WorldWideScience

Sample records for earthflows

  1. Historic drought puts the brakes on earthflows in Northern California

    Science.gov (United States)

    Bennett, G. L.; Roering, J. J.; Mackey, B. H.; Handwerger, A. L.; Schmidt, D. A.; Guillod, B. P.

    2016-06-01

    California's ongoing, unprecedented drought is having profound impacts on the state's resources. Here we assess its impact on 98 deep-seated, slow-moving landslides in Northern California. We used aerial photograph analysis, satellite interferometry, and satellite pixel tracking to measure earthflow velocities spanning 1944-2015 and compared these trends with the Palmer Drought Severity Index, a proxy for soil moisture and pore pressure that governs landslide motion. We find that earthflow velocities reached a historical low in the 2012-2015 drought, but that their deceleration began at the turn of the century in response to a longer-term moisture deficit. Our analysis implies depth-dependent sensitivity of earthflows to climate forcing, with thicker earthflows reflecting longer-term climate trends and thinner earthflows exhibiting less systematic velocity variations. These findings have implications for mechanical-hydrologic interactions that link landslide movement with climate change as well as sediment delivery in the region.

  2. Historic Drought puts the Brakes on Earthflows in Northern California

    Science.gov (United States)

    Bennett, G. L.; Roering, J. J.; Mackey, B.; Handwerger, A.; Schmidt, D. A.; Guillod, B. P.

    2016-12-01

    Understanding and predicting landslide response to climate change are significant challenges for Earth scientists, with landslides killing at least 5000 people each year around the world and costing 17% of the annual losses from all natural disasters. Much research on landslide response to climate surrounds their response to extreme rainfall events and melting permafrost, both of which are predicted to increase with climate change. However, landslide response to drought, also predicted to increase, remains largely unexplored. Further research on landslide response to drought as a climatic forcing event is needed to better understand the variable response of landslides, and more generally, geomorphic and hydrologic processes to climate change. California's ongoing drought reached historic proportions in 2015 with widespread consequences on the state's resources. We assessed the drought's impact on 98 deep-seated, slow-moving landslides in Northern California. We used a novel combination of aerial photograph analysis, satellite interferometry, and satellite pixel tracking to measure earthflow velocities spanning 1944-2015 for comparison with the Palmer Drought Severity Index, a proxy for soil moisture and pore pressure. We find that earthflow velocities reached a historical low in the extreme 2012-2015 drought, though their deceleration began at the turn of the century in response to a longer-term moisture deficit. Significantly, our analysis implies depth-dependent sensitivity of earthflows to climate forcing, with thicker earthflows reflecting longer-term climate trends and thinner earthflows exhibiting less systematic velocity variations. These findings have implications for our understanding of mechanical-hydrologic controls on earthflow movement as well as for predicting the response of slow-moving landslides to climate change.

  3. A Hot Knife Through Ice-Cream: Earthflow Response to Channel Incision (Or Channel Response to Earthflows?), Eel River Canyon, California

    Science.gov (United States)

    Mackey, B. H.; Roering, J. J.; McKean, J. A.

    2007-12-01

    Abundant glacier-like earthflow features are recognized as a primary erosional process in the highly erodable Franciscan Melange of the Eel River Basin, CA. Despite their prominence in this "melting ice-cream" topography, many questions regarding their effects on the long term sediment flux from this rapidly eroding basin remain unresolved. For example, does an earthflow's basal shear zone propagate vertically downwards with vertical river incision? What controls the upslope and lateral extent of individual earthflows? How does the erosive power of a river influence the rate of earthflow movement, or conversely do earthflow toe deposits regulate the rate of river incision? Here we present preliminary findings derived from study of 200km2 of lidar data (1m resolution) covering hillslopes adjacent to 30km of the Eel River. Lidar allows detailed analysis of the interaction between earthflows and the drainage network, and we document how inferred changes in local base level are propagated throughout adjacent hillslopes via earthflow movement. The most active earthflows (determined by field surveying and analysis of aerial photos rectified using lidar- generated digital topography) coincide with locally steep sections of channel, while downstream of the most active flows we frequently observe less-active or dormant earthflows. This observation supports the idea that the locations of the most active earthflows coincide with headward propagating knickpoints in the channel. The rate of earthflow movement appears to slow when an earthflow exhausts the upslope area of easily mobilized sediment. Earthflow toes can protrude directly into the channel, causing the channel to narrow and steepen, and even undercut the opposite bank. Large resistant boulders (>2m diameter) transported by the earthflow accumulate in the streambed and appear to both act as a check on further channel incision and earthflow movement. In contrast, areas adjacent to active earthflows exhibit smooth

  4. Evaluating controls on the aspect dependence of earthflows in the central California Coast Ranges

    Science.gov (United States)

    Nereson, A. L.; Finnegan, N. J.; Booth, A. M.

    2013-12-01

    Earthflows are an important mass-wasting process in many mountainous landscapes. In addition to radically changing the fabric of the landscape and damaging man-made infrastructure, earthflows deliver, for their area, a disproportionately large sediment load to rivers. In California, earthflows are typically restricted to clay-rich and mechanically-weak lithologies, such as the Franciscan mélange. In addition, several studies have observed that earthflows in California favor south-facing slopes, even in settings with spatially-uniform lithology. This fundamental observation remains largely unexplained under the current understanding of earthflow behavior. Here, we evaluate the controls on the aspect dependence of earthflows in the Alameda Creek watershed near Fremont, California, where many large, but relatively inactive earthflows are observed in the Franciscan mélange. We first apply spectral analysis to LiDAR-derived digital elevation models to objectively map the topographic signature of landslides and determine the degree of aspect dependence. We then explore several hypotheses that can explain our observation that earthflows tend to form on south-facing slopes, including: (1) lack of dense vegetation and trees with slope-stabilizing root systems on south-facing slopes; (2) higher pore fluid pressures due to relatively lower rates of evapotranspiration on sparsely vegetated south-facing slopes; (3) increased dessication and/or deformation cracking on south-facing earthflow surfaces, creating fast-flow pathways into the interior of landslides.

  5. The Long Term Evolution, Kinematics and Sediment Flux from an Active Earthflow

    Science.gov (United States)

    Mackey, B. H.; Roering, J. J.; McKean, J. A.

    2008-12-01

    Large, slow moving earthflows are pervasive in many rapidly eroding landscapes world wide. In the coast ranges of northern California, some earthflows are active (moving up to 2m/yr), but much of the landscape is imprinted with the ubiquitous subtle headscarps, toes and deflated transport zones from multiple generations of earthflows and landslides in various stages of dormancy. To better understand earthflow transport history and evolution, we aim to constrain the long term sediment flux, kinematics and topographic development of an individual earthflow. We undertake a multi-proxy study, focused on a 1.5km-long active earthflow entering Kekawaka Ck, an 85km2 tributary of the Eel River, southwest Trinity County, California. This classical earthflow has a steep amphitheater-like accumulation area which feeds into a narrow, elongate transport zone, and terminates at the