differed depending on their granulometry. There was a separation between coarser and finer soil particles in coarser textured soils, while finer textured soils were more homogeneous in all heights. This correlated with the preferential transport of Si-O from quartz and C-H, C=O and C-C from soil organic matter (SOM), which were transported in larger and/or denser particles at lower heights. O-H from clay minerals and C-O-C and C-O from polysaccharides, carbohydrates and derivatives from SOM were transported in higher heights. Despite similar SOC content in the bulk soils, both the amount and composition in the PM10 fractions was different. The SOC transported at higher heights was mostly composed of polysaccharides, carbohydrates and derivatives associated with clay minerals. The SOC in PM10 fractions of coarser-textured soils was dominated by labile C-H groups. According to the determined height

  17. Abundance, composition, and vertical transport of PAHs in marsh sediments.

    Science.gov (United States)

    White, Helen K; Xu, Li; Lima, Ana Lúcia C; Eglinton, Timothy I; Reddy, Christopher M

    2005-11-01

    Petroleum-derived hydrocarbons continue to persist in Wild Harbor, West Falmouth, MA, following a spill of No. 2 fuel oil in 1969 from the barge Florida. Recent analysis of marsh sediments revealed that residues of degraded oil are present with concentrations of total petroleum hydrocarbons as high as approximately 9 mg g(-1). Polycyclic aromatic hydrocarbons (PAHs) constitute only a minor fraction of these residues with maximum concentrations of 134 mirog g(-1), but their fate is of interest because of their potential toxicity to organisms. As compared to typical unweathered No. 2 fuel oil, the current distribution of PAHs in the sediments reflects substantial weathering by abiotic and biotic processes, specifically a preferential loss of naphthalenes relative to phenanthrenes, as well as isomer-specific biodegradation of alkylated PAHs. Based on comparison to results from an earlier study, it appears that little or no change has occurred to the distribution of PAHs since 1989, indicating that weathering at this site has stalled or is now proceeding at a significantly slower rate. To assess whether sediment-water partitioning and molecular diffusion in the interstitial medium are now the dominant processes controlling the vertical distribution of PAHs, downcore profiles were compared to a numerical model. While in some cases the model accurately reproduced the measured data, there were instances where the distribution of PAHs was slightly under or overestimated. Reasons for these discrepancies are discussed and are likely due to bioturbation, colloid-facilitated transport, or both. Assessment of the influence of these processes on the spilled oil expands our understanding of the overall fate of these compounds and their potential long-term effects on the environment.

  18. Sediment budgets, transport, and depositional trends in a large tidal delta

    Science.gov (United States)

    Morgan, Tara; Wright, Scott A.

    2016-01-01

    sediment supply (Wright and Schoellhamer, 2004). Today, one concern is whether the volume of sediment supplied from the upper watershed is sufficient to support ecological function and sustain the Delta landscape and ecosystem in the face of climate change, sea level rise, and proposed restoration associated with the Bay Delta Conservation Plan (http://baydeltaconservationplan.com). Ecosystem health is a management focus and 150,000 acres of restoration is currently proposed, therefore it is of increasingly important to understand the quantity of sediment available for marsh and wetland restoration throughout the Bay Delta Estuary. It is also important to understand the pathways for sediment transport and the sediment budget into each of three Delta regions (figure 1) to guide restoration planning, modeling, and management.

  19. Sediment Supply Versus Local Hydraulic Controls on Sediment Transport and Storage in the Rio Grande in the Big Bend Region

    Science.gov (United States)

    Dean, D. J.; Topping, D. J.; Schmidt, J. C.

    2015-12-01

    The Rio Grande in the Big Bend region of Texas, USA, and Chihuahua and Coahuila, Mexico, has a large sediment supply, and a variable hydrology resulting in rapid channel narrowing during years of low mean and peak flow, and channel widening during rare, large-magnitude floods. This dynamic nature makes the Rio Grande a useful natural laboratory to investigate the relative importance of flow strength and sediment supply in controlling channel change. We analyzed a suite of sediment-transport and geomorphic data to determine the cumulative influence of different flood types on changing channel form. In this study, physically-based analyses suggest that channel change on the Rio Grande is controlled by both changes in flow strength and sediment supply over different spatial and temporal scales. Channel narrowing is primarily caused by sediment supplied to the Rio Grande during flash floods on desert tributaries. Tributary floods have large suspended-sediment concentrations, occur for short durations, and attenuate rapidly downstream in the Rio Grande, depositing much of their sediment in downstream reaches. Long-duration floods on the mainstem are the only floods that have the capacity to enlarge the Rio Grande. These floods, released from upstream dams, can either erode or deposit sediment in the Rio Grande depending upon the antecedent in-channel sediment supply and the magnitude and duration of the flood. Geomorphic and sediment-transport analyses show that sand erosion and deposition during long-duration floods are most strongly controlled by the spatial distribution of flow strength as governed by channel slope. However, temporal changes in the grain size and amount of available sand within the channel, as inferred from comprehensive analyses of suspended-sediment concentration and grain size, control the degree of sediment evacuation or accumulation over large spatial scales.

  20. Relaxation approximation to bed-load sediment transport

    Science.gov (United States)

    Delis, A. I.; Papoglou, I.

    2008-04-01

    In this work we propose and apply a numerical method based on finite volume relaxation approximation for computing the bed-load sediment transport in shallow water flows, in one and two space dimensions. The water flow is modeled by the well-known nonlinear shallow water equations which are coupled with a bed updating equation. Using a relaxation approximation, the nonlinear set of equations (and for two different formulations) is transformed to a semilinear diagonalizable problem with linear characteristic variablesE A second order MUSCL-TVD method is used for the advection stage while an implicit-explicit Runge-Kutta scheme solves the relaxation stage. The main advantages of this approach are that neither Riemann problem solvers nor nonlinear iterations are required during the solution process. For the two different formulations, the applicability and effectiveness of the presented scheme is verified by comparing numerical results obtained for several benchmark test problems.

  1. Freshwater discharge and sediment transport to Kangerlussuaq Fjord, West Greenland

    DEFF Research Database (Denmark)

    Mikkelsen, Andreas Peter Bech

    surface albedo that amplified surface melt. This unprecedented amount of proglacial discharge would only be possible if the runoff was generated from the lower accumulation zone, where runoff is usually buffered by the air-filled pore space in the firn. This means that the water melted in the lower...... called firn zone are studied. Geomorphological processes studied are: Mass transfer from the glacial system and into the nearby fjord and delta systems. As a part of this glacial erosion rates are deduced. Extensive discharge and sediment transport measurements provided the basis for gaining insight...... accumulation zone of the GrIS is able to runoff directly and contribute to sea-level rise....

  2. The sediment and phosphorus transport in a large scale study

    Science.gov (United States)

    Bauer, Miroslav; Krása, Josef; Dostál, Tomáš; Jáchymová, Barbora

    2017-04-01

    In the name of the Water framework directive (2000/60/ES), there exists the demand to improve quality of water bodies. Basically, pollution of the flowing or stagnant water bodies comes from point and diffuse sources. To find the balance of point (mainly urban areas) and diffuse sources (drainage - N and soil erosion and sediment transport - P) in the scale of Moldau catchment is the task of the project. The area of interest is Moldau river catchment (29.500 km2) has been modelled with fully distributed approach of the WaTEM/SEDEM model. The model estimates the soil erosion as well as sediment a phosphorus transport through the river network. The results are combined with estimation of bounded nitrogen originated from drainage systems in agricultural landscape. The modelling has been done within three levels of accuracy. The simulation scale itself is defined by 10 m elements resolution with critical points net each approximately 300m in the river net (116.000 points). Subsequently, results were aggregated for sub-catchments of 4th order (ca 5 - 15 km2 each = almost 3000 individual sub-catchments) and sub-catchments of 3rd order = ca 400 sub-catchments). Each water reservoir in the system (larger than 0.25 hectares in the area) has been included, which count more than 12.000 reservoirs. The presented approach will be further use by Moldau river catchment managers for the planning of protection and elimination of the pollution in Moldau river catchment. This will lead to localize 3000 highly endangered hot spots which threaten the water bodies significantly. In this localities a detailed modelling and designing of the protection will be done. The research activities had been supported by QJ330118, SGS14/180/OHK1/3T/11, SGS17/090/OHK1/3T/11 grants.

  3. Regional Sediment Analysis of Mississippi River Sediment Transport and Hydrographic Survey Data

    National Research Council Canada - National Science Library

    Thorne, Colin

    2002-01-01

    ...s. Sediments generated through channel instability are carried downstream to cause sedimentation problems in flood control channels, destroy wetlands and lakes, adversely impact fish and wildlife...

  4. EVALUATION OF THE STATE-OF-THE-ART CONTAMINATED SEDIMENT TRANSPORT AND FATE MODELING SYSTEM

    Science.gov (United States)

    Modeling approaches for evaluating the transport and fate of sediment and associated contaminants are briefly reviewed. The main emphasis is on: 1) the application of EFDC (Environmental Fluid Dynamics Code), the state-of-the-art contaminated sediment transport and fate public do...

  5. Distribution of longshore sediment transport along the Indian coast based on empirical model

    Digital Repository Service at National Institute of Oceanography (India)

    Chandramohan, P.; Nayak, B.U.

    An empirical sediment transport model has been developed based on longshore energy flux equation. Study indicates that annual gross sediment transport rate is high (1.5 x 10 super(6) cubic meters to 2.0 x 10 super(6) cubic meters) along the coasts...

  6. A hybrid model of swash-zone longshore sediment transport on refelctive beaches

    NARCIS (Netherlands)

    Jiang, A.W.; Hughes, M.; Cowell, P.; Gordon, A.; Savioli, J.C.; Ranasinghe, R.W.M.R.J.B.

    2010-01-01

    The hydrodynamics and sediment transport in the swash zone is currently outside the domain of coastal-area models, which is a significant limitation in obtaining littoral sediment-transport estimates, especially on steep reflective beaches where the waves practically break on the beachface. In this

  7. Pathways of carbon oxidation in continental margin sediments off central Chile

    DEFF Research Database (Denmark)

    Thamdrup, B; Canfield, Donald Eugene

    1996-01-01

    Rates and oxidative pathways of organic carbon mineralization were determined in sediments at six stations on the shelf and slope off Concepcion Bay at 36.5 degrees S. The depth distribution of C oxidation rates was determined to 10 cm from accumulation of dissolved inorganic C in 1-5-d incubations...... the shelf was rich in NO3- and depleted of O2. Sediments at the four shelf stations were covered by mats of filamentous bacteria of the genera Thioploca and Beggiatoa. Carbon oxidation rates at these sites were extremely high near the sediment surface (>3 micromol cm-3 d-1) and decreased exponentially...

  8. A Tidally Averaged Sediment-Transport Model for San Francisco Bay, California

    Science.gov (United States)

    Lionberger, Megan A.; Schoellhamer, David H.

    2009-01-01

    A tidally averaged sediment-transport model of San Francisco Bay was incorporated into a tidally averaged salinity box model previously developed and calibrated using salinity, a conservative tracer (Uncles and Peterson, 1995; Knowles, 1996). The Bay is represented in the model by 50 segments composed of two layers: one representing the channel (>5-meter depth) and the other the shallows (0- to 5-meter depth). Calculations are made using a daily time step and simulations can be made on the decadal time scale. The sediment-transport model includes an erosion-deposition algorithm, a bed-sediment algorithm, and sediment boundary conditions. Erosion and deposition of bed sediments are calculated explicitly, and suspended sediment is transported by implicitly solving the advection-dispersion equation. The bed-sediment model simulates the increase in bed strength with depth, owing to consolidation of fine sediments that make up San Francisco Bay mud. The model is calibrated to either net sedimentation calculated from bathymetric-change data or measured suspended-sediment concentration. Specified boundary conditions are the tributary fluxes of suspended sediment and suspended-sediment concentration in the Pacific Ocean. Results of model calibration and validation show that the model simulates the trends in suspended-sediment concentration associated with tidal fluctuations, residual velocity, and wind stress well, although the spring neap tidal suspended-sediment concentration variability was consistently underestimated. Model validation also showed poor simulation of seasonal sediment pulses from the Sacramento-San Joaquin River Delta at Point San Pablo because the pulses enter the Bay over only a few days and the fate of the pulses is determined by intra-tidal deposition and resuspension that are not included in this tidally averaged model. The model was calibrated to net-basin sedimentation to calculate budgets of sediment and sediment-associated contaminants. While

  9. RANS-based simulation of wave-induced sheet-flow transport of graded sediments

    DEFF Research Database (Denmark)

    Calistan, Ugur; Fuhrman, David R.

    2017-01-01

    A one-dimensional vertical (1DV) turbulence-closure flow model, coupled with sediment transport capabilities,is extended to incorporate graded sediment mixtures. The hydrodynamic model solves the horizontalcomponent of the incompressible Reynolds-averaged Navier–Stokes (RANS) equations coupled...... with k–ωturbulence closure. The sediment transport description includes both bed and suspended load descriptions. Socalledhigh-concentration effects (turbulence damping and hindered settling velocities) are likewise included.The sediment transport model treats the bed and suspended load individually....... The sediment transport model is validated against sheet-flow experimentaloscillatory tunnel measurements beneath velocity-skewed wave signals, and demonstrates similar accuracy(transport rates generally within a factor of two) for both graded and uniform sands. The model is likewisevalidated against...

  10. Direct sampling during multiple sediment density flows reveals dynamic sediment transport and depositional environment in Monterey submarine canyon

    Science.gov (United States)

    Maier, K. L.; Gales, J. A.; Paull, C. K.; Gwiazda, R.; Rosenberger, K. J.; McGann, M.; Lundsten, E. M.; Anderson, K.; Talling, P.; Xu, J.; Parsons, D. R.; Barry, J.; Simmons, S.; Clare, M. A.; Carvajal, C.; Wolfson-Schwehr, M.; Sumner, E.; Cartigny, M.

    2017-12-01

    in the experiment. The comprehensive scale of the Monterey Coordinated Canyon Experiment allows us to integrate sediment traps with ADCP instrument data and seafloor core samples, which provides important new data to constrain how, when, and what sediment is transported through submarine canyons and how this is archived in seafloor deposits.

  11. Improving Sediment Transport Prediction by Assimilating Satellite Images in a Tidal Bay Model of Hong Kong

    Directory of Open Access Journals (Sweden)

    Peng Zhang

    2014-03-01

    Full Text Available Numerical models being one of the major tools for sediment dynamic studies in complex coastal waters are now benefitting from remote sensing images that are easily available for model inputs. The present study explored various methods of integrating remote sensing ocean color data into a numerical model to improve sediment transport prediction in a tide-dominated bay in Hong Kong, Deep Bay. Two sea surface sediment datasets delineated from satellite images from the Moderate Resolution Imaging Spectra-radiometer (MODIS were assimilated into a coastal ocean model of the bay for one tidal cycle. It was found that remote sensing sediment information enhanced the sediment transport model ability by validating the model results with in situ measurements. Model results showed that root mean square errors of forecast sediment both at the surface layer and the vertical layers from the model with satellite sediment assimilation are reduced by at least 36% over the model without assimilation.

  12. Quasi-Three-Dimensional Mathematical Modeling of Morphological Processes Based on Equilibrium Sediment Transport

    Science.gov (United States)

    Charafi, My. M.; Sadok, A.; Kamal, A.; Menai, A.

    A quasi-three-dimensional mathematical model has been developed to study the morphological processes based on equilibrium sediment transport method. The flow velocities are computed by a two-dimensional horizontal depth-averaged flow model (H2D) in combination with logarithmic velocity profiles. The transport of sediment particles by a flow water has been considered in the form of bed load and suspended load. The bed load transport rate is defined as the transport of particles by rolling and saltating along the bed surface and is given by the Van Rijn relationship (1987). The equilibrium suspended load transport is described in terms of an equilibrium sediment concentration profile (ce) and a logarithmic velocity (u). Based on the equilibrium transport, the bed change rate is given by integration of the sediment mass-balance equation. The model results have been compared with a Van Rijn results (equilibrium approach) and good agreement has been found.

  13. Coarse and fine sediment transportation patterns and causes downstream of the Three Gorges Dam

    Science.gov (United States)

    Li, Songzhe; Yang, Yunping; Zhang, Mingjin; Sun, Zhaohua; Zhu, Lingling; You, Xingying; Li, Kanyu

    2017-11-01

    Reservoir construction within a basin affects the process of water and sediment transport downstream of the dam. The Three Gorges Reservoir (TGR) affects the sediment transport downstream of the dam. The impoundment of the TGR reduced total downstream sediment. The sediment group d≤0.125 mm (fine particle) increased along the path, but the average was still below what existed before the reservoir impoundment. The sediments group d>0.125 mm (coarse particle) was recharged in the Yichang to Jianli reach, but showed a deposition trend downstream of Jianli. The coarse sediment in the Yichang to Jianli section in 2003 to 2007 was above the value before the TGR impoundment. However, the increase of both coarse and fine sediments in 2008 to 2014 was less than that in 2003 to 2007. The sediment retained in the dam is the major reason for the sediment reduction downstream. However, the retention in different river reaches is affected by riverbed coarsening, discharge, flow process, and conditions of lake functioning and recharging from the tributaries. The main conclusions derived from our study are as follows: 1) The riverbed in the Yichang to Shashi section was relatively coarse, thereby limiting the supply of fine and coarse sediments. The fine sediment supply was mainly controlled by TGR discharge, whereas the coarse sediment supply was controlled by the duration of high flow and its magnitude. 2) The supply of both coarse and fine sediments in the Shashi to Jianli section was controlled by the amount of total discharge. The sediment supply from the riverbed was higher in flood years than that in the dry years. The coarse sediment tended to deposit, and the deposition in the dry years was larger than that in the flood years. 3) The feeding of the fine sediment in the Luoshan to Hankou section was mainly from the riverbed. The supply in 2008 to 2014 was more than that in 2003 to 2007. Around 2010, the coarse sediments transited from depositing to scouring that was

  14. Sediment Transport into the Swinomish Navigation Channel, Puget Sound—Habitat Restoration versus Navigation Maintenance Needs

    Directory of Open Access Journals (Sweden)

    Tarang Khangaonkar

    2017-04-01

    Full Text Available The 11 mile (1.6 km Swinomish Federal Navigation Channel provides a safe and short passage to fishing and recreational craft in and out of Northern Puget Sound by connecting Skagit and Padilla Bays, US State abbrev., USA. A network of dikes and jetties were constructed through the Swinomish corridor between 1893 and 1936 to improve navigation functionality. Over the years, these river training dikes and jetties designed to minimize sedimentation in the channel have deteriorated, resulting in reduced protection of the channel. The need to repair or modify dikes/jetties for channel maintenance, however, may conflict with salmon habitat restoration goals aimed at improving access, connectivity and brackish water habitat. Several restoration projects have been proposed in the Skagit delta involving breaching, lowering, or removal of dikes. To assess relative merits of the available alternatives, a hydrodynamic model of the Skagit River estuary was developed using the Finite Volume Community Ocean Model (FVCOM. In this paper, we present the refinement and calibration of the model using oceanographic data collected from the years 2006 and 2009 with a focus on the sediment and brackish water transport from the river and Skagit Bay tide flats to the Swinomish Channel. The model was applied to assess the feasibility of achieving the desired dual outcome of (a reducing sedimentation and shoaling in the Swinomish Channel and (b providing a direct migration pathway and improved conveyance of freshwater into the Swinomish Channel. The potential reduction in shoaling through site-specific structure repairs is evaluated. Similarly, the potential to significantly improve of brackish water habitat through dike breach restoration actions using the McGlinn Causeway project example, along with its impacts on sediment deposition in the Swinomish Navigation Channel, is examined.

  15. Size segregation in bedload sediment transport at the particle scale

    Science.gov (United States)

    Frey, P.; Martin, T.

    2011-12-01

    Bedload, the larger material that is transported in stream channels, has major consequences, for the management of water resources, for environmental sustainability, and for flooding alleviation. Most particularly, in mountains, steep slopes drive intense transport of a wide range of grain sizes. Our ability to compute local and even bulk quantities such as the sediment flux in rivers is poor. One important reason is that grain-grain interactions in stream channels may have been neglected. An arguably most important difficulty pertains to the very wide range of grain size leading to grain size sorting or segregation. This phenomenon largely modifies fluxes and results in patterns that can be seen ubiquitously in nature such as armoring or downstream fining. Most studies have concerned the spontaneous percolation of fine grains into immobile gravels, because of implications for salmonid spawning beds, or stratigraphical interpretation. However when the substrate is moving, the segregation process is different as statistically void openings permit downward percolation of larger particles. This process also named "kinetic sieving" has been studied in industrial contexts where segregation of granular or powder materials is often non-desirable. We present an experimental study of two-size mixtures of coarse spherical glass beads entrained by a shallow turbulent and supercritical water flow down a steep channel with a mobile bed. The particle diameters were 4 and 6mm, the channel width 6.5mm and the channel inclination ranged from 7.5 to 12.5%. The water flow rate and the particle rate were kept constant at the upstream entrance. First only the coarser particle rate was input and adjusted to obtain bed load equilibrium, that is, neither bed degradation nor aggradation over sufficiently long time intervals. Then a low rate of smaller particles (about 1% of the total sediment rate) was introduced to study the spatial and temporal evolution of segregating smaller particles

  16. Rans-Based Numerical Simulation of Wave-Induced Sheet-Flow Transport of Graded Sediments

    DEFF Research Database (Denmark)

    Fuhrman, David R.; Caliskan, Ugur

    An existing one-dimensional vertical (1DV) turbulence-closure flow model, coupled with sediment transport capabilities, is extended to incorporate graded sediment mixtures. The hydrodynamic model solves the horizontal component of the incompressible Reynolds-averaged Navier–Stokes (RANS) equations...... coupled with k–ω turbulence closure. In addition to standard bed and suspended load descriptions, the sediment transport model incorporates so-called high-concentration effects (turbulence damping and hindered settling velocities). The sediment transport model treats the bed and suspended load......, and then translated to a common level, which conveniently enables use of a single computational grid for the simulation of suspended sediments. Parametric study shows that these effects combine to help alleviate an otherwise systematic tendency towards over- and under- predicted transport rates for fine and coarse...

  17. Quantifying fluvial sediment transport in a mountain catchment (Schöttlbach, Styria) using sediment impact sensors

    Science.gov (United States)

    Stangl, Johannes; Sass, Oliver; Schneider, Josef; Harb, Gabriele

    2013-04-01

    Sediment transport in river systems, being the output of geomorphic processes in the catchment, is a recurrent problem for geomorphological sediment budget studies, natural hazard assessment and river engineering. Sediment budgets of alpine catchments are likely to be modified by changing total precipitation and the probability of heavy precipitation events in the context of climate change, even if projections of precipitation change for Austria and the entire Alpine region are still very uncertain. Effective sediment management requires profound knowledge on the sediment cascade in the head-waters. However, bedload measurements at alpine rivers or torrents are rare; in Styria, they are altogether missing. Due to a three hour heavy rainfall event on 07-Jul 2011, which caused cata-strophic flooding with massive damage in the city of Oberwölz and its surrounding, we chose the catchment area of the Schöttlbach in the upper Mur river valley in Styria (Austria) as our study area. In the framework of the ClimCatch project, we intend to develop a conceptual model of coupled and decoupled sediment routing to quantify the most prominent sediment fluxes and sediment sinks, combining up-to-date geomorphological and river engineering techniques. Repeated Airborne Laser Scans will provide an overview of ongoing processes, diachronous TLS surveys (cut-and-fill analysis), ground-penetrating radar and 2D-geoelectric surveys should quantity the most important mass fluxes on the slopes and in the channels and derive a quantitative sediment budget, including the volume of temporary sediment stores. Besides quantifying slope processes, sediment sinks and total sediment output, the sediment trans-port in the torrents is of particular interest. We use sediment impact sensors (SIS) which were in-stalled in several river sections in the main stretch of the Schöttlbach and in its tributaries. The SIS mainly consists of two parts connected by a coated cable, the steel shell with the

  18. Pathways of carbon oxidation in continental margin sediments off central Chile

    DEFF Research Database (Denmark)

    Thamdrup, B; Canfield, Donald Eugene

    1996-01-01

    Rates and oxidative pathways of organic carbon mineralization were determined in sediments at six stations on the shelf and slope off Concepcion Bay at 36.5 degrees S. The depth distribution of C oxidation rates was determined to 10 cm from accumulation of dissolved inorganic C in 1-5-d incubatio...

  19. Wind erosion as an environmental transport pathway of glyphosate and AMPA

    Science.gov (United States)

    Bento, Célia P. M.; Goossens, Dirk; Rezaei, Mahrooz; Riksen, Michel; Mol, Hans G. J.; Ritsema, Coen J.; Geissen, Violette

    2017-04-01

    Glyphosate is the active ingredient of many commercial formulations of herbicides extensively used worldwide for weed control. Because glyphosate and its main metabolite aminomethylphosphonic acid (AMPA) are considered non-volatile, their loss to the atmosphere is considered negligible. Both compounds strongly adsorb to soil particles and wind-eroded sediment and dust are thus a possible environmental transport pathway. This can result in environmental and human exposure far beyond the agricultural areas where it has been applied. Therefore, special attention is required to the airborne transport of glyphosate and AMPA. In this study, we investigated the behavior of glyphosate and AMPA in wind-eroded sediment by measuring their content in different size fractions (median diameters between 715 and 8 µm) of a loess soil, during a period of 28 days after glyphosate application. Granulometrical extraction was done using a wind tunnel and a Soil Fine Particle Extractor. Extractions were conducted on days 0, 3, 7, 14, 21 and 28 after glyphosate application. Results indicated that glyphosate and AMPA contents were significantly higher in the finest particle fractions (median diameters between 8 and 18 µm), and lowered significantly with the increase in particle size. Glyphosate and AMPA contents correlated positively with clay, organic matter, and silt content. The dissipation of glyphosate over time was very low, which was associated to the low soil moisture content of the sediment. Consequently, the formation of AMPA was also very low. The low dissipation of glyphosate in our study indicates that the risk of glyphosate transport in dry sediment to off-target areas by wind can be very high. The highest glyphosate and AMPA contents were found in the smallest soil fractions (PM10 and less), which are easily inhaled. This contributes to the risk of human and animal exposure and, therefore, more attention should be paid to this route of exposure in environmental and human

  20. A phase resolving cross-shore sediment transport model for beach profile evolution

    DEFF Research Database (Denmark)

    Rakha, Karim A.; Deigaard, Rolf; Brøker, Ida

    1997-01-01

    -wave sediment concentrations are calculated. The net sediment transport rates are calculated, and the equation for conservation of sediment is solved to predict the beach profile evolution, The results of the present paper showed that the undertow contribution to the sediment transport rates is not dominating...... in all parts of the surf zone, even for eroding beaches, suggesting that other contributions should not be neglected. The present model also showed that for the same offshore wave energy the time series of the oscillatory motion is important and that the effect of wave groups cannot be disregarded. (C...

  1. Implications of sediment transport by subglacial water flow for interpreting contemporary glacial erosion rates

    Science.gov (United States)

    Beaud, Flavien; Flowers, Gwenn E.; Venditti, Jeremy G.

    2017-04-01

    The role of glaciers in landscape evolution is central to the interactions between climate and tectonic forces at high latitudes and in mountainous regions. Sediment yields from glacierized basins are used to quantify contemporary erosion rates on seasonal to decadal timescales, often under the assumption that subglacial water flow is the main contributor to these yields. Two recent studies have furthermore used such sediment fluxes to calibrate a glacial erosion rule, where erosion rate scales with ice sliding speed raised to a power greater than one. Subglacial sediment transport by water flow has however seldom been studied, thus the controls on sediment yield from glacierized basins remain enigmatic. To bridge this gap, we develop a 1-D model of morphodynamics in semi-circular bedrock-floored subglacial channels. We adapt a sediment conservation law from the fluvial literature, developed for both mixed bedrock / alluvial and alluvial conditions, to subglacial channels. Channel evolution is a function of the traditional melt-opening due to viscous heat dissipation from the water flow, and creep closure of the overlying ice, to which we add the closure or enlargement due to sediment deposition or removal, respectively. Using a simple ice geometry representing a land-terminating glacier, we find that the shear stresses produced by the water flow on the bed decrease significantly near the terminus. As the ice thins, creep closure decreases and large hydraulic potential gradients cannot be sustained. The resulting gradients in sediment transport lead to a bottleneck, and sediment accumulates if the sediment supply is adequate. A similar bottleneck occurs if a channel is well established and water discharge drops. Whether such constriction happens in space of time, in the presence of a sufficiently large sediment supply sediment accumulates temporarily near the terminus, followed shortly thereafter by enhanced sediment transport. Reduction in the cross-sectional area

  2. Role of submarine canyons in sediment transport on active Taiwan and passive Chinese margins in northernmost South China Sea

    Science.gov (United States)

    Wu, Y.; Hsiung, K.; Yu, H.

    2011-12-01

    The basin floor of the northernmost South China Sea (SCS) is manifested by flexure of the Chinese margin under the westward migrating overthrust belt of Taiwan, forming two distinct slopes facing each other: the SCS Slope to the Chinese margin and the Kaoping Slope to the Taiwan orogen, respectively. The oblique arc-continental collision being actively propagating from north to south, and consequently the basin floor of the northernmost SCS deepens and tilts towards south, forming a linear marine transport route along the basin axis. The Penghu Canyon is located along the tilting basin axis where is the physiographic boundary separating the SCS and Kaoping slopes. This canyon extends southward and continues to a deep-sea Penghu Channel around 21°N, and finally merges into the northern Manila Trench. The Kaoping Canyon is a distinctive canyon on the Kaoping Shelf/Slope and is the major sediment conduit for delivering Taiwan orogenic sediment to the SCS basin. On the passive margin, the Formosa Canyon is the major sediment pathway on the SCS Slope where it extends from the upper slope to the lower slope and merges into the lower Penghu Canyon. These three main canyons are draining sediment flows southward to the basin floor of SCS and finally to the Manila Trench. Longitudinal profiles for these three canyons are presented to interpret conditions of sedimentary processes in canyon floors. The longitudinal profile of Kaoping Canyon is characterized by linear geometry which is suggested to be erosion dominated. Similarly, the Penghu Canyon shows a linear curve in longitudinal profile indicating the canyon to be erosion type. In contrast, the longitudinal profile of Formosa Canyon shows nearly concave shape which indicates to be deposition dominated. Erosion of these three canyons is suggested to be removal of sediments on the canyon floor and transport down-canyon rather than to be down-cutting of canyon floor. These three main canyons provide sediment input from

  3. Sand sources and transport pathways for the San Francisco Bay coastal system, based on X-ray diffraction mineralogy

    Science.gov (United States)

    Hein, James R.; Mizell, Kira; Barnard, Patrick L.; Barnard, P.L.; Jaffee, B.E.; Schoellhamer, D.H.

    2013-01-01

    The mineralogical compositions of 119 samples collected from throughout the San Francisco Bay coastal system, including bayfloor and seafloor, area beaches, cliff outcrops, and major drainages, were determined using X-ray diffraction (XRD). Comparison of the mineral concentrations and application of statistical cluster analysis of XRD spectra allowed for the determination of provenances and transport pathways. The use of XRD mineral identifications provides semi-quantitative compositions needed for comparisons of beach and offshore sands with potential cliff and river sources, but the innovative cluster analysis of XRD diffraction spectra provides a unique visualization of how groups of samples within the San Francisco Bay coastal system are related so that sand-sized sediment transport pathways can be inferred. The main vector for sediment transport as defined by the XRD analysis is from San Francisco Bay to the outer coast, where the sand then accumulates on the ebb tidal delta and also moves alongshore. This mineralogical link defines a critical pathway because large volumes of sediment have been removed from the Bay over the last century via channel dredging, aggregate mining, and borrow pit mining, with comparable volumes of erosion from the ebb tidal delta over the same period, in addition to high rates of shoreline retreat along the adjacent, open-coast beaches. Therefore, while previously only a temporal relationship was established, the transport pathway defined by mineralogical and geochemical tracers support the link between anthropogenic activities in the Bay and widespread erosion outside the Bay. The XRD results also establish the regional and local importance of sediment derived from cliff erosion, as well as both proximal and distal fluvial sources. This research is an important contribution to a broader provenance study aimed at identifying the driving forces for widespread geomorphic change in a heavily urbanized coastal-estuarine system.

  4. Uncertanity Analysis in Parameter Estimation of Coupled Bacteria-Sediment Fate and Transport in Streams

    Science.gov (United States)

    Massoudieh, A.; Le, T.; Pachepsky, Y. A.

    2014-12-01

    E. coli is widely used as an fecal indicator bacteria in streams. It has been shown that the interaction between sediments and the bacteria is an important factor in determining its fate and transport in water bodies. In this presentation parameter estimation and uncertainty analysis of a mechanistic model of bacteria-sediment interaction respectively using a hybrid genetic algorithm and Makov-Chain Monte Carlo (MCMC) approach will be presented. The physically-based model considers the advective-dispersive transport of sediments as well as both free-floating and sediment-associated bacteria in the water column and also the fate and transport of bacteria in the bed sediments in a small stream. The bed sediments are treated as a distributed system which allows modeling the evolution of the vertical distribution of bacteria as a result of sedimentation and resuspension, diffusion and bioturbation in the sediments. One-dimensional St. Venant's equation is used to model flow in the stream. The model is applied to sediment and E. coli concentration data collected during a high flow event in a small stream historically receiving agricultural runoff. Measured total suspended sediments and total E. coli concentrations in the water column at three sections of the stream are used for the parameter estimation. The data on the initial distribution of E. coli in the sediments was available and was used as the initial conditions. The MCMC method is used to estimate the joint probability distribution of model parameters including sediment deposition and erosion rates, critical shear stress for deposition and erosion, attachment and detachment rate constants of E. coli to/from sediments and also the effective diffusion coefficients of E. coli in the bed sediments. The uncertainties associated with the estimated parameters are quantified via the MCMC approach and the correlation between the posterior distribution of parameters have been used to assess the model adequacy and

  5. Radionuclide particle transport, sedimentation and resuspension in the Forsmark and Laxemar coastal regions

    Energy Technology Data Exchange (ETDEWEB)

    Kling, Hanna; Doeoes, Kristofer (Dept. of Meteorology, Stockholm Univ., Stockholm (Sweden))

    2007-12-15

    In the safety assessment of a potential repository for spent nuclear fuel, it is important to assess the consequences of a hypothetical leak of radionuclides through the seabed and into a waterborne transport phase. Radionuclides adsorbed to sediment particles may be transported great distances through the processes of sedimentation and resuspension. This study investigates the transport patterns of sediment particles of two different sizes, released in the Forsmark and Laxemar area. The results show that the closed waters around Forsmark to a higher degree makes the particles stay in the area close to the release points

  6. Modified finite element transport model, FETRA, for sediment and radionuclide migration in open coastal waters

    International Nuclear Information System (INIS)

    Onishi, Y.; Arnold, E.M.; Mayer, D.W.

    1979-08-01

    The finite element model, FETRA, simulates transport of sediment and radionuclides (and other contaminants, such as heavy metals, pesticides, and other toxic substances) in surface water bodies. The model is an unsteady, two-dimensional (longitudinal and lateral) model which consists of the following three submodels coupled to include sediment-contaminant interactions: (1) sediment transport submodel, (2) dissolved contaminant transport submodel, and (3) particulate contaminant (contaminant adsorbed by sediment) transport submodel. Under the current phase of the study, FETRA was modified to include sediment-wave interaction in order to extend the applicability of the model to coastal zones and large lakes (e.g., the Great Lakes) where wave actions can be one of the dominant mechanisms to transport sediment and toxic contaminant. FETRA was further modified to handle both linear and quadratic approximations to velocity and depth distributions in order to be compatible with various finite element hydrodynamic models (e.g., RMA II and CAFE) which supply hydrodynamic input data to FETRA. The next step is to apply FETRA to coastal zones to simulate transport of sediment and radionuclides with their interactions in order to test and verify the model under marine and large lacustrine environments

  7. Importance of measuring discharge and sediment transport in lesser tributaries when closing sediment budgets

    Science.gov (United States)

    Griffiths, Ronald E.; Topping, David J.

    2017-11-01

    Sediment budgets are an important tool for understanding how riverine ecosystems respond to perturbations. Changes in the quantity and grain size distribution of sediment within river systems affect the channel morphology and related habitat resources. It is therefore important for resource managers to know if a river reach is in a state of sediment accumulation, deficit or stasis. Many sediment-budget studies have estimated the sediment loads of ungaged tributaries using regional sediment-yield equations or other similar techniques. While these approaches may be valid in regions where rainfall and geology are uniform over large areas, use of sediment-yield equations may lead to poor estimations of loads in regions where rainfall events, contributing geology, and vegetation have large spatial and/or temporal variability. Previous estimates of the combined mean-annual sediment load of all ungaged tributaries to the Colorado River downstream from Glen Canyon Dam vary by over a factor of three; this range in estimated sediment loads has resulted in different researchers reaching opposite conclusions on the sign (accumulation or deficit) of the sediment budget for particular reaches of the Colorado River. To better evaluate the supply of fine sediment (sand, silt, and clay) from these tributaries to the Colorado River, eight gages were established on previously ungaged tributaries in Glen, Marble, and Grand canyons. Results from this sediment-monitoring network show that previous estimates of the annual sediment loads of these tributaries were too high and that the sediment budget for the Colorado River below Glen Canyon Dam is more negative than previously calculated by most researchers. As a result of locally intense rainfall events with footprints smaller than the receiving basin, floods from a single tributary in semi-arid regions can have large (≥ 10 ×) differences in sediment concentrations between equal magnitude flows. Because sediment loads do not

  8. Importance of measuring discharge and sediment transport in lesser tributaries when closing sediment budgets

    Science.gov (United States)

    Griffiths, Ronald; Topping, David

    2017-01-01

    Sediment budgets are an important tool for understanding how riverine ecosystems respond to perturbations. Changes in the quantity and grain size distribution of sediment within river systems affect the channel morphology and related habitat resources. It is therefore important for resource managers to know if a river reach is in a state of sediment accumulation, deficit or stasis. Many sediment-budget studies have estimated the sediment loads of ungaged tributaries using regional sediment-yield equations or other similar techniques. While these approaches may be valid in regions where rainfall and geology are uniform over large areas, use of sediment-yield equations may lead to poor estimations of loads in regions where rainfall events, contributing geology, and vegetation have large spatial and/or temporal variability.Previous estimates of the combined mean-annual sediment load of all ungaged tributaries to the Colorado River downstream from Glen Canyon Dam vary by over a factor of three; this range in estimated sediment loads has resulted in different researchers reaching opposite conclusions on the sign (accumulation or deficit) of the sediment budget for particular reaches of the Colorado River. To better evaluate the supply of fine sediment (sand, silt, and clay) from these tributaries to the Colorado River, eight gages were established on previously ungaged tributaries in Glen, Marble, and Grand canyons. Results from this sediment-monitoring network show that previous estimates of the annual sediment loads of these tributaries were too high and that the sediment budget for the Colorado River below Glen Canyon Dam is more negative than previously calculated by most researchers. As a result of locally intense rainfall events with footprints smaller than the receiving basin, floods from a single tributary in semi-arid regions can have large (≥ 10 ×) differences in sediment concentrations between equal magnitude flows. Because sediment loads do not

  9. Bottom Boundary Layer Sediment Transport Processes in Fourleague Bay of Louisiana and Their Implication to Sediment Diversion and Coastal Restoration

    Science.gov (United States)

    Wang, J.; Xu, K.; Bentley, S. J.; Restreppo, G. A.

    2016-02-01

    Building land with a rising sea is a challenging problem in many major deltaic systems around the world. The Atchafalaya deltaic area is one of only a few growing sites in Louisiana coast. The sediment delivered to this deltaic area is mainly from three reservoirs: (1) sediment derived from ongoing fluvial delivery; (2) mobile sediment delivered to the coastal basin during the past year by cold fronts, tropical cyclones, and others; (3) more consolidated sediment stored in the seabed or bay floor for more than 12 months. In order to better understand the far-field dispersal and deposition of fine sediments in the Atchafalaya system, two tripods were used to study the hydrodynamics and sediment dynamics at two stations in Fourleague Bay, which are 15 km southeast of Atchafalaya Delta. One tripod was located at the middle of the bay, and the other was near the marsh edge. Six sensors including OBS (Optical Backscatter Sensor) 3A, OBS 5+, ADV (Acoustic Doppler Velocimeter) Ocean, Argonaut ADV, and two wave gauges were planned to deploy in the early summer and winter of 2015 for a month, respectively. Our study was focused on the near-bed sediment transport from each of the above three reservoirs to wetlands under fair weather and event condition. Based on the seasonal surface suspended sediment concentration (SSC), salinity, as well as turbidity, wave and current data, we have investigated the bottom boundary layer sediment dynamics, in order to illustrate sediment deposition and erosion processes under fair weather and energetic conditions in the bay. During an energetic event in early summer 2015, strong southeasterly wind waves carried salty water from inner Louisiana shelf northwestward into the bay, and led to increasing wave height, bottom shear stress, salinity, and near-bed turbidity. After the event, there was apparent decreasing of these parameters. SSC data in the bay showed an increasing trend since April, which is probably related to the fine sediment

  10. A study of sediment transport in the Herbert River, Australia, using plutonium AMS

    International Nuclear Information System (INIS)

    Everett, S.E.; Tims, S.G.; Fifield, L.K.; Hancock, G.J.

    2005-01-01

    The ANU and CSIRO have begun a new collaboration to study the human impacts of sediment transport into the Great Barrier Reef (GBR) lagoon. The project aims to use fallout plutonium for essentially the first time, as an isotopic tracer of soil and sediment movement. The study aims to assess how recent human activity in the river catchments that feed the GBR lagoon is influencing the distribution and quantity of sediment entering the lagoon. 2 figs

  11. Sediment transport capacity of concentrated flows on steep loessial slope with erodible beds.

    Science.gov (United States)

    Xiao, Hai; Liu, Gang; Liu, Puling; Zheng, Fenli; Zhang, Jiaqiong; Hu, Feinan

    2017-05-24

    Previous research on sediment transport capacity has been inadequate and incomplete in describing the detachment and transport process of concentrated flows on slope farmlands during rill development. An indoor concentrated flow scouring experiment was carried out on steep loessial soil slope with erodible bed to investigate the sediment transport capacity under different flow rates and slope gradients. The results indicated that the sediment transport capacity increases with increasing flow rate and slope gradient, and these relationships can be described by power functions and exponential functions, respectively. Multivariate, nonlinear regression analysis showed that sediment transport capacity was more sensitive to slope gradient than to flow rate, and it was more sensitive to unit discharge per unit width than to slope gradient for sediment transport capacity in this study. When similar soil was used, the results were similar to those of previous research conducted under both erodible and non-erodible bed conditions. However, the equation derived from previous research under non-erodible bed conditions with for river bed sand tends to overestimate sediment transport capacity in our experiment.

  12. Modeling chemical accumulation in sediment of small waterbodies accounting for sediment transport and water-sediment exchange processes over long periods.

    Science.gov (United States)

    Patterson, David Albert; Strehmel, Alexander; Erzgräber, Beate; Hammel, Klaus

    2017-12-01

    In a recent scientific opinion of the European Food Safety Authority it is argued that the accumulation of plant protection products in sediments over long time periods may be an environmentally significant process. Therefore, the European Food Safety Authority proposed a calculation to account for plant protection product accumulation. This calculation, however, considers plant protection product degradation within sediment as the only dissipation route, and does not account for sediment dynamics or back-diffusion into the water column. The hydraulic model Hydrologic Engineering Center-River Analysis System (HEC-RAS; US Army Corps of Engineers) was parameterized to assess sediment transport and deposition dynamics within the FOrum for Co-ordination of pesticide fate models and their USe (FOCUS) scenarios in simulations spanning 20 yr. The results show that only 10 to 50% of incoming sediment would be deposited. The remaining portion of sediment particles is transported across the downstream boundary. For a generic plant protection product substance this resulted in deposition of only 20 to 50% of incoming plant protection product substance. In a separate analysis, the FOCUS TOXSWA model was utilized to examine the relative importance of degradation versus back-diffusion as loss processes from the sediment compartment for a diverse range of generic plant protection products. In simulations spanning 20 yr, it was shown that back-diffusion was generally the dominant dissipation process. The results of the present study show that sediment dynamics and back-diffusion should be considered when calculating long-term plant protection product accumulation in sediment. Neglecting these may lead to a systematic overestimation of accumulation. Environ Toxicol Chem 2017;36:3223-3231. © 2017 SETAC. © 2017 SETAC.

  13. Longshore suspended sediment transport and its implications for submarine erosion off the Yangtze River Estuary

    Science.gov (United States)

    Deng, Bing; Wu, Hui; Yang, Shilun; Zhang, Jing

    2017-05-01

    Coastal currents that originate from large rivers play a key role in delivering sediment to shelf regions. Quantifying their transport capability is therefore essential to understanding the sediment budgets and the consequent deposition or erosion of coastal areas. In February 2012, we observed the sediment transport carried by the Min-Zhe Coastal Current that originates from the Yangtze River mouth and calculated a flux of 18.7 tons per second on a cross-shore section. In this period the coastal current was at a typical status, which allowed us to estimate a total annual sediment transport of 0.27billion tons southward. This result was more than three times the present annual Yangtze River sediment discharge, suggesting that considerable net sediment removal occurs in the coastal regions. The sediment transport 0.27 billion tons/year is probably the deposition/erosion threshold for the East China Sea coast north of our study site. Analysis of historical Yangtze River sediment influx records showed, that the onset and acceleration of coastal erosion was closely linked with the operation of the Three Gorges Dam (TGD) upstream of the Yangtze River.

  14. The role of geology in sediment supply and bedload transport patterns in coarse-grained streams

    Science.gov (United States)

    Sandra E. Ryan

    2007-01-01

    This paper compares gross differences in rates of bedload sediment moved at bankfull discharges in 19 channels on national forests in the Middle and Southern Rocky Mountains. Each stream has its own "bedload signal," in that the rate and size of materials transported at bankfull discharge largely reflect the nature of flow and sediment particular to that...

  15. Sediment transport capacity and its response to hydraulic parameters in experimental rill flow on steep slope

    NARCIS (Netherlands)

    Wang, Z.; Yang, X.; Liu, J.; Yuan, Y.

    2015-01-01

    Sediment transport capacity must be considered when developing physical models of soil erosion. The effects of related hydraulic parameters (e.g., flow discharge, slope gradient, and flow velocity), and of force predictors (e.g., shear stress, stream power, and unit stream power) on sediment

  16. Sediment transport in a large impounded river: The lower Ebro, NE Iberian Peninsula

    Science.gov (United States)

    Vericat, Damia; Batalla, Ramon J.

    2006-09-01

    The sediment transport of the highly regulated lower Ebro River is estimated on the basis of a measuring programme carried out between 2002 and 2004. Total sediment transport, including both suspended load and bedload, was measured upstream and downstream from the Mequinenza and Riba-roja reservoirs, with special attention to the transport during floods. Annual total load upstream from the dams is estimated at around 1.64·10 6 t, of which at least 99% is transported in suspension. Annual total load downstream from the dams is estimated at around 0.45·10 6 t, of which 60% is transported in suspension and the remaining 40% as bedload (mean D50-bl in the range of 32 mm). Total load represents 3% of what was transported at the beginning of the 20th century in the delta plain. Sediment yield is three to four times lower below the dams, a fact that is caused by the trapping of sediment within the reservoirs (around 90% in the case of suspended sediment and 100% in the case of bedload). As a consequence, sediment that is transported downstream from the dams is all entrained from the riverbed and eroded from the banks. The sediment deficit causes a mean riverbed incision of 30 mm per year, as estimated from bedload measurements and by means of scour chains and painted pebbles located between the lowermost dam and the measuring section 28 km downstream. Since floods have been reduced on average by 25% but sediment supply from upstream has been reduced to almost nothing, the river channel of the lower Ebro River will continue exporting sediment both during floods (> 2000 m 3/s, mostly bedload) and frequent high flows (1000 m 3/s to 2000 m 3/s), making the incision progressive unless restoration steps are taken.

  17. Long-distance electron transport by cable bacteria in mangrove sediments

    NARCIS (Netherlands)

    Burdorf, L.D.; Hidalgo-Martinez, S.; Cook, P.L.M.C.; Meysman, F.

    2016-01-01

    Cable bacteria are long, filamentoussulphur-oxidizing bacteria that induce long-distanceelectron transport in aquatic sediments. They turnthe seafloor into an electro-active environment, characterizedby currents and electrical fields, and whenpresent, they exert a strong impact on the

  18. Studies on sediment transport along Kerala Coast, south west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Sajeev, R.; Chandramohan, P.; Josanto, V.; Sanakaranarayanan, V.N.

    Longshore sediment transport characteristics of the Kerala Coast have been examined to delineate various physical processes affecting the different coastal environments. Monthly averages of the daily LEO (Littoral Environmental Observation) data...

  19. A systematic study of wave conditions and sediment transport near Mormugao harbour

    Digital Repository Service at National Institute of Oceanography (India)

    Reddy, M.P.M.

    Wave conditions and the nature of sediment transport in the Mormugao Harbour area have been evaluated in view of the proposed development project of this harbour It has been found from this study that generally high waves will be experienced...

  20. Nearshore waves and longshore sediment transport along Rameshwaram Island off the east coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Gowthaman, R.; SanilKumar, V.; Dwarakish, G.S.; Shanas, P.R.; Jena, B.K.; Singh, J.

    Wave-induced Longshore Sediment Transport (LST) play an important role in the dynamics of the Dhanushkodi sandspit located southeast of Rameshwaram. The LST along the Dhanushkodi coast is studied based on data collected simultaneously in Gulf...

  1. Assessment of bridge abutment scour and sediment transport under various flow conditions

    Science.gov (United States)

    Gilja, Gordon; Valyrakis, Manousos; Michalis, Panagiotis; Bekić, Damir; Kuspilić, Neven; McKeogh, Eamon

    2017-04-01

    Safety of bridges over watercourses can be compromised by flow characteristics and bridge hydraulics. Scour process around bridge foundations can develop rapidly during low-recurrence interval floods when structural elements are exposed to increased flows. Variations in riverbed geometry, as a result of sediment removal and deposition processes, can increase flood-induced hazard at bridge sites with catastrophic failures and destructive consequences for civil infrastructure. The quantification of flood induced hazard on bridge safety generally involves coupled hydrodynamic and sediment transport models (i.e. 2D numerical or physical models) for a range of hydrological events covering both high and low flows. Modelled boundary conditions are usually estimated for their probability of occurrence using frequency analysis of long-term recordings at gauging stations. At smaller rivers gauging station records are scarce, especially in upper courses of rivers where weirs, drops and rapids are common elements of river bathymetry. As a result, boundary conditions that accurately represent flow patterns on modelled river reach cannot be often reliably acquired. Sediment transport process is also more complicated to describe due to its complexity and dependence to local flow field making scour hazard assessment a particularly challenging issue. This study investigates the influence of flow characteristics to the development of scour and sedimentation processes around bridge abutments of a single span masonry arch bridge in south Ireland. The impact of downstream weirs on bridge hydraulics through variation of downstream model domain type is also considered in this study. The numerical model is established based on detailed bathymetry data surveyed along a rectangular grid of 50cm spacing. Acquired data also consist of riverbed morphology and water level variations which are monitored continuously on bridge site. The obtained data are then used to compare and calibrate

  2. Conceptual Site Model for Newark Bay—Hydrodynamics and Sediment Transport

    Directory of Open Access Journals (Sweden)

    Parmeshwar L. Shrestha

    2014-02-01

    Full Text Available A conceptual site model (CSM has been developed for the Newark Bay Study Area (NBSA as part of the Remedial Investigation/Feasibility Study (RI/FS for this New Jersey site. The CSM is an evolving document that describes the influence of physical, chemical and biological processes on contaminant fate and transport. The CSM is initiated at the start of a project, updated during site activities, and used to inform sampling and remediation planning. This paper describes the hydrodynamic and sediment transport components of the CSM for the NBSA. Hydrodynamic processes are influenced by freshwater inflows, astronomical forcing through two tidal straits, meteorological conditions, and anthropogenic activities such as navigational dredging. Sediment dynamics are driven by hydrodynamics, waves, sediment loading from freshwater sources and the tidal straits, sediment size gradation, sediment bed properties, and particle-to-particle interactions. Cohesive sediment transport is governed by advection, dispersion, aggregation, settling, consolidation, and erosion. Noncohesive sediment transport is governed by advection, dispersion, settling, armoring, and transport in suspension and along the bed. The CSM will inform the development and application of a numerical model that accounts for all key variables to adequately describe the NBSA’s historical, current, and future physical conditions.

  3. Multiple Drug Transport Pathways through human P-Glycoprotein(†)

    Science.gov (United States)

    McCormick, James W.; Vogel, Pia D.; Wise, John G.

    2015-01-01

    P-glycoprotein (P-gp) is a plasma membrane efflux pump that is commonly associated with therapy resistances in cancers and infectious diseases. P-gp can lower the intracellular concentrations of many drugs to subtherapeutic levels by translocating them out of the cell. Because of the broad range of substrates transported by P-gp, overexpression of P-gp causes multidrug resistance. We reported previously on dynamic transitions of P-gp as it moved through conformations based on crystal structures of homologous ABCB1 proteins using in silico targeted molecular dynamics techniques. We expanded these studies here by docking transport substrates to drug binding sites of P-gp in conformations open to the cytoplasm, followed by cycling the pump through conformations that opened to the extracellular space. We observed reproducible transport of two substrates, daunorubicin and verapamil, by an average of 11 to 12 Å through the plane of the membrane as P-gp progressed through a catalytic cycle. Methyl-pyrophosphate, a ligand that should not be transported by P-gp, did not show this movement through P-gp. Drug binding to either of two subsites on P-gp appeared to determine the initial pathway used for drug movement through the membrane. The specific side-chain interactions with drugs within each pathway seemed to be, at least in part, stochastic. The docking and transport properties of a P-gp inhibitor, tariquidar, were also studied. A mechanism of inhibition by tariquidar is presented that involves stabilization of an outward open conformation with tariquidar bound in intracellular loops or at the drug binding domain of P-gp. PMID:26125482

  4. Summertime Suspended Sediment Transport Patterns in the Partially-mixed Changjiang Estuary

    Science.gov (United States)

    Niroomandi, A.; Ma, G.

    2016-02-01

    Sediment deposition in the Northern Passage of the Changjiang Estuary, where the Deepwater Navigation Channel (DNC) is located, has been a major concern in the past decades. To understand the sediment transport patterns and sediment sources in the navigational channel, field data on tidal flow and suspended sediment concentration are collected and analyzed in this study. It is shown that sediment transport processes are dominated by ebb currents. As a result, the total sediment flux is generally toward the ocean and the maximum value is found to be in the middle of the passage. At the mouth of the estuary, the total sediment flux is toward the river in the lower layer of the water column confirming a two-layer tide-averaged flow pattern in this region. The effects of sediment on stratification and mixing in the northern passage is examined by calculating eddy viscosity. Results show that strong mixing occurs during ebb in the upper reach of the passage where river discharge has high influence on the estuary. Suspended sediment can dampen turbulence and reduce mixing in the water column. To reveal the major suspended sediment sources, bed shear stresses over the entire passage are calculated. It is found that, during ebb, the bed shear stress is generally larger than the critical value for sediment suspension. Sediment in the water column is suspended from the bed. During flood, the suspended sediment in the northern passage are likely coming from a neighboring shoal, where the water depth is shallow and bed shear stress is large.

  5. Sediment Transport Time Scales and Trapping Efficiency in a Tidal River

    Science.gov (United States)

    Ralston, David K.; Geyer, W. Rockwell

    2017-11-01

    Observations and a numerical model are used to characterize sediment transport in the tidal Hudson River. A sediment budget over 11 years including major discharge events indicates the tidal fresh region traps about 40% of the sediment input from the watershed. Sediment input scales with the river discharge cubed, while seaward transport in the tidal river scales linearly, so the tidal river accumulates sediment during the highest discharge events. Sediment pulses associated with discharge events dissipate moving seaward and lag the advection speed of the river by a factor of 1.5 to 3. Idealized model simulations with a range of discharge and settling velocity were used to evaluate the trapping efficiency, transport rate, and mean age of sediment input from the watershed. The seaward transport of suspended sediment scales linearly with discharge but lags the river velocity by a factor that is linear with settling velocity. The lag factor is 30-40 times the settling velocity (mm s-1), so transport speeds vary by orders of magnitude from clay (0.01 mm s-1) to coarse silt (1 mm s-1). Deposition along the tidal river depends strongly on settling velocity, and a simple advection-reaction equation represents the loss due to settling on depositional shoals. The long-term discharge record is used to represent statistically the distribution of transport times, and time scales for settling velocities of 0.1 mm s-1 and 1 mm s-1 range from several months to several years for transport through the tidal river and several years to several decades through the estuary.

  6. Field Observations of Hydrodynamics, Sediment Transport, and Water and Sediment Quality in the Hudson-Raritan Estuary

    Science.gov (United States)

    Bruno, M. S.; Glenn, S.; Chant, R.; Rankin, K.; Korfiatis, G.; Dimou, N.; Creed, E.; Fullerton, B.; Pence, A.; Burke, P.; Haldeman, C.; Hires, R.; Hunter, E.

    2002-12-01

    The New York-New Jersey Harbor estuary system is of enormous ecological and economic importance to the region. The presence of toxic chemicals in the water and sediments results in reduced water quality, fisheries restrictions/advisories, and general adverse impacts to the estuarine ecosystem. The Port of New York and New Jersey is central to the economy of the region. However, in recent years, problems associated with the management of contaminated dredged material, including high costs and the lack of suitable disposal/use alternatives, have threatened to impact the volume of shipping in the Harbor. Sources of contaminants include atmospheric deposition, municipal and industrial wastewater treatment facilities, combined sewer and stormwater outfalls, and rainfall-induced runoff (non-point sources). In addition, Harbor sediments can act as a continuing source as they are re-suspended and moved throughout the system by both natural and man-made means. As part of the New Jersey Toxics Reduction Workplan, Stevens Institute of Technology and Rutgers University are conducting hydrodynamic, sediment transport, and water and suspended sediment quality measurements in Newark Bay, the Arthur Kill and the Kill van Kull. The goals of the project include: (1) collection of high resolution (event-driven and long-term) hydrodynamic, sediment transport and water and suspended sediment quality measurements for use in the assessment of the dominant physics of the system and in the development of a combined hydrodynamic-sediment transport-water/sediment quality model for the region. (2) identification of those tributaries to NY-NJ Harbor that are significant sources of the chemicals of concern, and evaluation of the importance of non-point sources and existing contaminated bottom sediments as sources of the chemicals of concern. (3) identification of point discharges that represent significant sources of the chemicals of concern. Observations were obtained over a two-year period

  7. Study of sediment transport in Semarang coastal water using 198 Au radioactive tracer

    International Nuclear Information System (INIS)

    Supriatna, Dadang; Sukarmadijaya, Harun; Barokah

    2000-01-01

    Most nearshore aquatic system adjacent to urban centers are characterized by contaminated fine sediment deposits that were brought in from variety sources. Banjir Kanal Timur, Tambak Lorok and Tenggang are rivers that across of Semarang city and have a mouth at same location, that location are potential pollutant sources for Semarang coastal water, so the knowledge of sediment transport in Semarang coastal is very important for management and sustainable that area. One techniques to understand transport of sediment is radioactive tracer have several major advantages, high detection sensitivity, unique possibility of being measured in situ providu information in the shortest possible time. Specific gravity and particle size distribution analysis indicate that there was on differences between nature sediment compare whit labelled sediment. Contour of movement pattern of radiotracer shows sediment towards North, while disressing moved to left and right direction with mean velocity of 5.65 m/day. Sediment transport rate was calculated of 780.7 kg/m/day with the thickness of the mobile layer sediment 5.2 cm

  8. Modeling flow, sediment transport and morphodynamics in rivers

    Science.gov (United States)

    Nelson, Jonathan M.; McDonald, Richard R.; Shimizu, Yasuyuki; Kimura, Ichiro; Nabi, Mohamed; Asahi, Kazutake

    2016-01-01

    Predicting the response of natural or man-made channels to imposed supplies of water and sediment is one of the difficult practical problems commonly addressed by fluvial geomorphologists. This problem typically arises in three situations. In the first situation, geomorphologists are attempting to understand why a channel or class of channels has a certain general form; in a sense, this is the central goal of fluvial geomorphology. In the second situation, geomorphologists are trying to understand and explain how and why a specific channel will evolve or has evolved in response to altered or unusual sediment and water supplies to that channel. For example, this would include explaining the short-term response of a channel to an unusually large flood or predicting the response of a channel to long-term changes in flow or sediment supply due to various human activities such as damming or diversions. Finally, geomorphologists may be called upon to design or assess the design of proposed man-made channels that must carry a certain range of flows and sediment loads in a stable or at least quasi-stable manner. In each of these three situations, the problem is really the same: geomorphologists must understand and predict the interaction of the flow field in the channel, the sediment movement in the channel and the geometry of the channel bed and banks. In general, the flow field, the movement of sediment making up the bed and the morphology of the bed are intricately linked; the flow moves the sediment, the bed is altered by erosion and deposition of sediment and the shape of the bed is critically important for predicting the flow. This complex linkage is precisely what makes understanding channel form and process such a difficult and interesting challenge.

  9. Aeolian particle transport inferred using a ~150-year sediment record from Sayram Lake, arid northwest China

    Directory of Open Access Journals (Sweden)

    Long Ma

    2015-05-01

    Full Text Available We studied sediment cores from Sayram Lake in the Tianshan Mountains of northwest China to evaluate variations in aeolian transport processes over the past ~150 years. Using an end-member modeling algorithm of particle size data, we interpreted end members with a strong bimodal distribution as having been transported by aeolian processes, whereas other end members were interpreted to have been transported by fluvial processes. The aeolian fraction accounted for an average of 27% of the terrigenous components in the core. We used the ratio of aeolian to fluvial content in the Sayram Lake sediments as an index of past intensity of aeolian transport in the Tianshan Mountains. During the interval 1910-1930, the index was high, reflecting the fact that dry climate provided optimal conditions for aeolian dust transport. From 1930-1980, the intensity of aeolian transport was weak. From the 1980s to the 2000s, aeolian transport to Sayram Lake increased. Although climate in northwest China became more humid in the mid-1980s, human activity had by that time altered the impact of climate on the landscape, leading to enhanced surface erosion, which provided more transportable material for dust storms. Comparison of the Lake Sayram sediment record with sediment records from other lakes in the region indicates synchronous intervals of enhanced aeolian transport from 1910 to 1930 and 1980 to 2000.

  10. Transport and deposition of plutonium in the ocean: Evidence from Gulf of Mexico sediments

    International Nuclear Information System (INIS)

    Scott, M.R.; Salter, P.F.; Halverson, J.E.

    1983-01-01

    A study of sediments in the Gulf of Mexico shows dramatic gradients in Pu content and isotope ratios from the continental shelf to the Sigsbee Abyssal Plain. In terms of predicted direct fallout inventory of Pu, one shelf core contains 745% of the predicted inventory, while abyssal plain sediments contain only 15-20% of the predicted value. Absolute Pu concentrations of shelf sediments are also conspicuously high, up to 110 dpm/kg, compared to 13.5 dpm/kg in Mississippi River suspended sediment. There is no evidence of Pu remobilization in Gulf of Mexico shelf sediments, based on comparison of Pu profiles with Mn/Al and Fe/Al profiles. Horizontal transport of fallout nuclides from the open ocean to removal sites in ocean margin sediments is concluded to be the source of both the high concentrations and high inventories of Pu reported here. The shelf sediments show 240 Pu/ 239 Pu ratios close to 0.179, the average stratospheric fallout value, but the ratios decrease progressively across the Gulf to low values of 0.06 in abyssal plain sediments. The source of low-ratio Pu in deep-water sediments may be debris from low yield tests transported in the troposphere. Alternatively, it may represent a fraction of the Pu from global stratospheric fallout which has been separated in the water column from the remainder of the Pu in the ocean. In either case, the low-ratio material must have been removed rapidly to the sea floor where it composes a major fraction of the Pu in abyssal plain sediments. Pu delivered by global atmospheric fallout from the stratosphere has apparently remained for the most part in the water or has been transported horizontally and removed into shallow-water sediments. (orig.)

  11. Sediment transport off Bangladesh: the power of tropical cyclones recorded in a submarine canyon

    Science.gov (United States)

    Meyer, I.; Kudrass, H.; Palamenghi, L.

    2011-12-01

    Marine sediments offshore Bangladesh are mainly supplied by the Ganges-Brahmaputra river system and are accumulated on the shelf of Bangladesh. The average sediment discharge of the world's biggest river system is estimated to be 0.8-1 billion tons per year. The shallow shelf is cut by a steep and up to 1000 m deep anaerobic canyon, called the "Swatch of No Ground", which acts as a sediment trap. An extremely high annual sedimentation flux of 20-45 cm was determined for the last 50 years by 137Cs and 210Pb measurements. In order to investigate the sediment transport in the Bay of Bengal a marine sediment core was taken from the mid-part of the Swatch of No Ground (21°18N/89°34E) and analyzed for element composition and grain-size distributions. Results show a sequence of graded fine-sand-silt-clay layers. These sequences can be directly related to the historical record of tropical storms, which move across the northern Bay of Bengal during pre- and post-monsoon flood peak and mobilize huge amounts of the shallow marine and coastal sediments into turbid hyperpycnal water masses. Due to the anti-clockwise rotation of the cyclones and their northward path the main transport direction is westward. The coarse grained sediment, remobilized by storm waves, is supported by cyclone-induced currents toward the canyon while the fine grained fraction follows afterward supported by the storm swell plus the semi-diurnal tidal component. Despite the high riverine input the amount of sediment mobilized during normal weather conditions is minimal compared to the sediment mobilized by the cyclonic high-energy input. Similar cyclone-induced sediment transport probably also governs erosion and deposition in most tropical shelf areas affected by the monsoon regime.

  12. The influence of sediment transport rate on the development of structure in gravel bed rivers

    Science.gov (United States)

    Ockelford, Annie; Rice, Steve; Powell, Mark; Reid, Ian; Nguyen, Thao; Tate, Nick; Wood, Jo

    2013-04-01

    Although adjustments of surface grain size are known to be strongly influenced by sediment transport rate little work has systematically explored how different transport rates can affect the development of surface structure in gravel bed rivers. Specifically, it has been well established that the transport of mixed sized sediments leads to the development of a coarser surface or armour layer which occurs over larger areas of the gravel bed. Armour layer development is known to moderate overall sediment transport rate as well as being extremely sensitive to changes in applied shear stress. However, during this armouring process a bed is created where, smaller gain scale changes, to the bed surface are also apparent such as the development of pebble clusters and imbricate structures. Although these smaller scale changes affect the overall surface grain size distribution very little their presence has the ability to significantly increase the surface stability and hence alter overall sediment transport rates. Consequently, the interplay between the moderation of transport rate as a function of surface coarsening at a larger scale and moderation of transport rate as a function of the development of structure on the bed surface at the smaller scale is complicated and warrants further investigation. During experiments a unimodal grain size distribution (σg = 1.30, D50 = 8.8mm) was exposed to 3 different levels of constant discharge that produced sediment transport conditions ranging from marginal transport to conditions approaching full mobility of all size fractions. Sediment was re-circulated during the experiments surface grain size distribution bed load and fractional transport rates were measured at a high temporal resolution such that the time evolution of the beds could be fully described. Discussion concentrates on analysing the effects of the evolving bed condition sediment transport rate (capacity) and transported grain size (competence). The outcome of this

  13. History of heavy metal accumulation in the Svalbard area: Distribution, origin and transport pathways.

    Science.gov (United States)

    Zaborska, Agata; Beszczyńska-Möller, Agnieszka; Włodarska-Kowalczuk, Maria

    2017-12-01

    In this study temporal changes of Pb, Zn, Cd and Cu concentrations were studied in 19 dated sediment cores collected from Svalbard fjords and the Barents Sea. The main aim was to study spatial and historical variations in heavy metal concentrations, deposition rates and sources in the context of different metal transport pathways. Metal concentrations ranged from 5.7 to 45.8 mg kg -1 for Pb, from 13.4 to 54.5 mg kg -1 for Cu, from 0.01 to 0.90 mg kg -1 for Cd and from 55.6 to 130.4 mg kg -1 for Zn. Some fjords were unpolluted by heavy metals while in others a clear signal of metal enrichment was found (outer Kongsfjorden, Hornsund, Adventfjorden). Large-scale processes such as atmospheric and oceanic transport were found to be important drivers of heavy metal contaminant distribution. The significance of global drivers varied among the fjords, due to coupling with local processes. Outer fjord parts, the most impacted by oceanic transport, were characterized by the excess 206 Pb/ 207 Pb values of ∼1.17, while the inner basins were characterized by the excess 206 Pb/ 207 Pb of ∼1.14 suggesting possible different importance of Pb sources (marine currents and atmospheric transport). Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Critical review: Radionuclide transport, sediment transport, and water quality mathematical modeling; and radionuclide adsorption/desorption mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Onishi, Y.; Serne, R.J.; Arnold, E.M.; Cowan, C.E.; Thompson, F.L. [Pacific Northwest Lab., Richland, WA (United States)

    1981-01-01

    This report describes the results of a detailed literature review of radionuclide transport models applicable to rivers, estuaries, coastal waters, the Great Lakes, and impoundments. Some representatives sediment transport and water quality models were also reviewed to evaluate if they can be readily adapted to radionuclide transport modeling. The review showed that most available transport models were developed for dissolved radionuclide in rivers. These models include the mechanisms of advection, dispersion, and radionuclide decay. Since the models do not include sediment and radionuclide interactions, they are best suited for simulating short-term radionuclide migration where: (1) radionuclides have small distribution coefficients; (2) sediment concentrations in receiving water bodies are very low. Only 5 of the reviewed models include full sediment and radionuclide interactions: CHMSED developed by Fields; FETRA SERATRA, and TODAM developed by Onishi et al, and a model developed by Shull and Gloyna. The 5 models are applicable to cases where: (1) the distribution coefficient is large; (2) sediment concentrations are high; or (3) long-term migration and accumulation are under consideration. The report also discusses radionuclide absorption/desorption distribution ratios and addresses adsorption/desorption mechanisms and their controlling processes for 25 elements under surface water conditions. These elements are: Am, Sb, C, Ce, Cm, Co, Cr, Cs, Eu, I, Fe, Mn, Np, P, Pu, Pm, Ra, Ru, Sr, Tc, Th, {sup 3}H, U, Zn and Zr.

  15. Understanding Sediment Sources, Pathways, and Sinks in Regional Sediment Management: Application of Wash Load and Bed-Material Load Concept

    National Research Council Canada - National Science Library

    Biedenham, David S; Hubbard, Lisa C; Thome, Colin R; Watson, Chester C

    2006-01-01

    ... through the fluvial system for sediments derived from various bed, bank, gully, and catchment sources thereby providing a reliable analytical foundation for effective regional sediment management...

  16. Residual fluxes and suspended sediment transport in the lower reaches of Muvattupuzha River, southwest coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Revichandran, C.; Balachandran, K.K.; Xavier, J.K.; Rejendran, N.C.

    Spatial and seasonal variation of different physical processes governing the transport of salt and sediment of the Muvattupuzha River, in Kerala, India are discussed. Salt and suspended sediment due to tidal pumping was directed upstream, salt...

  17. Sediment and Fecal Indicator Bacteria Loading in a Mixed Land Use Watershed: Contributions from Suspended and Bed Load Transport

    Science.gov (United States)

    Water quality studies that quantify sediment and fecal bacteria loading commonly focus on suspended contaminants transported during high flows. Fecal contaminants in bed sediments are typically ignored and need to be considered because of their potential to increase pathogen load...

  18. Coupling climate conditions, sediment sources and sediment transport in an alpine basin

    Science.gov (United States)

    Rainato, Riccardo; Picco, Lorenzo; Cavalli, Marco; Mao, Luca; Neverman, Andrew J.; Tarolli, Paolo

    2017-04-01

    In a fluvial system, mountain basins control sediment export to the lowland rivers. Hence, the analysis of the erosion processes and sediment delivery patterns that act in mountain basins is important. Several studies have investigated the alterations triggered by recent climatic change on the hydrological regime, whilst only a few works have explored the consequences on the sediment dynamics. Here we combined and analyzed the quasi-unique dataset of climatic conditions, landscape response, and sediment export produced, since 1986 in the Rio Cordon basin (5 km2, Eastern Italian Alps) to examine the sediment delivery processes occurring in the last three decades. The temperature, precipitation, and fluvial sediment fluxes in the basin were analyzed using continuous measurement executed by a permanent monitoring station, while the landscape evolution was investigated by three sediment source inventories established in 1994, 2006, and 2016. Thus, the analysis focused on the trends exhibited during the periods 1986-1993, 1994-2006, and 2007-2015. In terms of climatic conditions, three distinct climate forcing stages can be observed in the periods analyzed: a relatively stable phase (1986-1993), a period characterized by temperature and rainfall fluctuations (1994-2006), and a more recent warmer and wetter phase (2007-2015). In the 1986-1993 period, the fluvial sediment fluxes reflected the stable trend exhibited by the climatic conditions. In the subsequent 1994-2006 period, the average temperature and precipitation were in line with that previously observed, although with higher interannual variability. Notwithstanding the climate forcing and the occurrence of high magnitude/low frequency floods that strongly influenced the source areas, between 1994 and 2006 the Rio Cordon basin showed relatively limited erosion activity. Hence, the climatic conditions and the landscape response can only partially explain the strong increase of sediment export recorded in the 1994

  19. Effect of hydraulic parameters on sediment transport capacity in overland flow over erodible beds

    NARCIS (Netherlands)

    Ali, M.; Sterk, G.; Seeger, K.M.; Boersema, M.P.; Peters, P.D.

    2012-01-01

    Sediment transport is an important component of the soil erosion process, which depends on several hydraulic parameters like unit discharge, mean flow velocity, and slope gradient. In most of the previous studies, the impact of these hydraulic parameters on transport capacity was studied for

  20. Review of the Field-Data Base for Longshore Sediment Transport

    CSIR Research Space (South Africa)

    Schoonees, JS

    1993-02-01

    Full Text Available A literature search was undertaken to collect field data on longshore sediment transport. This yielded a large number of data sets (273 points for bulk transport rates) from a variety of sites around the world. Data are especially lacking...

  1. Transport of typhoon-induced submarine sediment-laden flows off southwestern Taiwan

    Science.gov (United States)

    Su, C.; Cheng, Y.

    2012-12-01

    Since 2006, southern Taiwan experienced destructive typhoons and earthquakes which triggered large scale submarine landslides and turbidity currents and devastated many submarine cables off southwestern Taiwan. Most of cable breakages were located in the Gaoping (GPSC) and Fangliao (FLSC) submarine canyons which indicate submarine canyon is an important pathway for underwater gravity flows that induced by natural hazards. A series of investigations were conducted before and after Morakot typhoon, the sub-bottom profiler and core analysis results revealed the GPSC and FLSC may play different roles in transport sediment from coastal seas to the abyssal ocean during the typhoon invaded period. Off southwestern Taiwan, the GPSC and FLSC are incising from continental shelf to deep sea floor and both of them transport considerable amounts of sediment to the South China Sea. GPSC is directly connected to the Gaoping River on land. The hyperpycnal flows, formed during Typhoon Morakot, delivered coarse sands, gravels and branches of trees into GPSC and deposited at the upper reach. On the contrary, the FLSC, which is smaller, younger and confined to the slope, does not associate with any river on land. A series of turbidites and debrites, which composed by coarse slates, fractal shells, wood fragments and fresh leaves, were observed in cores collected from the head of FLSC through Gaoping slope to the lower reach of GPSC. It implies the torrential rains induced landslides at the southernmost Central Mountain Range may directly delivered large amount of slate fragments through narrow Gaoping shelf into the deep sea. Furthermore, according to Water Resources Agency's groundwater level monitoring data, during Typhoon Morakot, the groundwater level raised significantly at the coastal area of Pingtung Plain. The increased groundwater pressure may lead to high flux of submarine groundwater discharge and induced liquefaction on seafloor. From sub-bottom profiles, the liquefaction

  2. 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

  3. Morphodynamics and Sediment Transport on the Huanghe (Yellow River) Delta: Work in Progress

    Science.gov (United States)

    Kineke, G. C.; Calson, B.; Chadwick, A. J.; Chen, L.; Hobbs, B. F.; Kumpf, L. L.; Lamb, M. P.; Ma, H.; Moodie, A. J.; Mullane, M.; Naito, K.; Nittrouer, J. A.; Parker, G.

    2017-12-01

    Deltas are perhaps the most dynamic of coastal landforms with competing processes that deliver and disperse sediment. As part of the NSF Coastal SEES program, an interdisciplinary team of scientists from the US and China are investigating processes that link river and coastal sediment transport responsible for morphodynamic change of the Huanghe delta- an excellent study site due to its high sediment load and long history of natural and engineered avulsions, that is, abrupt shifts in the river course. A fundamental component of the study is a better understanding of sediment transport physics in a river system that transports mostly silt. Through theory and data analysis, we find that fine-grained rivers fail to develop full scale dunes, which results in faster water flow and substantially larger sediment fluxes as compared to sandy rivers (e.g. the Mississippi River). We also have developed new models for sediment-size dependent entrainment that are needed to make longer term predictions of river sedimentation patterns. On the delta front, we are monitoring the high sediment flux to the coast, which results in steep foresets and ideal conditions for off-shore sediment delivery via gravity flows. These constraints on sediment transport are being used to develop new theory for where and when rivers avulse - including the effects of variable flood discharge, sediment supply, and sea level rise -and how deltas ultimately grow through repeated cycles of lobe development. Flume experiments and field observations are being used to test these models, both in the main channel of the Huanghe and in channels abandoned after historic avulsions. Abandoned channels and floodplains are now dominated by coastal sediment transport through a combination of wave resuspension and tidal transport, settling lag and reverse estuarine circulation. Finally, the field and laboratory tested numerical models are being used as inputs to define a cost curve for efficient avulsion management of

  4. Anthropogenic disturbance on sediment transport processes in the tidal power plant

    Science.gov (United States)

    Ha, Ho Kyung; Kim, Jong-wook; Woo, Seung-Buhm; Kwon, Hyo Keun

    2017-04-01

    A series of in-situ mooring observations have been conducted to investigate the anthropogenic disturbance of sediment transport processes in the Sihwa tidal power plant (TPP). The mooring data show that the profiels of velocity and suspended sediment concentration (SSC) were significantly disturbed over the various time scales. On the short-term (flood-ebb) time scale, resuspension of bottom sediment is mainly controlled by the strong jet-flow (>2 m/s) and anticlockwise rotating vortex associated with the artificial discharge. During ebb phase, the strong flow resulted in suspension of high-concentration near-bed sediment and seaward transport of the suspended sediment. After turning to flood phase, the vortex produced secondary SSC peaks, transporting the suspended sediment toward the TPP. The most active suspension of bottom sediment predominantly occurred during 1-2 hr immediately after the start of artificial discharge. On the fortnightly (spring-neap) time scale, SSC during spring tide was approximately 2-5 times higher than that during neap tide. During the presentation, it will be discussed how the periodic artificial discharge can disturb the responses of SSC in the TPP.

  5. Sediment Transport Capacity and Channel Processes in a Humid Tropical Montane River - Rio Pacuare, Costa Rica

    Science.gov (United States)

    Lind, P.; McDowell, P. F.

    2017-12-01

    Investigating sediment transport capacity as well as the spatial and temporal variations of sediment flux are critical component of river research, especially for applications in resource management and conservation, hazards assessment and planning, and riverine ecology. The bedload fraction of sediment transported through montane rivers often defines channel and bed form processes. It is understood that humid tropical montane rivers are capable of producing some of the largest quantities of sediment per unit drainage area. Bedload flux reported on a few Southeast Asian humid tropical montane rivers show that bedload constituted 16-75% of the total sediment load - this is notably higher than the generally accepted 10% of a channel's sediment load. However, to date almost all of the research done on sediment transport in humid tropical systems has focused on suspended load. This study presents annual bedload transport rate estimates for six field sites distributed within 45 river kilometers (Rkm) of the montane portion of the Rio Pacuare, located in the Talamanca Mountains of Costa Rica. This research reveals that flows capable of mobilizing the D84 occur on average at least once but often multiple times a year in this river system. The Rio Pacuare has a sufficient supply of sediment to meet its high transport capacity needs. As a result, large active bars composed of imbricated boulders define channel form at moderate and low flows throughout the study area. Differences in the magnitude, as well as the spatial and temporal variations of sediment flux at each field site are discussed in relation to stream power, and annual/inter-annual precipitation patterns. A unique mix of field and remote sensing techniques were applied to address these questions and to overcome some of the challenges of tropical river research. For example, due to the large grain size and high stream energy, grain mobilization and validation of modeled shear stress requirements for transport

  6. Modeling sediment transport after ditch network maintenance of a forested peatland

    Science.gov (United States)

    Haahti, K.; Marttila, H.; Warsta, L.; Kokkonen, T.; Finér, L.; Koivusalo, H.

    2016-11-01

    Elevated suspended sediment (SS) loads released from peatlands after drainage operations and the resulting negative effect on the ecological status of the receiving water bodies have been widely recognized. Understanding the processes controlling erosion and sediment transport within the ditch network forms a prerequisite for adequate sediment control. While numerous experimental studies have been reported in this field, model based assessments are rare. This study presents a modeling approach to investigate sediment transport in a peatland ditch network. The transport model describes bed erosion, rain-induced bank erosion, floc deposition, and consolidation of the bed. Coupled to a distributed hydrological model, sediment transport was simulated in a 5.2 ha forestry-drained peatland catchment for 2 years after ditch cleaning. Comparing simulation results to measured SS concentrations suggested that the loose peat material, produced during excavation, contributed markedly to elevated SS concentrations immediately after ditch cleaning. Both snowmelt and summer rainstorms contributed critically to annual loads. Springtime peat erosion during snowmelt was driven by ditch flow whereas during summer rainfalls, bank erosion by raindrop impact was identified as an important process. Relating modeling results to observed spatial topographic changes in the ditch network was challenging and the results were difficult to verify. Nevertheless, the model has potential to identify risk areas for erosion. The results demonstrate that modeling is effective in separating the importance of different processes and complements pure experimental approaches. Modeling results can aid planning and designing efficient sediment control measures and guide the focus of experimental studies.

  7. Sources, Transport, and Storage of Sediment at Selected Sites in the Chesapeake Bay Watershed

    Science.gov (United States)

    Gellis, Allen C.; Hupp, Cliff R.; Pavich, Milan J.; Landwehr, Jurate M.; Banks, William S.L.; Hubbard, Bernard E.; Langland, Michael J.; Ritchie, Jerry C.; Reuter, Joanna M.

    2009-01-01

    The Chesapeake Bay Watershed covers 165,800 square kilometers and is supplied with water and sediment from five major physiographic provinces: Appalachian Plateau, Blue Ridge, Coastal Plain, Piedmont, and the Valley and Ridge. Suspended-sediment loads measured in the Chesapeake Bay Watershed showed that the Piedmont Physiographic Province has the highest rates of modern (20th Century) sediment yields, measured at U.S. Geological Survey streamflow-gaging stations, and the lowest rates of background or geologic rates of erosion (~10,000 years) measured with in situ beryllium-10. In the agricultural and urbanizing Little Conestoga Creek Watershed, a Piedmont watershed, sources of sediment using the 'sediment-fingerprinting' approach showed that streambanks were the most important source (63 percent), followed by cropland (37 percent). Cesium-137 inventories, which quantify erosion rates over a 40-year period, showed average cropland erosion of 19.39 megagrams per hectare per year in the Little Conestoga Creek Watershed. If this erosion rate is extrapolated to the 13 percent of the watershed that is in cropland, then cropland could contribute almost four times the measured suspended-sediment load transported out of the watershed (27,600 megagrams per hectare per year), indicating that much of the eroded sediment is being deposited in channel and upland storage. The Piedmont has had centuries of land-use change, from forest to agriculture, to suburban and urban areas, and in some areas, back to forest. These land-use changes mobilized a large percentage of sediment that was deposited in upland and channel storage, and behind thousands of mill dams. The effects of these land-use changes on erosion and sediment transport are still being observed today as stored sediment in streambanks is a source of sediment. Cropland is also an important source of sediment. The Coastal Plain Physiographic Province has had the lowest sediment yields in the 20th Century and with sandy

  8. Isotopic provenance analysis and terrane tectonics: a warning about sediment transport distances

    International Nuclear Information System (INIS)

    Bassett, K.N.

    1999-01-01

    Full text: In the last 10 years the field of provenance analysis has undergone a revolution with the development of single-crystal isotopic dating techniques, the most common being U/Pb zircon and 40Ar/39Ar techniques. These have allowed age determination of single crystals thus providing more detail about probable provenance of each individual grain rather than an averaged population of grains. The usefulness for resolving complex terrane accretion and translation histories was immediately obvious and there have been many studies in many different regions aimed at tracking terrane motions by provenance of individual grains upward through the stratigraphy of a basin. Recent research in the North American Cordilleran terranes and in the New Zealand Torlesse Superterrane show how widely used and powerful these provenance analysis techniques are. However, isotopic provenance analysis has often been presented as key information to resolve controversies around terrane translation histories with very little discussion of the context of sedimentary facies and sediment transport mechanisms. An example is the recent use of U/Pb detrital zircon ages as the supposedly controversy-ending evidence for the amount of lateral translation of the Insular Superterrane in British Columbia (Baja BC) (Mahoney et al., 1999). The zircon grains were separated from fine-grained turbidite deposits and could easily have been transported over very large distances by a variety of mechanisms; yet they were presented as definitively resolving the Baja BC controversy. Modern examples illustrate the problem of using the provenance of fine grained sediment to constrain terrane tectonics. Sediment in the tip of the Bengal submarine fan was transported ∼3000 km from source, first by fluvial processes then by sediment gravity flow in the submarine fan. The detrital isotopic ages of single grains are the same as the depositional ages indicating a very rapid unroofing and transport rate with minimal

  9. Cerebrospinal and interstitial fluid transport via the glymphatic pathway modeled by optimal mass transport.

    Science.gov (United States)

    Ratner, Vadim; Gao, Yi; Lee, Hedok; Elkin, Rena; Nedergaard, Maiken; Benveniste, Helene; Tannenbaum, Allen

    2017-05-15

    The glymphatic pathway is a system which facilitates continuous cerebrospinal fluid (CSF) and interstitial fluid (ISF) exchange and plays a key role in removing waste products from the rodent brain. Dysfunction of the glymphatic pathway may be implicated in the pathophysiology of Alzheimer's disease. Intriguingly, the glymphatic system is most active during deep wave sleep general anesthesia. By using paramagnetic tracers administered into CSF of rodents, we previously showed the utility of MRI in characterizing a macroscopic whole brain view of glymphatic transport but we have yet to define and visualize the specific flow patterns. Here we have applied an alternative mathematical analysis approach to a dynamic time series of MRI images acquired every 4min over ∼3h in anesthetized rats, following administration of a small molecular weight paramagnetic tracer into the CSF reservoir of the cisterna magna. We use Optimal Mass Transport (OMT) to model the glymphatic flow vector field, and then analyze the flow to find the network of CSF-ISF flow channels. We use 3D visualization computational tools to visualize the OMT defined network of CSF-ISF flow channels in relation to anatomical and vascular key landmarks from the live rodent brain. The resulting OMT model of the glymphatic transport network agrees largely with the current understanding of the glymphatic transport patterns defined by dynamic contrast-enhanced MRI revealing key CSF transport pathways along the ventral surface of the brain with a trajectory towards the pineal gland, cerebellum, hypothalamus and olfactory bulb. In addition, the OMT analysis also revealed some interesting previously unnoticed behaviors regarding CSF transport involving parenchymal streamlines moving from ventral reservoirs towards the surface of the brain, olfactory bulb and large central veins. Copyright © 2017. Published by Elsevier Inc.

  10. Predicting Coarse Sediment Transport from Patchy Beds in Ephemeral Channels

    Science.gov (United States)

    2012-04-01

    basin fill of Plio-Pleistocene plutonic or volcanic clasts approaching 900 m in thickness. Surficial ERDC/GSL TR-12-17 7 sediments were likely...flow velocity, D84 is grain size in which 84% of the channel bed grains are finer. The variable a is a channel shape factor defined as h R a D

  11. Influence of turbulence on bed load sediment transport

    DEFF Research Database (Denmark)

    Sumer, B. Mutlu; Chua, L.; Cheng, N. S.

    2003-01-01

    -bed experiments and the ripple-covered-bed experiments. In the former case, the flow in the presence of the turbulence generator was adjusted so that the mean bed shear stress was the same as in the case without the turbulence generator in order to single out the effect of the external turbulence on the sediment...

  12. Mechanics of flow and sediment transport in delta distributary channels

    Science.gov (United States)

    Nelson, Jonathan M.; Kinzel, Paul J.; Duc Toan, Duong; Shimizu, Yasuyuki; McDonald, Richard R.

    2011-01-01

    Predicting the planform and dimensions of a channel downstream from a confluence of two smaller channels with known sediment and water supplies is a fundamental, well-studied problem in geomorphology and engineering. An analogous but less well understood problem is found

  13. Influence of basin connectivity on sediment source, transport, and storage within the Mkabela Basin, South Africa

    Directory of Open Access Journals (Sweden)

    J. R. Miller

    2013-02-01

    Full Text Available The management of sediment and other non-point source (NPS pollution has proven difficult, and requires a sound understanding of particle movement through the drainage system. The primary objective of this investigation was to obtain an understanding of NPS sediment source(s, transport, and storage within the Mkabela Basin, a representative agricultural catchment within the KwaZulu–Natal Midlands of eastern South Africa, by combining geomorphic, hydrologic and geochemical fingerprinting analyses.

    The Mkabela Basin can be subdivided into three distinct subcatchments that differ in their ability to transport and store sediment along the axial valley. Headwater (upper catchment areas are characterized by extensive wetlands that act as significant sediment sinks. Mid-catchment areas, characterized by higher relief and valley gradients, exhibit few wetlands, but rather are dominated by a combination of alluvial and bedrock channels that are conducive to sediment transport. The lower catchment exhibits a low-gradient alluvial channel that is boarded by extensive riparian wetlands that accumulate large quantities of sediment (and NPS pollutants.

    Fingerprinting studies suggest that silt- and clay-rich layers found within wetland and reservoir deposits of the upper and upper-mid subcatchments are derived from the erosion of fine-grained, valley bottom soils frequently utilized as vegetable fields. Coarser-grained deposits within these wetlands and reservoirs result from the erosion of sandier hillslope soils extensively utilized for sugar cane, during relatively high magnitude runoff events that are capable of transporting sand-sized sediment off the slopes. Thus, the source of sediment to the axial valley varies as a function of sediment size and runoff magnitude. Sediment export from upper to lower catchment areas was limited until the early 1990s, in part because the upper catchment wetlands were hydrologically disconnected from

  14. Monitoring suspended sediment transport in an ice-affected river using acoustic Doppler current profilers

    Science.gov (United States)

    Moore, S. A.; Ghareh Aghaji Zare, S.; Rennie, C. D.; Ahmari, H.; Seidou, O.

    2013-12-01

    Quantifying sediment budgets and understanding the processes which control fluvial sediment transport is paramount to monitoring river geomorphology and ecological habitat. In regions that are subject to freezing there is the added complexity of ice. River ice processes impact flow distribution, water stage and sediment transport. Ice processes typically have the largest impact on sediment transport and channel morphodynamics when ice jams occur during ice cover formation and breakup. Ice jams may restrict flow and cause local acceleration when released. Additionally, ice can mechanically scour river bed and banks. Under-ice sediment transport measurements are lacking due to obvious safety and logistical reasons, in addition to a lack of adequate measurement techniques. Since some rivers can be covered in ice during six months of the year, the lack of data in winter months leads to large uncertainty in annual sediment load calculations. To address this problem, acoustic profilers are being used to monitor flow velocity, suspended sediment and ice processes in the Lower Nelson River, Manitoba, Canada. Acoustic profilers are ideal for under-ice sediment flux measurements since they can be operated autonomously and continuously, they do not disturb the flow in the zone of measurement and acoustic backscatter can be related to sediment size and concentration. In March 2012 two upward-facing profilers (1200 kHz acoustic Doppler current profiler, 546 KHz acoustic backscatter profiler) were installed through a hole in the ice on the Nelson River, 50 km downstream of the Limestone Generating Station. Data were recorded for four months, including both stable cover and breakup periods. This paper presents suspended sediment fluxes calculated from the acoustic measurements. Velocity data were used to infer the vertical distribution of sediment sizes and concentrations; this information was then used in the interpretation of the backscattered intensity data. It was found that

  15. Erosion and Sediment Transport Modelling in Shallow Waters: A Review on Approaches, Models and Applications.

    Science.gov (United States)

    Hajigholizadeh, Mohammad; Melesse, Assefa M; Fuentes, Hector R

    2018-03-14

    The erosion and sediment transport processes in shallow waters, which are discussed in this paper, begin when water droplets hit the soil surface. The transport mechanism caused by the consequent rainfall-runoff process determines the amount of generated sediment that can be transferred downslope. Many significant studies and models are performed to investigate these processes, which differ in terms of their effecting factors, approaches, inputs and outputs, model structure and the manner that these processes represent. This paper attempts to review the related literature concerning sediment transport modelling in shallow waters. A classification based on the representational processes of the soil erosion and sediment transport models (empirical, conceptual, physical and hybrid) is adopted, and the commonly-used models and their characteristics are listed. This review is expected to be of interest to researchers and soil and water conservation managers who are working on erosion and sediment transport phenomena in shallow waters. The paper format should be helpful for practitioners to identify and generally characterize the types of available models, their strengths and their basic scope of applicability.

  16. Erosion and Sediment Transport Modelling in Shallow Waters: A Review on Approaches, Models and Applications

    Science.gov (United States)

    Fuentes, Hector R.

    2018-01-01

    The erosion and sediment transport processes in shallow waters, which are discussed in this paper, begin when water droplets hit the soil surface. The transport mechanism caused by the consequent rainfall-runoff process determines the amount of generated sediment that can be transferred downslope. Many significant studies and models are performed to investigate these processes, which differ in terms of their effecting factors, approaches, inputs and outputs, model structure and the manner that these processes represent. This paper attempts to review the related literature concerning sediment transport modelling in shallow waters. A classification based on the representational processes of the soil erosion and sediment transport models (empirical, conceptual, physical and hybrid) is adopted, and the commonly-used models and their characteristics are listed. This review is expected to be of interest to researchers and soil and water conservation managers who are working on erosion and sediment transport phenomena in shallow waters. The paper format should be helpful for practitioners to identify and generally characterize the types of available models, their strengths and their basic scope of applicability. PMID:29538335

  17. Pesticide transport to tile-drained fields in SWAT model – macropore flow and sediment

    DEFF Research Database (Denmark)

    Lu, Shenglan; Trolle, Dennis; Blicher-Mathiesen, Gitte

    2015-01-01

    Tool (SWAT) to simulate transport of both mobile (e.g. Bentazon) and strongly sorbed (e.g. Diuron) pesticides in tile drains. Macropore flow is initiated when soil water content exceeds a threshold and rainfall intensity exceeds infiltration capacity. The amount of macropore flow is calculated...... as a fraction of effective rainfall and transported to the tile drains directly. Macropore sediment transport is calculated similarly to the MACRO model (Jarvis et al., 1999). Mobile pesticide transport is calculated with a decay function with the flow, whereas sorbed pesticides transport is associated...

  18. Sediment processes and mercury transport in a frozen freshwater fluvial lake (Lake St. Louis, QC, Canada).

    Science.gov (United States)

    Canário, João; Poissant, Laurier; O'Driscoll, Nelson; Vale, Carlos; Pilote, Martin; Lean, David

    2009-04-01

    An open-bottom and a closed-bottom mesocosm were developed to investigate the release of mercury from sediments to the water column in a frozen freshwater lake. The mesoscosms were deployed in a hole in the ice and particulate mercury (Hg(P)) and total dissolved mercury (TDHg) were measured in sediments and in water column vertical profiles. In addition, dissolved gaseous mercury (DGM) in water and mercury water/airflux were quantified. Concentrations of TDHg, DGM, and mercury flux were all higher in the open-bottom mesocosm than in the closed-bottom mesocosm. In this paper we focus on the molecular diffusion of mercury from the sediment in comparison with the TDHg accumulation in the water column. We conclude that the molecular diffusion and sediment resuspension play a minor role in mercury release from sediments suggesting that solute release during ebullition is an important transport process for mercury in the lake.

  19. Sediment transport and deposition on a river-dominated tidal flat: An idealized model study

    Science.gov (United States)

    Sherwood, Christopher R.; Chen, Shih-Nan; Geyer, W. Rockwell; Ralston, David K.

    2010-01-01

    A 3-D hydrodynamic model is used to investigate how different size classes of river-derived sediment are transported, exported and trapped on an idealized, river-dominated tidal flat. The model is composed of a river channel flanked by sloping tidal flats, a configuration motivated by the intertidal region of the Skagit River mouth in Washington State, United States. It is forced by mixed tides and a pulse of freshwater and sediment with various settling velocities. In this system, the river not only influences stratification but also contributes a significant cross-shore transport. As a result, the bottom stress is strongly ebb-dominated in the channel because of the seaward advance of strong river flow as the tidal flats drain during ebbs. Sediment deposition patterns and mass budgets are sensitive to settling velocity. The lateral sediment spreading scales with an advective distance (settling time multiplied by lateral flow speed), thereby confining the fast settling sediment classes in the channel. Residual sediment transport is landward on the flats, because of settling lag, but is strongly seaward in the channel. The seaward transport mainly occurs during big ebbs and is controlled by a length scale ratio Ld/XWL, where Ld is a cross-shore advective distance (settling time multiplied by river outlet velocity), and XWL is the immersed cross-shore length of the intertidal zone. Sediment trapping requires Ld/XWL stratification and reducing tidal range both favor sediment trapping, whereas varying channel geometries and asymmetry of tides has relatively small impacts. Implications of the modeling results on the south Skagit intertidal region are discussed.

  20. Managing erosion, sediment transport and water quality in drained peatland catchments

    OpenAIRE

    Marttila, H. (Hannu)

    2011-01-01

    Abstract Peatland drainage changes catchment conditions and increases the transport of suspended solids (SS) and nutrients. New knowledge and management methods are needed to reduce SS loading from these areas. This thesis examines sediment delivery and erosion processes in a number of peatland drainage areas and catchments in order to determine the effects of drainage on sediment and erosion dynamics and mechanics. Results from studies performed in peat mining, peatland forestry and distu...

  1. Flow and sediment transport induced by a plunging solitary wave

    DEFF Research Database (Denmark)

    Sumer, B. Mutlu; Sen, M.Berke; Karagali, Ioanna

    2011-01-01

    affected, by as much as a factor of 2, in the runup and hydraulic jump stages. The pore-water pressure measurements showed that the sediment at (or near) the surface of the bed experiences upward-directed pressure gradient forces during the downrush phase. The magnitude of this force can reach values......Two parallel experiments involving the evolution and runup of plunging solitary waves on a sloping bed were conducted: (1) a rigid-bed experiment, allowing direct (hot film) measurements of bed shear stresses, and (2) a sediment-bed experiment, allowing for the measurement of pore-water pressures...... is explained qualitatively in terms of the measured bed shear stress and the pressure gradient forces....

  2. Temporal dynamics of suspended sediment transport in a glacierized Andean basin

    Science.gov (United States)

    Mao, Luca; Carrillo, Ricardo

    2017-06-01

    Suspended sediment transport can affect water quality and aquatic ecosystems, and its quantification is of the highest importance for river and watershed management. Suspended sediment concentration (SSC) and discharge were measured at two locations in the Estero Morales, a Chilean Andean stream draining a small basin (27 km2) hosting glacierized areas of about 1.8 km2. Approximately half of the suspended sediment yield (470 t year- 1 km- 2) was transported during the snowmelt period and half during glacier melting. The hysteresis patterns between discharge and SSC were calculated for each daily hydrograph and were analysed to shed light on the location and activity of different sediment sources at the basin scale. During snowmelt, an unlimited supply of fine sediments is provided in the lower and middle part of the basin and hysteresis patterns tend to be clockwise as the peaks in SSC precede the peak of discharge in daily hydrographs. Instead, during glacier melting the source of fine sediments is the proglacial area, producing counterclockwise hysteresis. It is suggested that the analysis of hysteretic patterns over time provides a simple concept for interpreting variability of location and activity of sediment sources at the basin scale.

  3. Transport of Gas and Solutes in Permeable Estuarine Sediments

    Science.gov (United States)

    2010-09-30

    the orientation of the core. − Mapping of the spatial and temporal distribution of high sedimentary photosynthetic production and oxygen...used to map areas of benthic photosynthetic oxygen production . − Determination of gas content, distribution and migration in the surface sediment...generated by microalgae in the surface layer of submerged sand can be detected non-invasively with our acoustic method. The working hypothesis was that our

  4. Sensitivity and uncertainty analysis of the PATHWAY radionuclide transport model

    International Nuclear Information System (INIS)

    Otis, M.D.

    1983-01-01

    Procedures were developed for the uncertainty and sensitivity analysis of a dynamic model of radionuclide transport through human food chains. Uncertainty in model predictions was estimated by propagation of parameter uncertainties using a Monte Carlo simulation technique. Sensitivity of model predictions to individual parameters was investigated using the partial correlation coefficient of each parameter with model output. Random values produced for the uncertainty analysis were used in the correlation analysis for sensitivity. These procedures were applied to the PATHWAY model which predicts concentrations of radionuclides in foods grown in Nevada and Utah and exposed to fallout during the period of atmospheric nuclear weapons testing in Nevada. Concentrations and time-integrated concentrations of iodine-131, cesium-136, and cesium-137 in milk and other foods were investigated. 9 figs., 13 tabs

  5. Regional Sediment Management (RSM) Modeling Tools: Integration of Advanced Sediment Transport Tools into HEC-RAS

    Science.gov (United States)

    2014-06-01

    channels using this function is depicted in Figure 5. Sluicing and dam removal features. Classical bed change assumptions (i.e., the veneer method where...are encouraged to contact the authors. REGIONAL SEDIMENT MANAGEMENT IMPLICATIONS: As USACE considers aging infrastructure, climate change, limited

  6. RANS-based simulation of turbulent wave boundary layer and sheet-flow sediment transport processes

    DEFF Research Database (Denmark)

    Fuhrman, David R.; Schløer, Signe; Sterner, Johanna

    2013-01-01

    with bed and suspended load descriptions, the latter based on an unsteady turbulent-diffusion equation, for simulation of sheet-flow sediment transport processes. In addition to standard features common within such RANS-based approaches, the present model includes: (1) hindered settling velocities at high...... of a number of local factors important within cross-shore wave boundary layer and sediment transport dynamics. The hydrodynamic model is validated for both hydraulically smooth and rough conditions, based on wave friction factor diagrams and boundary layer streaming profiles, with the results in excellent...... agreement with experimental and/or previous numerical work. The sediment transport model is likewise validated against oscillatory tunnel experiments involving both velocity-skewed and acceleration-skewed flows, as well as against measurements beneath real progressive waves.Model capabilities are exploited...

  7. Analysis of diffusion ion transport in ocean sediments: subseafloor disposal of radioactive waste

    International Nuclear Information System (INIS)

    Nuttall, H.E.; Ray, A.K.; Davis, E.J.

    1981-01-01

    Diffusion-controlled transport of radioactive ions through seabed sediments is analyzed to determine the rates of transport between a buried canister releasing radioactive waste and the ocean floor. The general solution of the unsteady-state diffusion problem is obtained for an arbitrary release rate from the canister, and analytical solutions are obtained for two special cases: 1. instantaneous release of the ionic species; and 2. a constant discharge rate. The former case for a material with an infinite half-life represents the worst case condition. The analytical expressions for the ion concentration distributions, ionic flux to the ocean floor, total release rate to the ocean floor, and bio-loading show that the sediment thickness, canister depth, effective diffusivity, and ion half-life affect the transport rates, but the rates are insensitive to sediment porosity and bulk density over the narrow ranges in which they might be expected to vary

  8. Experiment on temporal variation of bed load transport in response to changes in sediment supply in streams

    Science.gov (United States)

    Elgueta-Astaburuaga, Maria A.; Hassan, Marwan A.

    2017-01-01

    A flume experiment was conducted to study channel adjustment to episodic sediment supply in mountain streams. The bulk sediment used for the bed and feed included grain sizes 0.5-64 mm with geometric mean Dg>(bulk>) of 5.7 mm. Water discharge was held constant for 40 h, and 300 kg of sediment was supplied through a range of scenarios. Bed slope, sediment storage, sediment transport, and bed surface texture responded to sediment supply. During the first of seven runs, bed slope decreased from 0.022 m/m (flume slope) to 0.018 m/m due to sediment starvation. Bed slope increased beginning in the second run as the bed aggraded due to preferential storage of grains >8 mm. Transport rate and bed-surface particle size were significantly affected by magnitude-frequency of sediment feed. Under constant feed, transport rate increased gradually and Dg >(surface>) ranged between 12 and 15 mm. Instead, sediment pulses caused a pronounced increase in sediment transport rate and surface fining, trends that were inverted as sediment evacuated. At the run scale, sediment transport and storage behaved as with constant feed if pulse relaxation time exceeded time between pulses. The increase in transport rate and surface fining were proportional to pulse size. After the 300 kg pulse, transport rate reached 100 g m-1 s-1 and Dg >(surface>) was g >(surface>) was >12 mm. Textural differences on the initial bed surface influenced the patterns of sediment transport. Channel adjustment was controlled by magnitude-frequency of sediment feed and not by total feed.

  9. Granulometric characterization of sediments transported by surface runoff generated by moving storms

    Directory of Open Access Journals (Sweden)

    J. L. M. P. de Lima

    2008-12-01

    Full Text Available Due to the combined effect of wind and rain, the importance of storm movement to surface flow has long been recognized, at scales ranging from headwater scales to large basins. This study presents the results of laboratory experiments designed to investigate the influence of moving rainfall storms on the dynamics of sediment transport by surface runoff. Experiments were carried out, using a rain simulator and a soil flume. The movement of rainfall was generated by moving the rain simulator at a constant speed in the upstream and downstream directions along the flume. The main objective of the study was to characterize, in laboratory conditions, the distribution of sediment grain-size transported by rainfall-induced overland flow and its temporal evolution. Grain-size distribution of the eroded material is governed by the capacity of flow that transports sediments. Granulometric curves were constructed using conventional hand sieving and a laser diffraction particle size analyser (material below 0.250 mm for overland flow and sediment deliveries collected at the flume outlet. Surface slope was set at 2%, 7% and 14%. Rainstorms were moved with a constant speed, upslope and downslope, along the flume or were kept static. The results of laboratory experiments show that storm movement, affecting the spatial and temporal distribution of rainfall, has a marked influence on the grain-size characteristics of sediments transported by overland flow. The downstream-moving rainfall storms have higher stream power than do other storm types.

  10. The relative contribution of near-bed vs. intragravel horizontal transport to fine sediment accumulation processes in river gravel beds

    Science.gov (United States)

    Casas-Mulet, Roser; Lakhanpal, Garima; Stewardson, Michael J.

    2018-02-01

    Understanding flow-sediment interactions is important for comprehending river functioning. Fine sediment accumulation processes, in particular, have key implications for ecosystem health. However, the amount of fines generated by intragravel flows and later accumulated in gravel streambeds may have been underestimated, as the hydraulic-related driving transport mechanisms in play are not clearly identified. Specifically, the relative contribution of fines from upper vs. lower sediment layers in gravel beds is not well understood. By recreating flooded and dewatered conditions in an experimental flume filled with natural sediment, we estimated such contributions by observing and collecting intragravel transported fines that were later accumulated into a void in the middle of the sediment matrix. Near-bed transport in the upper sediment layers (named Brinkman load) during flooded conditions accounted for most (90%) of the accumulated fines. Intragravel transport in the lower sediment layers (named Interstitial load) was the sole source of transport and accumulation during dewatered conditions with steeper hydraulic gradients. Interstitial load accounted for 10% of the total transport during flooded conditions. Although small, such estimations demonstrate that hydraulic-gradient transport in the lower sediment layers occurs in spite of the contradicting analytical assessments. We provide a case study to challenge the traditional approaches of assessing intragravel transport, and a useful framework to understand the origin and relative contribution of fine sediment accumulation in gravel beds. Such knowledge will be highly useful for the design of monitoring programs aiding river management, particularly in regulated rivers.

  11. Transport and Sources of Suspended Sediment in the Mill Creek Watershed, Johnson County, Northeast Kansas, 2006-07

    Science.gov (United States)

    Lee, Casey J.; Rasmussen, Patrick P.; Ziegler, Andrew C.; Fuller, Christopher C.

    2009-01-01

    The U.S. Geological Survey, in cooperation with the Johnson County Stormwater Management Program, evaluated suspended-sediment transport and sources in the urbanizing, 57.4 mi2 Mill Creek watershed from February 2006 through June 2007. Sediment transport and sources were assessed spatially by continuous monitoring of streamflow and turbidity as well as sampling of suspended sediment at nine sites in the watershed. Within Mill Creek subwatersheds (2.8-16.9 mi2), sediment loads at sites downstream from increased construction activity were substantially larger (per unit area) than those at sites downstream from mature urban areas or less-developed watersheds. Sediment transport downstream from construction sites primarily was limited by transport capacity (streamflow), whereas availability of sediment supplies primarily influenced transport downstream from mature urban areas. Downstream sampling sites typically had smaller sediment loads (per unit area) than headwater sites, likely because of sediment deposition in larger, less sloping stream channels. Among similarly sized storms, those with increased precipitation intensity transported more sediment at eight of the nine monitoring sites. Storms following periods of increased sediment loading transported less sediment at two of the nine monitoring sites. In addition to monitoring performed in the Mill Creek watershed, sediment loads were computed for the four other largest watersheds (48.6-65.7 mi2) in Johnson County (Blue River, Cedar, Indian, and Kill Creeks) during the study period. In contrast with results from smaller watersheds in Mill Creek, sediment load (per unit area) from the most urbanized watershed in Johnson County (Indian Creek) was more than double that of other large watersheds. Potential sources of this sediment include legacy sediment from earlier urban construction, accelerated stream-channel erosion, or erosion from specific construction sites, such as stream-channel disturbance during bridge

  12. Near-bed observations of high-concentration sediment transport in the Changjiang Estuary

    Science.gov (United States)

    Zhou, Z.; Ge, J.; Ding, P.

    2017-12-01

    The North Passage, the core of turbidity maximum in the Changjiang Estuary, is now under the strong sedimentation due to the abundant sediment supply from the upstream Changjiang River and the river-tide interacted dynamics. Recent studies suggested that strong siltation could be attributed to bottom high-concentration sediment transport, which however is very difficult to be detected and observed by vessel-anchored survey methods. To better understand the mechanisms of sediment transport and deposition in the channel region of the North Passage and its adjacent areas, we conducted continuous field observations which covered spring and neap tide period in the wintertime of 2016, the summertime of 2015 and 2017, focusing on near-bottom sediment transport. Tripods mounted with multiple instruments, including up-looking and down-looking Acoustic Doppler Current Profilers(ADCP), Vector Current Meter(ADV), Optical Backscatter Sensor(OBS), ASM, ALEC and RBR were used to observe the near-bottom physical process and its induced sediment dynamics. Results of these observations clearly described the current-wave-sediment interaction, which produced different patterns of bottom mud suspension at different tripods. Both hydrodynamic features and suspended sediment showed variations between spring and neap tide. Taking data of 2016 as an example, averaged suspended sediment concentration(SSC) at two tripods was 1.52 g/L and 2.13 g/L during the neap tide, 4.51 g/L and 5.75 g/L with the peak value reaching 25 g/L during the spring tide. At the tripod which was closer to the channel region, three peaks of SSC during the spring tide occurred near the flood slack with notable salinity increase, indicating the impact of saltwater intrusion on the bottom hydrodynamics. The results showed the occurrence of high-concentration suspended sediment was probably related to combined effects of bottom salinity intrusion, turbulent kinetic energy(TKE) and local stratification due to density

  13. Working Toward a Common Strategy for U.K. Sediment Transport Research

    Science.gov (United States)

    Souza, Alejandro J.; Bell, Paul S.; Amoudry, Laurent

    2010-02-01

    U.K. Sediment Initiative 2009: Developing Multidisciplinary Sediment Dynamics Research in a Strategic Context;Liverpool, United Kingdom, 27-29 April 2009; A workshop funded by the U.K. Natural Environment Research Council (NERC) brought together U.K.-based researchers, stakeholders, and policy makers with an interest in sediment processes to foster collaborative links and to help NERC theme leaders develop future Theme Action Plans (TAPs). This could be achieved only by identifying gaps in knowledge and prioritizing research needs toward formulating a U.K. sediment transport research strategy. More than 50 participants from NERC research and collaborative centers, U.K. higher education institution researchers, industry consultants, and government departments and agencies attended the workshop. The workshop was divided into three parts. First, in an introduction, guest speakers discussed the importance of sediment transport from different perspectives. The speakers included Darius Campbell (U.K. Department for Environment, Food, and Rural Affairs) on policy drivers, Richard Whitehouse (HR Wallingford, Ltd.) and David Lambkin (ABPMer, Ltd.) on industry needs, John Rees (NERC theme leader) on the NERC TAPs and possible funding opportunities, Alan Davies (University of Bangor) on the academic research perspective, and Chris Sherwood (U.S. Geological Survey) on international insight on large sediment transport projects and on developments of the U.S. National Community Sediment Transport Model project. Second, in a series of breakout sessions, participants considered the stakeholders’ needs, the different dynamic areas of the coastal ocean, and the process time scales. Third, the workshop group discussed possible funding streams and ways to better formulate a concerted research plan for presentation to funding bodies.

  14. Deschutes estuary feasibility study: hydrodynamics and sediment transport modeling

    Science.gov (United States)

    George, Douglas A.; Gelfenbaum, Guy; Lesser, Giles; Stevens, Andrew W.

    2006-01-01

    Continual sediment accumulation in Capitol Lake since the damming of the Deschutes River in 1951 has altered the initial morphology of the basin. As part of the Deschutes River Estuary Feasibility Study (DEFS), the United States Geological Survey (USGS) was tasked to model how tidal and storm processes will influence the river, lake and lower Budd Inlet should estuary restoration occur. Understanding these mechanisms will assist in developing a scientifically sound assessment on the feasibility of restoring the estuary. The goals of the DEFS are as follows. - Increase understanding of the estuary alternative to the same level as managing the lake environment.

  15. Simulating Landscape Sediment Transport Capacity by Using a Modified SWAT Model.

    Science.gov (United States)

    Bonumá, Nadia B; Rossi, Colleen G; Arnold, Jeffrey G; Reichert, José M; Minella, Jean P; Allen, Peter M; Volk, Martin

    2014-01-01

    Sediment delivery from hillslopes to rivers is spatially variable and may lead to long-term delays between initial erosion and related sediment yield at the watershed outlet. Consideration of spatial variability is important for developing sound strategies for water quality improvement and soil protection at the watershed scale. Hence, the Soil and Water Assessment Tool (SWAT) was modified and tested in this study to simulate the landscape transport capacity of sediment. The study area was the steeply sloped Arroio Lino watershed in southern Brazil. Observed sediment yield data at the watershed outlet were used to calibrate and validate a modified SWAT model. For the calibration period, the modified model performed better than the unaltered SWAT2009 version; the models achieved Nash-Sutcliffe efficiency (NSE) values of 0.7 and -0.1, respectively. Nash-Sutcliffe efficiencies were less for the validation period, but the modified model's NSE was higher than the unaltered model (-1.4 and -12.1, respectively). Despite the relatively low NSE values, the results of this first test are promising because the model modifications lowered the percent bias in sediment yield from 73 to 18%. Simulation results for the modified model indicated that approximately 60% of the mobilized soil is deposited along the landscape before it reaches the river channels. This research demonstrates the modified model's ability to simulate sediment yield in watersheds with steep slopes. The results suggest that integration of the sediment deposition routine in SWAT increases accuracy in steeper areas while significantly improving its ability to predict the spatial distribution of sediment deposition areas. Further work is needed regarding (i) improved strategies for spatially distributed sediment transport measurements (for improving process knowledge and model evaluation) and (ii) extensive model tests in other well instrumented experimental watersheds with differing topographic configurations

  16. Sediment Transport on Continental Shelves: Storm Bed Formation and Preservation in Heterogeneous Sediments

    Science.gov (United States)

    2012-01-01

    extends from fair-weather wave base to the beach berm or coastal dune . Observations and modelling studies show that some sand is removed from the...deposit. The top is wave rippled and overlain by fine sediment. (B) Example of hummocky cross stratification (HCS) from the Ferron Sand - stone in Utah...xDept. of Earth Science, Memorial University of Newfoundland, St. Johns, Newfoundland, Canada ABSTRACT Many storm beds are constructed of silt/ sand

  17. Lack of cross-shelf transport of sediments on the western margin of India: Evidence from clay mineralogy

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Nair, R.R.

    transported long distances along the shelf, cross-shelf transport appears to be minimal. Confirmatory evidence of qualitative differences in outer and inner shelf clays is provided by sediment trap clay mineralogy on the outer shelf. Clay bound pollutant...

  18. Estimation of 1 km Grid-based WATEM/SEDEM Sediment Transport Capacity Using 1 Minute Rainfall Data and SWAT Semi-distributed Sediment Transport Capacity Results for Han River Basin of South Korea

    OpenAIRE

    Jung, Chung-Gil; Jang, Won-Jin; Kim, Seongjoon

    2017-01-01

    When assessing the total sediment yield of a watershed through sediment transport from soil erosion process, the ratio of sediment delivery is a critical and uncertain factor during modelling. This study is to estimate watershed scale sediment yield distribution of 1 km by 1 km spatial resolution with the evaluation of RUSLE (Revised Universal Soil Loss Equation) rain erosivity (R factor) for 14 years (2000–2013) using 1 minute data from 16 rainfall gauging stations...

  19. Sediment transport to and from small impoundments in northeast Kansas, March 2009 through September 2011

    Science.gov (United States)

    Foster, Guy M.; Lee, Casey J.; Ziegler, Andrew C.

    2012-01-01

    The U.S. Geological Survey, in cooperation with the Kansas Water Office, investigated sediment transport to and from three small impoundments (average surface area of 0.1 to 0.8 square miles) in northeast Kansas during March 2009 through September 2011. Streamgages and continuous turbidity sensors were operated upstream and downstream from Atchison County, Banner Creek, and Centralia Lakes to study the effect of varied watershed characteristics and agricultural practices on sediment transport in small watersheds in northeast Kansas. Atchison County Lake is located in a predominantly agricultural basin of row crops, with wide riparian buffers along streams, a substantial amount of tile drainage, and numerous small impoundments (less than 0.05 square miles; hereafter referred to as “ponds”). Banner Creek Lake is a predominantly grassland basin with numerous small ponds located in the watershed, and wide riparian buffers along streams. Centralia Lake is a predominantly agricultural basin of row crops with few ponds, few riparian buffers along streams, and minimal tile drainage. Upstream from Atchison County, Banner Creek, and Centralia Lakes 24, 38, and 32 percent, respectively, of the total load was transported during less than 0.1 percent (approximately 0.9 days) of the time. Despite less streamflow in 2011, larger sediment loads during that year indicate that not all storm events transport the same amount of sediment; larger, extreme storms during the spring may transport much larger sediment loads in small Kansas watersheds. Annual sediment yields were 360, 400, and 970 tons per square mile per year at Atchison County, Banner, and Centralia Lake watersheds, respectively, which were less than estimated yields for this area of Kansas (between 2,000 and 5,000 tons per square mile per year). Although Centralia and Atchison County Lakes had similar percentages of agricultural land use, mean annual sediment yields upstream from Centralia Lake were about 2.7 times

  20. Sediment transport patterns and climate change: the downstream Tuul River case study, Northern Mongolia.

    Science.gov (United States)

    Pietroń, Jan; Jarsjö, Jerker

    2014-05-01

    Ongoing changes in the Central Asian climate including increasing temperatures can influence the hydrological regimes of rivers and the waterborne transport of sediments. Changes in the latter, especially in combination with adverse human activities, may severely impact water quality and aquatic ecosystems. However, waterborne transport of sediments is a result of complex processes and varies considerably between, and even within, river systems. There is therefore a need to increase our general knowledge about sediment transport under changing climate conditions. The Tuul River, the case site of this study, is located in the upper part of the basin of the Selenga River that is the main tributary to Lake Baikal, a UNESCO World Heritage Site. Like many other rivers located in the steppes of Northern Mongolia, the Tuul River is characterized by a hydrological regime that is not disturbed by engineered structures such as reservoirs and dams. However, the water quality of the downstream Tuul River is increasingly affected by adverse human activities - including placer gold mining. The largest contribution to the annual river discharge occurs during the relatively warm period in May to August. Typically, there are numerous rainfall events during this period that cause considerable river flow peaks. Parallel work has furthermore shown that due to climate change, the daily variability of discharge and numbers of peak flow events in the Tuul River Basin has increased during the past 60 years. This trend is expected to continue. We here aim at increasing our understanding of future sediment transport patterns in the Tuul River, specifically considering the scenario that peak flow events may become more frequent due to climate change. We use a one-dimensional sediment transport model of the downstream reach of the river to simulate natural patterns of sediment transport for a recent hydrological year. In general, the results show that sediment transport varies considerably

  1. Testing the effects of in-stream sediment sources and sinks on simulated watershed sediment yield using the coupled U.S. Army Corps of Engineers GSSHA Model and SEDLIB Sediment Transport Library

    Science.gov (United States)

    Floyd, I. E.; Downer, C. W.; Brown, G.; Pradhan, N. R.

    2017-12-01

    The Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model is the US Army Corps of Engineers' (USACE)'s only fully coupled overland/in-stream sediment transport model. While the overland sediment transport formulation in GSSHA is considered state of the art, the existing in-stream sediment transport formulation is less robust. A major omission in the formulation of the existing GSSHA in-stream model is the lack of in-stream sources of fine materials. In this effort, we enhanced the in-stream sediment transport capacity of GSSHA by linking GSSHA to the SEDLIB sediment transport library. SEDLIB was developed at the Coastal and Hydraulics Laboratory (CHL) under the System Wide Water Resources Program (SWWRP) and Flood and Coastal (F&C) research program. It is designed to provide a library of sediment flux formulations for hydraulic and hydrologic models, such as GSSHA. This new version of GSSHA, with the updated in-stream sediment transport simulation capability afforded by the linkage to SEDLIB, was tested in against observations in an experimental watershed that had previously been used as a test bed for GSSHA. The results show a significant improvement in the ability to model in-stream sources of fine sediment. This improved capability will broaden the applicability of GSSHA to larger watersheds and watersheds with complex sediment dynamics, such as those subjected to fire hydrology.

  2. 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.

  3. Design of a fuzzy differential evolution algorithm to predict non-deposition sediment transport

    Science.gov (United States)

    Ebtehaj, Isa; Bonakdari, Hossein

    2017-12-01

    Since the flow entering a sewer contains solid matter, deposition at the bottom of the channel is inevitable. It is difficult to understand the complex, three-dimensional mechanism of sediment transport in sewer pipelines. Therefore, a method to estimate the limiting velocity is necessary for optimal designs. Due to the inability of gradient-based algorithms to train Adaptive Neuro-Fuzzy Inference Systems (ANFIS) for non-deposition sediment transport prediction, a new hybrid ANFIS method based on a differential evolutionary algorithm (ANFIS-DE) is developed. The training and testing performance of ANFIS-DE is evaluated using a wide range of dimensionless parameters gathered from the literature. The input combination used to estimate the densimetric Froude number ( Fr) parameters includes the volumetric sediment concentration ( C V ), ratio of median particle diameter to hydraulic radius ( d/R), ratio of median particle diameter to pipe diameter ( d/D) and overall friction factor of sediment ( λ s ). The testing results are compared with the ANFIS model and regression-based equation results. The ANFIS-DE technique predicted sediment transport at limit of deposition with lower root mean square error (RMSE = 0.323) and mean absolute percentage of error (MAPE = 0.065) and higher accuracy ( R 2 = 0.965) than the ANFIS model and regression-based equations.

  4. Technetium-99m: From nuclear medicine applications to fine sediment transport studies

    Directory of Open Access Journals (Sweden)

    Bandeira Jefferson V.

    2017-12-01

    Full Text Available The present work is a contribution to rescue the history of development of the application of 99mTc, widely used in nuclear medicine, to its use as tracer for the study of the transport of fine sediment in suspension, in water environment. It addresses the usefulness of its application in obtaining important parameters in environmental studies, illustrating them with some applications already performed and the results obtained. This kind of study, when associated with information on hydrodynamic parameters, for example, river, tidal, wind and wave currents, are powerful tools for the understanding and quantification of fine sediment transport in suspension. Fine sediment is an important vector in the transportation of heavy metals, organic matter and nutrients in water environment, and the quantitative knowledge of its behaviour is mandatory for studies of environmental impacts. Fine sediment labelled with 99mTc, can also be used to study the effect of human interventions, such as dredging of reservoirs, access channels and harbours, and the dumping of dredged materials in water bodies. Besides that, it can be used to optimize dredging works, evaluating the technical and economic feasibility of dumping sites and their environmental impact. It is a valuable support in the calibration and validation of mathematical models for sediment dynamics.

  5. Numerical Modelling of Suspended Transport and Deposition of Highway Deposited Sediments

    DEFF Research Database (Denmark)

    Bentzen, Thomas Ruby; Larsen, Torben; Bach, Christine

    Good data for calibration and validation of numerical models are of high importance. In the natural environment data can be hard to archive and the stochastic nature have governing influence on the data archived. Hence for modelling of suspended transport and deposition of particles, originating...... from the highway surfaces, in highway detention ponds, four experiments are carried out. To simplify the complexity of a real pond and for easy control and measurement the sediment transports where carried out in two rectangular channels....

  6. Modelling the transport of sediments and plutonium from the Mururoa lagoon

    International Nuclear Information System (INIS)

    Rajar, R.; Zagar, D.

    1999-01-01

    The paper deals with the three-dimensional simulation of resuspension and transport of sediments from the Mururoa lagoon into the Pacific Ocean. These sediments were contaminated mainly by plutonium during French nuclear tests (from 1966 to 1996). Two cases were simulated: 'Normal conditions', taking into account permanent action of trade winds and tides and 'storm conditions', where the effect of a tropical cyclone with maximum wind velocity of 150 km/h and with a frequency of 1 storm per 10 years is simulated. The final results show, that the normal conditions cause an annual outflow of 8 x 10 4 tons of sediment and 8 GBq of plutonium, while one tropical cyclone would cause outflow of 3.9 x 10 6 tons of sediment and about 0.7 TBq of plutonium. (author)

  7. Sediment Transport and Slope Stability of Ship Shoal Borrow Areas for Coastal Restoration of Louisiana

    Science.gov (United States)

    Liu, H.; Xu, K.; Bentley, S. J.; Li, C.; Miner, M. D.; Wilson, C.; Xue, Z.

    2017-12-01

    Sandy barrier islands along Louisiana coast are degrading rapidly due to both natural and anthropogenic factors. Ship Shoal is one of the largest offshore sand resources, and has been used as a borrow area for Caminada Headland Restoration Project. Our knowledge of sediment transport and infilling processes in this new sandy and dynamic borrow area is rather limited. High resolution sub-bottom seismic data, side scan sonar images, multi-beam bathymetry and laser sediment grain size data were used to study seafloor morphological evolution and pit wall stability in response to both physical and geological processes. The multi-beam bathymetry and seismic profiling inside the pit showed that disequilibrium conditions led to rapid infilling in the pits at the beginning, but this process slowed down after the pit slope became stable and topography became smooth. We hypothesize that the erosion of the adjacent seabed sediment by energetic waves and longshore currents, the supply of suspended sediment from the rivers, and the erodible materials produced by local mass wasting on pit walls are three main types of infilling sediments. Compared with mud-capped dredge pits, this sandy dredge pit seems to have more gentle slopes on pit walls, which might be controlled by the angle of repose. Infilling sediment seems to be dominantly sandy, with some mud patches on bathymetric depressions. This study helps us better understand the impacts of mining sediment for coastal restoration and improves sand resource management efforts.

  8. Sediment transport in the lower Snake and Clearwater River Basins, Idaho and Washington, 2008–11

    Science.gov (United States)

    Clark, Gregory M.; Fosness, Ryan L.; Wood, Molly S.

    2013-01-01

    Sedimentation is an ongoing maintenance problem for reservoirs, limiting reservoir storage capacity and navigation. Because Lower Granite Reservoir in Washington is the most upstream of the four U.S. Army Corps of Engineers reservoirs on the lower Snake River, it receives and retains the largest amount of sediment. In 2008, in cooperation with the U.S. Army Corps of Engineers, the U.S. Geological Survey began a study to quantify sediment transport to Lower Granite Reservoir. Samples of suspended sediment and bedload were collected from streamgaging stations on the Snake River near Anatone, Washington, and the Clearwater River at Spalding, Idaho. Both streamgages were equipped with an acoustic Doppler velocity meter to evaluate the efficacy of acoustic backscatter for estimating suspended-sediment concentrations and transport. In 2009, sediment sampling was extended to 10 additional locations in tributary watersheds to help identify the dominant source areas for sediment delivery to Lower Granite Reservoir. Suspended-sediment samples were collected 9–15 times per year at each location to encompass a range of streamflow conditions and to capture significant hydrologic events such as peak snowmelt runoff and rain-on-snow. Bedload samples were collected at a subset of stations where the stream conditions were conducive for sampling, and when streamflow was sufficiently high for bedload transport. At most sampling locations, the concentration of suspended sediment varied by 3–5 orders of magnitude with concentrations directly correlated to streamflow. The largest median concentrations of suspended sediment (100 and 94 mg/L) were in samples collected from stations on the Palouse River at Hooper, Washington, and the Salmon River at White Bird, Idaho, respectively. The smallest median concentrations were in samples collected from the Selway River near Lowell, Idaho (11 mg/L), the Lochsa River near Lowell, Idaho (11 mg/L), the Clearwater River at Orofino, Idaho (13 mg

  9. Currents, drag, and sediment transport induced by a tsunami

    Science.gov (United States)

    Lacy, Jessica R.; Rubin, David M.; Buscombe, Daniel

    2012-01-01

    We report observations of water surface elevation, currents, and suspended sediment concentration (SSC) from a 10-m deep site on the inner shelf in northern Monterey Bay during the arrival of the 2010 Chile tsunami. Velocity profiles were measured from 3.5 m above the bed (mab) to the surface at 2 min intervals, and from 0.1 to 0.7 mab at 1 Hz. SSC was determined from the acoustic backscatter of the near-bed profiler. The initial tsunami waves were directed cross shore and had a period of approximately 16 min. Maximum wave height was 1.1 m, and maximum current speed was 0.36 m/s. During the strongest onrush, near-bed velocities were clearly influenced by friction and a logarithmic boundary layer developed, extending more than 0.3 mab. We estimated friction velocity and bed shear stress from the logarithmic profiles. The logarithmic structure indicates that the flow can be characterized as quasi-steady at these times. At other phases of the tsunami waves, the magnitude of the acceleration term was significant in the near-bed momentum equation, indicating unsteady flow. The maximum tsunami-induced bed shear stress (0.4 N/m2) exceeded the critical shear stress for the medium-grained sand on the seafloor. Cross-shore sediment flux was enhanced by the tsunami. Oscillations of water surface elevation and currents continued for several days. The oscillations were dominated by resonant frequencies, the most energetic of which was the fundamental longitudinal frequency of Monterey Bay. The maximum current speed (hourly-timescale) in 18 months of observations occurred four hours after the tsunami arrived.

  10. State-of-the-art in modeling solute and sediment transport in rivers

    International Nuclear Information System (INIS)

    Sayre, W.W.

    1980-01-01

    This overview is structured around a comprehensive general model based on the conservation of mass principle as applied to dissolved and particulate constituents in rivers, with a few restricted but more specific examples that illustrate the state-of-the-art in modeling typical physical, chemical, and biological processes undergone by selected constituents in rivers. These examples include: simplified one- and two-dimensional formulations focusing on the hydrodynamic advection and dispersion mechanisms; a two-dimensional biochemial oxygen demand-dissolved oxygen model; a one-dimensional polychlorinated biphenyl model that includes uptake and release of constituent by suspended sediment, and deposition and erosion of contaminated particles; and a one-dimensional sediment transport model that accounts for interactions between the flow and the bed, and is capable of tracking dispersing slugs of sediment through cycles of erosion, entrainment, transport in suspension and as bed load, and burial and storage in the bed

  11. The mountain-lowland debate: deforestation and sediment transport in the upper Ganga catchment.

    Science.gov (United States)

    Wasson, R J; Juyal, N; Jaiswal, M; McCulloch, M; Sarin, M M; Jain, V; Srivastava, P; Singhvi, A K

    2008-07-01

    The Himalaya-Gangetic Plain region is the iconic example of the debate about the impact on lowlands of upland land-use change. Some of the scientific aspects of this debate are revisited by using new techniques to examine the role of deforestation in erosion and river sediment transport. The approach is whole-of-catchment, combining a history of deforestation with a history of sediment sources from well before deforestation. It is shown that deforestation had some effect on one very large erosional event in 1970, in the Alaknanda subcatchment of the Upper Ganga catchment, but that both deforestation and its effects on erosion and sediment transport are far from uniform in the Himalaya. Large magnitude erosional events occur for purely natural reasons. The impact on the Gangetic Plain of erosion caused by natural events and land cover change remains uncertain.

  12. Transport of pollutants and sediment in the area of the Wave Hub (Celtic Sea)

    Science.gov (United States)

    Shapiro, Georgy; Huntley, David

    2010-05-01

    consequences. This paper presents some preliminary modelling results of a baseline study focussed on hind-cast and now-cast simulation of the 3D structure of temperature, salinity and current velocity in the area immediately adjacent to the location of the Wave Hub. Of the range of available 3D numerical models for shelf sea hydrodynamics, we have selected the Proudman Oceanographic Laboratory Coastal Modelling System (POLCOMS). The POLCOMS has successfully been used in a number of coastal/shelf sea regions to simulate circulation of coastal waters. Modelling is carried out in the region of approximately 200x 200 km with the variable vertical resolution typically less than 2 m. Such parameters allow resololution of the formation of coastal density fronts both within and outside the wave shadow zone, expected to be of the order of tens of kilometres. The meteorological parameters are obtained from the publicly available NCEP re-analyses data base. These parameters include components of the wind velocity and the surface heat fluxes, air pressure at sea level; temperature and humidity in the low troposphere; precipitation and cloudiness. In this study, the transport of pollution is simulated by a number of passive drifters located at a certain depth at a number of locations including the central point of the Wave Hub. Sediment transport is modelled using the Engelund-Hansen algorithm taking the current velocities produced by the POLCOMS as an input parameter. The Celtic sea is a tidally dominated region, and the modelling is run both in full-forcing and in tide-only modes in order to assess effects of density fronts on the residual (tidally averaged) circulation pattern. The results show that the pollution pathways are very sensitive to the formation of temperature fronts. In some cases the passive traces move in nearly opposite directions when the effect of temperature fronts is disregarded. Sediment transport is highly non-uniform spatially with some four areas along the

  13. Sediment transport analysis at event scale in a semi-arid basin of Southern-Italy

    Science.gov (United States)

    Bisantino, T.; Gentile, F.; Milillo, F.; Romano, G.; Trisorio Liuzzi, G.

    2009-04-01

    Erosion at basin scale is a main issue in nowadays research since it plays a role of first level in sustainable management of natural resources (land and water). In particular, in arid and semi-arid regions natural vegetative cover is sparse and runoff events cause high rates of sediment transport, while long periods of drought can be observed. Several types of erosion phenomena affect the torrents in the north-western area of the Puglia Region (Southern-Italy) where flood events are characterised by a considerable amount of suspended solids. In this area the solid load was monitored until 1989 by the National Hydrographic Service using manual sampling. To accurately estimate the sediment transport during flood events and in order to improve the methodologies to assess and predict soil erosion, a watershed representative of the area (Carapelle torrent) was selected, where an experimental station was set up for the continuous measuring of suspended solids. The station is equipped with a dual function infrared sensor (turbidity/suspended solids), a remote data acquisition system, an electromechanical and an ultrasound stage meter. A laboratory test of the turbidity sensor was preliminary performed to evaluate the dual functionality of the instrument (turbidity and suspended sediment concentration) in relation to the variations of sediment concentration and grain size distribution. Successively a field calibration was carried out to determine the relationship between optical and gravimetric data and to check the housing device. Afterwards, the high temporal resolution data collected over a 3-years period (2007-2009) were used to analyze the sediment transport dynamics. The aim of the study is to investigate the relationships in unsteady flows between the sediment concentration and the discharge, and to analyze the relationships at event scale between the sediment budget and some hydrological variables, in order to select the model that best represents the local

  14. Modeling of soil erosion and sediment transport in the East River Basin in southern China

    Science.gov (United States)

    Wu, Yping; Chen, Ji

    2012-01-01

    Soil erosion is a major global environmental problem that has caused many issues involving land degradation, sedimentation of waterways, ecological degradation, and nonpoint source pollution. Therefore, it is significant to understand the processes of soil erosion and sediment transport along rivers, and this can help identify the erosion prone areas and find potential measures to alleviate the environmental effects. In this study, we investigated soil erosion and identified the most seriously eroded areas in the East River Basin in southern China using a physically-based model, Soil and Water Assessment Tool (SWAT). We also introduced a classical sediment transport method (Zhang) into SWAT and compared it with the built-in Bagnold method in simulating sediment transport process along the river. The derived spatial soil erosion map and land use based erosion levels can explicitly illustrate the identification and prioritization of the critical soil erosion areas in this basin. Our results also indicate that erosion is quite sensitive to soil properties and slope. Comparison of Bagnold and Zhang methods shows that the latter can give an overall better performance especially in tracking the peak and low sediment concentrations along the river. We also found that the East River is mainly characterized by sediment deposition in most of the segments and at most times of a year. Overall, the results presented in this paper can provide decision support for watershed managers about where the best management practices (conservation measures) can be implemented effectively and at low cost. The methods we used in this study can also be of interest in sediment modeling for other basins worldwide.

  15. Medical radioisotopes in the environment - following the pathway from patient to river sediment.

    Science.gov (United States)

    Fischer, Helmut W; Ulbrich, Susanne; Pittauerová, Daniela; Hettwig, Bernd

    2009-12-01

    Motivated by the detection of (131)I in river sediment in routine long-term surveillance samples, a systematic short-term study of the wastewater treatment chain was planned and conducted. Inflow, effluent and primary sludge were collected on a daily basis during two weeks at a regional wastewater treatment plant. Samples were investigated by gamma spectroscopy. Four medically used isotopes could be identified ((131)I and (99m)Tc regularly, (153)Sm and (123)I sporadically). The concentration levels coincide well with literature data for (131)I, and with our own long-term data for (131)I and (99m)Tc for the same plant. Cosmogenic (7)Be activity in primary sludge correlated well with rainfall intensity. Surface sediment was sampled at low tide at both shores of the river, up- and downstream of the plant. (131)I was identified in all samples, with a sharp maximum (about 100 Bq kg(-1)d.m.) at the discharge point of the plant and lower levels elsewhere, decreasing monotonically in downstream direction. (7)Be and (137)Cs showed the same behaviour, but no peak at the discharge point. Predictions from simple equilibrium models for the transport and sedimentation of (131)I show good agreement with the experimental data and suggest that the wastewater treatment plant is the main source for this isotope.

  16. Distribution of polycyclic aromatic hydrocarbons in the coastal region off Macao, China: assessment of input sources and transport pathways using compositional analysis.

    Science.gov (United States)

    Mai, Bixian; Qi, Shihua; Zeng, Eddy Y; Yang, Qingshu; Zhang, Gan; Fu, Jiamo; Sheng, Guoying; Peng, Pingan; Wang, Zhishi

    2003-11-01

    The coastal region off Macao is a known depositional zone for persistent organic pollutants (POPs) in the Pearl River Delta and Estuary of southern China and an important gateway for the regional contributions of contamination to the globe. This paper presents a comprehensive assessment of the input sources and transport pathways of polycyclic aromatic hydrocarbons (PAHs) found in the coastal sediments of Macao, based on measurements of 48 2-7 ring PAHs and 7 sulfur/oxygenated (S/O) PAH derivatives in 45 sediment, 13 street dust, and 68 aerosol samples. Total sediment PAHs concentrations ranged from 294 to 12741 ng/g, categorized as moderate contamination compared to other regions of Asia and the world. In addition, the PAH compounds appeared to be bound more strongly to aromatics-rich soot particles than to natural organic matter, implying a prevailing atmospheric transport route for PAHs to Macao's coast. Compositional analysis and principal component analysis (PCA) suggested that different classes of PAHs in the coastal sediments of Macao may have been derived from different input sources via various transport pathways. For example, alkylated and S/O PAHs were likely derived from fossil fuel leakage and transported to sediments by both aerosols particles and street runoff. High-molecular-weight parent PAHs were predominantly originated from automobile exhausts and distributed by direct and indirect atmospheric deposition. Low-molecular-weight parent PAHs, on the other hand, may have stemmed from lower temperature combustion and fossil fuel (such as diesel) spillage from ships and boats and were transported to sediments by river runoff or direct discharge as well as by air-water exchange.

  17. How tides and waves enhance aeolian sediment transport at the sand motor mega-nourishment

    NARCIS (Netherlands)

    Hoonhout, B.M.; Luijendijk, A.P.; de Vries, S.; Roelvink, D.; Aagaard, T.; Deigaard, R.; Fuhrman, D.

    2017-01-01

    Expanding knowledge concerning the close entanglement between subtidal and subaerial processes in coastal environments initiated the development of the open-source Windsurf modeling framework that enables us to simulate
    multi-fraction sediment transport due to subtidal and subaerial processes

  18. The impact of storms and stratification on sediment transport in the Rhine region of freshwater influence

    NARCIS (Netherlands)

    Flores, Raúl P.; Rijnsburger, S.; Horner-Devine, Alexander R.; Souza, Alejandro J.; Pietrzak, J.D.

    2017-01-01

    We present measurements of along and across-shore sediment transport in a region of the Dutch coast 10 km north of the Rhine River mouth. This section of the coast is characterized by strong vertical density stratification because it is within the midfield region of the Rhine region of freshwater

  19. Transport and fate of viruses in sediment and stormwater from a managed aquifer recharge site

    Science.gov (United States)

    Enteric viruses are one of the major concerns in water reclamation and reuse at managed aquifer recharge (MAR) sites. In this study, the transport and fate of bacteriophages MS2, PRD1, and FX174 were studied in sediment and stormwater (SW) collected from a MAR site in Parafield, Australia. Column ex...

  20. Effect of vortex formation on sediment transport at dual pipe intakes

    Indian Academy of Sciences (India)

    /fulltext/sadh/041/09/1055-1061 ... The effect of vortex formation on rate of sediment transport at coastal dual pipe intakes was investigated using a scaled physical model. Experiments were performed on dual pipe intakes at three common ...

  1. Modeling of Sediment Transport and Self-Cleansing in Sea Outfalls

    DEFF Research Database (Denmark)

    Larsen, Torben; Ibro, I.

    2011-01-01

    The paper describes an on-going project on modeling of sediment transport in outfalls with special focus on the self-cleansing problem occurring due to the daily flow variations seen in outfalls. The two central elements of the project is the development of the numerical model and a matching phys...

  2. The effect of tides and storms on the sediment transport across a Dutch barrier island

    NARCIS (Netherlands)

    Wesselman, D.A.; de Winter, R.C.; Engelstad, A.C.; McCall, Robert; van Dongeren, Ap; Hoekstra, P.; Oost, Albert; van der Vegt, M.

    2017-01-01

    Under natural conditions, barrier islands might grow vertically and migrate onshore under the influence of long-term sea level rise. Sediment is transported onshore during storm-induced overwash and inundation. However, on many Dutch Wadden Islands, dune openings are closed off by artificial

  3. Variation of longshore current and sediment transport along the south Maharashtra coast, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Chandramohan, P.; SanilKumar, V.; Nayak, B; Pathak, K.C.

    on the field measurements, the estimated longshore sediment transport rates at Ratnagiri, Ambolgarh and Vengurla were 1.19 x 10 super(5), 1.9 x 10 super(5) and 0.53 x 10 super(5) m super(3) y/1 respectively and the direction was southward. Significance of field...

  4. A review and re-assessment of sediment transport along the Goa Coast, India

    Digital Repository Service at National Institute of Oceanography (India)

    Kunte, P.D.; Wagle, B; Yasuhiro Sugimori

    Although, a variety of methods have been employed to determine sediment transport along Goa coast, India, the results differ in some sections. Fifteen studies have been reviewed, compared, re-assessed and a corrected shore drift map of the Goa coast...

  5. Development of Prediction Techniques for Soil Loss and Sediment Transport at Army Training Areas.

    Science.gov (United States)

    1984-06-01

    tools needed to predict erosion-related Possible migration of fish to nonturbid waters effects must therefore be designed to accommodate the Since...calculating soil loss and sediment transport. SNatlft el Hadbook , Section 4,"Hydrology," The data base is that information needed to support NEN Notice

  6. Modeling of sediment transport along Mangalore coast using mike 21

    Digital Repository Service at National Institute of Oceanography (India)

    Babu, K.S.; Dwarakish, G.S.; Jayakumar, S.

    manmade constructions in particular with in the simulation period. 1. INTRODUCTION The coastal zone continuously changes due to natural processes and human interference. The importance of the coastal zone, with respect to safety, ecology, economy..., Goa, for having permitted to use MIKE 21 for this work. We are also grateful to the authorities ofNMPT, Mangalore for sharing the wave and wind data. REFERENCES (1] Bijker E.W. (1971), "Longshore Transport Computations", 10urnal of the Waterways...

  7. The timing of sediment transport down Monterey Submarine Canyon, offshore California

    Science.gov (United States)

    Stevens, Thomas; Paull, Charles K.; Ussler, William III; McGann, Mary; Buylaert, Jan-Pieter; Lundsten, Eve M.

    2013-01-01

    While submarine canyons are the major conduits through which sediments are transported from the continents out into the deep sea, the time it takes for sediment to pass down through a submarine canyon system is poorly constrained. Here we report on the first study to couple optically stimulated luminescence (OSL) ages of quartz sand deposits and accelerator mass spectrometry 14C ages measured on benthic foraminifera to examine the timing of sediment transport through the axial channel of Monterey Submarine Canyon and Fan, offshore California. The OSL ages date the timing of sediment entry into the canyon head while the 14C ages of benthic foraminifera record the deposition of hemipelagic sediments that bound the sand horizons. We use both single-grain and small (∼2 mm area) single-aliquot regeneration approaches on vibracore samples from fining-upward sequences at various water depths to demonstrate relatively rapid, decadal-scale sand transport to at least 1.1 km depth and more variable decadal- to millennial-scale transport to a least 3.5 km depth on the fan. Significant differences between the time sand was last exposed at the canyon head (OSL age) and the timing of deposition of the sand (from 14C ages of benthic foraminifera in bracketing hemipelagic sediments) are interpreted as indicating that the sand does not pass through the entire canyon instantly in large individual events, but rather moves multiple times before emerging onto the fan. The increased spread in single-grain OSL dates with water depth provides evidence of mixing and temporary storage of sediment as it moves through the canyon system. The ages also indicate that the frequency of sediment transport events decreases with distance down the canyon channel system. The amalgamated sands near the canyon head yield OSL ages that are consistent with a sub-decadal recurrence frequency while the fining-upward sand sequences on the fan indicate that the channel is still experiencing events with a 150

  8. Virus Dynamics Are Influenced by Season, Tides and Advective Transport in Intertidal, Permeable Sediments.

    Science.gov (United States)

    Vandieken, Verona; Sabelhaus, Lara; Engelhardt, Tim

    2017-01-01

    Sandy surface sediments of tidal flats exhibit high microbial activity due to the fast and deep-reaching transport of oxygen and nutrients by porewater advection. On the other hand during low tide, limited transport results in nutrient and oxygen depletion concomitant to the accumulation of microbial metabolites. This study represents the first attempt to use flow-through reactors to investigate virus production, virus transport and the impact of tides and season in permeable sediments. The reactors were filled with intertidal sands of two sites (North beach site and backbarrier sand flat of Spiekeroog island in the German Wadden Sea) to best simulate advective porewater transport through the sediments. Virus and cell release along with oxygen consumption were measured in the effluents of reactors during continuous flow of water through the sediments as well as in tidal simulation experiments where alternating cycles with and without water flow (each for 6 h) were operated. The results showed net rates of virus production (0.3-13.2 × 10 6 viruses cm -3 h -1 ) and prokaryotic cell production (0.3-10.0 × 10 5 cells cm -3 h -1 ) as well as oxygen consumption rates (56-737 μmol l -1 h -1 ) to be linearly correlated reflecting differences in activity, season and location of the sediments. Calculations show that total virus turnover was fast with 2 to 4 days, whereas virus-mediated cell turnover was calculated to range between 5-13 or 33-91 days depending on the assumed burst sizes (number of viruses released upon cell lysis) of 14 or 100 viruses, respectively. During the experiments, the homogenized sediments in the reactors became vertically structured with decreasing microbial activities and increasing impact of viruses on prokaryotic mortality with depth. Tidal simulation clearly showed a strong accumulation of viruses and cells in the top sections of the reactors when the flow was halted indicating a consistently high virus production during low tide. In

  9. Evaluating sediment transport in flood-driven ephemeral tributaries using direct and acoustic methods.

    Science.gov (United States)

    Stark, K.

    2017-12-01

    One common source of uncertainty in sediment transport modeling of large semi-arid rivers is sediment influx delivered by ephemeral, flood-driven tributaries. Large variations in sediment delivery are associated with these regimes due to the highly variable nature of flows within them. While there are many sediment transport equations, they are typically developed for perennial streams and can be inaccurate for ephemeral channels. Discrete, manual sampling is labor intensive and requires personnel to be on site during flooding. In addition, flooding within these tributaries typically last on the order of hours, making it difficult to be present during an event. To better understand these regimes, automated systems are needed to continuously sample bedload and suspended load. In preparation for the pending installation of an automated site on the Arroyo de los Piños in New Mexico, manual sediment and flow samples have been collected over the summer monsoon season of 2017, in spite of the logistical challenges. These data include suspended and bedload sediment samples at the basin outlet, and stage and precipitation data from throughout the basin. Data indicate a complex system; flow is generated primarily in areas of exposed bedrock in the center and higher elevations of the watershed. Bedload samples show a large coarse-grained fraction, with 50% >2 mm and 25% >6 mm, which is compatible with acoustic measuring techniques. These data will be used to inform future site operations, which will combine direct sediment measurement from Reid-type slot samplers and non-invasive acoustic measuring methods. Bedload will be indirectly monitored using pipe-style microphones, plate-style geophones, channel hydrophones, and seismometers. These instruments record vibrations and acoustic signals from bedload impacts and movement. Indirect methods for measuring of bedload have never been extensively evaluated in ephemeral channels in the southwest United States. Once calibrated

  10. Hydrodynamics and sediment transport at Muria Peninsula NPP Site

    International Nuclear Information System (INIS)

    Heni Susiati; Berni A Subki; Harman A

    2011-01-01

    Coastal along the coast of the Muria Peninsula, particularly the location of the Muria NPP site candidate is a dynamic region, the interaction between physical oceanographic factors such as currents, waves and tides in the coastal sediments cause abrasion or accretion. Interactions have resulted in coastal dynamics needs to be considered in siting NPP is essential in order to plan. Capacity of hydro-oceanographic data is essential in order to plan the development of the Muria NPP. The process of selecting a safe site for hydro-oceanographic aspects carried out according to IAEA safety standards on site selection. For the evaluation stage of hydro oceanographic potential site (site survey stage), the analysis is more focused on the tidal along the northern coast, bathymetry, potential water resources and hydrologic systems in the Muria NPP siting locations, Jepara. The method used is a secondary, confirmation of field data collection and interpretation of modeling results. The results showed that the preparation for the construction of NPP need to be evaluated further to coastal conditions with respect to the increase coastal erosion in the area of prospective NPP siting. (author)

  11. Slope, grain size, and roughness controls on dry sediment transport and storage on steep hillslopes

    Science.gov (United States)

    DiBiase, Roman A.; Lamb, Michael P.; Ganti, Vamsi; Booth, Adam M.

    2017-04-01

    Existing hillslope sediment transport models developed for low-relief, soil-mantled landscapes are poorly suited to explain the coupling between steep rocky hillslopes and headwater channels. Here we address this knowledge gap using a series of field and numerical experiments to inform a particle-based model of sediment transport by dry ravel—a mechanism of granular transport characteristic of steep hillslopes. We find that particle travel distance increases as a function of the ratio of particle diameter to fine-scale (1 m) topographic variability associated with rocky landscapes. Applying a 2-D dry-ravel-routing model to lidar-derived surface topography, we show how spatial patterns of local and nonlocal transport control connectivity between hillslopes and steep headwater channels that generate debris flows through failure of ravel-filled channels following wildfire. Our results corroborate field observations of a patchy transition from soil-mantled to bedrock landscapes and suggest that there is a dynamic interplay between sediment storage, roughness, grain sorting, and transport even on hillslopes that well exceed the angle of repose.

  12. Sediment transport processes in the Pearl River Estuary as revealed by grain-size end-member modeling and sediment trend analysis

    Science.gov (United States)

    Li, Tao; Li, Tuan-Jie

    2018-04-01

    The analysis of grain-size distribution enables us to decipher sediment transport processes and understand the causal relations between dynamic processes and grain-size distributions. In the present study, grain sizes were measured from surface sediments collected in the Pearl River Estuary and its adjacent coastal areas. End-member modeling analysis attempts to unmix the grain sizes into geologically meaningful populations. Six grain-size end-members were identified. Their dominant modes are 0 Φ, 1.5 Φ, 2.75 Φ, 4.5 Φ, 7 Φ, and 8 Φ, corresponding to coarse sand, medium sand, fine sand, very coarse silt, silt, and clay, respectively. The spatial distributions of the six end-members are influenced by sediment transport and depositional processes. The two coarsest end-members (coarse sand and medium sand) may reflect relict sediments deposited during the last glacial period. The fine sand end-member would be difficult to transport under fair weather conditions, and likely indicates storm deposits. The three remaining fine-grained end-members (very coarse silt, silt, and clay) are recognized as suspended particles transported by saltwater intrusion via the flood tidal current, the Guangdong Coastal Current, and riverine outflow. The grain-size trend analysis shows distinct transport patterns for the three fine-grained end-members. The landward transport of the very coarse silt end-member occurs in the eastern part of the estuary, the seaward transport of the silt end-member occurs in the western part, and the east-west transport of the clay end-member occurs in the coastal areas. The results show that grain-size end-member modeling analysis in combination with sediment trend analysis help to better understand sediment transport patterns and the associated transport mechanisms.

  13. Sediment transport processes in the Pearl River Estuary as revealed by grain-size end-member modeling and sediment trend analysis

    Science.gov (United States)

    Li, Tao; Li, Tuan-Jie

    2017-07-01

    The analysis of grain-size distribution enables us to decipher sediment transport processes and understand the causal relations between dynamic processes and grain-size distributions. In the present study, grain sizes were measured from surface sediments collected in the Pearl River Estuary and its adjacent coastal areas. End-member modeling analysis attempts to unmix the grain sizes into geologically meaningful populations. Six grain-size end-members were identified. Their dominant modes are 0 Φ, 1.5 Φ, 2.75 Φ, 4.5 Φ, 7 Φ, and 8 Φ, corresponding to coarse sand, medium sand, fine sand, very coarse silt, silt, and clay, respectively. The spatial distributions of the six end-members are influenced by sediment transport and depositional processes. The two coarsest end-members (coarse sand and medium sand) may reflect relict sediments deposited during the last glacial period. The fine sand end-member would be difficult to transport under fair weather conditions, and likely indicates storm deposits. The three remaining fine-grained end-members (very coarse silt, silt, and clay) are recognized as suspended particles transported by saltwater intrusion via the flood tidal current, the Guangdong Coastal Current, and riverine outflow. The grain-size trend analysis shows distinct transport patterns for the three fine-grained end-members. The landward transport of the very coarse silt end-member occurs in the eastern part of the estuary, the seaward transport of the silt end-member occurs in the western part, and the east-west transport of the clay end-member occurs in the coastal areas. The results show that grain-size end-member modeling analysis in combination with sediment trend analysis help to better understand sediment transport patterns and the associated transport mechanisms.

  14. Sediment transport in headwaters of a volcanic catchment—Kamchatka Peninsula case study

    Science.gov (United States)

    Chalov, Sergey R.; Tsyplenkov, Anatolii S.; Pietron, Jan; Chalova, Aleksandra S.; Shkolnyi, Danila I.; Jarsjö, Jerker; Maerker, Michael

    2017-09-01

    Due to specific environmental conditions, headwater catchments located on volcanic slopes and valleys are characterized by distinctive hydrology and sediment transport patterns. However, lack of sufficient monitoring causes that the governing processes and patterns in these areas are rarely well understood. In this study, spatiotemporal water discharge and sediment transport from upstream sources was investigated in one of the numerous headwater catchments located in the lahar valleys of the Kamchatka Peninsula Sukhaya Elizovskaya River near Avachinskii and Koryakskii volcanoes. Three different subcatchments and corresponding channel types (wandering rivers within lahar valleys, mountain rivers within volcanic slopes and rivers within submountain terrains) were identified in the studied area. Our measurements from different periods of observations between years 2012-2014 showed that the studied catchment was characterized by extreme diurnal fluctuation of water discharges and sediment loads that were influenced by snowmelt patterns and high infiltration rates of the easily erodible lahar deposits. The highest recorded sediment loads were up to 9•104 mg/L which was related to an increase of two orders of magnitude within a one day of observations. Additionally, to get a quantitative estimate of the spatial distribution of the eroded material in the volcanic substrates we applied an empirical soil erosion and sediment yield model-modified universal soil loss equation (MUSLE). The modeling results showed that even if the applications of the universal erosion model to different non-agricultural areas (e.g., volcanic catchments) can lead to irrelevant results, the MUSLE model delivered might be acceptable for non-lahar areas of the studied volcanic catchment. Overall the results of our study increase our understanding of the hydrology and associated sediment transport for prediction of risk management within headwater volcanic catchments.

  15. A Numerical Study of Hydrodynamics and Sediment Transport in Fourleague Bay, Louisiana

    Science.gov (United States)

    Hu, K.; Chen, Q. J.; Xu, K.; Bentley, S. J.; WANG, J.

    2017-12-01

    Fourleague Bay is a shallow and vertically well-mixed estuary in south-central Louisiana. This estuary is highly impacted by wind (e.g., cold fronts and tropical storms), river discharge from the Atchafalaya River and tides from the Gulf of Mexico, and is being used as an analog site to study impacts of sediment-diversion restoration strategies in the Mississippi River Delta. In this study, a coupled flow-wave Delft3D model was setup and applied to study hydrodynamics and sediment transport in this area. The model grid size is 1071x631 with a 50-m resolution in the bay. Vegetation is considered by rigid cylinders in both flow and wave modules. The offshore water level boundary conditions were provided by a Gulf-scale Delft3D model. Model parameters, especially for cohesive sediment transport such as settling velocity, erosion rate and critical bottom shear stress, were calibrated using the field observation data during three seasons from May 2015 to March 2016. The modeled water levels, currents, significant wave heights and suspended sediment concentrations agreed fairly well with measurements, which suggests a reasonable model performance. Seasonal variations were analyzed based on different scenarios. A series of numerical experiments were set up to quantify the contributions of different factors, such as river discharge, tides and waves to sediment transport in this area. This model will be further applied to be part of a landscape ecosystem model to test landscape and population change over time with manipulations to sediment delivery. This study was funded by the National Science Foundation (SEES-1427389 and CCF-1539567).

  16. Laboratory observations of sediment transport using combined particle image and tracking velocimetry (Conference Presentation)

    Science.gov (United States)

    Frank, Donya; Calantoni, Joseph

    2017-05-01

    Improved understanding of coastal hydrodynamics and morphology will lead to more effective mitigation measures that reduce fatalities and property damage caused by natural disasters such as hurricanes. We investigated sediment transport under oscillatory flow over flat and rippled beds with phase-separated stereoscopic Particle Image Velocimetry (PIV). Standard PIV techniques severely limit measurements at the fluid-sediment interface and do not allow for the observation of separate phases in multi-phase flow (e.g. sand grains in water). We have implemented phase-separated Particle Image Velocimetry by adding fluorescent tracer particles to the fluid in order to observe fluid flow and sediment transport simultaneously. While sand grains scatter 532 nm wavelength laser light, the fluorescent particles absorb 532 nm laser light and re-emit light at a wavelength of 584 nm. Optical long-pass filters with a cut-on wavelength of 550 nm were installed on two cameras configured to perform stereoscopic PIV to capture only the light emitted by the fluorescent tracer particles. A third high-speed camera was used to capture the light scattered by the sand grains allowing for sediment particle tracking via particle tracking velocimetry (PTV). Together, these overlapping, simultaneously recorded images provided sediment particle and fluid velocities at high temporal and spatial resolution (100 Hz sampling with 0.8 mm vector spacing for the 2D-3C fluid velocity field). Measurements were made under a wide range of oscillatory flows over flat and rippled sand beds. The set of observations allow for the investigation of the relative importance of pressure gradients and shear stresses on sediment transport.

  17. Hillslope sediment and soil carbon transport: can we model their movement?

    Science.gov (United States)

    Hancock, Greg; Kunkel, Veikko; Dever, Chris; Braggins, Matthew; Willgoose, Garry

    2016-04-01

    Quantifying and predicting the movement of hillslope sediment and soil organic carbon (SOC) is of huge scientific, agronomic and economic benefit. In particular, the movement and fate of SOC has attracted considerable recent attention. However, the reliable modelling and prediction of sediment and SOC movement has proved elusive. Here we examine the movement of sediment and SOC along a grazing hillslope in south-eastern Australia. The slope is linear, uniformly managed and has consistent vegetation (grassland). We quantify sediment and SOC transport using the environmental tracer 137-Ceasium. However, here we collect field samples using the conventional soil cores but also shallow samples to quantify the dynamics of the near surface. We also model the movement of sediment and SOC using a numerically based soil erosion and landscape evolution model. Our results show that the hillslope is erosional which is supported by field observation. However, there was no relationship between SOC and 137-Caesium suggesting that SOC and their movement and fate are not related. Significant relationships were observed between soil texture and SOC for the near surface but not for the deeper cores suggesting any movement and fate of SOC is more controlled by soil particle size at the near surface. The SIBERIA sediment transport model was calibrated and run for the site. Comparing the field derived erosion and SOC data with model prediction found no significant relationship. However, the numerical model was able to predict the cyclic pattern of 137-Ceasium and SOC as well as overall trends. Our findings demonstrate that the movement and fate of sediment and SOC is complex.

  18. Application of tracer techniques in studies of sediment transport in Vietnam

    International Nuclear Information System (INIS)

    Hai, P.S.; Quang, N.H.; Xuan, N.M.; Chuong, P.N.; Hien, P.Z.

    1997-01-01

    As a consequence of intensive erosion processes typical of the humid tropical one, as well as of human activities destroying tropical forests, grasslands and protective mangrove swamps, etc, most navigable estuaries in Vietnam suffer seriously from sedimentation. In order to maintain the necessary depth for the 7.000 ton vessels entering and leaving ports, a large amount of money is spent annually on dredging operation. A lot of hydraulic and sedimentary surveys were carried out in the past by different groups of researchers. However, owing to the complexity of sediment processes in estuarine areas under the hydrometeorological conditions typical of the southwest Pacific, the use of just any modelling approach is not suitable. In many cases, the conclusions inferred from mathematical models have been the controversial matter. The tracer techniques, which have been employed in the country since 1991, have provided a very efficient tool to obtain a dynamic idea of sediment transport. Many investigations of bedload transport using Sc-46 labelled glass and Ir-192 glass as radioactive tracers were carried out from 1992 to 1996 at Haiphong harbour area. Bedload transport rates under effect of northeast monsoon and southeast monsoon at 5 zones located on both sides of the navigation channel were estimated. In bedload transport studies, apart from conventional methods for assessment of transport thickness, a new method using the ratio of photoelectric peak to Compton region of spectra acquired directly on the sea bed was put forward and applied. The influence of dredging materials at two dumping sites under different tidal phases on in fill rate in the access channel was assessed by radioactive tracers. The qualitative and quantitative information on sediment transport at some experimental sites given by tracers was used by modelling specialists who have undertaken hydraulic and sedimentary surveys in this region

  19. Tracing cohesive sediment transportation at river mouths around Tokyo, Japan by Cesium originated from Fukushima Daiichi Power Plant

    Science.gov (United States)

    koibuchi, Y.

    2012-12-01

    Sediment transport at river mouths, which consists of suspended-load and bed-load, has not been fully understood, since bed-load transport of cohesive sand is difficult to observe. Especially, the impact of sediment transport on the total amount of fine-grained cohesive sediment has not been elucidated. Cesium-134 and cesium-137 were spread from the Fukushima Daiichi Nuclear Power Plant (FDNPP) after the earthquake of March 11 of 2011, and attached to the fine-grained sand on the land. The contaminated sand flowed into the river mouths through the rivers possibly due to the complex physical processes in estuarine areas. To evaluate the fine-grained sediment transport around Tokyo and Tokyo Bay, field observations were carried out utilizing radionuclide originated from FDNPP as an effective tracer. The cohesive sediment transport at three different river mouths around Tokyo was successfully quantified. The cohesive sediment transport deposited in the estuary was found to be greatly dependent on the land use, geometry, river discharge and salinity. In addition,the transport driven by the rainfall was minute, and its behavior was quite different from suspended solids. Although further field observations of radionuclide are necessary, it is clear that fine-grained sediment in the bay from rivers already settled on the river mouth by aggregation. The settled sand will not move even in rainfall events. Consequently, the transport of radionuclide to the Pacific Ocean may not occur.; Cesium distribution around Tokyo Bay ; Cesium Concentration in Edogawa river

  20. Transport of phosphorus, wash load and suspended sediment in the River Varde A in southwest Jutland, Denmark

    DEFF Research Database (Denmark)

    Thodsen, Hans; Hasholt, Bent; Pejrup, Morten

    2004-01-01

    Total phosphorus (TP) concentrations, suspended sediment concentrations (SSC) and wash load have been measured at three river monitoring stations in the River Varde Angstrom system since 1998. This provides the possibility of studying the link between SSC and wash load and concentrations of TP....... Transport rates of TP, suspended sediment and wash load at the three stations, calculated using rating curves, indicate the dependence of TP transport on the transport of suspended sediment and wash load. Two stations are located on tributaries flowing upstream of the third station located at a weir...... at the end of a small impoundment. Transport rates at the upstream stations were 57% higher for suspended sediment and 27% higher for wash load than at the downstream station, while transport of TP was the same. This indicates that phosphorus is transported adhered to the finest grain size fractions that do...

  1. Size graded sediment dynamics: from the processes characterization to the transport modelling in the English Channel

    International Nuclear Information System (INIS)

    Blanpain, O.

    2009-10-01

    The purpose of this work is the implementation of a sediment transport model in the English Channel. The design of such a model requires the identification of the physical processes, their modelling and their in-situ validation. Because of the sedimentary particularities of the study area, modelling of the mechanical behaviour of a non uniform mixture of sediments and particularly of the fine grains within a coarse matrix is required. This study focused on the characterization of the relevant processes by acquisition of experimental and in-situ data. Data acquired in hydro-sedimentary conditions comparable to those found in the English Channel are scarce. A new instrument and image processing technique were specifically conceived and implemented in-situ to observe and measure, with a high temporal resolution, the dynamics of a strongly heterogeneous mixture of particles in a grain-size scale. The data collected compared well with several existing formulations. One of these formulations was chosen to be adapted. The transfer dynamics of fine grains in coarse sediments and their depth of penetration were acquired from stratigraphic samples. The sediment transport model deals with multi-size grains and multi sedimentary layers, it is forced by swell and currents, and accounts for bead load and suspended load transports. It was applied to realistic scenarios for the English Channel. (author)

  2. Nitrate and colloid transport through coarse Hanford sediments under steady state, variably saturated flow

    Science.gov (United States)

    Cherrey, Kelly D.; Flury, Markus; Harsh, James B.

    2003-06-01

    At the U.S. Department of Energy's Hanford Reservation, colloid-facilitated transport is a potential mechanism for accelerated movement of radionuclides like Cs-137. Here we investigate the transport of colloids through Hanford sediments under steady state, unsaturated flow conditions. We isolated colloids from Hanford sediments by dispersion and sedimentation and determined colloid breakthrough curves in packed sediment columns. A column system was developed with which we could control volumetric water contents with accuracy better than 0.01 effective saturation and the water potentials to better than 0.06 cm-H2O. Inflow and outflow boundary conditions had to be meticulously controlled to ensure uniformity of water contents and water potentials inside the column. Colloid breakthrough curves were determined under a series of water contents ranging from 0.2 to 1.0 effective saturation. Colloids were mobile under all water saturations, but the total amount of colloids transported decreased with decreasing water saturation. Colloid behavior was described with the mobile-immobile model concept, including first-order deposition from the mobile phase only.

  3. 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

  4. Characteristics of Sediment Transportation in Two Contrasting Oak Forested Watersheds in the Lesser Central Himalaya, India

    Science.gov (United States)

    Qazi, N. U. Q.; Bruijnzeel, S., Sr.; Rai, S. P., Sr.

    2015-12-01

    Sediment transfer from mountainous areas to lowland areas is one of the most important geomorphological processes globally with the bulk of the sediment yield from such areas typically deriving from mass wastage processes. This study presents monthly, seasonal and annual variations in sediment transport (both suspended load and bedload) as well as dissolved loads over three consecutive water years (2008-2011) for two small forested watersheds with contrasting levels of forest disturbance in the Lesser Himalaya of Northwest India. Seasonal and annual suspended sediment yields were strongly influenced by amounts of rainfall and streamflow and showed a 10-63 fold range between wet and dry years. Of the annual load, some 93% was produced on average during the monsoon season (June-September). Sediment production by the disturbed forest catchment was 1.9-fold (suspended sediment) to 5.9-fold (bedload) higher than that for the well-stocked forest catchment. By contrast, dissolved loads varied much less between years, seasons (although minimal during the dry summer season), and degree of forest disturbance. Total mechanical denudation rates were 1.6 times and 4.6 times larger than chemical denudation rates for the little disturbed and the heavily disturbed forest catchment, respectively whereas overall denudation rates were estimated at 0.69 and 1.04 mm per 1000 years, respectively.

  5. California coast nearshore processes study. [nearshore currents, sediment transport, estuaries, and river discharge

    Science.gov (United States)

    Pirie, D. M.; Steller, D. D. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. Large scale sediment plumes from intermittent streams and rivers form detectable seasonal patterns on ERTS-1 imagery. The ocean current systems, as plotted from three California coast ERTS mosaics, were identified. Offshore patterns of sediment in areas such as the Santa Barbara Channel are traceable. These patterns extend offshore to heretofore unanticipated ranges as shown on the ERTS-1 imagery. Flying spot scanner enhancements of NASA tapes resulted in details of subtle and often invisible (to the eye) nearshore features. The suspended sediments off San Francisco and in Monterey Bay are emphasized in detail. These are areas of extremely changeable offshore sediment transport patterns. Computer generated contouring of radiance levels resulted in maps that can be used in determining surface and nearsurface suspended sediment distribution. Tentative calibrations of ERTS-1 spectral brightness against sediment load have been made using shipboard measurements. Information from the combined enhancement and interpretation techniques is applicable to operational coastal engineering programs.

  6. Radionuclides deposition and fine sediment transport in a forested watershed, central Japan

    Science.gov (United States)

    Nam, S.; Gomi, T.; Kato, H.; Tesfaye, T.; Onda, Y.

    2011-12-01

    We investigated radionuclides deposition and fine sediment transport in a 13 ha headwater watershed, Tochigi prefecture, located in 98.94 km north of Tokyo. The study site was within Karasawa experimental forest, Tokyo University of Agriculture and Technology. We conducted fingerprinting approach, based on the activities of fallout radionuclides, including caesium-134 (Cs-134) caesium-137 (Cs-137) and excess lead-210 (Pb-210ex). For indentifying specific sources of fine sediment, we sampled tree, soil on forested floor, soil on logging road surface, stream bed and stream banks. We investigated the radionuclides (i.e., as Cs-134, Cs-137 and Pb-210ex) deposition on tree after accident of nuclear power plants on March 11, 2011. We sampled fruits, leaves, branches, stems, barks on Japanese cedar (Sugi) and Japanese cypress (Hinoki). To analyze the samples, gammaray spectrometry was performed at a laboratory at the University of Tsukuba (Tsukuba City, Japan) using n-type coaxial low-energy HPGe gamma detectors (EGC-200-R and EGC25-195-R of EURYSIS Co., Lingolsheim, France) coupled with a multichannel analyzer. We also collected soil samples under the forest canopy in various soil depths from 2, 5, 10, 20, 30 cm along transect of hillslopes. Samples at forest road were collected road segments crossing on the middle section of monitoring watersheds. Fine sediment transport in the streams were collected at the outlet of 13 ha watersheds using integrated suspended sediment samplers. This study indicates the some portion of radio nuclide potentially remained on the tree surface. Part of the deposited radionuclides attached to soil particles and transported to the streams. Most of the fine sediment can be transported on road surface and/or near stream side (riparian zones).

  7. Sediment transport processes and their resulting stratigraphy: informing science and society

    Science.gov (United States)

    Nittrouer, J. A.

    2013-12-01

    Sediment transport physically shapes planetary surfaces by producing patterns of erosion and deposition, with the relative magnitudes of geomorphic actions varying according to environmental conditions. Where sediment fills accommodation space and generates accumulation, a stratigraphic archive develops that potentially harbors a trove of information documenting dynamic conditions during the periods of sediment production, transport and deposition. By investigating the stratigraphic record, it is possible to describe changes in surface environments, as well as hypothesize about the development of regional tectonic and climate regimes. Ultimately, information contained within the stratigraphic record is critical for evaluating the geological history of terrestrial planets. The enigma of stratigraphy, however, is that sediment deposition is finicky, there is no uninterrupted record, and while deposits may reflect only a brief temporal window, they may still be used to infer about conditions that encompass much longer periods of time. Consider a case where meter-scale dune foresets, deposited in a matter of minutes to hours, are in contact with sediments above and below that reflect entirely different depositional circumstances and are separated in time by a hiatus of thousands or perhaps millions of years. To effectively unlock the scientific trove bound in stratigraphy, it is first necessary to identify where such unconformities exist and the conditions that lead to their development. This challenge is made much simpler through scientific advances in understanding sediment transport processes -- the examination of how fluid and solids interact under modern conditions -- because this is precisely where sediment patterns first emerge to produce accumulation that builds a stratigraphic record. By advancing an understanding of process-based sedimentology, it is possible to enhance diagnostic evaluations of the stratigraphic record. Fortunately, over the past several

  8. Final report - Microbial pathways for the reduction of mercury in saturated subsurface sediments

    Energy Technology Data Exchange (ETDEWEB)

    Tamar barkay; Lily Young; Gerben Zylstra

    2009-08-25

    Mercury is a component of mixed wastes that have contaminated vast areas of the deep subsurface as a result of nuclear weapon and energy production. While this mercury is mostly bound to soil constituents episodes of groundwater contamination are known in some cases resulting in potable water super saturated with Hg(0). Microbial processes that reduce Hg(II) to the elemental form Hg(0) in the saturated subsurface sediments may contribute to this problem. When we started the project, only one microbial pathway for the reduction of Hg(II), the one mediated by the mer operon in mercury resistant bacteria was known. As we had previously demonstrated that the mer mediated process occurred in highly contaminated environments (Schaefer et al., 2004), and mercury concentrations in the subsurface were reported to be low (Krabbenhoft and Babiarz, 1992), we hypothesized that other microbial processes might be active in reducing Hg(II) to Hg(0) in saturated subsurface environments. The specific goals of our projects were: (1) Investigating the potential for Hg(II) reduction under varying electron accepting conditions in subsurface sediments and relating these potential to mer gene distribution; and (2) Examining the physiological and biochemical characteristics of the interactions of anaerobic bacteria with mercury. The results are briefly summarized with references to published papers and manuscripts in preparation where details about our research can be found. Additional information may be found in copies of our published manuscripts and conference proceedings, and our yearly reports that were submitted through the RIMS system.

  9. Use of sediment rating curves and optical backscatter data to characterize sediment transport in the Upper Yuba River watershed, California, 2001-03

    Science.gov (United States)

    Curtis, Jennifer A.; Flint, Lorraine E.; Alpers, Charles N.; Wright, Scott A.; Snyder, Noah P.

    2006-01-01

    Sediment transport in the upper Yuba River watershed, California, was evaluated from October 2001 through September 2003. This report presents results of a three-year study by the U.S. Geological Survey, in cooperation with the California Ecosystem Restoration Program of the California Bay-Delta Authority and the California Resources Agency. Streamflow and suspended-sediment concentration (SSC) samples were collected at four gaging stations; however, this report focuses on sediment transport at the Middle Yuba River (11410000) and the South Yuba River (11417500) gaging stations. Seasonal suspended-sediment rating curves were developed using a group-average method and non-linear least-squares regression. Bed-load transport relations were used to develop bed-load rating curves, and bed-load measurements were collected to assess the accuracy of these curves. Annual suspended-sediment loads estimated using seasonal SSC rating curves were compared with previously published annual loads estimated using the Graphical Constituent Loading Analysis System (GCLAS). The percent difference ranged from -85 percent to +54 percent and averaged -7.5 percent. During water year 2003 optical backscatter sensors (OBS) were installed to assess event-based suspended-sediment transport. Event-based suspended-sediment loads calculated using seasonal SSC rating curves were compared with loads calculated using calibrated OBS output. The percent difference ranged from +50 percent to -369 percent and averaged -79 percent. The estimated average annual sediment yield at the Middle Yuba River (11410000) gage (5 tons/mi2) was significantly lower than that estimated at the South Yuba River (11417500) gage (14 tons/mi2). In both rivers, bed load represented 1 percent or less of the total annual load throughout the project period. Suspended sediment at the Middle Yuba River (11410000) and South Yuba River (11417500) gages was typically greater than 85 percent silt and clay during water year 2003, and

  10. Investigation of sediment transport and optimization of dredging operations in Indian ports using radiotracer technique

    International Nuclear Information System (INIS)

    Pant, H.J.

    2012-01-01

    India has a long coastline of about 7,515 km and there are twelve major ports situated on the coastline. Out of them, six are situated on the West Coast whereas other six are situated on the East Coast. In addition to this, there are more than 140 minor ports and other marine establishments situated along the coastline. Each port and marine project has a navigation channel and depth of this navigation channel needs to be maintained to a level of at least 12-15 meters for smooth sailing of ships. Sediments continuously move along the coast due to alongshore currents generated by the waves and tides; and get deposited in navigation channels. For maintaining the required depth of the channels, the dredging operation is carried out. throughout the year or as and when required. Development of a new port or harbour also involves huge capital dredging. The dredged sediments generated during maintenance or capital dredging needs to be dumped at a suitable location, so that it does not find its way back to the channel and obstruct sailing of ships. Moreover the selected site should be such that the turn around time of the dredger is kept minimum to economize the dredging operation. In order to meet the above requirements, the knowledge of transport parameters such as the general direction of movement, extent of lateral and longitudinal movement, transport velocity, transport thickness and bed load movement rate is required. Radiotracer techniques are commonly used to investigate sediment transport on seabed and evaluate the suitability of the proposed dumping sites. Scandium-46 (half-life: 84 days, Gamma energies: 0.89 MeV (100%), 1.12 MeV (100%)) in the form of scandium glass powder is the most suitable radiotracer for tracing sediments on seabed. The activity used in an investigation ranges from 75-300 GBq (2-8 Ci). The suitably prepared particulate radiotracer is injected on seabed at the proposed site using a specially designed injection system and its movement is

  11. Nonlocal Sediment Transport on Steep Lateral Moraines, Eastern Sierra Nevada, California, USA

    Science.gov (United States)

    Doane, Tyler H.; Furbish, David Jon; Roering, Joshua J.; Schumer, Rina; Morgan, Daniel J.

    2018-01-01

    Recent work has highlighted the significance of long-distance particle motions in hillslope sediment transport. Such motions imply that the flux at a given hillslope position is appropriately described as a weighted function of surrounding conditions that influence motions reaching the given position. Although the idea of nonlocal sediment transport is well grounded in theory, limited field evidence has been provided. We test local and nonlocal formulations of the flux and compare their ability to reproduce land surface profiles of steep moraines in California. We show that nonlocal and nonlinear models better reproduce evolved land surface profiles, notably the amount of lowering and concavity near the moraine crest and the lengthening and straightening of the depositional apron. The analysis provides the first estimates of key parameters that set sediment entrainment rates and travel distances in nonlocal formulations and highlights the importance of correctly specifying the entrainment rate when modeling land surface evolution. Moraine evolution associated with nonlocal and nonlinear transport formulations, when described in terms of the evolution of the Fourier transform of the moraine surface, displays a distinct behavior involving growth of certain wave numbers, in contrast to the decay of all wave numbers associated with linear transport. Nonlinear and nonlocal formulations share key mathematical elements yielding a nonlinear relation between the flux and the land surface slope.

  12. Net sediment transport in tidal basins: quantifying the tidal barotropic mechanisms in a unified framework

    Science.gov (United States)

    Gatto, Vincenzo Marco; van Prooijen, Bram Christiaan; Wang, Zheng Bing

    2017-11-01

    Net sediment transport in tidal basins is a subtle imbalance between large fluxes produced by the flood/ebb alternation. The imbalance arises from several mechanisms of suspended transport. Lag effects and tidal asymmetries are regarded as dominant, but defined in different frames of reference (Lagrangian and Eulerian, respectively). A quantitative ranking of their effectiveness is therefore missing. Furthermore, although wind waves are recognized as crucial for tidal flats' morphodynamics, a systematic analysis of the interaction with tidal mechanisms has not been carried out so far. We review the tide-induced barotropic mechanisms and discuss the shortcomings of their current classification for numerical process-based models. Hence, we conceive a unified Eulerian framework accounting for wave-induced resuspension. A new methodology is proposed to decompose the sediment fluxes accordingly, which is applicable without needing (semi-) analytical approximations. The approach is tested with a one-dimensional model of the Vlie basin, Wadden Sea (The Netherlands). Results show that lag-driven transport is dominant for the finer fractions (silt and mud). In absence of waves, net sediment fluxes are landward and spatial (advective) lag effects are dominant. In presence of waves, sediment can be exported from the tidal flats and temporal (local) lag effects are dominant. Conversely, sand transport is dominated by the asymmetry of peak ebb/flood velocities. We show that the direction of lag-driven transport can be estimated by the gradient of hydrodynamic energy. In agreement with previous studies, our results support the conceptualization of tidal flats' equilibrium as a simplified balance between tidal mechanisms and wave resuspension.

  13. Sedimentation

    Science.gov (United States)

    Cliff R. Hupp; Michael R. Schening

    2000-01-01

    Sedimentation is arguably the most important water-quality concern in the United States. Sediment trapping is cited frequently as a major function of riverine-forested wetlands, yet little is known about sedimcntation rates at the landscape scale in relation to site parameters, including woody vegetation type, elevation, velocity, and hydraulic connection to the river...

  14. Long distance electron transport in marine sediments: Microbial and geochemical implications

    DEFF Research Database (Denmark)

    Risgaard-Petersen, Nils; Larsen, Steffen; Pfeffer, Christian

    redox half-reactions in distant regions of the sediment leads to formation of electrical fields, which modifies ion transport. The local proton producing and proton consuming half reactions induces pH extremes that accelerate dissolution of iron sulphides and calcium carbonates in anoxic layers...... and promotes the formation of Mg-calcite and iron oxides in the oxic zone. Oxygen seems to be the major electron acceptor, and more than 40% of the oxygen consumption in sediments can be driven by long distance electron transfer from distant electron donors. The major e-donor is sulfide, which is oxidized......-structural properties suggesting that they are living electric micro cables. The mode of action of these organisms has major impacts on element cycling by redox processes, pH balances, mineral dissolution/precipitations, and electro migration of ions in marine sediment. The ability of Desulfubulbus filaments to bridge...

  15. Transport of sediments, carbon and nutrients in areas of reforestation and grassland based on simulated rainfall

    Directory of Open Access Journals (Sweden)

    Adilson Pinheiro

    2013-08-01

    Full Text Available The objective of this study was to evaluate the soil losses, as well as carbon and chemical samples in runoff through areas of pine (Pinus taeda, eucalyptus (Eucalyptus dunni and a consortium of pasture with oat (Avena stringosa and ryegrass (Lolium multiflorium in the Fragosos river basin, in Concordia, SC. For this, rainfall simulations with mean intensities of 94 mm h-1 were conducted in September and November 2011, in plots of 1 m2 established in the three areas. Runoff, loads carried of the sediment, and carbon and chemical concentrations were quantified in the experiment. The results showed that the concentrations of sediment and organic carbon were higher in the eucalyptus area. The largest concentrations of chemicals for all areas were nitrate, calcium, magnesium and potassium. Total carbon, organic carbon, sediment and nitrate were transported in higher loads in the eucalyptus area. With the exception of nitrate and chloride, the chemical loads carried were higher in the pasture area.

  16. Sediment transport in the aftermath of the 2008 Wenchuan earthquake: constraints from landslide mapping, photo-sieving and reservoir accumulation

    Science.gov (United States)

    Li, G.; West, A. J.; Hammond, D. E.; Xiao, Z.; Okaya, D. A.; Densmore, A. L.; Hilton, R. G.; Jin, Z.; Zhang, F.; Wang, J.

    2014-12-01

    Understanding post-seismic sediment transport is important for assessing crustal mass redistribution by earthquakes and for managing seismically-induced geohazards, including channel aggradation and flooding. The 2008 Wenchuan earthquake (Mw 7.9) triggered over 60,000 landslides in the Longmen Shan range of the eastern Tibetan Plateau. Records from hydrometric gauging show enhanced regional suspended sediment fluxes following the earthquake, resulting from evacuation of the landslide sediment (Wang et al., in revision). In addition to the insights into suspended sediment dynamics from gauging stations, this large-magnitude seismic event provides an opportunity to study bedload sediment transport after a large earthquake. Here we present primary results from a comprehensive investigation of the Min Jiang river system following the Wenchuan earthquake. Using a landslide inventory map (Li et al., 2014) and a DEM-based river network, we mapped landslide-river network connectivity. With photo-sieving techniques, we estimated the grain size distribution of medium-grained (mm to cm scale) landslide deposits. These data provide constraints on sediment sources. The mass of sediment in transport has been estimated from river sediment quartz 10Be measurements (West et al., 2014), supplemented here by constraints from rates of sediment infill in a downstream reservoir, determined by bathymetric profiling and analysis of sediment cores. Together with hydrometric data, this dataset provides the basic parameters for modeling sediment transport in the Min Jiang river system after the Wenchuan earthquake and promises insight into the mechanisms controlling post-earthquake sediment transport. References Li et al., 2014 , Geochem. Geophys. Geosyst., 15, 833-844, Wang et al., in revision West et al., 2014, Earth Planet Sc. Lett., 396, 143-153

  17. Modes of sediment transport in channelized water flows with ramifications to the erosion of the Martian outflow channels

    Science.gov (United States)

    Komar, P. D.

    1980-01-01

    The paper discusses application to Martian water flows of the criteria that determine which grain-size ranges are transported as bed load, suspension, and wash load. The results show nearly all sand-sized material and finer would have been transported as wash load and that basalt pebbles and even cobbles could have been transported at rapid rates of suspension. An analysis of the threshold of sediment motion on Mars further indicates that the flows would have been highly competent, the larger flows having been able to transport boulder-sized material. Comparisons with terrestrial rivers which transport hyperconcentration levels of sediments suggest that the Martian water flows could have achieved sediment concentrations up to 70% in weight. Although it is possible that flows could have picked up enough sediment to convert to pseudolaminar mud flows, they probably remained at hyperconcentration levels and fully turbulent in flow character.

  18. Effects of Vegetative Buffers on Sediment and its Associated Pollutants Transport and Deposition

    Science.gov (United States)

    Akram, S.; Yu, B.

    2016-12-01

    Grass buffer strips impact overland flow hydraulics and consequently sediment delivery from hillslopes. Mathematical models facilitate the evaluation of performance of grass strips in reducing sediment delivery by simulating and predicting flow characteristics and sediment transport adjacent to and within grass strips. GUSED-VBS 2 model is developed to simulate flow, erosion and deposition processes in the upstream area and within grass strips. The model is capable of estimating proportion and amount of different sediment size classes in the outflow. The modified Green-Ampt equation was used to simulate infiltration. Gradually varied flow and a kinematic wave approximation were used to simulate flow characteristics upstream and within grass strips. The GUEST model was modified in order to use its basic approaches in the sediment transport module for grass strips. Model predictions agree well with measured data from two sets of controlled experiments. The sensitivity analysis showed that the initial soil moisture and flow rate were the most sensitive parameters in predicting runoff loss. Increasing the slope steepness and flow rate dramatically decreased the efficiency of grass strips in reducing sediment concentration and sediment delivery. Comparing the results of the model simulations for different prevalent scenarios showed that the backwater region upstream of dense grass strips is the main region for sediment deposition on low slopes. In agreement with the experimental observations, the model predicted the proportion of coarse particles to be higher in the deposited material upstream of grass strips compared with the deposited material within the grass strip. The efficiency of grass strips in reducing the concentration of sediment is much higher for coarser than finer particles. Grass strips can substantially decrease the delivery of fine particles if a significant reduction in runoff (i.e. infiltration) occurs within the strip. As no backwater forms on high

  19. Modelling of Sediment Transport of the Mehadica River, Caras Severin County, Romania

    Science.gov (United States)

    Grozav, Adia; Beilicci, Robert; Beilicci, Erika

    2017-10-01

    Study case is situated in Caras-Severin County. Every sediment transport model application is different both in terms of time and space scale, study objectives, required accuracy, allocated resources, background of the study team etc. For sediment transport modelling, it is necessary to know the characteristics of the sediment in the river bed. Therefore, it is recommended to collect a number of bed sediment grap samples. These samples should be analysing in terms of grain size distribution. To solve theoretical problems of movement of water in the river Mehadica, it requires modelling of water flow in this case. Numerical modelling was performed using the program MIKE11. MIKE 11 is a user-friendly, fully dynamic, one-dimensional modelling tool for the detailed analysis, design, management and operation of both simple and complex river and channel systems. With its exceptional flexibility, speed and user friendly environment, MIKE 11 provides a complete and effective design environment for engineering, water resources, water quality management and planning applications. The Hydrodynamic (HD) module is the nucleus of the MIKE 11 modelling system and forms the basis for most modules including Flood Forecasting, Advection- Dispersion, Water Quality and Non-cohesive sediment transport modules. The MIKE 11 HD module solves the vertically integrated equations for the conservation of mass and momentum, i.e. the Saint-Venant equations. The input data are: area plan with location of cross sections; cross sections topographical data and roughness of river bed; flood discharge hydrograph. Advanced computational modules are included for description of flow over hydraulic structures, including possibilities to describe structure operation.

  20. Transport behavior of groundwater protozoa and protozoan-sized microspheres in sandy aquifer sediments

    Science.gov (United States)

    Harvey, R.W.; Kinner, N.E.; Bunn, A.; MacDonald, D.; Metge, D.

    1995-01-01

    Transport behaviors of unidentified flagellated protozoa (flagellates) and flagellate-sized carboxylated microspheres in sandy, organically contaminated aquifer sediments were investigated in a small-scale (1 to 4-m travel distance) natural-gradient tracer test on Cape Cod and in flow-through columns packed with sieved (0.5-to 1.0-mm grain size) aquifer sediments. The minute (average in situ cell size, 2 to 3 ??m) flagellates, which are relatively abundant in the Cape Cod aquifer, were isolated from core samples, grown in a grass extract medium, labeled with hydroethidine (a vital eukaryotic stain), and coinjected into aquifer sediments along with bromide, a conservative tracer. The 2-??m flagellates appeared to be near the optimal size for transport, judging from flowthrough column experiments involving a polydispersed (0.7 to 6.2 ??m in diameter) suspension of carboxylated microspheres. However, immobilization within the aquifer sediments accounted for a log unit reduction over the first meter of travel compared with a log unit reduction over the first 10 m of travel for indigenous, free-living groundwater bacteria in earlier tests. High rates of flagellate immobilization in the presence of aquifer sediments also was observed in the laboratory. However, immobilization rates for the laboratory-grown flagellates (initially 4 to 5 ??m) injected into the aquifer were not constant and decreased noticeably with increasing time and distance of travel. The decrease in propensity for grain surfaces was accompanied by a decrease in cell size, as the flagellates presumably readapted to aquifer conditions. Retardation and apparent dispersion were generally at least twofold greater than those observed earlier for indigenous groundwater bacteria but were much closer to those observed for highly surface active carboxylated latex microspheres. Field and laboratory results suggest that 2- ??m carboxylated microspheres may be useful as analogs in investigating several abiotic

  1. 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)

  2. Great expectations: Flow restoration and sediment transport in the Waimea River, Kaua'i

    Science.gov (United States)

    Gomez, Basil

    2018-04-01

    Conventional and novel observations made in the Waimea River basin between 1960 and 1995 permit the total riverine mass flux to be estimated and the influence that flow restoration will have on sediment dynamics in the river's lower reaches to be assessed. Flows between the threshold for sediment transport ( 6.0 m3 s-1) and the most effective flow (80.7 m3 s-1) recur annually and transport 60% of the Waimea River's suspended sediment load. Discharges of this magnitude essentially were unaffected by plantation era agricultural diversions of 2.3 ± 0.7 m3 s-1. The modern-day mass flux from the Waimea River basin is 155 ± 38 t km-2 y-1, and comparison with an independent cosmogenic nuclide-based estimate implies that it has remained at about this level for the past 10 ky. Previous work indicated that: (i) most of the sand the Waimea River transports to the coast is derived from steep, rapidly eroding, sparsely vegetated, bedrock-dominated hillslopes; and (ii) the sediment transport regime of the Waimea River is supply-limited at very high discharges (recurrence interval > 2.5 years). Consequently, major floods tend to remove sand from the estuary. Climate change has caused a statewide decline in heavy rainfall, and a commensurate decline in the magnitude of peak flows in the basin's pristine, undiverted headwaters over the past 97 years. The effect this secular change in climate presently is having on streamflow was foreshadowed in the late 1970s by a naturally occurring, warm Pacific Decadal Oscillation phase reduction in the magnitude of flows with low exceedance probabilities. Additionally, the controlling base level at the river mouth has risen and been displaced seaward. Simple proportionality approximations show that, for a constant sediment supply, aggradation will occur if either the magnitude of flows with a low exceedance probability declines and/or base level rises. Thus, anthropogenic stresses on Waimea River's lower reaches are not derived from the

  3. Release of Aged Contaminants from weathered sediments: Effects of sorbate speciation on scaling of reactive transport

    Energy Technology Data Exchange (ETDEWEB)

    Chorover, Jon [Univ. of Arizona, Tucson, AZ (United States); Perdrial, Nico [Univ. of Arizona, Tucson, AZ (United States); Mueller, Karl [Pennsylvania State Univ., University Park, PA (United States); Strepka, Caleb [Pennsylvania State Univ., University Park, PA (United States); O' Day, Peggy [Univ. of California, Merced, CA (United States); Rivera, Nelson [Univ. of California, Merced, CA (United States); Um, Wooyong [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Chang, Hyun-Shik [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Steefel, Carl [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Thompson, Aaron [Univ. of Georgia, Athens, GA (United States)

    2012-08-14

    Hanford sediments impacted by hyperalkaline high level radioactive waste have undergone incongruent silicate mineral weathering concurrent with contaminant uptake (Chorover et al., 2008). In this project, we studied the impact of background pore water (BPW) on strontium, cesium and iodine desorption and transport in Hanford sediments that were experimentally weathered by contact with simulated hyperalkaline tank waste leachate (STWL) solutions. Using those lab-weathered Hanford sediments (HS) and model precipitates formed during nucleation from homogeneous STWL solutions (HN), we (i) provided thorough characterization of reaction products over a matrix of field-relevant gradients in contaminant concentration, PCO2, and reaction time; (ii) improved molecular-scale understanding of how sorbate speciation controls contaminant desorption from weathered sediments upon removal of caustic sources; and (iii) developed a mechanistic, predictive model of meso- to field-scale contaminant reactive transport under these conditions. Below, we provide some detailed descriptions of our results from this three year study, recently completed following a one-year no cost extension.

  4. Release of aged contaminants from weathered sediments: Effects of sorbate speciation on scaling of reactive transport

    Energy Technology Data Exchange (ETDEWEB)

    Chorover, Jon; Perdrial, Nico; Mueller, Karl; Strepka, Caleb; O’Day, Peggy; Rivera, Nelson; Um, Wooyong; Chang, Hyun-Shik; Steefel, Carl; Thompson, Aaron

    2012-11-05

    Hanford sediments impacted by hyperalkaline high level radioactive waste have undergone incongruent silicate mineral weathering concurrent with contaminant uptake. In this project, we studied the impact of background pore water (BPW) on strontium, cesium and iodine desorption and transport in Hanford sediments that were experimentally weathered by contact with simulated hyperalkaline tank waste leachate (STWL) solutions. Using those lab-weathered Hanford sediments (HS) and model precipitates formed during nucleation from homogeneous STWL solutions (HN), we (i) provided thorough characterization of reaction products over a matrix of field-relevant gradients in contaminant concentration, partial pressure of carbon dioxide, and reaction time; (ii) improved molecular-scale understanding of how sorbate speciation controls contaminant desorption from weathered sediments upon removal of caustic sources; and (iii) developed a mechanistic, predictive model of meso- to field-scale contaminant reactive transport under these conditions. In this final report, we provide detailed descriptions of our results from this three-year study, completed in 2012 following a one-year no cost extension.

  5. Sensitivity and uncertainty analysis of a sediment transport model: a global approach

    Science.gov (United States)

    Chang, C.; Yang, J.; Tung, Y.

    1993-12-01

    Computerized sediment transport models are frequently employed to quantitatively simulate the movement of sediment materials in rivers. In spite of the deterministic nature of the models, the outputs are subject to uncertainty due to the inherent variability of many input parameters in time and in space, along with the lack of complete understanding of the involved processes. The commonly used first-order method for sensitivity and uncertainty analyses is to approximate a model by linear expansion at a selected point. Conclusions from the first-order method could be of limited use if the model responses drastically vary at different points in parameter space. To obtain the global sensitivity and uncertainty features of a sediment transport model over a larger input parameter space, the Latin hypercubic sampling technique along with regression procedures were employed. For the purpose of illustrating the methodologies, the computer model HEC2-SR was selected in this study. Through an example application, the results about the parameters sensitivity and uncertainty of water surface, bed elevation and sediment discharge were discussed.

  6. Characterizing long-term hydrologic-response and sediment-transport for the R-5 catchment.

    Science.gov (United States)

    Heppner, Christopher S; Loague, Keith

    2008-01-01

    Recently there have been several calls to establish long-term data collection networks to monitor near-surface hydrologic response and landscape evolution. The focus of this paper is a long-term dataset from the International Hydrologic Decade (1965-1974). The small upland catchment, known as R-5, located near Chickasha, Olahoma, has been the subject of considerable attention within the event-based hydrologic modeling community for more than 30 yr. Here, for the first time, 8 yr of continuous near-surface hydrologic-response and sediment-transport data are analyzed to show trends in the catchment's long-term behavior. The datasets include precipitation, temperature, solar radiation, soil-water content, infiltration, water discharge, and sediment discharge. Potential and actual evapotranspiration rates were estimated and used to calculate an average annual water balance for the catchment. Findings include, for example, that rainfall intensity rarely exceeds the threshold for Horton-type runoff, soil-water content is both spatially and temporally variable, and the water and sediment discharge rates are positively correlated. The R-5 data provide a unique opportunity to test (and refine) process-based models of continuous hydrologic response and sediment transport at the catchment scale for applications in the emerging fields of hydroecology and hydrogeomorphology.

  7. Khnifiss Beach's Black Sand: Provenance and Transport Pathways Investigation Using Heavy Minerals' Characterization

    Science.gov (United States)

    Adnani, M.; Elbelrhiti, H.; Ahmamou, M.; Masmoudi, L.

    2014-12-01

    Arid areas in south of Morocco suffer from silting problem causing destruction of villages infrastructure, roads, agriculture land and oasis heritage. Black sand on Khnifiss beach near Tarfaya city (S-W Morocco) is marked by enrichment of heavy minerals. This later is an important fraction that could help to assess the provenance and transport pathways of sediment. The sand's origin investigation could be useful to fight against erosion and silting problems from the source of supply, to this end, mineralogical analysis was carried out in Khnifiss beach's sand using Optic Microscope and Scanning Electronic Microscope with dispersive energy (SEM- EDS), in addition to physico-chemical analysis provided by Electronic Microprobe. The results revealed: (i) a high grade of oxides (Rutile, Ilmenite, Magnetite, Ulvöspinel) in samples, (ii) silicates (Quartz, Clinopyroxene, feldspar, Zircon), (iii) phosphate (apatite) and (iv) carbonate (calcite). The dominance of iron oxides justifies the black sand's colour. Then, the mineral composition supposes interference between different origins: proximal source (Calcareous cliff) for calcite, distal sources of oxides and silicates are supposed to be eroded and carried by Drâa valley from granite and igneous rocks in Anti-Atlasic field. Another source supposed might be a proximal volcanic island (Canaries island).

  8. Mechanics and modeling of flow, sediment transport and morphologic change in riverine lateral separation zones

    Science.gov (United States)

    Logan, Brandy L.; Nelson, Jonathan M.; McDonald, Richard R.; Wright, Scott A.

    2010-01-01

    Lateral separation zones or eddies in rivers are critically important features for sediment storage and for a variety of roles they play in riparian and aquatic ecology. As part of a larger effort to predict the morphology of lateral separation zones in the Colorado River in Grand Canyon for a selection of sediment supply and discharge scenarios, we evaluated the performance of two modeling techniques for predicting flow, sediment transport, and morphodynamics in eddies using field data. In order to understand the relative roles of various exchange mechanisms between the main channel and eddies, we applied two-dimensional unsteady and three-dimensional unsteady models in a reach containing a lateral separation zone. Both models were developed, calibrated, and evaluated using detailed field data comprising acoustic-Doppler velocity measurements, water-surface elevations, sediment concentration by size class, and bathymetry measured during a flood event in the Colorado River. Model results and measurements are used to develop a better understanding of the mechanics of water and sediment exchange between the eddy and the mainstem and other factors that control the morphology of the reach.

  9. The USA Nr Inventory: Dominant Sources and Primary Transport Pathways

    Science.gov (United States)

    Sabo, R. D.; Clark, C.; Sobota, D. J.; Compton, J.; Cooter, E. J.; Schwede, D. B.; Bash, J. O.; Rea, A.; Dobrowolski, J. P.

    2016-12-01

    Efforts to mitigate the deleterious effects of excess reactive nitrogen (Nr) on human health and ecosystem goods and service while ensuring food, biofuel, and fiber availability, is one of the most pressing environmental management challenges of this century. Effective management of Nr requires up to date inventories that quantitatively characterize the sources, transport, and transformation of Nr through the environment. The inherent complexity of the nitrogen cycle, however, through multiple exchange points across air, water, and terrestrial media, renders such inventories difficult to compile and manage. Previous Nr Inventories are for 2002 and 2007, and used data sources that have since been improved. Thus, this recent inventory will substantially advance the methodology across many sectors of the inventory (e.g. deposition and biological fixation in crops and natural systems) and create a recent snapshot that is sorely needed for policy planning and trends analysis. Here we use a simple mass balance approach to estimate the input-output budgets for all United States Geologic Survey Hydrologic Unit Code-8 watersheds. We focus on a recent year (i.e. 2012) to update the Nr Inventory, but apply the analytical approach for multiple years where possible to assess trends through time. We also compare various sector estimates using multiple methodologies. Assembling datasets that account for new Nr inputs into watersheds (e.g., atmospheric NOy deposition, food imports, biologic N fixation) and internal fluxes of recycled Nr (e.g., manure, Nr emmissions/volatilization) provide an unprecedented, data driven computation of N flux. Input-output budgets will offer insight into 1) the dominant sources of Nr in a watershed (e.g., food imports, atmospheric N deposition, or fertilizer), 2) the primary loss pathways for Nr (e.g., crop N harvest, volatilization/emissions), and 3) what watersheds are net sources versus sinks of Nr. These insights will provide needed clarity for

  10. BeachWin: Modelling groundwater effects on swash sediment transport and beach profile changes

    OpenAIRE

    Li, L.; Barry, D. A.; Pattiaratchi, C. B.; Masselink, G.

    2002-01-01

    Field and laboratory observations have shown that a relatively low beach groundwater table enhances beach accretion. These observations have led to the beach dewatering technique (artificially lowering the beach water table) for combating beach erosion. Here we present a process-based numerical model that simulates the interacting wave motion on the beach, coastal groundwater flow, swash sediment transport and beach profile changes. Results of model...

  11. 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

  12. Predicting Sediment Transport Dynamics in Ephemeral Channels: A Review of Literature

    Science.gov (United States)

    2006-09-01

    Montana, USA, and Nahal Yatir and Nahal Estemoa, Israel. Lecture notes in Earth Sciences, 52, Dynamics and Geomorphology of Mountain Rivers , Berlin...Graf, W. H. 1971. Hydraulics of sediment transport. New York: McGraw Hill. Graf, W. L. 1988. Fluvial processes in dryland rivers . Berlin: Springer...north central New Mexico approaching 200,000 ppm by weight and Nordin (1963) reported concentrations in the Rio Puerco, Paria, and Little Colorado

  13. Numerical modeling of cohesive sediment transport and bed morphology in estuaries

    OpenAIRE

    Leupi, Célestin; Deville, Michel; Altinakar, Mustafa S.

    2007-01-01

    Two major lines of investigation have been pursued in this thesis: (1) More efficient, robust and realistic numerical techniques are designed for the simulation of complex turbulent fluid flows; (2) A new algorithm and its analysis is performed in the context of multiphasic fluid flow, for a cohesive fine-grained sediment (fluid mud) transport in estuaries. Estuaries exist between marine and freshwater system where waters of different physical, chemical and biological composition meet, combin...

  14. Regulatory pathways for ATP-binding cassette transport proteins in kidney proximal tubules.

    Science.gov (United States)

    Masereeuw, Rosalinde; Russel, Frans G M

    2012-12-01

    The ATP-binding cassette transport proteins (ABC transporters) represent important determinants of drug excretion. Protective or excretory tissues where these transporters mediate substrate efflux include the kidney proximal tubule. Regulation of the transport proteins in this tissue requires elaborate signaling pathways, including genetic, epigenetic, nuclear receptor mediated, posttranscriptional gene regulation involving microRNAs, and non-genomic (kinases) pathways triggered by hormones and/or growth factors. This review discusses current knowledge on regulatory pathways for ABC transporters in kidney proximal tubules, with a main focus on P-glycoprotein, multidrug resistance proteins 2 and 4, and breast cancer resistance protein. Insight in these processes is of importance because variations in transporter activity due to certain (disease) conditions could lead to significant changes in drug efficacy or toxicity.

  15. The effect of tides and storm surges on sediment transport during overwash events

    Science.gov (United States)

    Wesselman, Daan; de Winter, Renske; Hoekstra, Piet; Oost, Albert; McCall, Robert; van der Vegt, Maarten

    2017-04-01

    Storm events generally result in elevated water levels at the meso-tidal Wadden Sea coast, the Netherlands. This can lead to overwash and inundation of parts of the barrier islands. Currently, large parts of the Dutch barriers are closed off by artificial dunes which prevent overwash during storms. In view of future sea-level rise measures to heighten the hinterland of the barriers island are investigated. A hypothesis is that on the long term the cross-shore sediment transport, caused by overwash and inundation events, can contribute to the vertical accretion of the barriers. Therefore, the partial re-opening of the dunes on the barrier island is considered by the Dutch management authorities. We identify the dominant cross-shore hydrodynamic and sediment transport processes during an overwash event to study the potential long-term sediment transport. In addition, we focus on the role of the back-barrier basin on overwash dynamics. An XBeach model was set-up and validated against field data collected during overwash on East-Schiermonnikoog, a non-vegetated tip of a barrier island. The simulated wave heights, periods, water levels and flow velocities agree well with the field data. With the validated XBeach model, simulations are executed for a wide variety of storm and tidal characteristics. From the model simulations we conclude that: (1) The erosion and transport of sediment across the beach crest is mainly driven by the cross-shore currents. Infragravity waves and short waves are less important for the sediment transport over the barrier island. (2) Maximum onshore transport occurs during more gentle storms (storm surge level of 1.5-2.0 m) instead of severe storms (storm surge level of 2.5-3.0 m). (3) For mixed-energy, meso-tidal barrier systems like the Wadden Sea, the dynamics of the back-barrier basin have to be taken into account. Water level gradients across the barrier island are strongly influenced by the tidal phase propagation and the difference in

  16. Spatio-temporal scaling effects on longshore sediment transport pattern along the nearshore zone

    Science.gov (United States)

    Khorram, Saeed; Ergil, Mustafa

    2018-03-01

    A measure of uncertainties, entropy has been employed in such different applications as coastal engineering probability inferences. Entropy sediment transport integration theories present novel visions in coastal analyses/modeling the application and development of which are still far-reaching. Effort has been made in the present paper to propose a method that needs an entropy-power index for spatio-temporal patterns analyses. Results have shown that the index is suitable for marine/hydrological ecosystem components analyses based on a beach area case study. The method makes use of six Makran Coastal monthly data (1970-2015) and studies variables such as spatio-temporal patterns, LSTR (long-shore sediment transport rate), wind speed, and wave height all of which are time-dependent and play considerable roles in terrestrial coastal investigations; the mentioned variables show meaningful spatio-temporal variability most of the time, but explanation of their combined performance is not easy. Accordingly, the use of an entropy-power index can show considerable signals that facilitate the evaluation of water resources and will provide an insight regarding hydrological parameters' interactions at scales as large as beach areas. Results have revealed that an STDDPI (entropy based spatio-temporal disorder dynamics power index) can simulate wave, long-shore sediment transport rate, and wind when granulometry, concentration, and flow conditions vary.

  17. Hybrid sediment transport model for the “linguado” channel, state of Santa Catarina, Brazil

    Directory of Open Access Journals (Sweden)

    Edison Conde Perez dos Santos

    2017-12-01

    Full Text Available This study involves an assessment of various artificial intelligence-related techniques which aim to produce a more robust system for sediment transport modeling. The intelligent systems developed in this research are directly applicable to academic knowledge and use data from a report on "water circulation assessment in the “Linguado” Channel and Babitonga Bay ,”Santa Catarina”, Brazil, developed by  Military Engineering Institute (IME. The solution employed for sediment transport was built using an intelligent system from the conception of two hybrid models. The first was a Neuro-Fuzzy (ANFIS hybrid model for the study of hydrodynamic behavior, aiming to determine flow rate in the channel. The second was a fuzzy genetic model, able to assess sediment transport in the “Linguado” Channel. The study's conclusion compares the different effects involved in the dredging equilibrium in the “Linguado” Channel according to this hybrid model with the results obtained using a finite element model in the MIKE21® software.

  18. Satellite-Based Assessment of Sediment Transport, Distribution and Resuspension Associated with the Atchafalaya River Discharge Plume

    Science.gov (United States)

    Walker, Nan; Roberts, Harry; Stone, Gregory; Bentley, Samuel; Huh, Oscar; Sheremet, Alexandru; Rouse, Larry; Inoue, Masamichi; Welsh, Susan; Hsu, S. A.

    2002-01-01

    Tbe Atchafalaya River discharges over 80 x 10(exp 6) tons of sediment annually onto the broad shallow continental shelf of central and western Louisiana. Satellite imagery from the NOAA AVHRR and Terra MODIS are used in this paper to quantify suspended sediment concentrations and to assess sediment transport processes along the Louisiana shelf under varying conditions of river discharge and wind forcing. The image data reveal the maim sources of sediment, direction of transport amd regional extent of wind-wave resuspension. The prevailing easterly winds transport much of the suspended sediments westward toward the Chernier Plain in a well-defined mud stream. Westerly flow rates of 25-50 cm/s (21-43 km per day) have been measured, yielding a transit time of about 1.5-2.5 days from the mouth of Atchafalaya Bay to the Chernier Plain. Progradation rates along the Chernier Plain coast reach 50 m per year. The westward-flowing Atchafalaya "mud stream" is rapidly disrupted by westerly winds and northerly winds, which accompany frequent winter storms and less frequent tropical storms or hurricanes. During these events, the coastal current reverses and sediments are rapidly transported out of Atchafalaya Bay and offshore where substantial sedimentary deposits can also be found. Offshore sediment fluxes during storm events, in combination with wind-wave resuspension, can result in surface sediment "plumes" extending 70 km offshore and 150 km alongshore. Field measurements of suspended sediment concentrations, current and wind velocities, and directions are used to assess sediment transport processes on the shelf. These combined processes are extending the pro-delta deposits of the Atchafalaya-Wax Lake delta complex far onto the continental shelf and supplying sediments for a renewal era of progradation along tbe downdrift Chernier Plain coast.

  19. Phase transition behavior of sediment transport at the sand-mud interface, across scales from flumes to the large rivers

    Science.gov (United States)

    Ma, H.; Nittrouer, J. A.; Wu, B.; Zhang, Y.; Mohrig, D. C.; Lamb, M. P.; Wang, Y.; Fu, X.; Moodie, A. J.; Naito, K.; Parker, G.

    2017-12-01

    Sediment dispersal and deposition creates deltaic landscapes, establishes coastlines, and produces fertile floodplains, all of which serve as critical landforms inhabited by a large proportion of humankind. If poorly managed, sediment loads in these environments can elevate and clog channels, thereby enhancing hazards such as severe flooding. Predictive descriptions of sediment loads, however, are not well constrained, especially for fine-grained (silt and very-fine sand) dispersal systems, which often include river deltas and coastlines. Here, we show efforts to collect and analyze an extensive sediment load database for fine-grained channels, spanning from small flume experiments to large rivers, in order to evaluate the nature of sediment flux. Our analyses determined that sediment transport exhibits two distinct transport phases, separated by a discontinuous transition, whereby sediment flux differs by one to two orders of magnitude. It is determined that the transition responds to the bed material grain size, and we propose a phase diagram based on this metric alone. These findings help elucidate why previous theories of sediment transport at the sand-silt interface, which are typically continuous, are not able to give satisfactory predictions across different scales and environments. Our work serves to help evaluate anthropic influences on rivers, deltas, and coastlines, and can be applied to better constrain sediment flux of paleo-fluvial systems found on Earth and Mars. For example, in situ measurements of sediment flux for the silty-sandy bed of the lower Yellow River, China, validate the aforementioned phase transition behavior, and illustrate that the channel resides near the transition of high to low efficiency transport modes. Recent dam construction and resulting downstream coarsening of the bed via armoring, however, might lead to the unintended consequence of enhancing flood risk by driving the system to a low efficiency transport mode with high

  20. Natural equilibria and anthropic effects on sediment transport in big river systems: The Nile case

    Science.gov (United States)

    Garzanti, Eduardo; Andò, Sergio; Padoan, Marta; Vezzoli, Giovanni; Villa, Igor

    2014-05-01

    The Nile River flows for ~ 6700 km, from Burundi and Rwanda highlands south of the Equator to the Mediterranean Sea at northern subtropical latitudes. It is thus the longest natural laboratory on Earth, a unique setting in which we are carrying out a continuing research project to investigate changes in sediment composition associated with a variety of chemical and physical processes, including weathering in equatorial climate and hydraulic sorting during transport and deposition. Petrographic, mineralogical, chemical, and isotopic fingerprints of sand and mud have been monitored along all Nile branches, from the Kagera and White Nile draining Archean, Paleoproterozoic and Mesoproterozoic basements uplifted along the western branch of the East African rift, to the Blue Nile and Atbara Rivers sourced in Ethiopian volcanic highlands made of Oligocene basalt. Downstream of the Atbara confluence, the Nile receives no significant tributary water and hardly any rainfall across the Sahara. After construction of the Aswan High Dam in 1964, the Nile ceased to be an active conveyor-belt in Egypt, where the mighty river has been tamed to a water canal; transported sediments are thus chiefly reworked from older bed and levee deposits, with minor contributions from widyan sourced in the Red Sea Hills and wind-blown desert sand and dust. Extensive dam construction has determined a dramatic sediment deficit at the mouth, where deltaic cusps are undergoing ravaging erosion. Nile delta sediments are thus recycled under the effect of dominant waves from the northwest, the longest Mediterranean fetch direction. Nile sands, progressively enriched in more stable minerals such as quartz and amphiboles relative to volcanic rock fragments and pyroxene, thus undergo multistep transport by E- and NE-directed longshore currents all along the coast of Egypt and Palestine, and are carried as far as Akko Bay in northern Israel. Nile mud reaches the Iskenderun Gulf in southern Turkey. A full

  1. Lateral baroclinic forcing enhances sediment transport from shallows to channel in an estuary

    Science.gov (United States)

    Lacy, Jessica R.; Gladding, Steve; Brand, Andreas; Collignon, Audric; Stacey, Mark

    2014-01-01

    We investigate the dynamics governing exchange of sediment between estuarine shallows and the channel based on field measurements at eight stations spanning the interface between the channel and the extensive eastern shoals of South San Francisco Bay. The study site is characterized by longitudinally homogeneous bathymetry and a straight channel, with friction more important than the Coriolis forcing. Data were collected for 3 weeks in the winter and 4 weeks in the late summer of 2009, to capture a range of hydrologic and meteorologic conditions. The greatest sediment transport from shallows to channel occurred during a pair of strong, late-summer wind events, with westerly winds exceeding 10 m/s for more than 24 h. A combination of wind-driven barotropic return flow and lateral baroclinic circulation caused the transport. The lateral density gradient was produced by differences in temperature and suspended sediment concentration (SSC). During the wind events, SSC-induced vertical density stratification limited turbulent mixing at slack tides in the shallows, increasing the potential for two-layer exchange. The temperature- and SSC-induced lateral density gradient was comparable in strength to salinity-induced gradients in South Bay produced by seasonal freshwater inflows, but shorter in duration. In the absence of a lateral density gradient, suspended sediment flux at the channel slope was directed towards the shallows, both in winter and during summer sea breeze conditions, indicating the importance of baroclinically driven exchange to supply of sediment from the shallows to the channel in South San Francisco Bay and systems with similar bathymetry.

  2. The Bagnold Dunes in Southern Summer: Active Sediment Transport on Mars Observed by the Curiosity rover

    Science.gov (United States)

    Baker, M. M.; Lapotre, M. G. A.; Bridges, N. T.; Minitti, M. E.; Newman, C. E.; Ehlmann, B. L.; Vasavada, A. R.; Edgett, K. S.; Lewis, K. W.

    2017-12-01

    Since its landing at Gale crater five years ago, the Curiosity rover has provided us with unparalleled data to study active surface processes on Mars. Repeat imaging campaigns (i.e. "change-detection campaigns") conducted with the rover's cameras have allowed us to study Martian atmosphere-surface interactions and characterize wind-driven sediment transport from ground-truth observations. Utilizing the rover's periodic stops to image identical patches of ground over multiple sols, these change-detection campaigns have revealed sediment motion over a wide range of grain sizes. These results have been corroborated in images taken by the rover's hand lens imager (MAHLI), which have captured sand transport occurring on the scale of minutes. Of particular interest are images collected during Curiosity's traverse across the Bagnold Dune Field, the first dune field observed to be active in situ on another planet. Curiosity carried out the first phase of the Bagnold Dunes campaign (between Ls 72º and 109º) along the northern edge of the dune field at the base of Aeolis Mons, where change-detection images showed very limited sediment motion. More recently, a second phase of the campaign was conducted along the southern edge of the dune field between Ls 312º to 345º; here, images captured extensive wind-driven sand motion. Observations from multiple cameras show ripples migrating to the southwest, in agreement with predicted net transport within the dune field. Together with change-detection observations conducted outside of the dune field, the data show that ubiquitous Martian landscapes are seasonally active within Gale crater, with the bulk of the sediment flux occurring during southern summer.

  3. Impacts of Suspended Sediment and Estuarine - Shelf Exchange Pathways on Shelf Ecosystem Dynamics in the Northern Gulf of Mexico

    Science.gov (United States)

    Wiggert, J. D.; Pan, C.; Dinniman, M. S.; Lau, Y.; Fitzpatrick, P. J.; O'Brien, S. J.; Bouchard, C.; Quas, L. M.; Miles, T. N.; Cambazoglu, M. K.; Dykstra, S. L.; Dzwonkowski, B.; Jacobs, G. A.; Church, I.; Hofmann, E. E.

    2017-12-01

    A circulation model based on the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System, with coupled biogeochemical and sediment transport modules, has been implemented for Mississippi Sound and the adjacent continental shelf region. The model has 400-m horizontal resolution, 24 vertical layers, and includes wetting/drying capability to resolve shallow inshore regions. The circulation model was spun-up using oceanographic initial and lateral boundary conditions provided by a 1-km resolution regional implementation of the Navy Coastal Ocean Model (NCOM) in the Gulf of Mexico. The biogeochemical module includes multiple size classes of phytoplankton, zooplankton and detritus, a fish larvae compartment, and explicitly tracks dissolved oxygen with benthic cycling interaction. The sediment transport model is implemented based on benthic mapping data that provides bottom sediment type distributions and spatio-temporal validation. A regionally specific atmospheric forcing product that provides improved spatial and temporal resolution, including diurnal sea breeze impacts, has been developed and applied. Model experiments focus on periods when comprehensive ship-based sampling was deployed by the CONCORDE (Consortium for Coastal River-Dominated Ecosystems) research program, which was established to investigate the complex fine-scale biological, chemical and physical interactions in a marine system controlled by pulsed-river plume dynamics. Biophysical interactions and biogeochemical variability associated with estuarine - shelf exchanges between nearshore lagoonal estuarine waters and the continental shelf revealed by the model provide new insight into how seasonal variation of hydrological forcing conditions influence ecological and biogeochemical processes in the highly productive Northern Gulf region. Application of the COAWST-based model system with and without inclusion of the sediment transport module demonstrates how suspended sediment in the

  4. Desiccation of sediments affects assimilate transport within aquatic plants and carbon transfer to microorganisms.

    Science.gov (United States)

    von Rein, I; Kayler, Z E; Premke, K; Gessler, A

    2016-11-01

    With the projected increase in drought duration and intensity in future, small water bodies, and especially the terrestrial-aquatic interfaces, will be subjected to longer dry periods with desiccation of the sediment. Drought effects on the plant-sediment microorganism carbon continuum may disrupt the tight linkage between plants and microbes which governs sediment carbon and nutrient cycling, thus having a potential negative impact on carbon sequestration of small freshwater ecosystems. However, research on drought effects on the plant-sediment carbon transfer in aquatic ecosystems is scarce. We therefore exposed two emergent aquatic macrophytes, Phragmites australis and Typha latifolia, to a month-long summer drought in a mesocosm experiment. We followed the fate of carbon from leaves to sediment microbial communities with 13 CO 2 pulse labelling and microbial phospholipid-derived fatty acid (PLFA) analysis. We found that drought reduced the total amount of carbon allocated to stem tissues but did not delay the transport. We also observed an increase in accumulation of 13 C-labelled sugars in roots and found a reduced incorporation of 13 C into the PLFAs of sediment microorganisms. Drought induced a switch in plant carbon allocation priorities, where stems received less new assimilates leading to reduced starch reserves whilst roots were prioritised with new assimilates, suggesting their use for osmoregulation. There were indications that the reduced carbon transfer from roots to microorganisms was due to the reduction of microbial activity via direct drought effects rather than to a decrease in root exudation or exudate availability. © 2016 German Botanical Society and The Royal Botanical Society of the Netherlands.

  5. Unified theory of non-suspended sediment transport mediated by a Newtonian fluid

    Science.gov (United States)

    Pähtz, Thomas; Durán, Orencio

    2017-04-01

    We present a unified theory of steady, homogeneous, non-suspended transport of nearly uniform spheres mediated by an arbitrary Newtonian fluid. The theory consists of elements that are rigorously derived from Newton's axioms and of semi-empirical elements that well describe simulation data, obtained using a coupled DEM/RANS numerical model of sediment transport in a Newtonian fluid (Durán et al., POF 103306, 2012), for the entire simulated range of the particle-fluid-density ratio s=ρ_p/ρ_f, particle Reynolds number Re_p=√{(s-1)gd^3}/ν, and Shields number Θ=τ/[(ρ_p-ρ_f)gd], where g is the gravitational constant, d the mean particle diameter, and ν the kinematic viscosity. The theory takes into account our recent numerical finding that the mode of entrainment of bed sediment is controlled by the `impact number' Im=Re_p√{s+0.5} (https://arxiv.org/abs/1605.07306), with entrainment through particle-bed impacts dominating most conditions (including turbulent bedload transport). Despite not being fitted to experimental data, the theory simultaneously reproduces measurements in air (s≈2100) and liquids (s≈1{-}5) of the transport cessation threshold Θ^ext (https://arxiv.org/abs/1602.07079), obtained from extrapolation to vanishing transport, and the dimensionless value Q^\\ast=Q/(ρ_p√{(s-1)gd^3}) of the sediment transport rate Q. From the theory and simulations, we learn that considering added-mass, lubrication, fluid lift, and/or history forces is not required to quantitatively reproduce measurements. However, collisions between transported particles cannot be neglected as they are strongly influencing the scaling of Q_\\ast with Θ. We find such collisions are behind the asymptotic scaling Q_\\ast∝Θ^3Rep measured for transport in viscous liquids and also indirectly behind a transition from a linear scaling Q_\\ast∝√{Θ^ex_t}(Θ-Θ^ex_t) to a non-linear scaling Q_\\ast∝√{Θ}(Θ-Θ^ex_t) of the transport rate in turbulent bedload and

  6. Denitrification pathways and rates in the sandy sediments of the Georgia continental shelf, USA

    OpenAIRE

    Ingall Ellery; Vance-Harris Cynthia

    2005-01-01

    Denitrification in continental shelf sediments has been estimated to be a significant sink of oceanic fixed nitrogen (N). The significance and mechanisms of denitrification in organic-poor sands, which comprise 70% of continental shelf sediments, are not well known. Core incubations and isotope tracer techniques were employed to determine processes and rates of denitrification in the coarse-grained, sandy sediments of the Georgia continental shelf. In these sediments, heterotrophic denitrifi...

  7. Investigation of the pathway of contaminated soil transported to plant surfaces by raindrop splash

    International Nuclear Information System (INIS)

    Dreicer, M.; Hakonson, T.E.; Whicker, F.W.; White, G.C.

    1983-01-01

    The environmental transport pathway of soil-borne radioisotopes to vegetation surfaces via raindrop splash was studied. The data show that soil can significantly contribute to the contamination found on plants. Further detailed study is needed to calculate the rate constant for the raindrop splash and retention pathways. 8 references, 1 figure

  8. SIMULATION OF SEDIMENT TRANSPORT IN THE JEZIORO KOWALSKIE RESERVOIR LOCATED IN THE GLOWNA RIVER

    Directory of Open Access Journals (Sweden)

    Joanna Jaskuła

    2015-07-01

    Full Text Available The purpose of the presented research is the analysis of bed elevation changes caused by sediment accumulation in the Jezioro Kowalskie reservoir. The Jezioro Kowalskie reservoir is a two stage reservoir constructed in such a way that the upper preliminary zone is separated from the main part of the reservoir. The split of the reservoir parts is done with a small pre-dam, located in Jerzykowo town. The analysis of such a construction impact on changes of bed elevations in the reservoir in different flow conditions is presented. The HEC-RAS 5.0 Beta model is used for simulations. The sediment transport intensity is calculated from England-Hansen and Meyer-Peter and Muller formulae. The results showed the processes of sediment accumulation and slight erosion occuring in the preliminary zone of the reservoir. The choice of the flow intensity does not have a huge importance. Similar results are obtained for low as well as high flows. The results confirm, that two stage construction with separated preliminary zone is effective method preventing from the sedimentation of the reservoir.

  9. Generation of a Design Flood-Event Scenario for a Mountain River with Intense Sediment Transport

    Directory of Open Access Journals (Sweden)

    Alessio Radice

    2016-12-01

    Full Text Available International directives encourage the incorporation of sediment transport analyses into flood risk assessment, in recognition of the significant role played by sediment in flood hazard. However, examples of risk analysis frameworks incorporating the effect of sediment transport are still not widespread in the literature, resulting in a lack of clear guidelines. This manuscript considers a study site in the Italian Alps and presents a hydro-morphologic model for generation of flood scenarios towards hazard assessment. The analysis is concentrated on a design flood event with 100-year return period, for which an outflowing discharge is computed as a result of the river modeling. However, it is also argued how suitable model input parameter values can be obtained from analyses of river flows in a yearly duration curve. Modeling tools are discussed with respect to their capabilities and limitations. The results of the analysis are site-specific, but the proposed methodology can be exported to other hydro-graphic basins.

  10. Predicting uncertainty in sediment transport and landscape evolution - the influence of initial surface conditions

    Science.gov (United States)

    Hancock, G. R.; Coulthard, T. J.; Lowry, J. B. C.

    2016-05-01

    Numerical landscape evolution models were initially developed to examine natural catchment hydrology and geomorphology and have become a common tool to examine geomorphic behaviour over a range of time and space scales. These models all use a digital elevation model (DEM) as a representation of the landscape surface and a significant issue is the quality and resolution of this surface. Here we focus on how subtle perturbations or roughness on the DEM surface can produce alternative model results. This study is carried out by randomly varying the elevations of the DEM surface and examining the effect on sediment transport rates and geomorphology for a proposed rehabilitation design for a post-mining landscape using multiple landscape realisations with increasing magnitudes of random changes. We show that an increasing magnitude of random surface variability does not appear to have any significant effect on sediment transport over millennial time scales. However, the random surface variability greatly changes the temporal pattern or delivery of sediment output. A significant finding is that all simulations at the end of the 10,000 year modelled period are geomorphologically similar and present a geomorphological equifinality. However, the individual patterns of erosion and deposition were different for repeat simulations with a different sequence of random perturbations. The alternative positions of random perturbations strongly influence local patterns of hillslope erosion and evolution together with the pattern and behaviour of deposition. The findings demonstrate the complex feedbacks that occur even within a simple modelled system.

  11. On integrated sediment transport modelling for flash events in mountain environments

    Science.gov (United States)

    Radice, Alessio; Giorgetti, Elisa; Brambilla, Davide; Longoni, Laura; Papini, Monica

    2012-02-01

    Sediment production and transport in mountain basins during short-term, intense events depend on a variety of processes. Available models typically consider a limited portion of the phenomenological chain, frequently either sediment supply or solid transport along the waterways. On the other hand, proper depiction of on-site processes requires ability to model all the process stages and suitable integration between different models. In this manuscript, an integrated modelling is attempted for small catchments in Italian Alpine foothills. The integrated approach has involved: (i) hydrologic estimation of peak discharge, (ii) evaluation of the volumetric sediment supply into the stream, and (iii) computation of the morphologic evolution of the river bed. The results are discussed focussing on: (i) the feasibility of a joint modelling like the one presented, in the light of all the limitations imposed by the different nature of hillslope-devoted and river-devoted models; and (ii) the sensitivity of the obtained results to some parameters, for an assessment of result reliability.

  12. Sediment-driven mercury transport in post-fire storm runoff

    Science.gov (United States)

    Burke, M. P.; Ferreira, M.; Hogue, T. S.; Jay, J.; Rademacher, L. K.

    2009-12-01

    Wildfire alters terrestrial stores of mercury (Hg) within a watershed, releasing Hg to the atmosphere and creating conditions that can be conducive to Hg export in streamwater. Hg transport to terrestrial waters is often associated with suspended sediments and organic matter, and particulate-bound Hg delivery to downstream water bodies may be enhanced following wildfire. Burned watersheds experience increased overland flow, soil erosion, sediment transport, and, consequently, transport of sediment bound contaminants during early post-fire storm events. Southern California’s September 2006 Day Fire consumed 660km2 and almost 50% of the 512km2 Piru Creek watershed. Piru Creek drains into Pyramid Lake, a storage reservoir for the California State Water Project, which provides drinking water for Los Angeles. Streamwater was collected from Piru Creek watershed over a 1.5 year period following the Day Fire, on a monthly basis during low flow periods, and every two hours during storm events using an automated sampler. Samples were analyzed for both dissolved and total Hg, total suspended solids, and basic anions and cations. Low Hg concentrations (> 1ng Hg/ L dissolved and > 5ng Hg/L total) were measured in inter-storm samples. The first winter (2006-07) following the Day Fire was one of the driest on record, with precipitation totals (130mm) less than one third of normal. The only significant storm measured total Hg concentrations just slightly higher than the inter-storm samples, while no change was observed in the dissolved Hg concentrations. However, these total Hg concentrations were well correlated to TSS measurements (r2 = 0.91) and followed the storm hydrograph. The following winter (2007-08) brought higher precipitation totals (370mm) and more intense storms. Elevated, turbid stream flow was observed in Piru Creek during many of the 2007-08 storms. Little change was observed in the dissolved Hg concentrations of the storm samples; however, a two-order magnitude

  13. Sediment transport along the Cap de Creus Canyon flank during a mild, wet winter

    Directory of Open Access Journals (Sweden)

    J. Martín

    2013-05-01

    Full Text Available Cap de Creus Canyon (CCC is known as a preferential conduit for particulate matter leaving the Gulf of Lion continental shelf towards the slope and the basin, particularly in winter when storms and dense shelf water cascading coalesce to enhance the seaward export of shelf waters. During the CASCADE (CAscading, Storm, Convection, Advection and Downwelling Events cruise in March 2011, deployments of recording instruments within the canyon and vertical profiling of the water column properties were conducted to study with high spatial-temporal resolution the impact of such processes on particulate matter fluxes. In the context of the mild and wet 2010–2011 winter, no remarkable dense shelf water formation was observed. On the other hand, the experimental setup allowed for the study of the impact of E-SE storms on the hydrographical structure and the particulate matter fluxes in the CCC. The most remarkable feature in terms of sediment transport was a period of dominant E-SE winds from 12 to 16 March, including two moderate storms (maximum significant wave heights = 4.1–4.6 m. During this period, a plume of freshened, relatively cold and turbid water flowed at high speeds along the southern flank of the CCC in an approximate depth range of 150–350 m. The density of this water mass was lighter than the ambient water in the canyon, indicating that it did not cascade off-shelf and that it merely downwelled into the canyon forced by the strong cyclonic circulation induced over the shelf during the storms and by the subsequent accumulation of seawater along the coast. Suspended sediment load in this turbid intrusion recorded along the southern canyon flank oscillated between 10 and 50 mg L−1, and maximum currents speeds reached values up to 90 cm s−1. A rough estimation of 105 tons of sediment was transported through the canyon along its southern wall during a 3-day-long period of storm-induced downwelling. Following the veering of the wind

  14. Hydrodynamic sorting and transport of terrestrially derived organic carbon in sediments of the Mississippi and Atchafalaya Rivers

    Science.gov (United States)

    Bianchi, Thomas S.; Galler, John J.; Allison, Mead A.

    2007-06-01

    Over the course of two years, four cruises were conducted at varying levels of discharge in the lower Mississippi and Atchafalaya Rivers (MR and AR) where grab samples were collected from sand- and mud-dominated sediments. The tetramethylammonium hydroxide (TMAH) thermochemolysis method was used to determine sources of terrestrially derived organic carbon (OC) in these two sediment types, to examine the effects of hydrodynamic sorting on lignin sources in river sediments. Average lignin concentrations in the lower MR were 1.4 ± 1.1 mg gOC -1 at English Turn (ET) and 10.4 ± 27.4 mg gOC -1 at Venice. Using these concentrations, annual lignin fluxes to the Gulf of Mexico, from tidal and estuarine mud remobilization at ET and Venice, were 3.1 ± 2.5 × 10 5 kg and 11.4 ± 30.0 × 10 5 kg, respectively. Much of the lignin-derived materials in muddy sediments appeared to be derived from non-woody grass-like sources - which should decay more quickly than the woody materials typically found in the sandy deposits. The average total OC% (1.93 ± 0.47) of English Turn sands yields an annual flux of 0.34 ± 0.09 × 10 9 kg. Lignin flux in the English Turn sands (3.6 ± 2.6 mg gC -1) using the numbers above would be 12.2 ± 9.4 × 10 5 kg. The extensive amounts of sand-sized woody materials (coffee-grinds) found in the sandy sediments in both the AR and MR are likely derived from woody plant materials. This is the first time it has been demonstrated that sandy sediments in the MR provide an equally important pathway (compared to muds) for the transport of terrestrially derived organic matter to the northern Gulf of Mexico. Using the AR average %OC in sand (1.16 ± 0.72), we estimated an annual flux of OC to the shelf of 0.13 ± 0.07 × 10 9 kg. Lignin flux for AR sands was estimated to be 12.4 ± 12.1 × 10 5 kg. Despite the high error associated with these numbers, we observe for the first time that the flux of lignin in sandy sediments in the AR to the northern Gulf of

  15. Assimilation of remote sensing observations into a sediment transport model of China's largest freshwater lake: spatial and temporal effects.

    Science.gov (United States)

    Zhang, Peng; Chen, Xiaoling; Lu, Jianzhong; Zhang, Wei

    2015-12-01

    Numerical models are important tools that are used in studies of sediment dynamics in inland and coastal waters, and these models can now benefit from the use of integrated remote sensing observations. This study explores a scheme for assimilating remotely sensed suspended sediment (from charge-coupled device (CCD) images obtained from the Huanjing (HJ) satellite) into a two-dimensional sediment transport model of Poyang Lake, the largest freshwater lake in China. Optimal interpolation is used as the assimilation method, and model predictions are obtained by combining four remote sensing images. The parameters for optimal interpolation are determined through a series of assimilation experiments evaluating the sediment predictions based on field measurements. The model with assimilation of remotely sensed sediment reduces the root-mean-square error of the predicted sediment concentrations by 39.4% relative to the model without assimilation, demonstrating the effectiveness of the assimilation scheme. The spatial effect of assimilation is explored by comparing model predictions with remotely sensed sediment, revealing that the model with assimilation generates reasonable spatial distribution patterns of suspended sediment. The temporal effect of assimilation on the model's predictive capabilities varies spatially, with an average temporal effect of approximately 10.8 days. The current velocities which dominate the rate and direction of sediment transport most likely result in spatial differences in the temporal effect of assimilation on model predictions.

  16. Vitamin B12 transport from food to the body's cells--a sophisticated, multistep pathway

    DEFF Research Database (Denmark)

    Nielsen, Marianne J; Rasmussen, Mie R; Andersen, Christian B F

    2012-01-01

    Vitamin B(12) (B(12); also known as cobalamin) is a cofactor in many metabolic processes; deficiency of this vitamin is associated with megaloblastic anaemia and various neurological disorders. In contrast to many prokaryotes, humans and other mammals are unable to synthesize B(12). Instead...... in the transport pathway are also known culprits of functional B(12) deficiency. Biochemical and genetic approaches have identified novel proteins in the B(12) transport pathway--now known to involve more than 15 gene products--delineating a coherent pathway for B(12) trafficking from food to the body's cells...

  17. Runoff and suspended sediment transport after plantation interventions in experimental catchments with contrasting rainfall conditions, Chile

    Science.gov (United States)

    Iroume, A.; Schuller, P.; Bronstert, A.; Carey, P.; Palacios, H.; Ulloa, H.

    2012-04-01

    Experimental catchments located in sites with contrasting annual rainfall (Nacimiento, 37° 28" S, 72° 42" W, long term mean annual rainfall ~ 1,200 mm, and Los Ulmos, 40° 02" S, 73° 06" W, long term mean annual rainfall ~ 2,500 mm) are been monitored to study the long term effects of different forest plantation practices on runoff and suspended sediment transport. In each site, one control and one treatment catchment (12.6 and 7.7 ha in Nacimiento and 19.8 and 7.7 ha in Los Ulmos) are monitored. All the catchments are controlled by purpose-built V-notch weir gauging stations equipped with continuous water level recorders and suspended sediment is quantified in these stations from automatically collected integrated water samples. After a calibration period the plantation of one paired catchment in each site was clearfelled. Treated and control catchments will be from now on identified as NT and LUT and NC and LUT respectively. The Pinus radiata plantation in NT was clearfelled during the first half of April 2010, while the Eucalyptus globulus plantation in LUT was partially clearfelled in November 2009 and then completed in April 2010. After clearfelling runoff increases were observed in both harvested catchments as compared with the pre-treatment runoff trend between treatment and control catchments. In the Nacimiento site, mean monthly values for suspended sediment loads registered for the pre, during and post-treatment periods are not much different for NT and NC. For the pre-treatment period (April 2008 to March 2010), mean monthly suspended sediment loads were 12.8 kg/ha in NC and 16.2 kg/ha in NT, and 0.9 kg/ha in NC and 2.7 kg/ha in NT during the harvesting operations (April 2010). Mean monthly suspended sediment loads during the first year of the post-harvesting period (May to December 2010) were 69.9 kg/ha in NC and 59 kg/ha in NT and 0.9 kg/ha in NC and 6.2 kg/ha in NT during the year after clearfelling (January to June 2011). Year 2010 was extremely

  18. Transport and deposition of asbestos-rich sediment in the Sumas River, Whatcom County, Washington

    Science.gov (United States)

    Curran, Christopher A.; Anderson, Scott W.; Barbash, Jack E.; Magirl, Christopher S.; Cox, Stephen E.; Norton, Katherine K.; Gendaszek, Andrew S.; Spanjer, Andrew R.; Foreman, James R.

    2016-02-08

    Heavy sediment loads in the Sumas River of Whatcom County, Washington, increase seasonal turbidity and cause locally acute sedimentation. Most sediment in the Sumas River is derived from a deep-seated landslide of serpentinite that is located on Sumas Mountain and drained by Swift Creek, a tributary to the Sumas River. This mafic sediment contains high amounts of naturally occurring asbestiform chrysotile. A known human-health hazard, asbestiform chrysotile comprises 0.25–37 percent, by mass, of the total suspended sediment sampled from the Sumas River as part of this study, which included part of water year 2011 and all of water years 2012 and 2013. The suspended-sediment load in the Sumas River at South Pass Road, 0.6 kilometers (km) downstream of the confluence with Swift Creek, was 22,000 tonnes (t) in water year 2012 and 49,000 t in water year 2013. The suspended‑sediment load at Telegraph Road, 18.8 km downstream of the Swift Creek confluence, was 22,000 t in water year 2012 and 27,000 t in water year 2013. Although hydrologic conditions during the study were wetter than normal overall, the 2-year flood peak was only modestly exceeded in water years 2011 and 2013; runoff‑driven geomorphic disturbance to the watershed, which might have involved mass wasting from the landslide, seemed unexceptional. In water year 2012, flood peaks were modest, and the annual streamflow was normal. The fact that suspended-sediment loads in water year 2012 were equivalent at sites 0.6 and 18.8 km downstream of the sediment source indicates that the conservation of suspended‑sediment load can occur under normal hydrologic conditions. The substantial decrease in suspended-sediment load in the downstream direction in water year 2013 was attributed to either sedimentation in the intervening river reach, transfer to bedload as an alternate mode of sediment transport, or both.The sediment in the Sumas River is distinct from sediment in most other river systems because of the

  19. Linking Arenicola marina irrigation behavior to oxygen transport and dynamics in sandy sediments

    DEFF Research Database (Denmark)

    Timmermann, Karen; Banta, Gary T.; Glud, Ronnie Nøhr

    2007-01-01

    In this study we examine how the irrigation behavior of the common lugworm Arenicola marina affects the distribution, transport and dynamics of oxygen in sediments using microelectrodes, planar optodes and diagenetic modeling. The irrigation pattern was characterized by a regular recurring periods....... Model results indicated that oxygen consumption also was higher in the feeding pocket/funnel compared to the activity in surface sediments. An oxygen budget revealed that 49% of the oxygen pumped into the burrow during lugworm irrigation was consumed by the worm itself while 23% supported the diffusive...... of active irrigation lasting approximately 15 min separated by a 15 min rest period. The mean pumping rate during irrigation was 52 ml h-1. Oxygen dynamics and distribution around the tail shaft was closely related to irrigation pattern but independent of pumping rate. During irrigation the oxygen...

  20. Transport of Water, Carbon, and Sediment Through the Yukon River Basin

    Science.gov (United States)

    Brabets, Timothy P.; Schuster, Paul F.

    2008-01-01

    INTRODUCTION In 2001, the U.S. Geological Survey (USGS) began a water-quality study of the Yukon River. The Yukon River Basin (YRB), which encompasses 330,000 square miles in northwestern Canada and central Alaska (fig. 1), is one of the largest and most diverse ecosystems in North America. The Yukon River is more than 1,800 miles long and is one of the last great uncontrolled rivers in the world, and is essential to the eastern Bering Sea and Chukchi Sea ecosystems, providing freshwater runoff, sediments, and nutrients (Brabets and others, 2000). Despite its remoteness, recent studies (Hinzman and others, 2005; Walvoord and Striegl, 2007) indicate the YRB is changing. These changes likely are in response to a warming trend in air temperature of 1.7i??C from 1951 to 2001 (Hartmann and Wendler, 2005). As a result of this warming trend, permafrost is thawing in the YRB, ice breakup occurs earlier on the main stem of the Yukon River and its tributaries, and timing of streamflow and movement of carbon and sediment through the basin is changing (Hinzman and others, 2005; Walvoord and Striegl, 2007). One of the most striking characteristics in the YRB is its seasonality. In the YRB, more than 75 percent of the annual streamflow runoff occurs during a five month period, May through September. This is important because streamflow determines when, where, and how much of a particular constituent will be transported. As an example, more than 95 percent of all sediment transported during an average year also occurs during this period (Brabets and others, 2000). During the other 7 months, streamflow, concentrations of sediment and other water-quality constituents are low and little or no sediment transport occurs in the Yukon River and its tributaries. Streamflow and water-quality data have been collected at more than 50 sites in the YRB (Dornblaser and Halm, 2006; Halm and Dornblaser, 2007). Five sites have been sampled more than 30 times and others have been sampled twice

  1. The role of suspension events in cross-shore and longshore suspended sediment transport in the surf zone

    Science.gov (United States)

    Jaffe, Bruce E.

    2015-01-01

    Suspension of sand in the surf zone is intermittent. Especially striking in a time series of concentration are periods of intense suspension, suspension events, when the water column suspended sediment concentration is an order of magnitude greater than the mean concentration. The prevalence, timing, and contribution of suspension events to cross-shore and longshore suspended sediment transport are explored using field data collected in the inner half of the surf zone during a large storm at Duck, NC. Suspension events are defined as periods when the concentration is above a threshold. Events tended to occur during onshore flow under the wave crest, resulting in an onshore contribution to the suspended sediment transport. Even though large events occurred less than 10 percent of the total time, at some locations onshore transport associated with suspension events was greater than mean-current driven offshore-directed transport during non-event periods, causing the net suspended sediment transport to be onshore. Events and fluctuations in longshore velocity were not correlated. However, events did increase the longshore suspended sediment transport by approximately the amount they increase the mean concentration, which can be up to 35%. Because of the lack of correlation, the longshore suspended sediment transport can be modeled without considering the details of the intensity and time of events as the vertical integration of the product of the time-averaged longshore velocity and an event-augmented time-averaged concentration. However, to accurately model cross-shore suspended sediment transport, the timing and intensity of suspension events must be reproduced.

  2. Carbonate Geochemistry of Marine Authigenic Carbonates and Host Sediments: Exploring Mineral Formation Pathways and Organic Preservation Potential in Modern Sediments

    Science.gov (United States)

    Smirnoff, M. N.; Loyd, S. J.

    2016-12-01

    Ancient authigenic dolomites (e.g., concretions) have been long studied in order to determine formation conditions and provide insight into shallow diagenetic environments. The formation of these dolomites is commonly attributed to the anaerobic microbial degradation of organic matter (a process that can increase the local pore water alkalinity), based on carbon isotope as well as other geochemical data. Authigenic dolomites also occur in modern, "still soft" sediments rich in organic matter. However, a comprehensive carbon isotopic characterization of these precipitates has yet to be conducted. Preliminary data show a wide range of δ13C values (about -11 to +12‰). Positive values that typify dolomites of the Gulf of California and the southwestern African margin indicate methanogenesis. Dolomites of the Peru margin and Cariaco Basin yield negative values that may represent a variety of organic matter degradation mechanisms. Regardless of specific mechanisms, organic matter degradation can promote authigenesis. Ultimately, mineralization encases primary sedimentary components and may act to preserve organic matter from subsequent degradation due to permeability reduction resulting from cementation. Concretionary carbonates have been found to preserve macro and micro fossils, metastable sedimentary grains, magnetic minerals, sedimentary structures, various specific organic compounds, and overmature organic matter exposed in outcrop. However, a similar protective relationship has not been demonstrated for disseminated, bulk organic matter in still-soft sediments. The study of these sediments 1) reveal the relationship between organic carbon degradation and authigenesis and 2) may provide insight into the potential of cementation to preserve organic matter during subsequent burial.

  3. Preliminary study on performance of a coupled hydrodynamic and sediment transport model on small domain

    Science.gov (United States)

    Rasyif, Teuku M.; Kato, Shigeru; Syamsidik, Okabe, Takumi

    2017-10-01

    Numerical simulation is one of the useful tools to analyze natural phenomena in the earth such as the tsunami disaster. Several numerical models can simulate the tsunami wave from its generation, propagation, and inundation. However, most tsunami models do not include the sediment transport module. The tsunami wave actually induces a lot of sediment during the propagation in the coastal area. In the case of Indian Ocean Tsunami in 2004, massive morphological changes were caused by the tsunami waves around Sumatra coast. In Aceh, some areas eroded by the tsunami wave were living place for a local community. It is indispensable for the resident in the coastal area to estimate the risk of morphological changes due to a tsunami wave. Therefore, a model that can investigate the morphological changes due tsunami wave is necessary. The result of this model can be used to consider a countermeasure for tsunami wave impact in the coastal area, such as land-use management and planning. The COMCOT-SED model had been developed by several researchers. This model combines the hydrodynamic module and the sediment module. The aim of this study is to get general information about performance of the COMCOT-SED model and to modify the model for more accurate results. Firstly, the model was demonstrated in the ideal condition to confirm the model validity. Then, we evaluated the model performance comparing the model results and the laboratory experiment data which was conducted by other researcher. The authors found that the results of water level and bottom profile by the original model in the ideal condition are not suitable. The model modification will give us more suitable results. The modified model will be applied to simulate the tsunami wave and sediment transport in the small area.

  4. Vitamin B12 transport from food to the body's cells--a sophisticated, multistep pathway.

    Science.gov (United States)

    Nielsen, Marianne J; Rasmussen, Mie R; Andersen, Christian B F; Nexø, Ebba; Moestrup, Søren K

    2012-05-01

    Vitamin B(12) (B(12); also known as cobalamin) is a cofactor in many metabolic processes; deficiency of this vitamin is associated with megaloblastic anaemia and various neurological disorders. In contrast to many prokaryotes, humans and other mammals are unable to synthesize B(12). Instead, a sophisticated pathway for specific uptake and transport of this molecule has evolved. Failure in the gastrointestinal part of this pathway is the most common cause of nondietary-induced B(12) deficiency disease. However, although less frequent, defects in cellular processing and further downstream steps in the transport pathway are also known culprits of functional B(12) deficiency. Biochemical and genetic approaches have identified novel proteins in the B(12) transport pathway--now known to involve more than 15 gene products--delineating a coherent pathway for B(12) trafficking from food to the body's cells. Some of these gene products are specifically dedicated to B(12) transport, whereas others embrace additional roles, which explains the heterogeneity in the clinical picture of the many genetic disorders causing B(12) deficiency. This Review describes basic and clinical features of this multistep pathway with emphasis on gastrointestinal transport of B(12) and its importance in clinical medicine.

  5. Meta-analysis: abundance, behavior, and hydraulic energy shape biotic effects on sediment transport in streams.

    Science.gov (United States)

    Albertson, L K; Allen, D C

    2015-05-01

    An increasing number of studies have emphasized the need to bridge the disciplines of ecology and geomorphology. A large number of case studies show that organisms can affect erosion, but a comprehensive understanding of biological impacts on sediment transport conditions is still lacking. We use meta-analysis to synthesize published data to quantify the effects of the abundance, body size, and behavior of organisms on erosion in streams. We also explore the influence of current velocity, discharge, and sediment grain size on the strength of biotic effects on erosion. We found that species that both increase erosion (destabilizers) and decrease erosion (stabilizers) can alter incipient sediment motion, sediment suspension, and sediment deposition above control conditions in which the organisms were not present. When abundance was directly manipulated, these biotic effects were consistently stronger in the higher abundance treatment, increasing effect sizes by 66%. Per capita effect size and per capita biomass were also consistently positively correlated. Fish and crustaceans were the most studied organisms, but aquatic insects increased the effect size by 550 x compared to other types of organisms after accounting for biomass. In streams with lower discharge and smaller grain sizes, we consistently found stronger biotic effects. Taken collectively, these findings provide synthetic evidence that biology can affect physical processes in streams, and these effects can be mediated by hydraulic energy. We suggest that future studies focus on understudied organisms, such as biofilms, conducting experiments under realistic field conditions, and developing hypotheses for the effect of biology on erosion and velocity currents in the context of restoration to better understand the forces that mediate physical disturbances in stream ecosystems.

  6. Sediment transport in steep forested catchments - An assessment of scale and disturbance

    Science.gov (United States)

    Hancock, G. R.; Hugo, J.; Webb, A. A.; Turner, L.

    2017-04-01

    Stream sediment loads (both bedload and suspended sediment) are problematic to measure due to the time and equipment needed. There is a dearth of such data sets globally let alone for Australia. However, such data are needed to quantify sediment transport type and rates, landscape evolution, effect of human disturbance as well as patterns and temporal response. Here we present the findings from 8 steepslope forested catchments dominated by headwater streams (size range 15-100 ha) in south-eastern Australia where both bedload and suspended load have been measured over multiple years. The results demonstrate that suspended load is the dominant component and there is no consistent suspended to bedload ratio for the catchments. The suspended sediment to bedload ratio appears to be catchment specific. There was no relationship between total load (or bedload/suspended load) and average catchment slope, stream length, shape or any geomorphic descriptor. However catchment total load was found to be significantly related to catchment area. Of the 8 catchments examined here, 6 had been harvested for timber in previous decades (with large areas of forest removed) while 2 catchments had minimal disturbance (Control catchments). There was no difference in sediment loads from the harvested and Control catchments. The results demonstrate that although land disturbance had previously occurred the management practices employed in each catchment were effective in the long term. This provides confidence that the forest harvesting and subsequent management do not produce detrimental effects in the medium to long term. An assessment of erosion rates and likely soil production rates suggests that the catchments are eroding soil at the rate it is being produced.

  7. Sediment transport in the San Francisco Bay Coastal System: An overview

    Science.gov (United States)

    Barnard, Patrick L.; Schoellhamer, David H.; Jaffe, Bruce E.; Lester J. McKee,

    2013-01-01

    The papers in this special issue feature state-of-the-art approaches to understanding the physical processes related to sediment transport and geomorphology of complex coastal-estuarine systems. Here we focus on the San Francisco Bay Coastal System, extending from the lower San Joaquin-Sacramento Delta, through the Bay, and along the adjacent outer Pacific Coast. San Francisco Bay is an urbanized estuary that is impacted by numerous anthropogenic activities common to many large estuaries, including a mining legacy, channel dredging, aggregate mining, reservoirs, freshwater diversion, watershed modifications, urban run-off, ship traffic, exotic species introductions, land reclamation, and wetland restoration. The Golden Gate strait is the sole inlet connecting the Bay to the Pacific Ocean, and serves as the conduit for a tidal flow of ~ 8 x 109 m3/day, in addition to the transport of mud, sand, biogenic material, nutrients, and pollutants. Despite this physical, biological and chemical connection, resource management and prior research have often treated the Delta, Bay and adjacent ocean as separate entities, compartmentalized by artificial geographic or political boundaries. The body of work herein presents a comprehensive analysis of system-wide behavior, extending a rich heritage of sediment transport research that dates back to the groundbreaking hydraulic mining-impact research of G.K. Gilbert in the early 20th century.

  8. Geological evidence and sediment transport modelling for the 1946 and 1960 tsunamis in Shinmachi, Hilo, Hawaii

    Science.gov (United States)

    Chagué, Catherine; Sugawara, Daisuke; Goto, Kazuhisa; Goff, James; Dudley, Walter; Gadd, Patricia

    2018-02-01

    The Japanese community of Shinmachi, established on low-lying land between downtown Hilo and Waiakea, Hawaii, was obliterated by the 1946 Aleutian tsunami but was rebuilt, only to be destroyed again by the 1960 Chilean tsunami. The aim of this study was to find out if any geological evidence of these well documented events had been preserved in the sedimentary record in Wailoa River State Park, which replaced Shinmachi after the 1960 tsunami. This was achieved by collecting cores in the park and performing sedimentological, chronological and geochemical analyses, the latter also processed by principal component analysis. Sediment transport modelling was carried out for both tsunamis, to infer the source of the sediment and areas of deposition on land. The field survey revealed two distinct units within peat and soil, a thin lower unit composed of weathered basalt fragments within mud (Unit 1) and an upper unit dominated by fine volcanic sand within fine silt exhibiting subtle upward fining and coarsening (Unit 2, consisting of Unit 2A and Unit 2B), although these two anomalous units only occur on the western shore of Waiakea Mill Pond. Analysis with an ITRAX core scanner shows that Unit 1 is characterised by high Mn, Fe, Rb, La and Ce counts, combined with elevated magnetic susceptibility. Based on its chemical and sedimentological characteristics, Unit 1 is attributed to a flood event in Wailoa River that occurred around 1520-1660 CE, most probably as a result of a tropical storm. The sharp lower contact of Unit 2 coincides with the appearance of arsenic, contemporaneous with an increase in Ca, Sr, Si, Ti, K, Zr, Mn, Fe, La and Ce. In this study, As is used as a chronological and source material marker, as it is known to have been released into Wailoa River Estuary and Waiakea Mill Pond by the Canec factory between 1932 and 1963. Thus, not only the chemical and sedimentological evidence but also sediment transport modelling, corroborating the historical record

  9. Suspended sediment transport in a semiarid watershed, Wadi Abd, Algeria (1973 1995)

    Science.gov (United States)

    Achite, Mohamed; Ouillon, Sylvain

    2007-09-01

    SummaryA quantification of the fine sediment budget of a wadi (dryland river) in NW Algeria is presented for a period of 22 hydrological years (1973-1995). The climate is Mediterranean over the Wadi Abd basin (2480 km 2), the mean annual precipitation is 250 mm and the mean annual discharge is 1.0 m 3 s -1 at the gauging station. Regression relationships between water discharge Q and suspended sediment concentration C are calculated from 1432 paired measurements in the Wadi Abd, leading to power-law equations of the type C = a Qb. The variability of coefficients a and b, calculated for 138 floods and flood stages, is analyzed. The median value of b is 0.757, indicating that C is almost proportional to Q3/4. Given that the ( a, b) pairs are correctly aligned ( r2 = 0.578), the coefficients a and b are not independent. Regression relationships between daily Q and daily suspended sediment concentration and discharge Qs are calculated from 702 input data. The performances of these regression relationships are shown to be equivalent, leading to over-estimations of 20-25% of the suspended sediment flux. The non-biased C- Q sediment rating curve is used to extrapolate a time series of C measurements, and thus to analyze the long-term patterns in suspended sediment transport. Average sediment wash-down (136 t km -2 yr -1) is similar to the mean global value. The ratio of sediment wash-down to the river water discharge is 10.7 × 10 6 t km 3, 20 times greater than the average ratio in the Earth's eastern hemisphere, and illustrates the highly erosive power of wadis. Variability is shown to be significant at the seasonal scale (CV = 89%) and higher at the interannual scale (CV = 139%). The fine sediment flux mainly occurs in autumn (48.4%) and spring (32.7%). Although precipitation decreased, it was more irregular from one year to another over the period 1985-1995 than during the period 1973-1985, and the Wadi Abd, which was a perennial river, became intermittent in the late

  10. Interactions Between Channel Topography and Hydrokinetic Turbines: Sediment Transport, Turbine Performance, and Wake Characteristics

    Science.gov (United States)

    Hill, Craig Steven

    Accelerating marine hydrokinetic (MHK) renewable energy development towards commercial viability requires investigating interactions between the engineered environment and its surrounding physical and biological environments. Complex and energetic hydrodynamic and morphodynamic environments desired for such energy conversion installations present difficulties for designing efficient yet robust sustainable devices, while permitting agency uncertainties regarding MHK device environmental interactions result in lengthy and costly processes prior to installing and demonstrating emerging technologies. A research program at St. Anthony Falls Laboratory (SAFL), University of Minnesota, utilized multi-scale physical experiments to study the interactions between axial-flow hydrokinetic turbines, turbulent open channel flow, sediment transport, turbulent turbine wakes, and complex hydro-morphodynamic processes in channels. Model axial-flow current-driven three-bladed turbines (rotor diameters, dT = 0.15m and 0.5m) were installed in open channel flumes with both erodible and non-erodible substrates. Device-induced local scour was monitored over several hydraulic conditions and material sizes. Synchronous velocity, bed elevation and turbine performance measurements provide an indication into the effect channel topography has on device performance. Complimentary experiments were performed in a realistic meandering outdoor research channel with active sediment transport to investigate device interactions with bedform migration and secondary turbulent flow patterns in asymmetric channel environments. The suite of experiments undertaken during this research program at SAFL in multiple channels with stationary and mobile substrates under a variety of turbine configurations provides an in-depth investigation into how axial-flow hydrokinetic devices respond to turbulent channel flow and topographic complexity, and how they impact local and far-field sediment transport characteristics

  11. Report on data from the Nearshore Sediment Transport Study experiment at Leadbetter Beach, Santa Barbara, California, January-February 1980 (NODC Accession 8200080)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — THIS DATA SET CONSISTS OF THE RESULTS OF THE NEARSHORE SEDIMENT Nearshore Sediment Transport Study at Leadbetter Beach, Santa Barbara, California. These data from 28...

  12. Runoff and sediment transport in the arid regions of Argentina and India - a case study in comparative hydrology

    NARCIS (Netherlands)

    Sharma, K.D.; Menenti, M.; Huygen, J.; Fernandez, P.C.; Vich, A.

    1996-01-01

    The arid zones of Argentina and India have been compared. In both regions run-off is often generated by the Hortonian infiltration surplus overland flow, and run-off response to precipitation input tends to be rapid. The sediment transport is governedby the transport capacity of run-off rather than

  13. Spatial glyphosate and AMPA redistribution on the soil surface driven by sediment transport processes – A flume experiment

    NARCIS (Netherlands)

    Bento, Célia P.M.; Commelin, Meindert C.; Baartman, Jantiene E.M.; Yang, Xiaomei; Peters, Piet; Mol, Hans G.J.; Ritsema, Coen J.; Geissen, Violette

    2018-01-01

    This study investigates the influence of small-scale sediment transport on glyphosate and AMPA redistribution on the soil surface and on their off-site transport during water erosion events. Both a smooth surface (T1) and a surface with “seeding lines on the contour” (T2) were tested in a rainfall

  14. Morphology and Sediment Transport Dynamics of a Trough-Blowout Dune, Bodega Marine Reserve, Northern California

    Science.gov (United States)

    Jorgenson, D.; Dunleavy, C. J.; Smith, M. E.

    2014-12-01

    Blowout dunes are a primary mechanism for transporting sand within vegetated coastal dune systems. Understanding the fine-scale variation in sediment transport within these systems is critical to predicting their formation and migration. Previous investigations of a coastal dune system located at the Bodega Marine Reserve, on the Sonoma Coast of Northern California have indicated that aeolian sand flux in unvegetated sand is ~450x greater than in vegetated areas. To better understand sand flux and its relationship with wind speed, direction and precipitation, we deployed an array of 12 sand traps within a single blowout area adjacent to the BOON marine climatology station. The blowout is trough- shaped, approximately 50 meters long and 15 meters wide. Its main 'fairway' is 5-10 meters below the surrounding beach grass (Ammophila)-covered land surface. Surface sediment within the blowout is fine-grained to granule-sized lithic to sub-lithic sand, and is coarsest in the center. Dune sediment in the Bodega Marine Reserve has been transported by aeolian processes from Salmon Creek Beach to the NW. Within the blowout, typical bedforms include 15-25 cm-wavelength, ~10 cm high sinuous to lingoid ripples arranged perpendicularly to the dominant wind direction (~280 degrees). An 8-10 meter-high mound at the downwind end has accumulated due to the trapping of sand flux by vegetation. Sediment flux across the studied blowout was sampled monthly over a 10-month period of 2013-2014. Sand traps were constructed using modified PVC cylinders, and are 0.5 meter high and 0.3 meter in diameter, with a 0.74-micron mesh screen. Based on measured sand flux, the sites can be categorized into three groups-axial, medial, and peripheral. Rates increase downwind within the blowout. Inter-site sand flux variability within unvegetated locations of the blowout is greater than two orders of magnitude. Axial sites, which experience the greatest sand flux, occur on the edge of the blowout adjacent

  15. 3D Modelling of Transport, Deposition and Resuspension of Highway Deposited Sediments in wet Detention Ponds

    DEFF Research Database (Denmark)

    Bentzen, Thomas Ruby

    2010-01-01

    concrete channel with width of 0.8m and a water depth of approximately 0.8m and in circular flume experiments in order to reproduce near-bed specific processes such as resuspension and consolidation. With a fairly good agreement with measurements, modelling of hydrodynamics, transport of dissolved...... pollutants and particles in wet detention ponds is possible with application of a three dimensional RANS model and the advection/dispersion equation taken physical phenomena like wind, waves, deposition, erosion and consolidation of the bottom sediment into account....

  16. Transport processes for Chernobyl-labelled sediments: preliminary evidence from upland mid-Wales

    International Nuclear Information System (INIS)

    Bonnett, P.J.P.; Leeks, G.J.L.; Cambray, R.S.

    1989-01-01

    The nuclear accident at Chernobyl in April 1986 resulted in a significant increase in the inventory of radiocaesium retained in the soil in many regions of the United Kingdom. The deposition of 134 Cs provides a convenient tool for the examination of erosional processes in upland systems. Detailed soil sampling has been undertaken within the Plynlimon experimental catchments to establish the pattern of deposition of Chernobyl-derived radionuclides. The preliminary results of a combined radiometric and mineral magnetic approach to the study of the transport of Chernobyl-labelled sediments and their source areas on these upland catchments in mid-Wales are described. (author)

  17. Diffuser Design for Marine Outfalls in Areas with Strong Currents, High waves and Sediment Transport

    DEFF Research Database (Denmark)

    Larsen, Torben

    1995-01-01

    The design of marine outfalls is often based on environmental criteria for a minimum initial dilution. Accordingly advanced diffuser arrangement are designed to fulfil these requirements. A large number of examples of malfunction and blocking in sea outfalls have occurred around the world...... as a result of this uncompromising consent to environmental demands. Two examples of unconventional design are given in this paper. Both cases involved risk of blockage of the diffuser section because of wave and current induced sediment transport The paper also discusses how acceptable far field dilution...

  18. Numerical simulation of sediment transport from Ba Lat Mouth and the process of coastal morphology

    International Nuclear Information System (INIS)

    Chung, Dang Huu

    2008-01-01

    This paper presents an application of a 3D numerical model to simulate one vertical layer sediment transport and coastal morphodynamical process for the Hai Hau coastal area located in the north of Vietnam, where a very large amount of suspended sediment is carried into the sea from Ba Lat Mouth every year. Four simulations are based on the real data of waves supplied by the observation station close to Ba Lat Mouth. The conditions of wind and suspended sand concentration at Ba Lat Mouth are basically assumed from practice. The computed results show that the hydrodynamic factors strongly depend on the wind condition and these factors govern the direction and the range of suspended sand transport, especially in the shallow-water region. In the deep-water region this influence is not really clear when the wind force is not strong enough to modify the tidal current. In the area close to Ba Lat Mouth the flow velocity is very large with the maximum flood flow about 2.6 m s −1 and the maximum ebb flow about 1 m s −1 at the mouth, and this is one of the reasons for strong erosion. In the case of tidal flow only, the suspended sand concentration decreases resulting in local deposition. Therefore, the area influenced by suspended transport is small, about 12 km from the mouth. In the condition of wind and waves, the suspended sand transport reaches the end of the computation area within a few days, especially the cases with wind from the north-east-north. Through these simulation results, a common tendency of sediment movement from the north to the south is specified for the Hai Hau coastal area. In addition, the results also show that the coast suffers from strong erosion, especially the region near Ba Lat Mouth. From the simulation results it can be seen that the movement of the Red River sand along the Vietnamese coast is quite possible, which is an answer to a long-standing question. Furthermore, although the suspended sediment concentration is quite large, it is

  19. Processes affecting suspended sediment transport in the mid-field plume region of the Rhine River, Netherlands.

    Science.gov (United States)

    Flores, R. P.; Rijnsburger, S.; Horner-Devine, A.; Souza, A. J.; Pietrzak, J.

    2016-02-01

    This work will describe dominant processes affecting suspended sediment transport along the Dutch coast, in the mid-field plume region of the Rhine River. We will present field observations from two long-term deployments conducted in the vicinity of the Sand Engine, a mega-nourishment experiment located 10 km north of the Rhine river mouth. To investigate the role of density stratification, winds, tides, waves and river plume processes on sediment transport, frames and moorings were deployed within the excursion of the tidal plume front generated by the freshwater outflow from the Rhine River for 4 and 6 weeks during years 2013 and 2014, respectively. The moorings were designed to measure vertical profiles of suspended sediment concentration (SSC) and salinity, using arrays of CTDs and OBS sensors. Mean tidal velocities were measured using bottom-mounted ADCPs. The near-bed dynamics and the near-bottom sediment concentrations were measured as well using a set of synchronized ADVs and OBSs. By combining the two deployments we observe hydrodynamics and suspended sediment dynamics under a wide range of forcing conditions. Preliminary observations indicate that stratification is highly dependent on wind magnitude and direction, and its role is primarily identified as to induce significant cross-shore sediment transport product of the generation of cross-shore velocities due to the modification of the tidal ellipses and the passage of the surface plume front. The passage of the surface plume front generates strong offshore currents near the bottom, producing transport events that can be similar in magnitude to the dominant alongshore transport. Preliminary results also indicate that storms play an important role in alongshore transport primarily by wave-induced sediment resuspension, but as stratification is suppressed due to the enhancement of mixing processes, no significant cross-shore transport is observed during very energetic conditions.

  20. Sedimentation

    Digital Repository Service at National Institute of Oceanography (India)

    Rixen, T.; Guptha, M.V.S.; Ittekkot, V.

    through the water column but their trapping efficiency, and thus, their accuracy can be biased by hydrodynamic and biological effects (Lee et al., 1988; Gust et al., 1992; 1994). Scholten et al. (2001) showed that the 230 Thorium trapping efficiency... of sediment traps moored at different sites and water depths in eastern North Atlantic Ocean varies between 9 and 143%. In general, these trapping efficiencies increase with increasing water-depth (Scholten et al., 2001). By comparing data from various ocean...

  1. Suspended-sediment transport from the Green-Duwamish River to the Lower Duwamish Waterway, Seattle, Washington, 2013–17

    Science.gov (United States)

    Senter, Craig A.; Conn, Kathleen E.; Black, Robert W.; Peterson, Norman; Vanderpool-Kimura, Ann M.; Foreman, James R.

    2018-02-28

    The Green-Duwamish River transports watershed-derived sediment to the Lower Duwamish Waterway Superfund site near Seattle, Washington. Understanding the amount of sediment transported by the river is essential to the bed sediment cleanup process. Turbidity, discharge, suspended-sediment concentration (SSC), and particle-size data were collected by the U.S. Geological Survey (USGS) from February 2013 to January 2017 at the Duwamish River, Washington, within the tidal influence at river kilometer 16.7 (USGS streamgage 12113390; Duwamish River at Golf Course at Tukwila, WA). This report quantifies the timing and magnitude of suspended-sediment transported in the Duwamish River. Regression models were developed between SSC and turbidity and SSC and discharge to estimate 15- minute SSC. Suspended-sediment loads were calculated from the computed SSC and time-series discharge data for every 15-minute interval during the study period. The 2014–16 average annual suspended-sediment load computed was 117,246 tons (106,364 metric tons), of which 73.5 percent or (86,191 tons; 78,191 metric tons) was fine particle (less than 0.0625 millimeter in diameter) suspended sediment. The seasonality of this site is apparent when you divide the year into "wet" (October 16– April 15) and "dry" (April 16–October 15) seasons. Most (97 percent) of the annual suspended sediment was transported during the wet season, when brief periods of intense precipitation from storms, large releases from the Howard Hanson Dam, or a combination of both were much more frequent.

  2. Realistic representation of grain shapes in CFD-DEM simulations of sediment transport with a bonded-sphere approach

    Science.gov (United States)

    Sun, Rui; Xiao, Heng; Sun, Honglei

    2017-09-01

    Development of algorithms and growth of computational resources in the past decades have enabled simulations of sediment transport processes with unprecedented fidelities. The Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) is one of the high-fidelity approaches, where the motions of and collisions among the sediment grains as well as their interactions with surrounding fluids are resolved. In most DEM solvers the particles are modeled as soft spheres due to computational efficiency and implementation complexity considerations, although natural sediments are usually a mixture of non-spherical (e.g., disk-, blade-, and rod-shaped) particles. Previous attempts to extend sphere-based DEM to treat irregular particles neglected fluid-induced torques on particles, and the method lacked flexibility to handle sediments with an arbitrary mixture of particle shapes. In this contribution we proposed a simple, efficient approach to representing common sediment grain shapes with bonded spheres, where the fluid forces are computed and applied on each sphere. The proposed approach overcomes the aforementioned limitations of existing methods and has improved efficiency and flexibility over existing approaches. We use numerical simulations to demonstrate the merits and capability of the proposed method in predicting the falling characteristics, terminal velocity, threshold of incipient motion, and transport rate of natural sediments. The simulations show that the proposed method is a promising approach for faithful representation of natural sediment, which leads to accurate simulations of their transport dynamics. While this work focuses on non-cohesive sediments, the proposed method also opens the possibility for first-principle-based simulations of the flocculation and sedimentation dynamics of cohesive sediments. Elucidation of these physical mechanisms can provide much needed improvement on the prediction capability and physical understanding of muddy coast

  3. Analysis of Sediment Transport for Rivers in South Korea based on Data Mining technique

    Science.gov (United States)

    Jang, Eun-kyung; Ji, Un; Yeo, Woonkwang

    2017-04-01

    The purpose of this study is to calculate of sediment discharge assessment using data mining in South Korea. The Model Tree was selected for this study which is the most suitable technique to explicitly analyze the relationship between input and output variables in various and diverse databases among the Data Mining. In order to derive the sediment discharge equation using the Model Tree of Data Mining used the dimensionless variables used in Engelund and Hansen, Ackers and White, Brownlie and van Rijn equations as the analytical condition. In addition, total of 14 analytical conditions were set considering the conditions dimensional variables and the combination conditions of the dimensionless variables and the dimensional variables according to the relationship between the flow and the sediment transport. For each case, the analysis results were analyzed by mean of discrepancy ratio, root mean square error, mean absolute percent error, correlation coefficient. The results showed that the best fit was obtained by using five dimensional variables such as velocity, depth, slope, width and Median Diameter. And closest approximation to the best goodness-of-fit was estimated from the depth, slope, width, main grain size of bed material and dimensionless tractive force and except for the slope in the single variable. In addition, the three types of Model Tree that are most appropriate are compared with the Ackers and White equation which is the best fit among the existing equations, the mean discrepancy ration and the correlation coefficient of the Model Tree are improved compared to the Ackers and White equation.

  4. Wave Glider Monitoring of Sediment Transport and Dredge Plumes in a Shallow Marine Sandbank Environment.

    Directory of Open Access Journals (Sweden)

    Vera Van Lancker

    Full Text Available As human pressure on the marine environment increases, safeguarding healthy and productive seas increasingly necessitates integrated, time- and cost-effective environmental monitoring. Employment of a Wave Glider proved very useful for the study of sediment transport in a shallow sandbank area in the Belgian part of the North Sea. During 22 days, data on surface and water-column currents and turbidity were recorded along 39 loops around an aggregate-extraction site. Correlation with wave and tidal-amplitude data allowed the quantification of current- and wave-induced advection and resuspension, important background information to assess dredging impacts. Important anomalies in suspended particulate matter concentrations in the water column suggested dredging-induced overflow of sediments in the near field (i.e., dynamic plume, and settling of finer-grained material in the far field (i.e., passive plume. Capturing the latter is a successful outcome to this experiment, since the location of dispersion and settling of a passive plume is highly dependent on the ruling hydro-meteorological conditions and thus difficult to predict. Deposition of the observed sediment plumes may cause habitat changes in the long-term.

  5. Spatially resolved data on sediment transport: 1) field application examining fluorescent soil particle movement from tillage

    Science.gov (United States)

    Quinton, John; Hardy, Robert; Pates, Jacqueline; James, Michael

    2017-04-01

    Understanding where sediment originates from and where it travels to, in what quantities and at which rate is at the heart of many questions surrounding sediment transport. Progress towards unravelling these questions and deepening our understanding has come from a wide range of approaches, including laboratory and field experiments conducted at a variety of scales. In seeking to understand the connectivity of sources and sinks of sediment scientists have spent considerable energy in developing tracing technologies. These have included numerous studies that have relied on the chemical properties of the soil and sediment to establish source-sink connectivity, and the use of 137Ceasium, from radioactive fall-out, to map sediment redistribution. More recently there has been an upsurge in interest in the use of artificially applied soil tracers, including rare earth element oxides and magnetic minerals. However all these tracing methods have a significant drawback: they rely on the collection of samples to assess their concentration. This means that their spatial distribution cannot easily be established in situ and that the environment that is being studied is damaged by the sampling process; nor can data be collected in real time which allows a dynamic understanding of erosion and transport processes to be developed. Here we report on the field application of a fluorescent sand sized tracer at the hillslope scale during a tillage erosion experiment. Here we trialled both intensity based and particle counting methodologies for tracer enumeration. After simulating seven years of tillage on a hillslope we were able to precisely determine the distribution of the fluorescent tracer and also its incorporation and distribution within the soil profile. Single grains of tracer could be found over 35 m from the insertion point. In a second abstract we report on an application that combines novel fluorescent videography techniques with custom image processing to trace the

  6. Effects of episodic sediment supply on bedload transport rate in mountain rivers. Detecting debris flow activity using continuous monitoring

    Science.gov (United States)

    Uchida, Taro; Sakurai, Wataru; Iuchi, Takuma; Izumiyama, Hiroaki; Borgatti, Lisa; Marcato, Gianluca; Pasuto, Alessandro

    2018-04-01

    Monitoring of sediment transport from hillslopes to channel networks as a consequence of floods with suspended and bedload transport, hyperconcentrated flows, debris and mud flows is essential not only for scientific issues, but also for prevention and mitigation of natural disasters, i.e. for hazard assessment, land use planning and design of torrent control interventions. In steep, potentially unstable terrains, ground-based continuous monitoring of hillslope and hydrological processes is still highly localized and expensive, especially in terms of manpower. In recent years, new seismic and acoustic methods have been developed for continuous bedload monitoring in mountain rivers. Since downstream bedload transport rate is controlled by upstream sediment supply from tributary channels and bed-external sources, continuous bedload monitoring might be an effective tool for detecting the sediments mobilized by debris flow processes in the upper catchment and thus represent an indirect method to monitor slope instability processes at the catchment scale. However, there is poor information about the effects of episodic sediment supply from upstream bed-external sources on downstream bedload transport rate at a single flood time scale. We have examined the effects of sediment supply due to upstream debris flow events on downstream bedload transport rate along the Yotagiri River, central Japan. To do this, we have conducted continuous bedload observations using a hydrophone (Japanese pipe microphone) located 6.4 km downstream the lower end of a tributary affected by debris flows. Two debris flows occurred during the two-years-long observation period. As expected, bedload transport rate for a given flow depth showed to be larger after storms triggering debris flows. That is, although the magnitude of sediment supply from debris flows is not large, their effect on bedload is propagating >6 km downstream at a single flood time scale. This indicates that continuous bedload

  7. The Impact of Urbanization on Temporal Changes in Sediment Transport in a Gravel Bed Channel in Southern Ontario, Canada

    Science.gov (United States)

    Plumb, B. D.; Annable, W. K.; Thompson, P. J.; Hassan, M. A.

    2017-10-01

    A field investigation has been undertaken to characterize the event-based bed load transport dynamics of a highly urbanized gravel bed stream. A combination of direct bed load and tracer particle measurements were taken over a 3 year period during which time approximately 30 sediment mobilizing events occurred. Sediment transport measurements were used to calibrate a fractional bed load transport model and combined with hydrometric data which represent four different land use conditions (ranging from rural to highly urbanized) to analyze the differences in discharge magnitude and frequency and its impact on sediment transport. Fractional transport analysis of the bed load measurements indicates that frequent intermediate discharge events can mobilize sand and fine gravel to an approximate equally mobile condition, however, the transport rates at these discharges exhibit greater variability than at discharges above the bankfull discharge. Path lengths of the coarse fraction, measured using tracer clasts, are insensitive to peak discharge, and instead transport at distances less than those reported in other gravel bed channels, which is attributed to the shorter duration discharge events common to urban streams. The magnitude-frequency analysis reveals that the frequency, time, and volume of competent sediment mobilizing events are increasing with urbanization. Variability in effective discharges suggests that a range of discharges, spanning between frequent, low magnitude events to less frequent, high magnitude events are geomorphically significant. However, trends in the different land use scenarios suggest that urbanization is shifting the geomorphic significance toward more frequent, lower magnitude events.

  8. Fluid dynamics, sediment transport and turbulent mixing at large confluences of the Amazon River

    Science.gov (United States)

    Trevethan, Mark; Gualtieri, Carlo; Filizola, Naziano; Ianniruberto, Marco

    2014-05-01

    The Clim-Amazon Project aims to study temporal sedimentary records to understand the mechanisms involved in climate and geodynamic changes and the processes involved in dissolved and suspended load evolution of the Amazon River basin from the Miocene to present. The knowledge of the present Amazon River sediment discharge and of its variability is fundamental since it can be linked to the on-going climatic and erosion processes at the regional scale. Understanding the relationships between these processes will be helpful to better interpret the observations of the past sedimentation rates. Within this general objective the aim of this study is to investigate the complex fluid dynamics, sediment transport and water quality processes occurring at the large confluences in the Amazon River, through a combination of theoretical, experimental (field) and numerical research. In the last decades a wide body of theoretical, experimental, and field research has emerged on the fluvial dynamics of river confluences, which are integral and ubiquitous features of river networks. Through this research substantial advances have been made into understanding the hydrodynamics and morphodynamics of river confluences which will be outlined here. However, to date most experimental studies have focused either on laboratory confluences or on small to medium sized natural confluences, whereas an extremely limited number of investigations about the confluences on large rivers. Presently little is understood about how river confluence hydrodynamics may vary with the size of the river, especially in the largest rivers. The Amazon River is the largest river in the World, with approximately 15,000 sub-branches joining the Amazon River within the Amazon Basin including some of the largest confluences on Earth. A study region containing three of the larger confluences between Manacapuru and Itacoatiara will be used as part of this study, with the primary focus being the confluence of the Rio

  9. MORPHOLOGICAL EFFECT OF FLOOD WATER PATHWAY IN RESERVOIRS ON THE DISTRIBUTION OF SEDIMENTATION

    Directory of Open Access Journals (Sweden)

    Nsiri Ines

    2014-01-01

    Full Text Available In the North Africa countries, sediments deposition in the reservoir dams reduces the available surface water resources by 2 to 5% per year. In Tunisia, even many efforts are made to protect reservoir dams against soil erosion, the sedimentation still very important and constitute a limitation their time duration. In order to better understand these phenomena, bathymetry, turbidity, suspended soil particles and sediments were monitored for two reservoir dams in Tunisia: Joumine and Sejnane. These data will be interpreted in order to better characterize the sedimentation process and identify the determinant factors. Geostatistical Technics are applied to the bathymetric data in order to simulate the evolution, in time and in space, of the morphology of the reservoir dams and to estimate the distribution of the sediments deposits. The results for the two dams will permit to better understand the influence of the initial geometry of the reservoir dams on the sedimentation process and to deduce the main water flow path lines. Turbidity, suspended particles and sediments particles size profiles established for fixed stations in the reservoir dams will be interpreted in order to better understand the sedimentation process in the reservoirs dams and to characterize the influence of the initial reservoir geometry.

  10. Linking Meander Initation to Instability in the Cross-Sectional Sediment Transport Field

    Science.gov (United States)

    Eaton, B. C.

    2005-12-01

    Recent theoretical and experimental work on reach-scale channel dynamics suggests that stream channel response to changes in the discharge or sediment supply regime produce adjustments that are consistent with the optimality criteria (or extremal hypotheses) proposed by rational regime modellers. However, a general form of the optimality criteria based on the maximization of system-scale flow resistance permits multiple channel responses to the same imposed change, and is thus inadequate for predicting channel response, absent additional information. The way forward is to identify the geomorphic processes that produce various possible channel responses, and to develop an understanding of the conditions under which these processes may or may not be effective. Using a simple analytic model relating local sediment transport capacity to variance in the transverse shear stress distribution I develop a physically based conceptual model of the initiation of meandering in straight, bedload dominated streams as a result of a feedback mechanism. This corresponds to a channel response that is dominated by changes the energy slope, which appears to be dominant in channels having relatively erodible banks and transporting their bed material load at conditions near the threshold for entrainment. The feedback maximizes the cross sectional shear stress variance and, in order to achieve stability, minimizes the energy slope at repeated locations along the channel. These locations develop into pools in a fully developed meandering channel; they represent attractor states wherein sediment continuity is satisfied using the least possible energy expenditure per unit length of channel. Between two successive pools, a stream occupies a metastable, higher energy state (corresponding to a riffle) that requires greater energy expenditure per unit length of channel to transport the same volume of sediment. The model links processes at the scale of a channel width to adjustments of the

  11. The dynamics of channel slope, width, and sediment transport in tectonically actively river systems

    Science.gov (United States)

    Yanites, B.

    2016-12-01

    River profiles form the framework of mountainous landscapes. As such, their dynamics constitute a vital link in the interaction among the atmosphere, lithosphere, and biosphere as they control the topographic response to tectonics and climate. River dynamics in such regions are a result of the interactions of tectonics, rock-type, water discharge, and sediment. Here I present a new method for modeling the influence of channel width and sediment supply on river profile evolution. The approach balances computational efficiency with the complexities of channel geometry-sediment transport tradeoffs by utilizing a channel optimization algorithm coupled with a 1-D river profile model. Through a series of numerical experiments, I show that current models quantifying river dynamics to tectonic and climatic changes likely over predict the topographic response in a number of mountainous landscapes, especially if sediment is an important control on river dynamics. The main model experiment quantifies the impact of a 5-fold increase in rock-uplift on river profile and channel geometry for three erosion models: (1) a shear-stress detachment limited model, (2) a sediment cover-shear stress model, and (3) a saltation abrasion model. The detachment limited model shows the greatest sensitivity to rock-uplift, showing a 4-fold increase in fluvial relief following the increase in rock-uplift. If channel width is held static and not allowed to change in repsonse to the transient adjustment, the relief increases by 5-fold. For the sediment cover model, fluvial relief increases only 2.5 fold. The reason for the reduced topographic response is that channel width changes increase both the erosion potential (i.e. shear stress) as well as the frequency of bedrock exposure. The saltation abrasion model results in a 1.5-fold increase in fluvial relief. Further model experiments explore the morphological predictions of a river flowing over a fold showing diagnostic signatures in the morphology

  12. [Effect of the Runoff-sediment Control of the Xiaolangdi Reservoir on DOC Transport].

    Science.gov (United States)

    Zhang, Yong-ling; Wang, Ming-shi; Dong, Yu-long

    2015-04-01

    The sampling was carried out in Sanmenxia hydrological station, Xiaolangdi hydrological station and Huayuankou hydrological station from November 2011 to October 2012. The impact of the runoff-sediment control of the Xiaolangdi reservoir on DOC transport,was analyzed. The results were as follows. DOC contents in Sanmenxia station, Xiaolangdi station and Huayuankou station were 1.97-2.71 mg-L(-1), 1.87-2.76 mg x L(-1) and 2.07-2.93 mg x L(-1), respectively, during the normal operation period of Xiaolangdi Reservoir and Sanmenxia reservoir, and the DOC content in the three reservoirs had obvious seasonal change. DOC contents in the three stations were 2.14-3.32 mg x L(-1), 2.21-2.84 mg x L(-1) and 2.11-2.84 mg x L(-1), respectively, during the runoff-sediment control, and the DOC content in the sediment-releasing period of reservoir was higher than that in the water-releasing period of reservoir. DOC content had no significant correlation with TSS and flow either during the normal operation or during the water-sediment regulation of the reservoir. But the DOC content had significant correlation with water temperature during the normal operation of the reservoir. DOC flux in Sanmenxia station was similar to that in Xiaolangdi station from November to March. DOC flux in Sanmenxia station was obviously less than that in Xiaolangdi station from April to July. And the DOC flux in Sanmenxia station was much higher than that in Xiaolangdi station from August to October. The result showed that DOC was retained from August to October by Xiaolangdi reservoir and discharged from Xiaolangdi reservoir from April to July. The yearly DOC fluxes were 8.6 x 10(10), 9.0 x 10(10) and 9.7 x 10(10) g respectively in Sanmenxia station, Xiaolangdi station and Huayuankou station. The DOC flux of Sanmenxia station was the highest in September, which accounted for 22.0% of the yearly DOC flux, and the DOC flux of Xiaolangdi station was the highest in June, which accounted for 17.6% of the

  13. Interaction between transcellular and paracellular water transport pathways through Aquaporin 5 and the tight junction complex

    OpenAIRE

    Kawedia, Jitesh D.; Nieman, Michelle L.; Boivin, Gregory P.; Melvin, James E.; Kikuchi, Ken-Ichiro; Hand, Arthur R.; Lorenz, John N.; Menon, Anil G.

    2007-01-01

    To investigate potential physiological interactions between the transcellular and paracellular pathways of water transport, we asked whether targeted deletion of Aquaporin 5 (AQP5), the major transcellular water transporter in salivary acinar cells, affected paracellular transport of 4-kDa FITC-labeled dextran (FITC-D), which is transported through the paracellular but not the transcellular route. After i.v. injection of FITC-D into either AQP5 wild-type or AQP5−/− mice and saliva collection ...

  14. ANALYSIS OF POTENTIAL INTENSITY OF SEDIMENT TRANSPORT ON SELECTED REACH OF THE NER RIVER

    Directory of Open Access Journals (Sweden)

    Ewelina Szałkiewicz

    2015-11-01

    Full Text Available The aim of this study was to perform a simulation of sediment transport for the section of the river Ner, while also utilizing GIS tools. Using the ArcGIS numerical model of channel and stream valleys were developed, and motion simulations and sediment transport set for 5 ten-year periods were performed in HEC-RAS. Updated geometries after the simulations were created using the tools of RAS Mapper. ArcGIS was used again for analysing the results. It was used to generate ordinates of bottom in the initial state and final. The difference between them illustrated the magnitude of erosion and accumulation. The process of erosion occurred in 13 sections of the analysed model (the standard differential ordinates negative, while the accumulation in 53 sections. The maximum value of shallowing bottom was 1.24 m (cross-section at km 18 + 868, while the largest deepening occurred at km 8 + 654 (– 0.76 m. All values, using ArcGIS, were marked on othophotomap.

  15. Nearshore waves and longshore sediment transport along Rameshwaram Island off the east coast of India

    Directory of Open Access Journals (Sweden)

    Rajamanickam Gowthaman

    2015-11-01

    Full Text Available Wave-induced Longshore Sediment Transport (LST play an important role in the dynamics of the Dhanushkodi sandspit located southeast of Rameshwaram. The LST along the Dhanushkodi coast is studied based on data collected simultaneously in Gulf of Mannar (GoM and Palk Bay (PB using directional waverider buoys. The numerical model REF/DIF1 was used to calculate the nearshore waves and the LST rate was estimated using three different formulae. The model validation was done based on the measured nearshore waves using InterOcean S4DW. Numerical model LITPACK was also used for simulating non-cohesive sediment transport and the LITLINE module was used to study the shoreline evolution over 5 years. Low net annual LST along PB (~0.01 × 106 m3 compared to the GoM region (0.3 × 106 m3 were due to the weak waves. Accretion in the region led to growth of the Dhanushkodi sandspit by 65 m during the period 2010-2015.

  16. Arsenic and uranium transport in sediments near abandoned uranium mines in Harding County, South Dakota

    International Nuclear Information System (INIS)

    Kipp, Gregory G.; Stone, James J.; Stetler, Larry D.

    2009-01-01

    Sediment samples were analyzed as part of ongoing environmental investigations of historical U mining impacts within Custer National Forest in Harding County, South Dakota. Correlations between As and U content, grain size and soil mineralogy were determined to identify contaminant fate and transport mechanisms. Soil samples collected near the mining source zone and up to 61 km downgradient of the minesites were analyzed. Samples were homogenized and wet sieved through polymer screens, and metal(loid) concentrations were determined using inductively coupled plasma mass spectrometry (ICP-MS). Powder X-ray diffraction (XRD) analysis identified quartz as the primary mineral for all size fractions, with varying amounts of analcime, indicative of volcanic origin. Selected samples were examined for trace mineral composition using scanning electron microscopy (SEM). The presence of Fe sulfides and Fe (hydr)oxides indicate heterogeneity in redox potentials on a microscopic scale. Elevated metal(loid) concentrations were associated with trace concentrations of Fe sulfide, indicating an influence on metal transport during weathering. Sequential chemical extractions (SCE) performed on source sediment fractions demonstrated that most As and U was adsorbed to Fe- and Mn-oxides and carbonates with lesser amounts bound by ion exchange, organics and Fe sulfides. Large changes in U/Th and As/Th ratios were observed to coincide with geochemical changes in the watershed, suggesting that metal(loid)-Th ratios may be used in environmental investigations to identify geochemically-significant watershed conditions.

  17. Transport and fate of viruses in sediment and stormwater from a Managed Aquifer Recharge site

    Science.gov (United States)

    Sasidharan, Salini; Bradford, Scott A.; Šimůnek, Jiří; Torkzaban, Saeed; Vanderzalm, Joanne

    2017-12-01

    Enteric viruses are one of the major concerns in water reclamation and reuse at Managed Aquifer Recharge (MAR) sites. In this study, the transport and fate of bacteriophages MS2, PRD1, and ΦX174 were studied in sediment and stormwater (SW) collected from a MAR site in Parafield, Australia. Column experiments were conducted using SW, stormwater in equilibrium with the aquifer sediment (EQ-SW), and two pore-water velocities (1 and 5 m day-1) to encompass expected behavior at the MAR site. The aquifer sediment removed >92.3% of these viruses under all of the considered MAR conditions. However, much greater virus removal (4.6 logs) occurred at the lower pore-water velocity and in EQ-SW that had a higher ionic strength and Ca2+ concentration. Virus removal was greatest for MS2, followed by PRD1, and then ΦX174 for a given physicochemical condition. The vast majority of the attached viruses were irreversibly attached or inactivated on the solid phase, and injection of Milli-Q water or beef extract at pH = 10 only mobilized a small fraction of attached viruses (Virus breakthrough curves (BTCs) were successfully simulated using an advective-dispersive model that accounted for rates of attachment (katt), detachment (kdet), irreversible attachment or solid phase inactivation (μs), and blocking. Existing MAR guidelines only consider the removal of viruses via liquid phase inactivation (μl). However, our results indicated that katt > μs > kdet > μl, and katt was several orders of magnitude greater than μl. Therefore, current microbial risk assessment methods in the MAR guideline may be overly conservative in some instances. Interestingly, virus BTCs exhibited blocking behavior and the calculated solid surface area that contributed to the attachment was very small. Additional research is therefore warranted to study the potential influence of blocking on virus transport and potential implications for MAR guidelines.

  18. [Placental passage of macromolecules: transport pathway and mode].

    Science.gov (United States)

    Challier, J C; Bintein, T

    1989-09-01

    In vivo and in vitro data have recently shown that macromolecules cross the hemochorial placenta. This feature contrats with the size selectivity of the sheep placenta which exclude molecules of 0.45 nm radius. Macromolecules moves by diffusion or endocytosis. In addition to size selectivity, the electrical charges of the macromolecules might be involved in placental transfer. The main resistance to placental transfer lie in the trophoblastic layer and the pathways of specific or unspecific transcytosis are not elicited. Membrane or fluid phase markers (peroxydases), carrier molecules (LDL, transferrin...), hormones and growth factors (insuline, EGF) are internalized by endocytosis into the trophoblast and further degraded or recycled. Immunoglobulins G, which are protected from degradation, reach the fetal circulation. The endothelial layer looks less selective and permits passage either by interendothelial diffusion or transcytosis.

  19. Understanding Dissolved and Colloidal Metal Transport and Transformation - Pathways for Aquatic Toxicity

    Science.gov (United States)

    Kimball, B. A.; Besser, J. M.

    2004-05-01

    Hundreds of miles of streams in the western United States are affected by the release of metals from weathering of mineralized bedrock and mine wastes. In many cases, historical mining has accelerated these weathering processes and increased concentrations of metals in affected streams. Copper and zinc are two metals that affect aquatic health in such streams. Aquatic toxicity from copper and zinc is thought to be related principally to their dissolved concentrations. But there are alternative pathways that may lead to toxicity. Movement of many metals associated with mine drainage is affected by iron colloidal solids. The initial precipitation of iron hydroxides results in nanometer-sized colloids that subsequently aggregate to form a continuum of particle sizes from about one nanometer to greater than one micrometer. This behavior makes the popular or legal definition of dissolved metals at 0.45 micrometers meaningless in streams affected by mine drainage. Ultrafiltration, using tangential-flow across 10,000-Dalton membranes, provides a means to understand dissolved and colloidal metal concentrations. When ultrafiltration is combined with methods to determine mass loading, it is possible to quantify sources and chemical reactions affecting metals. For example, results from a mass-loading study in Mineral Creek, Colorado, indicate that copper and zinc are contributed to the stream from both mined and unmined sources. As the pH of Mineral Creek changes in response to both neutral and acidic inflows, copper was repeatedly transferred between dissolved and colloidal phases through sorption reactions. When the colloidal phase was dominant, the total load of copper consistently decreased because the colloids are entrained by algae on cobbles and strained by the streambed during hyporheic exchange. Zinc load also decreased during transport, but this was a result of the physical process of water exchange with the hyporheic zone, and not a result of colloidal

  20. Final Project Report: Release of aged contaminants from weathered sediments: Effects of sorbate speciation on scaling of reactive transport

    Energy Technology Data Exchange (ETDEWEB)

    Jon Chorover, University of Arizona; Peggy O' €™Day, University of California, Merced; Karl Mueller, Penn State University; Wooyong Um, Pacific Northwest National Laboratory; Carl Steefel, Lawrence Berkeley National Laboratory

    2012-10-01

    Hanford sediments impacted by hyperalkaline high level radioactive waste have undergone incongruent silicate mineral weathering concurrent with contaminant uptake. In this project, we studied the impact of background pore water (BPW) on strontium, cesium and iodine desorption and transport in Hanford sediments that were experimentally weathered by contact with simulated hyperalkaline tank waste leachate (STWL) solutions. Using those lab-weathered Hanford sediments (HS) and model precipitates formed during nucleation from homogeneous STWL solutions (HN), we (i) provided detailed characterization of reaction products over a matrix of field-relevant gradients in contaminant concentration, PCO2, and reaction time; (ii) improved molecular-scale understanding of how sorbate speciation controls contaminant desorption from weathered sediments upon removal of caustic sources; and (iii) developed a mechanistic, predictive model of meso- to field-scale contaminant reactive transport under these conditions.

  1. Sediment transport and capacity change in three reservoirs, Lower Susquehanna River Basin, Pennsylvania and Maryland, 1900-2012

    Science.gov (United States)

    Langland, Michael J.

    2015-01-01

    The U.S. Geological Survey (USGS) has conducted numerous sediment transport studies in the Susquehanna River and in particular in three reservoirs in the Lower Susquehanna River Basin to determine sediment transport rates over the past century and to document changes in storage capacity. The Susquehanna River is the largest tributary to Chesapeake Bay and transports about one-half of the total freshwater input and substantial amounts of sediment and nutrients to the bay. The transported loads are affected by deposition in reservoirs (Lake Clarke, Lake Aldred, and Conowingo Reservoir) behind three hydropower dams. The geometry and texture of the deposited sediments in each reservoir upstream from the three dams has been a subject of research in recent decades. Particle size deposition and sediment scouring processes are part of the reservoir dynamics. A Total Maximum Daily Load (TMDL) for nitrogen, phosphorus, and sediment was established for Chesapeake Bay to attain water-quality standards. Six states and the District of Columbia agreed to reduce loads to the bay and to meet load allocation goals for the TMDL. The USGS has been estimating annual sediment loads at the Susquehanna River at Marietta, Pennsylvania (above Lake Clarke), and Susquehanna River at Conowingo, Maryland (below Conowingo Reservoir), since the mid-1980s to predict the mass balance of sediment transport through the reservoir system. Using streamflow and sediment data from the Susquehanna River at Harrisburg, Pennsylvania (upstream from the reservoirs), from 1900 to 1981, sediment loads were greatest in the early to mid-1900s when land disturbance activities from coal production and agriculture were at their peak. Sediment loads declined in the 1950s with the introduction of agricultural soil conservation practices. Loads were dominated by climatic factors in the 1960s (drought) and 1970s (very wet) and have been declining since the 1980s through 2012. The USGS developed a regression equation to

  2. Simulation of the fate of faecal bacteria in estuarine and coastal waters based on a fractionated sediment transport model

    Science.gov (United States)

    Yang, Chen; Liu, Ying

    2017-08-01

    A two-dimensional depth-integrated numerical model is refined in this paper to simulate the hydrodynamics, graded sediment transport process and the fate of faecal bacteria in estuarine and coastal waters. The sediment mixture is divided into several fractions according to the grain size. A bed evolution model is adopted to simulate the processes of the bed elevation change and sediment grain size sorting. The faecal bacteria transport equation includes enhanced source and sink terms to represent bacterial kinetic transformation and disappearance or reappearance due to sediment deposition or re-suspension. A novel partition ratio and dynamic decay rates of faecal bacteria are adopted in the numerical model. The model has been applied to the turbid water environment in the Bristol Channel and Severn estuary, UK. The predictions by the present model are compared with field data and those by non-fractionated model.

  3. Using organic biomarkers to trace the transport pathways of livestock-derived organic matter in the soil subsurface.

    Science.gov (United States)

    Lloyd, Charlotte; Michaelides, Katerina; Evershed, Richard; Chadwick, David; Dungait, Jennifer

    2010-05-01

    We explore the use of organic biomarkers as tracers for different components of livestock-derived organic matter (LD-OM) at two different spatial scales. We conducted six small-scale rainfall simulation experiments on a 30 × 30 × 30 cm soil lysimeter, following an application of bovine slurry at a rate of 5 l m-2. Throughout the experiment timed samples of leachate from the base of the lysimeter were collected, then soil cores were taken following the rainfall simulation. These samples were analysed in order to identify the most suitable biomarkers to trace dissolved and sediment-bound LD-OM respectively. The results showed that ammonium was an important tracer compound for dissolved LD-OM, along with other key low molecular weight compounds such as carbohydrates and amino acids. Analysis of the soil cores confirmed that compounds 5-β sigmastanol and 5-β epistigmastanol (5-β stanols) could be used very effectively to trace the sediment-bound and colloidal component of LD-OM. These specific organic compounds, which are identifiable by GC/MS analysis, only occur due to biohydrogenation of plant sterols in a ruminant gut, providing a unique opportunity to trace bovine faecal matter via sediment pathways. These tracers were then applied to a larger 3-D hillslope system by using University of Bristol's TRACE (Test Rig for Advancing Connectivity Experiments) facility. TRACE is a large-scale dual axis soil-slope measuring 6 m long × 2.5 m wide × 0.3 m deep accompanied by a 6-nozzle rainfall simulator. In these experiments slurry was only applied to the top 1 m section of the hillslope, in order to trace how the LD-OM was transported in the soil system. The slope allows the collection of leachate from the soil surface, from lateral through-flow and infiltrated water which reached the soil base (indicating deeper pathways). This enabled the distinction between LD-OM transported via different hydrological pathways. Soil cores were also taken across the soil surface

  4. What drives nearshore sediment transport controls on the depletion of beach placers at Manavalakurichi, Southwest Coast of India?.

    Digital Repository Service at National Institute of Oceanography (India)

    DineshKumar, P.K.; ManiMurali, R.; Babu, M.T.; Sudheesh, K.; Vethamony, P.; NaveenKumar, K.R.

    ,2008). However, the processes of sediment transport controls for this phenomenon are less explained and less understood. Numerical modelling of coastal processes, validated with field studies has great potential to assist with the understanding... with the prominent southward currents, owing to the lack of an effective physiographic feature to inhibit the southward movement of sediment. From the results obtained, it appears that numerical modeling of coastal processes has great potential to assist...

  5. Parameterizing the Transport Pathways for Cell Invasion in Complex Scaffold Architectures.

    Science.gov (United States)

    Ashworth, Jennifer C; Mehr, Marco; Buxton, Paul G; Best, Serena M; Cameron, Ruth E

    2016-05-01

    Interconnecting pathways through porous tissue engineering scaffolds play a vital role in determining nutrient supply, cell invasion, and tissue ingrowth. However, the global use of the term "interconnectivity" often fails to describe the transport characteristics of these pathways, giving no clear indication of their potential to support tissue synthesis. This article uses new experimental data to provide a critical analysis of reported methods for the description of scaffold transport pathways, ranging from qualitative image analysis to thorough structural parameterization using X-ray Micro-Computed Tomography. In the collagen scaffolds tested in this study, it was found that the proportion of pore space perceived to be accessible dramatically changed depending on the chosen method of analysis. Measurements of % interconnectivity as defined in this manner varied as a function of direction and connection size, and also showed a dependence on measurement length scale. As an alternative, a method for transport pathway parameterization was investigated, using percolation theory to calculate the diameter of the largest sphere that can travel to infinite distance through a scaffold in a specified direction. As proof of principle, this approach was used to investigate the invasion behavior of primary fibroblasts in response to independent changes in pore wall alignment and pore space accessibility, parameterized using the percolation diameter. The result was that both properties played a distinct role in determining fibroblast invasion efficiency. This example therefore demonstrates the potential of the percolation diameter as a method of transport pathway parameterization, to provide key structural criteria for application-based scaffold design.

  6. Investigating transport capacity equations in sediment yield modelling for the Cariri semi-arid region of Paraiba-PB/Brazil

    Directory of Open Access Journals (Sweden)

    E. E. De Figueiredo

    2015-03-01

    Full Text Available In the semi arid Cariri region of the state of Paraiba, Brazil, runoff is of the Hortonian type generated by excess of rainfall over infiltration capacity, and soil erosion is governed by rainfall intensity and sediment size. However, the governing sediment transport mechanism is not well understood. Sediment transport generally depends on the load of sediment provided by soil erosion and on the transport capacity of the flow. The latter is mainly governed by mechanisms such as water shear stress, or stream power. Accordingly, the load of sediment transported by the flow may vary depending on the mechanism involved in the equation of estimation. Investigation of the sediment transport capacity of the flow via a distributed physically-based model is an important and necessary task, but quite rare in semi-arid climates, and particularly in the Cariri region of the state of Paraíba/Brazil. In this study, the equations of Yalin, Engelund & Hansen, Laursen, DuBoys and Bagnold have been coupled with the MOSEE distributed physically based model aiming at identifying the mechanisms leading to the best model simulations when compared with data observed at various basin scales and land uses in the study region. The results obtained with the investigated methods were quite similar and satisfactory suggesting the feasibility of the mechanisms involved, but the observed values were better represented with Bagnold’s equation, which is physically grounded on the stream power, and we recommend it for simulations of similar climate, runoff generation mechanisms and sediment characteristics as in the study region.

  7. SedFoam-2.0: a 3-D two-phase flow numerical model for sediment transport

    Directory of Open Access Journals (Sweden)

    J. Chauchat

    2017-11-01

    Full Text Available In this paper, a three-dimensional two-phase flow solver, SedFoam-2.0, is presented for sediment transport applications. The solver is extended from twoPhaseEulerFoam available in the 2.1.0 release of the open-source CFD (computational fluid dynamics toolbox OpenFOAM. In this approach the sediment phase is modeled as a continuum, and constitutive laws have to be prescribed for the sediment stresses. In the proposed solver, two different intergranular stress models are implemented: the kinetic theory of granular flows and the dense granular flow rheology μ(I. For the fluid stress, laminar or turbulent flow regimes can be simulated and three different turbulence models are available for sediment transport: a simple mixing length model (one-dimensional configuration only, a k − ε, and a k − ω model. The numerical implementation is demonstrated on four test cases: sedimentation of suspended particles, laminar bed load, sheet flow, and scour at an apron. These test cases illustrate the capabilities of SedFoam-2.0 to deal with complex turbulent sediment transport problems with different combinations of intergranular stress and turbulence models.

  8. Continental-scale transport of sediments by the Baltic Ice Stream elucidated by coupled grain size and Nd provenance analyses

    Science.gov (United States)

    Boswell, Steven M.; Toucanne, Samuel; Creyts, Timothy T.; Hemming, Sidney R.

    2018-05-01

    We introduce a methodology for determining the transport distance of subglacially comminuted and entrained sediments. We pilot this method on sediments from the terminal margin of the Baltic Ice Stream, the largest ice stream of the Fennoscandian Ice Sheet during the Last Glacial Maximum. A strong correlation (R2 = 0.83) between the εNd and latitudes of circum-Baltic river sediments enables us to use εNd as a calibrated measure of distance. The proportion of subglacially transported sediments in a sample is estimated from grain size ratios in the silt fraction (Stream sediments located near the Åland sill, more than 850 km upstream from the terminal moraines. This result is in agreement with both numerical modeling and geomorphological investigations of Fennoscandinavian erosion, and is consistent with rapid ice flow into the Baltic basins prior to the Last Glacial Maximum. The methodology introduced here could be used to infer the distances of glacigenic sediment transport from Late Pleistocene and earlier glaciations.

  9. Suspended sediment transport in the Deepwater Navigation Channel, Yangtze River Estuary, China, in the dry season 2009: 2. Numerical simulations

    Science.gov (United States)

    Song, Dehai; Wang, Xiao Hua

    2013-10-01

    A three-dimensional wave-current-sediment coupled numerical model with wetting and drying process is developed to understand hydrodynamics and sediment transport dynamics in the Deepwater Navigation Channel (DNC), the North Passage of the Yangtze River Estuary (YRE), China. The model results are in good agreement with observed data, and statistics show good model skill scores and correlation coefficients. The model well reproduces the spring-neap variation between a well-mixed estuary and a highly stratified estuary. Model results indicate that the estuarine gravitational circulation plays the most important role in the estuarine turbidity maximum (ETM) formation in the DNC. The upstream nonlocal sediment intrusion through the spillover mechanism is a major source of sediment trapping in the North Passage after the morphological changes. Numerical studies are conducted to show scenarios in the YRE under the effects of different forcings (river discharges, waves, and winds). Between these study cases, surface-wave-breaking relieves the sediment trapping and bottom-wave-current-interaction aggravates the bed erosion and elevates the SSC in the ETM; the former and the latter have the least and largest influence on the suspended sediment transport in the DNC. The wind effects have a greater influence on sediment trapping than the river discharges, and the steady northwesterly wind condition favors the siltation in the DNC most. The significance of density-driven turbidity current is also assessed, which can enhance the saline-water intrusion and suppress the turbulent mixing in the bottom boundary layer.

  10. Transport pathway and source area for Artemisia pollen in Beijing, China

    Science.gov (United States)

    Qin, Xiaoxin; Li, Yiyin; Sun, Xu; Meng, Ling; Wang, Xiaoke

    2017-12-01

    Artemisia pollen is an important allergen responsible for allergic rhinitis in Beijing, China. To explore the transport pathways and source areas of Artemisia pollen, we used Burkard 7-day traps to monitor daily pollen concentrations in 2016 in an urban and suburban locality. Backward trajectories of 24- and 96-h and their cluster analysis were performed to identify transport pathways of Artemisia pollen using the HYSPLIT model on 0.5° × 0.5° GADS meteorological data. The potential source contribution function (PSCF) and concentration weighted trajectory (CWT) were calculated to further identify the major potential source areas at local, regional, and long-range scales. Our results showed significant differences in Artemisia pollen concentration between urban and suburban areas, attributed to differences in plant distribution and altitude of the sampling locality. Such differences arisen from both pollen emission and air mass movements, hence pollen dispersal. At local or regional scales, source area of northwestern parts of Beijing City, Hebei Province and northern and northwestern parts of Inner Mongolia influenced the major transport pathways of Artemisia pollen. Transport pathway at a long-range scale and its corresponding source area extended to northwestern parts of Mongolia. The regional-scale transport affected by wind and altitude is more profound for Artemisia pollen at the suburban than at the urban station.

  11. Dam-break flows with resistance as agents of sediment transport

    Science.gov (United States)

    Emmett, M.; Moodie, T. B.

    2008-08-01

    When a semi-infinite body of fluid initially at rest behind a vertical retaining wall is suddenly released by the removal of the barrier, the resulting flow over either a horizontal or a sloping bed is referred to as a dam-break flow. When resistance to the flow is neglected, the exact solution in the case of a horizontal bed with or without "tail water" may be obtained on the basis of shallow-water theory via the method of characteristics, and the results are well known. The inclusion of the effects of resistance in the form of basal friction that are needed in order to bring the mathematical solutions into closer harmony with the experimental results modifies the wave speed and flow profile near the head of the wave significantly and the simple exact solution of the shallow-water equations can no longer be employed as a reasonable description of the flow field. It is our intention here to study dam-break flows as agents of sediment transport taking into account basal friction and the attendant changes in depth profiles near the head, as well as the effects of particle concentrations on the flow dynamics including both erosion and deposition of particles arising through the interaction of the flow with the bed material. We shall consider shallow flows over dry beds and investigate the effects of changes in the depositional and erosional models employed as well as in the nature of the drag acting on the flow. These models offer some insight into the transport of sediment in the worst case scenario of complete and instantaneous collapse of a dam. They are also anticipated to provide information on other sheet flow events where particle transport plays a significant role in the flow dynamics.

  12. Potential Use of BEST® Sediment Trap in Splash - Saltation Transport Process by Simultaneous Wind and Rain Tests.

    Directory of Open Access Journals (Sweden)

    Mustafa Basaran

    Full Text Available The research on wind-driven rain (WDR transport process of the splash-saltation has increased over the last twenty years as wind tunnel experimental studies provide new insights into the mechanisms of simultaneous wind and rain (WDR transport. The present study was conducted to investigate the efficiency of the BEST® sediment traps in catching the sand particles transported through the splash-saltation process under WDR conditions. Experiments were conducted in a wind tunnel rainfall simulator facility with water sprayed through sprinkler nozzles and free-flowing wind at different velocities to simulate the WDR conditions. Not only for vertical sediment distribution, but a series of experimental tests for horizontal distribution of sediments was also performed using BEST® collectors to obtain the actual total sediment mass flow by the splash-saltation in the center of the wind tunnel test section. Total mass transport (kg m-2 were estimated by analytically integrating the exponential functional relationship using the measured sediment amounts at the set trap heights for every run. Results revealed the integrated efficiency of the BEST® traps at 6, 9, 12 and 15 m s-1 wind velocities under 55.8, 50.5, 55.0 and 50.5 mm h-1 rain intensities were, respectively, 83, 106, 105, and 102%. Results as well showed that the efficiencies of BEST® did not change much as compared with those under rainless wind condition.

  13. Sediment transport in forested head water catchments - Calibration and validation of a soil erosion and landscape evolution model

    Science.gov (United States)

    Hancock, G. R.; Webb, A. A.; Turner, L.

    2017-11-01

    Sediment transport and soil erosion can be determined by a variety of field and modelling approaches. Computer based soil erosion and landscape evolution models (LEMs) offer the potential to be reliable assessment and prediction tools. An advantage of such models is that they provide both erosion and deposition patterns as well as total catchment sediment output. However, before use, like all models they require calibration and validation. In recent years LEMs have been used for a variety of both natural and disturbed landscape assessment. However, these models have not been evaluated for their reliability in steep forested catchments. Here, the SIBERIA LEM is calibrated and evaluated for its reliability for two steep forested catchments in south-eastern Australia. The model is independently calibrated using two methods. Firstly, hydrology and sediment transport parameters are inferred from catchment geomorphology and soil properties and secondly from catchment sediment transport and discharge data. The results demonstrate that both calibration methods provide similar parameters and reliable modelled sediment transport output. A sensitivity study of the input parameters demonstrates the model's sensitivity to correct parameterisation and also how the model could be used to assess potential timber harvesting as well as the removal of vegetation by fire.

  14. Interference of a short-chain phospholipid with ion transport pathways in frog skin

    DEFF Research Database (Denmark)

    Unmack, M A; Frederiksen, O; Willumsen, N J

    1997-01-01

    The effects of mucosal application of the short-chain phospholipid didecanoyl-L-alpha-phosphatidylcholine (DDPC; with two saturated 10-carbon acyl chains) on active Na+ transport and transepithelial conductance (G) in the frog skin (Rana temporaria) were investigated. Active Na+ transport...... of the frog skin epithelium and opens a paracellular tight junction pathway. Both effects may be caused by incorporation of DDPC in the apical cell membrane....

  15. Thermal, chemical, and mass transport processes induced in abyssal sediments by the emplacement of nuclear wastes: Experimental and modelling results

    International Nuclear Information System (INIS)

    McVey, D.F.; Erickson, K.L.; Seyfried, W.E. Jr.

    1983-01-01

    In this chapter the authors discuss the current status of heat and mass transport studies in the marine red clay sediments that are being considered as a nuclear waste isolation medium and review analytical and experimental studies. Calculations based on numerical models indicate that for a maximum allowable sediment-canister interface temperatures of 200 0 to 250 0 C, the sediment can absorb about 1.5kW initial power from waste buried 30 m in the sediment in a canister that is 3 m long and 0.3 m in diameter. The resulting fluid displacement due to convections is found to be small, less than 1 m. Laboratory studies of the geochemical effects induced by heating sediment-seawater mixtures indicate that the canister and waste form should be designed to resist a hot, relatively acidic oxidizing environment. Since the thermally altered sediment volume of about 5.5 m/sup 3/ is small relative to the sediment volume overlying the canister, the acid and oxidizing conditions should significantly affect the properties of the far field only if thermodiffusional process (Soret effect) prove to be significant. If thermodiffusional effects are important, however, near-field chemistry will differ considerably from that predicted from results of constant temperature sediment-seawater interaction experiments

  16. Denitrification pathways and rates in the sandy sediments of the Georgia continental shelf, USA

    Directory of Open Access Journals (Sweden)

    Ingall Ellery

    2005-02-01

    Full Text Available Denitrification in continental shelf sediments has been estimated to be a significant sink of oceanic fixed nitrogen (N. The significance and mechanisms of denitrification in organic-poor sands, which comprise 70% of continental shelf sediments, are not well known. Core incubations and isotope tracer techniques were employed to determine processes and rates of denitrification in the coarse-grained, sandy sediments of the Georgia continental shelf. In these sediments, heterotrophic denitrification was the dominant process for fixed N removal. Processes such as coupled nitrification-denitrification, anammox (anaerobic ammonium oxidation, and oxygen-limited autotrophic nitrification-denitrification were not evident over the 24 and 48 h time scale of the incubation experiments. Heterotrophic denitrification processes produce 22.8–34.1 μmole N m-2 d-1 of N2 in these coarse-grained sediments. These denitrification rates are approximately two orders of magnitude lower than rates determined in fine-grained shelf sediments. These lower rates may help reconcile unbalanced marine N budgets which calculate global N losses exceeding N inputs.

  17. Ammonia gas transport and reactions in unsaturated sediments: Implications for use as an amendment to immobilize inorganic contaminants

    International Nuclear Information System (INIS)

    Zhong, L.; Szecsody, J.E.; Truex, M.J.; Williams, M.D.; Liu, Y.

    2015-01-01

    Highlights: • Ammonia transport can be predicted from gas movement and equilibrium partitioning. • Ammonia diffusion rate in unsaturated sediment is a function of water contents. • High pH induced by ammonia causes mineral dissolution and sequential precipitation. • Ammonia treatment effectively immobilized uranium from contaminated sediments. - Abstract: Use of gas-phase amendments for in situ remediation of inorganic contaminants in unsaturated sediments of the vadose zone may be advantageous, but there has been limited development and testing of gas remediation technologies. Treatment with ammonia gas has a potential for use in treating inorganic contaminants (such as uranium) because it induces a high pore-water pH, causing mineral dissolution and subsequent formation of stable precipitates that decrease the mobility of some contaminants. For field application of this treatment, further knowledge of ammonia transport in porous media and the geochemical reactions induced by ammonia treatment is needed. Laboratory studies were conducted to support calculations needed for field treatment design, to quantify advective and diffusive ammonia transport in unsaturated sediments, to evaluate inter-phase (gas/sediment/pore water) reactions, and to study reaction-induced pore-water chemistry changes as a function of ammonia delivery conditions, such as flow rate, gas concentration, and water content. Uranium-contaminated sediment was treated with ammonia gas to demonstrate U immobilization. Ammonia gas quickly partitions into sediment pore water and increases the pH up to 13.2. Injected ammonia gas advection front movement can be reasonably predicted by gas flow rate and equilibrium partitioning. The ammonia gas diffusion rate is a function of the water content in the sediment. Sodium, aluminum, and silica pore-water concentrations increase upon exposure to ammonia and then decline as aluminosilicates precipitate when the pH declines due to buffering. Up to 85% of

  18. Colloid-facilitated transport of cesium in vadose-zone sediments: the importance of flow transients.

    Science.gov (United States)

    Cheng, Tao; Saiers, James E

    2010-10-01

    Colloid-sized particles are commonly detected in vadose-zone pore waters and are capable of binding chemicals with sorptive affinities for geologic materials. Published research demonstrates that colloids are capable of facilitating the transport of sorptive contaminants under conditions of steady pore water flow, when volumetric moisture content and pore water velocity are constant. Less is known about the role of colloids in governing contaminant mobility under transient-flow conditions, which are characteristic of natural vadose-zone environments. The objective of this study is to elucidate the influences of flow transients on the mobilization and transport of in situ colloids and colloid-associated contaminants. We conducted column experiments in which the mobilization of in situ colloids and (137)Cs was induced by transients associated with the drainage and imbibition of (137)Cs contaminated-sediments. Our results demonstrate that substantial quantities of in situ colloids and colloid-associated (137)Cs are mobilized as volumetric moisture content declines during porous-medium drainage and as volumetric moisture content increases during porous-medium imbibition. We also find that the colloid-effect on (137)Cs transport is sensitive to changes in pore water ionic strength. That is, the quantities of colloids mobilized and the capacity of the these colloids to bind (137)Cs decrease with increasing ionic strength, leading to a decrease of the mass of (137)Cs eluted from the columns during porous-medium drainage and imbibition.

  19. An approximate analytical solution for describing surface runoff and sediment transport over hillslope

    Science.gov (United States)

    Tao, Wanghai; Wang, Quanjiu; Lin, Henry

    2018-03-01

    Soil and water loss from farmland causes land degradation and water pollution, thus continued efforts are needed to establish mathematical model for quantitative analysis of relevant processes and mechanisms. In this study, an approximate analytical solution has been developed for overland flow model and sediment transport model, offering a simple and effective means to predict overland flow and erosion under natural rainfall conditions. In the overland flow model, the flow regime was considered to be transitional with the value of parameter β (in the kinematic wave model) approximately two. The change rate of unit discharge with distance was assumed to be constant and equal to the runoff rate at the outlet of the plane. The excess rainfall was considered to be constant under uniform rainfall conditions. The overland flow model developed can be further applied to natural rainfall conditions by treating excess rainfall intensity as constant over a small time interval. For the sediment model, the recommended values of the runoff erosion calibration constant (cr) and the splash erosion calibration constant (cf) have been given in this study so that it is easier to use the model. These recommended values are 0.15 and 0.12, respectively. Comparisons with observed results were carried out to validate the proposed analytical solution. The results showed that the approximate analytical solution developed in this paper closely matches the observed data, thus providing an alternative method of predicting runoff generation and sediment yield, and offering a more convenient method of analyzing the quantitative relationships between variables. Furthermore, the model developed in this study can be used as a theoretical basis for developing runoff and erosion control methods.

  20. Cambrian rivers and floodplains: the significance of microbial cementation, groundwater and aeolian sediment transport

    Science.gov (United States)

    Reesink, A. J. H.; Best, J.; Freiburg, J. T.; Nathan, W.

    2016-12-01

    Rivers that existed before land plants colonized the Earth are commonly considered to be unaffected by microbial activity on their floodplains, because the limited cementation produced by microbial activity is insufficient to stabilize the river banks. Although this assumption is likely correct, such emphasis on channel dynamics ignores the potential role of floodplain dynamics as an integral component of the river system. Detailed analysis of cores from the Cambrian Mount Simon Sandstone, Illinois, suggests that a significant proportion of the terrestrial sequence is composed of flat-bedded `crinkly' structures that provide evidence of cementation by soil crusts and microbial biofilms, and that promoted the adhesion of sediment to sticky surfaces. Wind ripples and local desert pavements were abundant. These findings highlight that sediment deposition on Cambrian floodplains was often dominated by wind in locations where the ground water table reached the surface, and was thus likely independent of sediment transport within the river channel. Erosion by wind would thus have been hindered by surface cementation and the formation of desert pavements. Such ground water control on deposition, and resistance to erosion by floodplain surface hardening, appear to have been the primary controls on Cambrian floodplain topography. Because floodplain topography poses a key control on channel and floodplain flow, these processes may have affected patterns of erosion and deposition, as well as reach-scale dynamics such as channel avulsions. The autonomous operation of wind-and-groundwater controlled floodplains makes pre-vegetated river systems more sensitive to climatic conditions such as precipitation and evaporation, and strikingly different from those that occurred after the development of land plants.

  1. Organic sediments of the equatorial east Atlantic: Effects of origin, transport, diagenesis, and climate

    International Nuclear Information System (INIS)

    Westerhausen, L.

    1992-01-01

    The origins and diagenesis of organic matter in recent sediments of the equatorial Eastern Atlantic are assessed on the basis of the 13 C/ 12 C composition of the organic carbon (δ 13 C TOC ), the C/N ratio, and molecular biomarkers from terrigenic and marine sources. Also investigated was the effect of global climate on the 13 C/ 12 C ratios of marine organic carbon and on the origins of organic matter on sedimentary cores. The terrigenic fraction of organic carbon is calculated using a binary δ 13 C TOC mixing model. To begin with, the δ 13 C TOC values were standardized to a uniform surface water temperature and water depth. The calculated terrigenic TOC fractions amount to more than 60% for shelf sediments off the coast of Eastern Liberia, Ivory Coast, and the continental shelf of Gabun. The higher terrigenic TOC fractions of up to 20% in recent sediments on the continental shelf along the coast of Guinea to Ivory Coast are interpreted in terms of a transport of terrigenic substances in down hill direction and parallel to the coast. The effects of the global climate on the TOC accumulation rates and on the 13 C/ 12 C ratio of organic carbon were investigated in a pelogic sedimentary core (M16772) from the tropical Eastern Atlantic. Prior to this, the δ 13 C TOC values were standardized to a uniform surface temperature and a uniform 13 C/ 12 C ratio of the dissolved inorganic carbon using the UK 37 index and the δ 13 C values of G.ruber. During the cold periods the export production increases, which - together with the low CO 2 partial pressure in the atmosphere, and thus also in the surface water -induces 13 C accumulation in the marine organic carbon. There is nothing to suggest an effect of 13 C-accumulating phytoplancton, e.g. dinoflagellats, on the 13 C/ 12 C ratio. (orig./KW). 32 figs., 8 tabs [de

  2. Electric-Field Control of Interfering Transport Pathways in a Single-Molecule Anthraquinone Transistor

    Science.gov (United States)

    Koole, Max; Thijssen, Jos M.; Valkenier, Hennie; Hummelen, Jan C.; Zant, Herre S. J. van der

    2015-08-01

    It is understood that molecular conjugation plays an important role in charge transport through single-molecule junctions. Here, we investigate electron transport through an anthraquinone based single-molecule three-terminal device. With the use of an electric-field induced by a gate electrode, the molecule is reduced resulting into a ten-fold increase in the off-resonant differential conductance. Theoretical calculations link the change in differential conductance to a reduction-induced change in conjugation, thereby lifting destructive interference of transport pathways.

  3. Impact of LDL apheresis on atheroprotective reverse cholesterol transport pathway in familial hypercholesterolemia

    NARCIS (Netherlands)

    Orsoni, Alexina; Villard, Elise F.; Bruckert, Eric; Robillard, Paul; Carrie, Alain; Bonnefont-Rousselot, Dominique; Chapman, M. John; Dallinga-Thie, Geesje M.; Le Goff, Wilfried; Guerin, Maryse

    2012-01-01

    In familial hypercholesterolemia (FH), low HDL cholesterol (HDL-C) levels are associated with functional alterations of HDL particles that reduce their capacity to mediate the reverse cholesterol transport (RCT) pathway. The objective of this study was to evaluate the consequences of LDL apheresis

  4. Evidence of a sewer vapor transport pathway at the USEPA vapor intrusion research duplex

    Science.gov (United States)

    The role of sewer lines as preferential pathways for vapor intrusion is poorly understood. Although the importance of sewer lines for volatile organic compound (VOC) transport has been documented at a small number of sites with vapor intrusion, sewer lines are not routinely sampl...

  5. Modelling the transport of radioactive cesium released from the Fukushima Dai-ichi NPP with sediments through the hydrologic system

    Science.gov (United States)

    Kinouchi, T.; Omata, T.; Wei, L.; Liu, T.; Araya, M.

    2013-12-01

    Due to the accident of the Fukushima Dai-ichi Nuclear Power Plant on March 2011, a huge amount of radionuclides including Cesium-134 and Cesium-137 was deposited over the main island of Japan and the Pacific Ocean, resulting in further transfer and diffusion of Cesium through the atmospheric flow, watershed hydrological processes, and terrestrial ecosystem. Particularly, for the transfer of Cesium-134 and Cesium-137, sediments eroded and transported by the rainfall-runoff processes play an important role as Cesium tends to be strongly adsorbed to soil particles such as clay and silt. In this study, we focus on the transport of sediment and adsorbed Cesium in the watershed-scale hydrologic system to predict the long-term change of distribution of Cesium and its discharge to rivers and ocean. We coupled a physically-based distributed hydrological model with the modules of erosion and transport of sediments and adsorbed Cesium, and applied the coupled model to the Abukuma River watershed, which is located over the area of higher deposition of Cesium. In the model, complex land use and land cover distributions, and the effect of human activities such as irrigation, dam control and urban drainage system are taken into accounts. Simulation was conducted for the period of March 2011 until August 2012, with initial spatial distribution of Cesium-134 and Cesium-137 obtained by the airborne survey. Simulated flow rates and sediment concentrations agreed well with observed, and found that since the accident, two major storms in July and September 2011 transported about 50% of total sediments transported during the simulated periods. Cesium concentration in the sediment was reproduced well except for the difference in the initial periods. This difference is attributable to the uncertainty arisen from the initial distribution of Cesium in the soil and the transfer of Cesium from the forest canopy.

  6. Hydrodynamic and Sediment Transport Modelling of Suralaya Coastal Area, Cilegon, Indonesia

    Science.gov (United States)

    Fattah, A. H.; Suntoyo; Damerianne, H. A.; Wahyudi

    2018-03-01

    The coastal zone of Suralaya is located in the district Pulomerak, Cilegon City, Province Banten. This region is a part of the Sunda Strait region that is very important area to support the ongoing activities such as, industries, power plant, ports, and tourism. However, those various activities will certainly give effect to the surrounding environment. To determine the environmental conditions of Suralaya Coast, it is necessary to study the hydrodynamics analysis and sediment transport modelling including the analysis of currents patterns. Tidal elevation observation was conducted for 15 days used to validate the water elevation simulation results, in which a good agreement between the observed data and the model result was obtained with the error value of 1.6%. The dominant current direction is from northeast in west season, while in the east season predominant current direction is from northwest with a speed average current 12,44 cm/s. The dominant wave direction is from the west. The average temperature is at 27°C and the bottom sediment dominant form is fine sand.

  7. Physical and logistical considerations of using ultrasonic anemometers in aeolian sediment transport research

    Science.gov (United States)

    Walker, Ian J.

    2005-05-01

    Recently, ultrasonic anemometers (UAs) have become available for precise, high-frequency measurement of three-dimensional velocity and turbulence properties. Except for a few wind tunnel and computational fluid dynamics (CFD) simulations, advances in aeolian sediment transport and bedform research have been limited to field studies using instrumentation that is either incapable of measuring turbulence (e.g., cup anemometers) or unable to withstand sediment-laden airflow (e.g., hotfilms). In contrast, extensive progress has occurred in fluvial research where turbulence instrumentation has been available for some time. This paper provides a pragmatic discussion on using UAs in aeolian research. Recent advances using this technology are reviewed and key physical and logistical considerations for measuring airflow properties and near-surface shear stress using UAs over complex terrain are discussed. Physical considerations include limitations of applying boundary layer theory to flow over natural surfaces such as non-logarithmic velocity profiles resulting from roughness- and topographically induced effects and the inability of instrumentation to measure within the thin constant-stress region. These constraints hinder accurate shear velocity ( u*), shear stress and sand transport estimation. UAs allow measurement of turbulent Reynolds stress (RS) that, in theory, should equal profile-derived shear stress. Discrepancies often exist between these quantities however due to three-dimensional (spanwise) flow components and rapid distortion effects (i.e., unbalanced production and dissipation of turbulence) common in flow over complex terrain. While the RS approach yields information on turbulent contributions to near-surface stress generation, little evidence exists showing that RS is a better measure of forces responsible for sediment transport. Consequently, predictive equations for sediment transport using RS do not exist. There is also a need to identify the role of

  8. Modeling Input Errors to Improve Uncertainty Estimates for Sediment Transport Model Predictions

    Science.gov (United States)

    Jung, J. Y.; Niemann, J. D.; Greimann, B. P.

    2016-12-01

    Bayesian methods using Markov chain Monte Carlo algorithms have recently been applied to sediment transport models to assess the uncertainty in the model predictions due to the parameter values. Unfortunately, the existing approaches can only attribute overall uncertainty to the parameters. This limitation is critical because no model can produce accurate forecasts if forced with inaccurate input data, even if the model is well founded in physical theory. In this research, an existing Bayesian method is modified to consider the potential errors in input data during the uncertainty evaluation process. The input error is modeled using Gaussian distributions, and the means and standard deviations are treated as uncertain parameters. The proposed approach is tested by coupling it to the Sedimentation and River Hydraulics - One Dimension (SRH-1D) model and simulating a 23-km reach of the Tachia River in Taiwan. The Wu equation in SRH-1D is used for computing the transport capacity for a bed material load of non-cohesive material. Three types of input data are considered uncertain: (1) the input flowrate at the upstream boundary, (2) the water surface elevation at the downstream boundary, and (3) the water surface elevation at a hydraulic structure in the middle of the reach. The benefits of modeling the input errors in the uncertainty analysis are evaluated by comparing the accuracy of the most likely forecast and the coverage of the observed data by the credible intervals to those of the existing method. The results indicate that the internal boundary condition has the largest uncertainty among those considered. Overall, the uncertainty estimates from the new method are notably different from those of the existing method for both the calibration and forecast periods.

  9. The Role of Grain Dynamics in the Onset of Sediment Transport

    Science.gov (United States)

    Clark, A., IV; Shattuck, M. D.; Ouellette, N. T.; O'Hern, C.

    2016-12-01

    Despite decades of research, the grain-scale mechanisms that control the onset of sediment transport are still not well understood. A large collection of data, known as the Shields curve, shows that Θ c, which is the minimum dimensionless shear stress at the bed for grains to move, is primarily a function of the shear Reynolds number Re*. To understand this collapse, it is typically assumed that the onset of grain motion is determined by the conditions at which fluid forces violate static equilibrium for surface grains. Re* compares the grain size to the size of the viscous sublayer in the fluid flow, so the relevant fluid lift and drag forces vary with Re*. A complimentary approach, which remains relatively unexplored, is to ask instead when mobilized grains can stop. In this case, Re* is the ratio of two important time scales related to grain motion: (1) the time for a grain to equilibrate to the fluid flow and (2) the time for the shear stress to accelerate a grain over the characteristic bed roughness. Thus, Re* controls whether grains are accelerated significantly between collisions with the bed. To test how this effect relates to the Shields curve, we perform simulations of granular beds sheared by a model fluid flow, where Re* is varied only through the fluid-grain coupling, which alters the grain dynamics. We find good qualitative agreement with the Shields curve, and the quantitative discrepancies are consistent with lift forces calculations at varying Re*. Our results suggest that the onset of sediment transport may be better described as when mobile grains are able to stop, which varies significantly with Re*, and theoretical descriptions that account for this effect may be more successful than those that consider only static equilibrium.

  10. Effects of oil dispersants on settling of marine sediment particles and particle-facilitated distribution and transport of oil components.

    Science.gov (United States)

    Cai, Zhengqing; Fu, Jie; Liu, Wen; Fu, Kunming; O'Reilly, S E; Zhao, Dongye

    2017-01-15

    This work investigated effects of three model oil dispersants (Corexit EC9527A, Corexit EC9500A and SPC1000) on settling of fine sediment particles and particle-facilitated distribution and transport of oil components in sediment-seawater systems. All three dispersants enhanced settling of sediment particles. The nonionic surfactants (Tween 80 and Tween 85) play key roles in promoting particle aggregation. Yet, the effects varied with environmental factors (pH, salinity, DOM, and temperature). Strongest dispersant effect was observed at neutral or alkaline pH and in salinity range of 0-3.5wt%. The presence of water accommodated oil and dispersed oil accelerated settling of the particles. Total petroleum hydrocarbons in the sediment phase were increased from 6.9% to 90.1% in the presence of Corexit EC9527A, and from 11.4% to 86.7% for PAHs. The information is useful for understanding roles of oil dispersants in formation of oil-sediment aggregates and in sediment-facilitated transport of oil and PAHs in marine eco-systems. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. Direct measurements of lift and drag on shallowly submerged cobbles in steep streams: Implications for flow resistance and sediment transport

    Science.gov (United States)

    Lamb, Michael P.; Brun, Fanny; Fuller, Brian M.

    2017-09-01

    Steep mountain streams have higher resistance to flow and lower sediment transport rates than expected by comparison with low gradient rivers, and often these differences are attributed to reduced near-bed flow velocities and stresses associated with form drag on channel forms and immobile boulders. However, few studies have directly measured drag and lift forces acting on bed sediment for shallow flows over coarse sediment, which ultimately control sediment transport rates and grain-scale flow resistance. Here we report on particle lift and drag force measurements in flume experiments using a planar, fixed cobble bed over a wide range of channel slopes (0.004 < S < 0.3) and water discharges. Drag coefficients are similar to previous findings for submerged particles (CD ˜ 0.7) but increase significantly for partially submerged particles. In contrast, lift coefficients decrease from near unity to zero as the flow shallows and are strongly negative for partially submerged particles, indicating a downward force that pulls particles toward the bed. Fluctuating forces in lift and drag decrease with increasing relative roughness, and they scale with the depth-averaged velocity squared rather than the bed shear stress. We find that, even in the absence of complex bed topography, shallow flows over coarse sediment are characterized by high flow resistance because of grain drag within a roughness layer that occupies a significant fraction of the total flow depth, and by heightened critical Shields numbers and reduced sediment fluxes because of reduced lift forces and reduced turbulent fluctuations.

  12. Particle sorting in Filter Porous Media and in Sediment Transport: A Numerical and Experimental Study

    Science.gov (United States)

    Glascoe, L. G.; Ezzedine, S. M.; Kanarska, Y.; Lomov, I. N.; Antoun, T.; Smith, J.; Hall, R.; Woodson, S.

    2014-12-01

    Understanding the flow of fines, particulate sorting in porous media and fractured media during sediment transport is significant for industrial, environmental, geotechnical and petroleum technologies to name a few. For example, the safety of dam structures requires the characterization of the granular filter ability to capture fine-soil particles and prevent erosion failure in the event of an interfacial dislocation. Granular filters are one of the most important protective design elements of large embankment dams. In case of cracking and erosion, if the filter is capable of retaining the eroded fine particles, then the crack will seal and the dam safety will be ensured. Here we develop and apply a numerical tool to thoroughly investigate the migration of fines in granular filters at the grain scale. The numerical code solves the incompressible Navier-Stokes equations and uses a Lagrange multiplier technique. The numerical code is validated to experiments conducted at the USACE and ERDC. These laboratory experiments on soil transport and trapping in granular media are performed in constant-head flow chamber filled with the filter media. Numerical solutions are compared to experimentally measured flow rates, pressure changes and base particle distributions in the filter layer and show good qualitative and quantitative agreement. To further the understanding of the soil transport in granular filters, we investigated the sensitivity of the particle clogging mechanism to various parameters such as particle size ratio, the magnitude of hydraulic gradient, particle concentration, and grain-to-grain contact properties. We found that for intermediate particle size ratios, the high flow rates and low friction lead to deeper intrusion (or erosion) depths. We also found that the damage tends to be shallower and less severe with decreasing flow rate, increasing friction and concentration of suspended particles. We have extended these results to more realistic heterogeneous

  13. Regional Sediment Budgets for the Haleiwa Region, Oahu, Hawaii

    Science.gov (United States)

    2014-06-01

    ERDC/CHL CHETN-XIV-38 June 2014 Approved for public release; distribution is unlimited. Regional Sediment Budgets for the Haleiwa Region, Oahu ...regional sediment budgets (RSB) for the Haleiwa Region on the island of Oahu , Hawaii, as part of the Hawaii Regional Sediment Management (RSM) Program...morphology and coastal processes have on sediment pathways and transport volumes. In the Southeast Oahu Region, Mokapu Point to Makapuu Point RSB

  14. Fun at Antarctic grounding lines: Ice-shelf channels and sediment transport

    Science.gov (United States)

    Drews, Reinhard; Mayer, Christoph; Eisen, Olaf; Helm, Veit; Ehlers, Todd A.; Pattyn, Frank; Berger, Sophie; Favier, Lionel; Hewitt, Ian H.; Ng, Felix; Fürst, Johannes J.; Gillet-Chaulet, Fabien; Bergeot, Nicolas; Matsuoka, Kenichi

    2017-04-01

    Meltwater beneath the polar ice sheets drains, in part, through subglacial conduits. Landforms created by such drainages are abundant in areas formerly covered by ice sheets during the last glacial maximum. However, observations of subglacial conduit dynamics under a contemporary ice sheet are lacking. We present results from ice-penetrating radar to infer the existence of subglacial conduits upstream of the grounding line of Roi Baudouin Ice Shelf, Antarctica. The conduits are aligned with ice-shelf channels, and underlain by esker ridges formed from sediment deposition due to reduced water outflow speed near the grounding line. In turn, the eskers modify local ice flow to initiate the bottom topography of the ice-shelf channels, and create small surface ridges extending onto the shelf. Relict features on the shelf are interpreted to indicate a history of these interactions and variability of past subglacial drainages. Because ice-shelf channels are loci where intense melting occurs to thin an ice shelf, these findings expose a novel link between subglacial drainage, sedimentation, and ice-shelf stability. To investigate the role of sediment transport beneath ice sheets further, we model the sheet-shelf system of the Ekstömisen catchment, Antarctica. A 3D finite element model (Elmer/ICE) is used to solve the transients full Stokes equation for isotropic, isothermal ice with a dynamic grounding line. We initialize the model with surface topography from the TanDEM-X satellites and by inverting simultaneously for ice viscosity and basal drag using present-day surface velocities. Results produce a flow field which is consitent with sattelite and on-site observations. Solving the age-depth relationship allows comparison with radar isochrones from airborne data, and gives information about the atmospheric/dynamic history of this sector. The flow field will eventually be used to identify potential sediment sources and sinks which we compare with more than 400 km of

  15. Incision of the Jezero Crater Outflow Channel by Fluvial Sediment Transport

    Science.gov (United States)

    Holo, S.; Kite, E. S.

    2017-12-01

    Jezero crater, the top candidate landing site for the Mars 2020 rover, once possessed a lake that over-spilled and eroded a large outflow channel into the Eastern rim. The Western deltaic sediments that would be the primary science target of the rover record a history of lake level, which is modulated by the inflow and outflow channels. While formative discharges for the Western delta exist ( 500 m3/s), little work has been done to see if these flows are the same responsible for outflow channel incision. Other models of the Jezero outflow channel incision assume that a single rapid flood (incision timescales of weeks), with unknown initial hydraulic head and no discharge into the lake (e.g. from the inflow channels or the subsurface), incised an open channel with discharge modulated by flow over a weir. We present an alternate model where, due to an instability at the threshold of sediment motion, the incision of the outflow channel occurs in concert with lake filling. In particular, we assume a simplified lake-channel-valley system geometry and that the channel is hydraulically connected to the filling/draining crater lake. Bed load sediment transport and water discharge through the channel are quantified using the Meyer-Peter and Mueller relation and Manning's law respectively. Mass is conserved for both water and sediment as the lake level rises/falls and the channel incises. This model does not resolve backwater effects or concavity in the alluvial system, but it does capture the non-linear feedbacks between lake draining, erosion rate, channel flow rate, and slope relaxation. We identify controls on incision of the outflow channel and estimate the time scale of outflow channel formation through a simple dynamical model. We find that the observed 300m of channel erosion can be reproduced in decades to centuries of progressive bed load as the delta forming flows fill the lake. This corresponds to time scales on the order of or smaller than the time scale

  16. Can Computational Sediment Transport Models Reproduce the Observed Variability of Channel Networks in Modern Deltas?

    Science.gov (United States)

    Nesvold, E.; Mukerji, T.

    2017-12-01

    River deltas display complex channel networks that can be characterized through the framework of graph theory, as shown by Tejedor et al. (2015). Deltaic patterns may also be useful in a Bayesian approach to uncertainty quantification of the subsurface, but this requires a prior distribution of the networks of ancient deltas. By considering subaerial deltas, one can at least obtain a snapshot in time of the channel network spectrum across deltas. In this study, the directed graph structure is semi-automatically extracted from satellite imagery using techniques from statistical processing and machine learning. Once the network is labeled with vertices and edges, spatial trends and width and sinuosity distributions can also be found easily. Since imagery is inherently 2D, computational sediment transport models can serve as a link between 2D network structure and 3D depositional elements; the numerous empirical rules and parameters built into such models makes it necessary to validate the output with field data. For this purpose we have used a set of 110 modern deltas, with average water discharge ranging from 10 - 200,000 m3/s, as a benchmark for natural variability. Both graph theoretic and more general distributions are established. A key question is whether it is possible to reproduce this deltaic network spectrum with computational models. Delft3D was used to solve the shallow water equations coupled with sediment transport. The experimental setup was relatively simple; incoming channelized flow onto a tilted plane, with varying wave and tidal energy, sediment types and grain size distributions, river discharge and a few other input parameters. Each realization was run until a delta had fully developed: between 50 and 500 years (with a morphology acceleration factor). It is shown that input parameters should not be sampled independently from the natural ranges, since this may result in deltaic output that falls well outside the natural spectrum. Since we are

  17. Modelling the cohesive sediment transport in the marine environment: the case of Thermaikos Gulf

    Directory of Open Access Journals (Sweden)

    Y. N. Krestenitis

    2007-01-01

    Full Text Available The transport of fine-grained sediments in the marine environment entails risks of pollutant intrusions from substances absorbed onto the cohesive flocks' surface, gradually released to the aquatic field. These substances include nutrients such as nitrate, phosphate and silicate compounds from drainage from fertilization of adjacent cultivated areas that enter the coastal areas through rivers and streams, or trace metals as remainders from urban and industrial activities. As a consequence, knowledge on the motion and distribution of sediment particles coming from a given pollutant source is expected to provide the 'bulk' information on pollutant distribution, necessary for determining the region of influence of the source and to estimate probable trophic levels of the seawater and potential environmental risks. In that aim a numerical model has been developed to predict the fate of the sediments introduced to the marine environment from different pollution sources, such as river outflows, erosion of the seabed, aeolian transported material and drainage systems. The proposed three-dimensional mathematical model is based on the particle tracking method, according to which matter concentration is expressed by particles, each representing a particular amount of sedimentary mass, passively advected and dispersed by the currents. The processes affecting characteristics and propagation of sedimentary material in the marine environment, incorporated in the parameterization, apart from advection and dispersion, include cohesive sediment and near-bed processes. The movement of the particles along with variations in sedimentary characteristics and state, carried by each particle as personal information, are traced with time. Specifically, concerning transport processes, the local seawater velocity and the particle's settling control advection, whereas the random Brownian motion due to turbulence simulates turbulent diffusion. The

  18. Pathways and regulation of carbon, sulfur and energy transfer in marine sediments overlying methane gas hydrates on the Opouawe Bank (New Zealand)

    Science.gov (United States)

    Dale, A. W.; Sommer, S.; Haeckel, M.; Wallmann, K.; Linke, P.; Wegener, G.; Pfannkuche, O.

    2010-10-01

    This study combines sediment geochemical analysis, in situ benthic lander deployments and numerical modeling to quantify the biogeochemical cycles of carbon and sulfur and the associated rates of Gibbs energy production at a novel methane seep. The benthic ecosystem is dominated by a dense population of tube-building ampharetid polychaetes and conspicuous microbial mats were unusually absent. A 1D numerical reaction-transport model, which allows for the explicit growth of sulfide and methane oxidizing microorganisms, was tuned to the geochemical data using a fluid advection velocity of 14 cm yr -1. The fluids provide a deep source of dissolved hydrogen sulfide and methane to the sediment with fluxes equal to 4.1 and 18.2 mmol m -2 d -1, respectively. Chemosynthetic biomass production in the subsurface sediment is estimated to be 2.8 mmol m -2 d -1 of C biomass. However, carbon and oxygen budgets indicate that chemosynthetic organisms living directly above or on the surface sediment have the potential to produce 12.3 mmol m -2 d -1 of C biomass. This autochthonous carbon source meets the ampharetid respiratory carbon demand of 23.2 mmol m -2 d -1 to within a factor of 2. By contrast, the contribution of photosynthetically-fixed carbon sources to ampharetid nutrition is minor (3.3 mmol m -2 d -1 of C). The data strongly suggest that mixing of labile autochthonous microbial detritus below the oxic layer sustains high measured rates of sulfate reduction in the uppermost 2 cm of the sulfidic sediment (100-200 nmol cm -3 d -1). Similar rates have been reported in the literature for other seeps, from which we conclude that autochthonous organic matter is an important substrate for sulfate reducing bacteria in these sediment layers. A system-scale energy budget based on the chemosynthetic reaction pathways reveals that up to 8.3 kJ m -2 d -1 or 96 mW m -2 of catabolic (Gibbs) energy is dissipated at the seep through oxidation reactions. The microorganisms mediating sulfide

  19. The Effect of Suspended Sediment Transport and Deposition on Streambed Clogging Under Losing and Gaining Flow Conditions

    Science.gov (United States)

    Fox, A.; Packman, A. I.; Preziosi-Ribero, A.; Li, A.; Arnon, S.

    2017-12-01

    Sediment transport and deposition in streams can affect streambed hydraulic characteristics due to clogging, reduce water fluxes through the hyporheic zone, and thus expected to affect biogeochemical processes. Processes affecting deposition of suspended particles were systematically studied under various overlying velocities but without taking into account the interactions with groundwater. This is despite the fact that the interaction with groundwater were shown to play an important role in deposition patterns of fine sediments in field studies. The objective of this study was to evaluate the effect of losing and gaining fluxes on suspended sediment depositional patterns and on hyporheic exchange fluxes. Experiments were conducted in a laboratory flume system (640 cm long and 30 cm wide) that has a capacity to enforce losing or gaining flow conditions. The flume was packed with homogenous sand, while suspended sediment deposition was evaluated by adding kaolinite particles to the water and following the deposition rate by particle disappearance from the bulk water. Consecutive additions of kaolinite were done, while hyporheic exchange fluxes were evaluated by conducting NaCl tracer experiments between each kaolinite additions. Furthermore, dye injections were used to visualize the flow patterns in the streambed using time-lapse photography through the transparent sidewalls of the flume. Hyporheic exchange and particle tracking simulations were done to assess the results of particle deposition and feedbacks between hyporheic flow, particle transport, and streambed clogging. Experimental results showed that the deposition of clay decreases with increasing amount of clay concentration in the sediment. Hyporheic exchange flux decreases linearly with increasing amount of clay added to the system and the region of active hyporheic exchange was confined to the upper part of the sediment. Understanding the particle deposition mechanisms under losing and gaining flow

  20. Sediment transport processes in the Gulf of Alaska: a morphological analysis of channel and fan sedimentary features

    Science.gov (United States)

    Morey, S.; Swartz, J. M.; Gulick, S. P. S.

    2016-12-01

    The Alaskan Abyssal Plain is home to three active channel/fan systems: the Surveyor, Chirikov, and Baranof systems. Individual studies of the Surveyor and Baranof fans indicate that these systems derive their sediments from the glacially dominated Northeast Pacific North American coast. The Pleistocene aged sediments found in the Surveyor Fan record some of the highest sediment accumulation rates (up to 130 cm/kyr) ever documented and show that this system is one of the youngest recognized large submarine fans. Further, the Surveyor and Baranof systems are two of the largest submarine fans in the world and their development has been significantly influenced by climatic and tectonic forcing. Specifically, these fans either developed or expanded with increased glacial activity in the Pleistocene that resulted in increased sediment flux to the Gulf of Alaska. While this influence is widely accepted, the depositional processes within the modern and past systems are poorly understood. A thorough investigation of these deep ocean sediment transport processes can further inform our understanding of this high-latitude source-to-sink system. Although the existence of multiple fans on a margin isn't exclusive to Alaska, the slope of the Gulf's basin floor indicates a relatively unique condition. As channels in the Gulf of Alaska carry sediment away from the continental slope margin—parallel to the Aleutian Trench—the basin floor between the adjacent channels generally slopes towards the Aleutian Trench. The presence of large scale bedforms on this sloped surface indicate the potential for significant sediment remobilization on the basin floor between active channels. Additionally, these systems are characterized by higher relief western channel banks and varying states of equilibrium, as well as differing degrees of sinuosity and channel width/depth. We intend to quantify these and other morphological features in the Gulf of Alaska with the goal of investigating active

  1. Cadmium immobilization in river sediment using stabilized nanoscale zero-valent iron with enhanced transport by polysaccharide coating.

    Science.gov (United States)

    Huang, Danlian; Hu, Zhengxun; Peng, Zhiwei; Zeng, Guangming; Chen, Guomin; Zhang, Chen; Cheng, Min; Wan, Jia; Wang, Xi; Qin, Xiang

    2018-03-15

    Proper management of metal-contaminated sediment plays a key role in sediment recovery and reuse. This study synthesized two kinds of stabilized nanoscale zero-valent iron (nZVI) with starch (S-nZVI) and carboxymethyl cellulose (C-nZVI) for the in situ immobilization of Cd(II) in river sediment and investigated their transport in porous media. Experimental data showed that when the sediment sample was treated with C-nZVI for 56 days at a dosage ranging from 5 to 10 mg/g-sediment as Fe 0 , the TCLP (toxicity characteristic leaching procedure) leachability of Cd(II) in the sediment decreased by 93.75-96.43%, and the PBET (physiologically-based extraction test) bioaccessibility of Cd(II) decreased by 22.79-71.32%. Additionally, the acid soluble fraction of Cd(II) was partially transformed to a residual fraction, resulting in a 32.4-33.1% decrease of acid soluble Cd(II) and a 125.4-205.6% increase of the residual-Cd(II) fraction. Surface complexation with iron oxyhydroxide minerals might be the main mechanism of Cd(II) immobilization in sediment. Column experiments indicate that starch or carboxymethyl cellulose (CMC) could extend the travel distance of nZVI, but inherent site physical and chemical heterogeneities still posed challenges for nanoparticle transport. Over all, this study verifies the effectiveness of stabilized nZVI for Cd(II) immobilization in sediment and discusses the potential immobilization mechanism. Copyright © 2018 Elsevier Ltd. All rights reserved.

  2. Sediment transport, light and algal growth in the Markermeer : a two-dimensional water quality model for a shallow lake

    NARCIS (Netherlands)

    Duin, van E.H.S.

    1992-01-01

    This thesis reports on a study of the water quality in the Markermeer, focusing on the relationships between sediment transport, the light field and the growth of Oscillatoria agardhii . The study comprises two aspects: an extensive data collection program with the data

  3. A semi-analytical study on the residual transport of salinity and sediment trapping in well-mixed estuaries

    NARCIS (Netherlands)

    Wei, X.; Kumar, M.; Schuttelaars, H.M.

    2016-01-01

    Along-channel and cross-channel sediment transport in tidal estuaries is usually driven by tides, density gradients, Coriolis’s force, wind stress, channel curvature and bathymetric variations. Since the water motion is influenced by density-induced gravitational circulation which in turn affects

  4. An inversion of the estuarine circulation by sluice water discharge and its impact on suspended sediment transport

    NARCIS (Netherlands)

    Schulz, K.; Gerkema, T.

    2018-01-01

    The Wadden Sea is characterized by a complex topography of branching channels and intertidal flats, in which the interplay between fresh water discharges, wind forcing and the tidal current causes sediment transport rates and direction to be highly variable in space and time. During three field

  5. GPS based surface displacements – a proxy for discharge and sediment transport from the Greenland Ice Sheet

    DEFF Research Database (Denmark)

    Hasholt, Bent; Khan, Shfaqat Abbas; Mikkelsen, Andreas Bech

    2014-01-01

    The elastic respond of the Earth’s surface to mass changes has been measured with Global Positioning System (GPS). Mass loss as accumulated runoff and sediment transport from a 10000 km2 segment of the Greenland Ice Sheet (GrIS) correlated very well (R2=0.83) with GPS measured uplift. Accumulated...

  6. Near shore waves, long-shore currents and sediment transport along micro-tidal beaches, central west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Philip, C.S.; SanilKumar, V.; Dora, G.U.; Johnson, G.

    breaker parameters are estimated at two micro-tidal beaches along central west coast of India. Model results are validated with measured values. From the breaker parameters, long-shore current and long-shore sediment transport rates (LSTR) are computed...

  7. Experimental observation and modelling of roughness variation due to supply-limited sediment transport in uni-directional flow

    NARCIS (Netherlands)

    Tuijnder, Arjan; Ribberink, Jan S.

    2012-01-01

    This paper presents a study on the relationship between supply-limited bedform formation and the hydraulic roughness of the riverbed. The results of several new sets of flume experiments with supply-limited or partial transport conditions with bimodal sediment are presented. The results show that

  8. Glyphosate distribution in loess soils as a result of dynamic sediment transport processes during a simulated rainstorm

    Science.gov (United States)

    Commelin, Meindert; Martins Bento, Celia; Baartman, Jantiene; Geissen, Violette

    2016-04-01

    Glyphosate is one of the most widely used herbicides in the world. The wide and extensive use of glyphosate makes it important to be certain about the safety of glyphosate to off-target environments and organisms. This research aims to create more detailed insight into the distribution processes of glyphosate, and the effect that dynamic sediment transport processes have on this distribution, during water erosion in agricultural fields. Glyphosate distribution characteristics are investigated for two different soil surfaces: a smooth surface, and a surface with seeding lines on the contour. The capacity to transport glyphosate for different sediment groups was investigated. These groups were water-eroded sediment and sedimentation areas found on the plot surface. The contribution of particle bonded and dissolved transport to total overland transportation of glyphosate was analysed with a mass balance study. The experiment was conducted in the Wageningen UR rainfall simulator. Plots of 0.5m2 were used, with a 5% slope, and a total of six experimental simulations were done. A rainfall event with an intensity of 30mm/h was simulated, applied in four showers of 15 minutes each with 30 minutes pause in between. Glyphosate (16mg/kg) was applied on the top 20cm of each plot, and in the downstream part, soil samples were taken. Glyphosate analysis was done using HPLC-MS/MS (High Performance Liquid Chromatography tandem Mass Spectrometry). Besides that, photo analysis with eCognition was used to derive the soil surface per sediment group. The results show that particle bonded transport of glyphosate contributes significantly (for at least 25%) to glyphosate transport during a rainstorm event. Particle size and organic matter have a large influence on the mobility of glyphosate and on the transported quantity to off-target areas. Moreover, seeding lines on the soil surface decreased total overland transport, both of sediment and glyphosate. Taking this into account, plots

  9. Validation of a combined sediment transport modelling approach for the morphodynamic simulation of the upper Hungarian Danube River

    Science.gov (United States)

    Török, Gergely T.; Baranya, Sándor; Rüther, Nils

    2017-04-01

    The reliable numerical modelling of morphological changes of rivers is still an unsolved problem, particularly in non-uniform river bed. Several sediment transport formulas were developed for mixed bed materials, however, none of them works well for any general case. For instance, a given non-uniform transport formula is expected and proved to calculate the bed armouring process well. On the other hand, it might estimate the movement and settling of the eroded finer particles less accurately. In order to overcome this issue the authors have elaborated and presented a combined approach implemented in a 3D numerical flow and sediment transport model. The combined approach means that the model applies two models at the same time but spatially differentiated based on the bed material conditions. Here, we use the sediment transport models of van Rijn (1984) and the Wilcock and Crowe (2003). Recent numerical model validation using laboratory data demonstrated the benefits of this novel method (Török et al., 2017). The main goal of this study is to prove the advantages of the combined approach for field environment. Thus, the upper Hungarian Danube River with non-uniform bed material was selected for morphodynamic modelling purposes. The morphological processes at this river reach are considerably complex, e.g. bed armouring process in the main channel, side gravel bar formation, silting up between the river training structures and sediment deposition in the floodplain caused by floods can be observed. Field measurement data provided hydrological and morphological data for the parameterization of a 3D CFD model. The effect of the historical flood wave in 2013 June was analysed. The results show that the combined approach resulted in a more accurate simulation of the morphological changes, compared to the separate application of the sediment transport formulas. The Wilcock and Crowe formula calculated reliably the armored bed surface in the main channel which resulted in

  10. Data processing in studies of diffusion for seawage disposal and of sediment transportation

    International Nuclear Information System (INIS)

    Szulak, C.; Agudo, E.G.

    1974-01-01

    The radiotracer applications on diffusion studies for sewage disposal in sea waters, as well as some large scale experiments on sediments transportation, are characterized by the bulky amount data obtained in the field. Data processing and plotting is a very time consuming task if they are to be handled manually, as may occurs in small research institutes. In order to overcome this difficulty, a program suitable for a 9810-A, Model Hewlett Packard calculator with plotter, was been developed. Through this program the following sequence of operations is performed: 1 - Background and decay corrections on activity measurements; 2 - conversion of angular position data taken with sextants, to rectangular coordinates; 3 - Position corrections as a function of the mean transport velocity of the radioactive cloud; 4 - Interpolation and plotting for each cloud section; of the points belonging ro preselected values of isoactivity curves; 5 - Interpolation and plotting between maximum activity points from two consecutive trajectories of the points belonging to preselected isoactivity curves. As a result of each data processing and plotting, a definition of shape of the radioactive, as well as the instantaneous concentration distribution are obtained. Interpolating a curve through the points with same activity, the preselected isoactivity lines are easily drawn [pt

  11. Sediment deposition and trends and transport of phosphorus and other chemical constituents, Cheney Reservoir watershed, south-central Kansas

    Science.gov (United States)

    Mau, D.P.

    2001-01-01

    Sediment deposition, water-quality trends, and mass transport of phosphorus, nitrogen, selected trace elements, and selected pesticides within the Cheney Reservoir watershed in south-central Kansas were investigated using bathymetric survey data and reservoir bottom-sediment cores. Sediment loads in the reservoir were investigated by comparing 1964 topographic data to 1998 bathymetric survey data. Approximately 7,100 acre-feet of sediment deposition occurred in Cheney Reservoir from 1965 through 1998. As of 1998, sediment had filled 27 percent of the reservoir's inactive conservation storage pool, which is less than the design estimate of 34 percent. Mean annual sediment deposition was 209 acre-feet per year, or 0.22 acre-feet per year per square mile, and the mean annual sediment load was 453 million pounds per year. During the 3-year period from 1997 through 1999, 23 sediment cores were collected from the reservoir, and subsamples were analyzed for nutrients (phosphorus and nitrogen species), selected trace elements, and selected organic pesticides. Mean concentrations of total phosphorus in reservoir bottom sediment ranged from 94 milligrams per kilogram at the upstream end of the reservoir to 710 milligrams per kilogram farther downstream near the reservoir dam. The mean concentration for all sites was 480 milligrams per kilogram. Total phosphorus concentrations were greatest when more silt- and clay-sized particles were present. The implications are that if anoxic conditions (inadequate oxygen) occur near the dam, phosphorus could be released from the sediment and affect the drinking-water supply. Analysis of selected cores also indicates that total phosphorus concentrations in the reservoir sediment increased over time and were probably the result of nonpoint-source activities in the watershed, such as increased fertilizer use and livestock production. Mean annual phosphorus loading to Cheney Reservoir was estimated to be 226,000 pounds per year on the basis

  12. Assessing saltmarsh resilience to sea-level rise by examining sediment transport trends in the Great Marsh, MA.

    Science.gov (United States)

    Hughes, Z. J.; Georgiou, I. Y.; Gaweesh, A.; Hanegan, K.; FitzGerald, D.; Hein, C. J.

    2017-12-01

    Under accelerating sea-level rise (SLR), marshes are vulnerable to increased inundation, dependent on their ability to accrete vertically or expand into upland areas. Accretion is a function of organic and inorganic contributions from plant biomass and suspended sediment deposition, respectively. Along the east coast of the US, present rates of SLR are higher than they have been for over 1000 years and are expected to increase in the near future. To predict the resilience of saltmarshes, we urgently need improved understanding of spatial patterns of sediment transport and deposition within these systems. This study examines time-series of suspended sediment concentration and flow collected using ADCP-OBS units, deployed throughout the Great Marsh System. We compare the data to model results and observations of short and long term deposition throughout the system. Field observations show that tidal amplitude and phase vary throughout the Great Marsh. Tidal asymmetry increases inland from the estuary mouth, and the maximum phase lag is 2 hours. This effect is strongest during low slack tide; with a delay of only 30-45 minutes at high tide. Tidal velocities exhibit strong asymmetry, reflected in pulses of sediment movement. Sediment transport initiates at mid ebb, peaking 1.5-2.5 hours later, decreasing through low slack tide for 7-9 hours until high slack tide. The results have broad implications for the potential input of inorganic sediment to the marsh platform. Results from a validated Delft3D model reproduce field observations and expand spatial sediment transport trends. We experiment by releasing sediment in different parts of the estuary, mimicking marsh edge or tidal flat erosion, and tracking mud and sand transport trajectories. Sands remains proximal to the erosion site, whereas mud is more mobile and travels farther, reaching the inlet within days of erosion. Longer simulations suggest that despite higher mobility, muds remain mostly in the channels and

  13. An alternative membrane transport pathway for phosphate and adenine nucleotides in mitochondria and its possible function

    Science.gov (United States)

    Reynafarje, Baltazar; Lehninger, Albert L.

    1978-01-01

    This paper describes the properties and a possible biological role of a transport process across the inner membrane of rat liver mitochondria resulting in the exchange of ATP4- (out) for ADP3- (in) + 0.5 phosphate2- (in). This transmembrane exchange reaction, designated as the ATP-ADP-phosphate exchange, is specific for the ligands shown, electroneutral, insensitive to N-ethylmaleimide or mersalyl, inhibited by atractyloside, and appears to occur only in the direction as written. It is thus distinct from the well-known phosphate-hydroxide and phosphate-dicarboxylate exchange systems, which are inhibited by mersalyl, and from the ATP-ADP exchanger, which does not transport phosphate. During ATP hydrolysis by mitochondria, half of the phosphate formed from ATP passes from the matrix to the medium by the mersalyl-insensitive ATP-ADP-phosphate exchange and the other half by the well-known mersalyl-sensitive phosphate-hydroxide exchange. These and other considerations have led to a hypothesis for the pathway and stoichiometry of ATP-dependent reverse electron transport, characterized by a requirement of 1.33 molecules of ATP per pair of electrons reversed and by the utilization of a different membrane transport pathway for phosphate and adenine nucleotides than is taken in forward electron flow and oxidative phosphorylation. The possible occurrence of independent pathways for ATP-forming forward electron flow and ATP-consuming reverse electron flow is consonant with the fact that the opposing degradative and synthetic pathways in the central routes of cell metabolism generally have different pathways that are independently regulated. PMID:283393

  14. Sediment Characteristics of Tennessee Streams and Reservoirs

    National Research Council Canada - National Science Library

    Trimble, Stanley W; Carey, William P

    1984-01-01

    Suspended-sediment and reservoir sedimentation data have been analyzed to determine sediment yields and transport characteristics of Tennessee streams Data from 31 reservoirs plus suspended-sediment...

  15. Sediment Transport On The Vegetated Bank of The Soil Bioengineering Test Flume At The Wien River

    Science.gov (United States)

    Meixner, H.; Rauch, H. P.; Schreiber, J.; Vollsinger, St.

    Soil bioengineering structures are frequently used to protect river banks. Studies by WEITZER / DOPPLER / FLORINETH (1998) on measuring the pull-out resistance and by OPLATKA (1998) on the effective flow acting on willows show that a high hydraulic load by itself does not lead to failure or dislodging of the plants but that the slopeSs instability is caused by the erosion of bed material. The onset of erosion is indicated by a critical shear stress, determined by the combination of a number of factors such as flow velocity, lift force, turbulence, grain size, grain shape, stratifica- tion of the river bed material and the type and density of the vegetation. Investigations into the stability of a variety of soil bioengineering structures (brush mattress with wil- lows, branch layers, fascine layers) are carried out at the soil bioengineering test flume along the Wien river, where artificial flooding runs expose the plant/soil complex to extreme hydraulic loads. Marked, surveyed and weighed gravel material of different grain diameters (10, 20, 40, 60, 80 and 100 mm) and variable layer arrangements is put into the bed or bank of the test flume to determine the critical shear stress. The exact grain position is identified before and after each artificial flooding, so that the mean sediment transport path can be determined for each grain diameter. By comparing sed- iment transport paths for different grain sizes, a critical grain diameter can be defined for each soil bioengineering structure. The critical grain diameter thus obtained is used as an input parameter in calculating the critical shear stress from bed load transport equations. Based on the data thus collected and their analysis it is possible to present and interpret initial findings.

  16. Representation of aerosol particles and associated transport pathways in regional climate modelling in Africa

    CSIR Research Space (South Africa)

    Garland, Rebecca M

    2016-11-01

    Full Text Available particles and associated transport pathways in regional climate modelling in Africa Rebecca M. Garland1,2,*, Hannah M. Horowitz3, Christien J. Engelbrecht4, Zane Dedkind1, Mary-Jane M. Bopape5, Stuart J Piketh2, and Francois A. Engelbrecht1,5 1... coast out to the Atlantic Ocean (Garstang et al., 1996; Swap et al., 2003). This latter exit pathway aligns with the stratocumulus cloud deck that forms off of the southwestern coast, and is an area of large uncertainty in modelling aerosol...

  17. Interactions of Flow, Sediment Transport, and Vegetation in the Long-Term Evolution of Arroyos

    Science.gov (United States)

    Perignon, M. C.; Griffin, E. R.; Tucker, G. E.; Friedman, J. M.; Overeem, I.

    2014-12-01

    Arroyos in the Southwestern United States have experienced multiple cut-and-fill cycles in the late Quaternary. Extensive studies fo the Lower Rio Puerco, New Mexico, USA, show that it has most recently progressed from an (1) unincised state with a broad floodplain in the mid 1800s, through a period of (2) incision, forming a deep gully with steep walls by the early 1900s, and to the (3) present-day stage of arroyo widening and filling. The arroyo cycle is driven by a combination of autogenic processes and external forcings, although the relative influence of each process is under debate. We use the morphodynamic model ANUGA to explore the influences of discharge, sediment transport, and vegetation on the geomorphic evolution of the Lower Rio Puerco through the arroyo cycle. The predictive power of the numerical model is first established by using it to hind-cast the morphologic evolution of a reach of the river during a large flood in 2006, and comparing the model predictions to real-world magnitudes and patterns of topographic change recorded for this event by multi-temporal airborne lidar. The morphodynamic model is then used to simulate the response of this stream to floods in the past. A comprehensive dataset of the topography and hydrology of the Lower Rio Puerco since the 1920s is used to reproduce the morphology of the arroyo at multiple points in time, and historical descriptions serve to extrapolate these into the 19th century. We test the sensitivity of the reconstructed landscapes to changes in peak discharge, sediment supply, and the distribution and characteristics of vegetation in order to determine the relative influence of each forcing in the evolution of the stream, and to understand how the interactions of different processes could drive its progression through the arroyo cycle.

  18. Particle Tracking Model for Suspended Sediment Transport and Streambed Clogging Under Losing and Gaining Conditions

    Science.gov (United States)

    Preziosi-Ribero, A.; Fox, A.; Packman, A. I.; Escobar-Vargas, J.; Donado-Garzon, L. D.; Li, A.; Arnon, S.

    2017-12-01

    Exchange of mass, momentum and energy between surface water and groundwater is a driving factor for the biology, ecology and chemistry of rivers and water bodies in general. Nonetheless, this exchange is dominated by different factors like topography, bed morphology, and large-scale hydraulic gradient. In the particular case of fine sediments like clay, conservative tracer modeling is impossible because they are trapped in river beds for long periods, thus the normal advection dispersion approach leads to errors and results do not agree with reality. This study proposes a numerical particle tracking model that represents the behavior of kaolinite in a sand flume, and how its deposition varies according to different flow conditions, namely losing and gaining flow. Since fine particles do not behave like solutes, kaolinite dynamics are represented using settling velocity and a filtration coefficient allowing the particles to be trapped in the bed. This approach allows us to use measurable parameters directly related with the fine particle features as size and shape, and hydraulic parameters. Results are then compared with experimental results from lab experiments obtained in a recirculating flume, in order to assess the impact of losing and gaining conditions on sediment transport and deposition. Furthermore, our model is able to identify the zones where kaolinite deposition concentrates over the flume due to the bed geometry, and later relate these results with clogging of the bed and hence changes in the bed's hydraulic conductivity. Our results suggest that kaolinite deposition is higher under losing conditions since the vertical velocity of the flow is added to the deposition velocity of the particles modeled. Moreover, the zones where kaolinite concentrates varies under different flow conditions due to the difference in pressure and velocity in the river bed.

  19. EVALUATION OF BIOAEROSOL COMPONENTS, GENERATION FACTORS, AND AIRBORNE TRANSPORT ASSOCIATED WITH LIME TREATMENT OF CONTAMINATED SEDIMENT

    Science.gov (United States)

    Lime treatment has been used in contaminated sediment management activities for many purposes such as dewatering, improvement of physical properties, and reducing contaminant mobility. Exothermic volatilization of volatile organic compounds from lime-treated sediment is well kno...

  20. Ocean Transport Pathways to a World Heritage Fringing Coral Reef: Ningaloo Reef, Western Australia.

    Directory of Open Access Journals (Sweden)

    Jiangtao Xu

    Full Text Available A Lagrangian particle tracking model driven by a regional ocean circulation model was used to investigate the seasonally varying connectivity patterns within the shelf circulation surrounding the 300 km long Ningaloo Reef in Western Australia (WA during 2009-2010. Forward-in-time simulations revealed that surface water was transported equatorward and offshore in summer due to the upwelling-favorable winds. In winter, however, water was transported polewards down the WA coast due to the seasonally strong Leeuwin Current. Using backward-in-time simulations, the subsurface transport pathways revealed two main source regions of shelf water reaching Ningaloo Reef: (1 a year-round source to the northeast in the upper 100 m of water column; and (2 during the summer, an additional source offshore and to the west of Ningaloo in depths between ~30 and ~150 m. Transient wind-driven coastal upwelling, onshore geostrophic transport and stirring by offshore eddies were identified as the important mechanisms influencing the source water origins. The identification of these highly time-dependent transport pathways and source water locations is an essential step towards quantifying how key material (e.g., nutrients, larvae, contaminants, etc. is exchanged between Ningaloo Reef and the surrounding shelf ocean, and how this is mechanistically coupled to the complex ocean dynamics in this region.

  1. Long-term environmental and health implications of morphological change and sediment transport with respect to contaminants

    Science.gov (United States)

    Sneddon, Christopher; Copplestone, David; Tyler, Andrew; Hunter, Peter; Smith, Nick

    2014-05-01

    The EPSRC-funded Adaptation and Resilience of Coastal Energy Supply (ARCoES) project encompasses four research strands, involving 14 institutions and six PhD studentships. ARCoES aims to determine the threats posed to future energy generation and the distribution network by flooding and erosion, changing patterns of coastal sedimentation, water temperature and the distribution of plants and animals in the coastal zone. Whilst this research has direct benefits for the operation of coastal power stations, ARCoES aims to have a wider stakeholder engagement through assessing how the resilience of coastal communities may be altered by five hundred years of coastal evolution. Coastal evolution will have substantial implications for the energy sector of the North West of England as former waste storage sites are eroded and remobilised within the intertidal environment. The current intertidal environmental stores of radioactivity will also experience reworking as ocean chemistry changes and saltmarsh chronologies are reworked in response to rising sea levels. There is a duel requirement to understand mass sediment movement along the North West coast of England as understanding the sediment transport dynamics is key to modelling long term coastal change and understanding how the environmental store of radioactivity will be reworked. The University of Stirling is researching the long-term environmental and health implications of remobilisation and transport of contaminated sediments around the UK coastline. Using a synergy of hyperspectral and topographic information the mobilisation of sediment bound contaminants within the coastal environment will be investigated. Potential hazards posed by contaminants are determined by a set of environmental impact test criteria which evaluate the bio-accessibility and ionising dose of contaminants. These test criteria will be used to comment on the likely environmental impact of modelled sediment transport and anticipated changes in

  2. Modeling sediment transport processes and residence times in the shallow coastal bay complex of the Virginia Coast Reserve

    Science.gov (United States)

    Safak, I.; Wiberg, P. L.

    2011-12-01

    Patterns of sediment transport and particle residence times influence the morphology and ecology of shallow coastal bays in important ways. The Virginia Coast Reserve (VCR), a barrier island-lagoon-marsh system on the Eastern Shore of Virginia, is typical of many shallow coastal bay complexes that lack a significant fluvial source of freshwater and sediment. Sediment redistribution within the bays in response to storms and sea-level rise, together with the dynamics of marsh and lagoon-bottom plants, largely governs the morphological evolution of this system. There are also important feedbacks between sediment and ecosystem dynamics. This is particularly true in the VCR, which is relatively unaffected by human activities. As a step towards evaluating the impact of hydrodynamics on sediment and ecological processes in the VCR, a single unified model that accounts for circulation, surface waves, wave-current interaction, and sediment processes is employed. This three-dimensional unstructured grid finite-volume coastal ocean model (FVCOM) is validated with field observations of wind- and tide-induced water flow (water level and current velocities) in Hog Island Bay, centrally located within the VCR. Here, the resulting patterns of sediment transport and particle residence times over event and seasonal time scales are presented. Water and particle exchange within the VCR and between the VCR and the ocean is examined with the Lagrangian particle-tracking module in FVCOM. We focus on three bays with strongly varying bathymetry and coastline geometry, which are also located along a gradient of nitrogen input to the system. The results indicate that residence time of particles within the system vary greatly depending on the location of particle release, bay morphology, and wind conditions. The implications for morphologic evolution and ecosystem response to climate and land-use changes are evaluated.

  3. Avoiding, transforming, transitioning: pathways to sustainable low carbon passenger transport in developing countries

    DEFF Research Database (Denmark)

    Meza, Maria Josefina Figueroa; Fulton, Lewis; Tiwari, Geetam

    2013-01-01

    This review examines conditions affecting road passenger transport in developing countries that can be instrumental to building a pathway for reducing carbon emissions while concurrently meeting sustainable development goals. By contrasting present and future status of these conditions a vision...... emerges where non-OECD passenger travel increases of up to 200% can be accommodated via strong investments in transit and non-motorized modes and a recasting of informal transport services into self-organized systems, with lower levels of car ownership and avoidance of carbon emissions. Reductions...

  4. Distribution, source apportionment, and transport of PAHs in sediments from the Pearl River Delta and the northern South China Sea

    Energy Technology Data Exchange (ETDEWEB)

    Luo, X.J.; Chen, S.J.; Mai, B.X.; Sheng, G.Y.; Fu, J.M.; Zeng, E.Y. [Chinese Academy of Sciences, Ghangzhou (China)

    2008-07-15

    Polycyclic aromatic hydrocarbons (PAHs) were measured in 59 surface sediments from rivers in the Pearl River Delta and the northern continental shelf of the South China Sea. Total PAH concentrations varied from 138 to 6,793 ng/g dry weight. The sources of PAH inputs to sediments in the Pearl River Delta were qualitatively and quantitatively determined by diagnostic ratios and principal components analysis with multiple linear regression. The results showed that on average coal and wood combustion, petroleum spills, vehicle emissions, and nature sources contributed 36%, 27%, 25%, and 12% of total PAHs, respectively. Coal and biomass combustion was the main source of PAHs in sediments of the South China Sea, whereas petroleum combustion was the main source of pyrolytic PAHs in riverine and estuarine sediments of the Pearl River Delta. Perylene was formed in situ in river sediments and then transported to coastal areas along with other PAHs. The relative abundance of perylene from five-ring PAHs can be used to estimate the contribution of riverine-discharged PAHs to coastal sediments.

  5. Origin and transport of (238)U and (226)Ra in riverine, estuarine and marine sediments of the Krka River, Croatia.

    Science.gov (United States)

    Cukrov, Neven; Mlakar, Marina; Cuculić, Vlado; Barisić, Delko

    2009-06-01

    Spatial distribution of (238)U and (226)Ra activities in sediment columns along the Krka River and estuary, were studied using gamma spectrometry. Markedly different (238)U and (226)Ra activities between riverine, estuarine and marine sediments were observed. Distribution of these radionuclides, as well as their anthropogenic and natural origin, was evaluated by activity measurements, taking into account sedimentation rates estimated by (137)Cs distribution in sediment columns. Naturally present (238)U and (226)Ra activities were highest in riverine and lowest in marine sediments. (238)U and (226)Ra activities in historic riverine sediments revealed anthropogenic influence from town of Knin, which diminished for 15-20% in 1990s due to warfare that caused stop of industrial, agricultural and transport activities. Drainage of the flysch material naturally elevates (238)U and (226)Ra activities in the vicinity of its inflow in the upper part of estuary. (238)U and (226)Ra from the phosphate ore discharge in the port of Sibenik did not spread further in estuary, which was also confirmed by (238)U and (226)Ra activities detected in Mytilus sp. mussels' tissue.

  6. Sediment transport and deposition, Walnut and Pacheco Creeks, Contra Costa County, California, August 1965-April 1970

    Science.gov (United States)

    Porterfield, George

    1972-01-01

    Average annual sediment discharge in Pacheco Creek basin, Contra Costa County, Calif., was larger during August 1965-April 1970 than the historical annual sediment discharge (1909-62) by a factor of about 1.3. This increas in sediment discharge is attributed primarily to an increased frequency of peak streamflows and to a larger average annual streamflow during the 1965-70 period.

  7. Influence of forest road buffer zones on sediment transport in the Southern Appalachian Region

    Science.gov (United States)

    Johnny M. Grace; Stanley J. Zarnoch

    2013-01-01

    A gap exists in the understanding of the effectiveness of forest road best management practices (BMP) in controlling sediment movement and minimizing risks of sediment delivery to forest streams. The objective of this paper is to report the findings of investigations to assess sediment travel distances downslope of forest roads in the Appalachian region, relate...

  8. Radiotracer method to study the transport of mercury(II)chloride from water to sediment and air

    International Nuclear Information System (INIS)

    Karaca, F.; Aras, N.K.

    2004-01-01

    The fate of dissolved Hg(II) in surface waters is an important component of the Hg cycle. A simple experimental methodology was used to understand and measure the transport of Hg(II) from water to air and sediment. The use of radioactive dissolved Hg tracer for the determination of evasion and deposition is found to be a very useful technique. The evasion of mercury was investigated during a 140-hour period. It was observed that about a quarter of mercury chloride remained in the water phase, the other quarter was emitted via the evasion process and half of it deposited in sediment. (author)

  9. Interaction between breaking/broken waves and infragravity-scale phenomena to control sediment suspension transport in the surf zone

    CSIR Research Space (South Africa)

    Smith, GG

    2002-07-30

    Full Text Available error due to air bubbles was reduced by an average of 52%. MARGO 3183 24-7-02 G.G. Smith, G.P. Mocke/ Marine Geology 187 (2002) 329^345 5. Results 5.1. The role of breaking and broken waves 5.1.1. Transition zone In investigating sediment suspension.../broken waves and infragravity-scale phenomena to control sediment suspension transport in the surf zone G.G. Smith C3, G.P. Mocke CSIR, Division of Water, Environment and Forestry Technology, Jan Cilliers Street, 7599 Stellenbosch, South Africa Received 30...

  10. Modeling radiocesium transport from a river catchment based on a physically-based distributed hydrological and sediment erosion model.

    Science.gov (United States)

    Kinouchi, Tsuyoshi; Yoshimura, Kazuya; Omata, Teppei

    2015-01-01

    The accident at the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) in March 2011 resulted in the deposition of large quantities of radionuclides, such as (134)Cs and (137)Cs, over parts of eastern Japan. Since then high levels of radioactive contamination have been detected in large areas, including forests, agricultural land, and residential areas. Due to the strong adsorption capability of radiocesium to soil particles, radiocesium migrates with eroded sediments, follows the surface flow paths, and is delivered to more populated downstream regions and eventually to the Pacific Ocean. It is therefore important to understand the transport of contaminated sediments in the hydrological system and to predict changes in the spatial distribution of radiocesium concentrations by taking the land-surface processes related to sediment migration into consideration. In this study, we developed a distributed model to simulate the transport of water and contaminated sediment in a watershed hydrological system, and applied this model to a partially forested mountain catchment located in an area highly contaminated by the radioactive fallout. Observed discharge, sediment concentration, and cesium concentration measured from June 2011 until December 2012 were used for calibration of model parameters. The simulated discharge and sediment concentration both agreed well with observed values, while the cesium concentration was underestimated in the initial period following the accident. This result suggests that the leaching of radiocesium from the forest canopy, which was not considered in the model, played a significant role in its transport from the catchment. Based on the simulation results, we quantified the long-term fate of radiocesium over the study area and estimated that the effective half-life of (137)Cs deposited in the study area will be approximately 22 y due to the export of contaminated sediment by land-surface processes, and the amount of (137)Cs remaining in the

  11. Climate change and the impact of increased rainfall variability on sediment transport and catchment scale water quality

    Science.gov (United States)

    Hancock, G. R.; Willgoose, G. R.; Cohen, S.

    2009-12-01

    Recently there has been recognition that changing climate will affect rainfall and storm patterns with research directed to examine how the global hydrological cycle will respond to climate change. This study investigates the effect of different rainfall patterns on erosion and resultant water quality for a well studied tropical monsoonal catchment that is undisturbed by Europeans in the Northern Territory, Australia. Water quality has a large affect on a range of aquatic flora and fauna and a significant change in sediment could have impacts on the aquatic ecosystems. There have been several studies of the effect of climate change on rainfall patterns in the study area with projections indicating a significant increase in storm activity. Therefore it is important that the impact of this variability be assessed in terms of catchment hydrology, sediment transport and water quality. Here a numerical model of erosion and hydrology (CAESAR) is used to assess several different rainfall scenarios over a 1000 year modelled period. The results show that that increased rainfall amount and intensity increases sediment transport rates but predicted water quality was variable and non-linear but within the range of measured field data for the catchment and region. Therefore an assessment of sediment transport and water quality is a significant and complex issue that requires further understandings of the role of biophysical feedbacks such as vegetation as well as the role of humans in managing landscapes (i.e. controlled and uncontrolled fire). The study provides a robust methodology for assessing the impact of enhanced climate variability on sediment transport and water quality.

  12. Unusual Sediment Transportation Processes Under Low Pressure Environments and Implications For Gullies and Recurring Slope Lineae (RSL)

    Science.gov (United States)

    Raack, J.; Herny, C.; Conway, S. J.; Balme, M. R.; Carpy, S.; Patel, M.

    2017-12-01

    Recently and presently active mass wasting features such as gullies and recurring slope lineae (RSL) are common on the surface of Mars, but their origin and triggering mechanisms are under intense debate. While several active mass wasting features have been linked to sublimation of CO2ice, dry granular flows (avalanches), or a combination of both effects, others have been more closely linked to liquid water or briny outflows (e.g. for RSL). However, liquid water on the surface of Mars is unstable under present-day low pressures and surface temperatures. Nevertheless, numerical modeling and remote sensing data have shown that maximum surface temperatures can exceed the frost point of water and that liquid water could exist on the surface of actual Mars in a transient state. But to explain the observed spatial extent of RSL and recent modification of gullies, it is estimated that relatively large amounts of liquid water are necessary. It is proving challenging to generate such quantities from the atmosphere. In this contribution we explore the potential effects of boiling water (boiling occurs at martian pressures slightly above the frost point of 273 K) on sediment transport. We will present the outcomes of a series of experiments under low surface and water temperatures (between 278 and 297 K, analogous to surface temperatures observed near RSL) and low pressures (between 8 and 11 mbar). We simulate sediment transport by boiling liquid water over a sloping bed of unconsolidated sediment. Our results reveal a suite of unusual and very reactive sediment transportation processes, which are not produced under terrestrial pressures. We will discuss the impact of these unusual sediment transport processes on estimates of water budgets for active mass wasting processes.

  13. A pre-dam-removal assessment of sediment transport for four dams on the Kalamazoo River between Plainwell and Allegan, Michigan

    Science.gov (United States)

    Syed, Atiq U.; Bennett, James P.; Rachol, Cynthia M.

    2005-01-01

    Four dams on the Kalamazoo River between the cities of Plainwell and Allegan, Mich., are in varying states of disrepair. The Michigan Department of Environmental Quality (MDEQ) and U.S. Environmental Protection Agency (USEPA) are considering removing these dams to restore the river channels to pre-dam conditions. This study was initiated to identify sediment characteristics, monitor sediment transport, and predict sediment resuspension and deposition under varying hydraulic conditions. The mathematical model SEDMOD was used to simulate streamflow and sediment transport using three modeling scenarios: (1) sediment transport simulations for 730 days (Jan. 2001 to Dec. 2002), with existing dam structures, (2) sediment transport simulations based on flows from the 1947 flood at the Kalamazoo River with existing dam structures, and (3) sediment transport simulations based on flows from the 1947 flood at the Kalamazoo River with dams removed. Sediment transport simulations based on the 1947 flood hydrograph provide an estimate of sediment transport rates under maximum flow conditions. These scenarios can be used as an assessment of the sediment load that may erode from the study reach at this flow magnitude during a dam failure. The model was calibrated using suspended sediment as a calibration parameter and root mean squared error (RMSE) as an objective function. Analyses of the calibrated model show a slight bias in the model results at flows higher than 75 m3/s; this means that the model-simulated suspended-sediment transport rates are higher than the observed rates; however, the overall calibrated model results show close agreement between simulated and measured values of suspended sediment. Simulation results show that the Kalamazoo River sediment transport mechanism is in a dynamic equilibrium state. Model results during the 730-day simulations indicate significant sediment erosion from the study reach at flow rates higher than 55 m3/s. Similarly, significant

  14. Copper-transporting P-type ATPases use a unique ion-release pathway

    DEFF Research Database (Denmark)

    Andersson, Magnus; Mattle, Daniel; Sitsel, Oleg

    2014-01-01

    Heavy metals in cells are typically regulated by PIB-type ATPases. The first structure of the class, a Cu(+)-ATPase from Legionella pneumophila (LpCopA), outlined a copper transport pathway across the membrane, which was inferred to be occluded. Here we show by molecular dynamics simulations...... that extracellular water solvated the transmembrane (TM) domain, results indicative of a Cu(+)-release pathway. Furthermore, a new LpCopA crystal structure determined at 2.8-Å resolution, trapped in the preceding E2P state, delineated the same passage, and site-directed-mutagenesis activity assays support...... a functional role for the conduit. The structural similarities between the TM domains of the two conformations suggest that Cu(+)-ATPases couple dephosphorylation and ion extrusion differently than do the well-characterized PII-type ATPases. The ion pathway explains why certain Menkes' and Wilson's disease...

  15. Fingerprint methods for suspended sediment transport processes by using X-ray fluorescence analysis

    Science.gov (United States)

    Nakayama, K.; Beitia, C.; Ohtsu, N.; Yamasaki, S.; Yasuyuki, M.; Yamane, M.

    2014-12-01

    Suspended sediment (SS) can have significant impacts on ecological system, and high SS concentration can have significant impacts on human life. In the previous studies, radionuclide analysis has been applied to evaluate the production of SS in the river basins, which demonstrated that the surface soil erosion can be estimated by using radionuclide Pb-210ex. However, radionuclide analysis cannot indicate the relative amounts of SS transported from each individual sub-basin to the downstream end. Thus, X-ray Fluorescence Analysis (XRF Analysis) can be considered as an alternative method to radionuclide analysis because the XRF Analysis can measure 21 chemical compositions, Na2O, MgO, Al2O3, SiO2, P2O5, SO3, Cl, K2O, CaO, TiO2, Cr2O3, MnO, Fe2O3, Co2O3, NiO, CuO, ZnO, Rb2O, SrO, BaO, and Y2O3 by using X-ray Fluorescence Analyzer. In June of 2007, high turbidity, which is more than 10,000 (NTU), was measured in the Oromushi River basin of Hokkaido in Japan. Therefore, this study aims to clarify the mechanism of the transport of SS in the Oromushi River basin. We measured chemical compositions of soil with diameter less than 63 μm in the Oromushi River basin in order to pay attention to SS by using XRF. The Principal Component Analysis revealed that SiO2, Al2O3, Fe2O3, CaO and Na2O are the dominant chemical compositions. Although the predominant composition was the same in a river basin including the downstream end, significant differences were found in the pattern of chemical compositions. Therefore, by using the chemical compositions of SiO2, Al2O3, Fe2O3, CaO and Na2O, the Mixing Stable Isotope Analysis in R model (MixSIAR) based on Bayesian statistics was applied to estimate the transportation rate of SS from each sub-basin to the downstream end, which agreed with the field experiment results very well. As a result, spatial patterns of SS transportation rate are found to be strongly related to surface soil type.

  16. Sources and transport pathways of micropollutants into surface waters - an overview

    Science.gov (United States)

    Stamm, Christian

    2017-04-01

    Micropollutants reach water bodies from a large range of sources through different transport pathways. They consist of hundreds or thousands of compounds rendering exposure assessment an analytical challenge. Prominent examples of micropollutants are wastewater-born pharmaceuticals and hormones or plant protection products originating from diffuse agricultural sources. This presentation reviews the possible origin of micropollutants and their transport pathways. It demonstrates that considering municipal wastewater and agriculture may fall short of comprising all relevant source-pathway combination in a given watershed by providing examples from industry, animal production, or leaching to groundwater. The diversity of source-pathway leads on the one hand to a large number of possible chemicals to be considered including parent compounds of end products, their transformation products, legacy compounds but also intermediates used during industrial synthesis processes. On the other hand, it leads to a wide range of temporal dynamics by which these compounds reach streams and rivers. This combination makes a comprehensive exposure assessment for micropollutants a real scientific challenge. An outlook into new development in sampling and analytics will suggest possible solution for this challenge.

  17. Oblique second-order sand transport pathways on an intertidal sand flat in a natural tidal inlet system

    DEFF Research Database (Denmark)

    Ernstsen, Verner Brandbyge; Lefebvre, Alice; Kroon, Aart

    2013-01-01

    A detailed digital elevation model (DEM) of an intertidal sand flat in the Knudedyb tidal inlet in the Danish Wadden Sea, derived from high-resolution Light Detection And Ranging (LiDAR) data, reveals a large elongated bedform field with complex bedform morphologies and drainage channel networks....... This indicates distinct second-order sand transport pathways oblique to the main tidal transport pathways. A conceptual model for the development of the bedforms and channels is presented, which comprises hypotheses of the hydrodynamic forcing of the different second-order sand transport pathways. During flood...... tide, sand is transported along ESE-oriented pathways across the intertidal flat towards the inner tidal basin. During the late stages of ebb tide, sand is transported in drainage channels (WSWoriented) from the intertidal flat towards the inlet channel. During storm events with winds from SW, wave...

  18. Sediment Transport, Complex Topography, and Hydrokinetic Turbines: Bedform Dynamics, Local Scour, and the Effect on Turbine Performance.

    Science.gov (United States)

    Guala, M.; Hill, C.; Kozarek, J. L.; Sotiropoulos, F.

    2015-12-01

    Multi-scale experiments on the interactions between axial-flow marine hydrokinetic (MHK) turbines, sediment transport and complex channel topography were performed at St. Anthony Falls Laboratory (SAFL), University of Minnesota. Model axial-flow three-bladed turbines (rotor diameters, dT = 0.15m and 0.5m) were installed in open channel flumes with both erodible and non-erodible substrates. In erodible channels, device-induced local scour was monitored over several hydraulic conditions (clear water vs. live bedload transport) and material sizes. Synchronous velocity, bed elevation and turbine performance measurements provide an indication into the effect channel topography has on device performance. A novel data acquisition imaging system provided methods for monitoring the dynamics of bedform transport as they approached and migrated past an operating axial-flow turbine. Experiments were also performed in a realistic meandering outdoor research channel with active sediment transport to investigate MHK turbine interactions with bedform migration and turbulent flow in asymmetric channels, providing new insight into turbine-sediment interactions and turbine wake behavior in curving channels. Results provide the foundation for investigating advanced turbine control strategies for optimal power production in non-stationary environments, while also providing robust data for computational model validation enabling further investigations into the interactions between energy conversion devices and the physical environment.

  19. Sediment pathways and emergence of Himalayan source material in the Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Krishna, K.S.; Ismaiel, M.; Srinivas, K.; Gopala Rao, D.; Mishra, J.; Saha, D.

    Basin and ECMI), following the structural architecture of the BoB. The velocities obtained from the present dataset (wide–angle seismic reflections and drill wells A and B) and from pub- lished refraction data31 were largely followed to calculate... with strong supportive evidences – onlap un- conformity, buried channels, fan architecture and apex location – for discharge of sediments through the Ganges–Brahmaputra delta to the BoB. Around this time in the Himalayan foreland basin, a major Oligocene...

  20. Migration pathways in soils

    International Nuclear Information System (INIS)

    Gronow, J.R.

    1986-01-01

    This study looked at diffusive migration through three types of deformation; the projectile pathways, hydraulic fractures of the sediments and faults, and was divided into three experimental areas: autoradiography, the determination of diffusion coefficients and electron microscopy of model projectile pathways in clay. For the autoradiography, unstressed samples were exposed to two separate isotopes, Pm-147 (a possible model for Am behaviour) and the poorly sorbed iodide-125. The results indicated that there was no enhanced migration through deformed kaolin samples nor through fractured Great Meteor East (GME) sediment, although some was evident through the projectile pathways in GME and possibly through the GME sheared samples. The scanning electron microscopy of projectile pathways in clay showed that emplacement of a projectile appeared to have no effect on the orientation of particles at distances greater than two projectile radii from the centre of a projectile pathway. It showed that the particles were not simply aligned with the direction of motion of the projectile but that, the closer to the surface of a particular pathway, the closer the particles lay to their original orientation. This finding was of interest from two points of view: i) the ease of migration of a pollutant along the pathway, and ii) possible mechanisms of hole closure. It was concluded that, provided that there is no advective migration, the transport of radionuclides through sediments containing these defects would not be significantly more rapid than in undeformed sediments. (author)

  1. Insulin and phorbol ester stimulate conductive Na+ transport through a common pathway

    International Nuclear Information System (INIS)

    Civan, M.M.; Peterson-Yantorno, K.; O'Brien, T.G.

    1988-01-01

    Insulin stimulates Na + transport across frog skin, toad urinary bladder, and the distal renal nephron. This stimulation reflects an increase in apical membrane Na + permeability and a stimulation of the basolateral membrane Na,K-exchange pump. Considerable indirect evidence has suggested that the apical natriferic effect of insulin is mediated by activation of protein kinase C. However, no direct information has been available documenting that insulin and protein kinase C indeed share a common pathway in stimulating Na + transport across frog skin. In the present work, the authors have studied the interaction of insulin and phorbol 12-myristate 13-acetate (PMA), a documented activator of protein kinase C. Preincubation of skins with 1,2-dioctanoylglycerol, another activator of protein kinase C, increases baseline Na + transport and reduces the subsequent natriferic response to PMA. Preincubation with PMA markedly reduces the subsequent natriferic action of insulin. This effect does not appear to primarily reflect PMA-induced internalization of insulin receptors. The insulin receptors are localized on the basolateral surface of frog skin, but the application of PMA to this surface is much less effective than mucosal treatment in reducing the response to insulin. The current results provide documentation that insulin and protein kinase C share a common pathway in stimulating Na + transport across frog skin. The data are consistent with the concept that the natriferic effect of insulin on frog skin is, at least in part, mediated by activation of protein kinase C

  2. Alternative photosynthetic electron transport pathways during anaerobiosis in the green alga Chlamydomonas reinhardtii.

    Science.gov (United States)

    Hemschemeier, Anja; Happe, Thomas

    2011-08-01

    Oxygenic photosynthesis uses light as energy source to generate an oxidant powerful enough to oxidize water into oxygen, electrons and protons. Upon linear electron transport, electrons extracted from water are used to reduce NADP(+) to NADPH. The oxygen molecule has been integrated into the cellular metabolism, both as the most efficient electron acceptor during respiratory electron transport and as oxidant and/or "substrate" in a number of biosynthetic pathways. Though photosynthesis of higher plants, algae and cyanobacteria produces oxygen, there are conditions under which this type of photosynthesis operates under hypoxic or anaerobic conditions. In the unicellular green alga Chlamydomonas reinhardtii, this condition is induced by sulfur deficiency, and it results in the production of molecular hydrogen. Research on this biotechnologically relevant phenomenon has contributed largely to new insights into additional pathways of photosynthetic electron transport, which extend the former concept of linear electron flow by far. This review summarizes the recent knowledge about various electron sources and sinks of oxygenic photosynthesis besides water and NADP(+) in the context of their contribution to hydrogen photoproduction by C. reinhardtii. This article is part of a Special Issue entitled: Regulation of Electron Transport in Chloroplasts. Copyright © 2011 Elsevier B.V. All rights reserved.

  3. PATHWAY: a simulation model of radionuclide-transport through agricultural food chains

    International Nuclear Information System (INIS)

    Kirchner, T.B.; Whicker, F.W.; Otis, M.D.

    1982-01-01

    PATHWAY simulates the transport of radionuclides from fallout through an agricultural ecosystem. The agro-ecosystem is subdivided into several land management units, each of which is used either for grazing animals, for growing hay, or for growing food crops. The model simulates the transport of radionuclides by both discrete events and continuous, time-dependent processes. The discrete events include tillage of soil, harvest and storage of crops,and deposition of fallout. The continuous processes include the transport of radionuclides due to resuspension, weathering, rain splash, percolation, leaching, adsorption and desorption of radionuclides in the soil, root uptake, foliar absorption, growth and senescence of vegetation, and the ingestion assimilation, and excretion of radionuclides by animals. Preliminary validation studies indicate that the model dynamics and simulated values of radionuclide concentrations in several agricultural products agree well with measured values when the model is driven with site specific data on deposition from world-wide fallout

  4. Transport Pathways for Light Duty Vehicles: Towards a 2° Scenario

    Directory of Open Access Journals (Sweden)

    François Cuenot

    2013-04-01

    Full Text Available The transport sector is the second largest and one of the fastest growing energy end-use sectors, representing 24% of global energy-related greenhouse gas emissions. The International Energy Agency has developed scenarios for the transport sector within the overall concept of mitigation pathways that would be required to limit global w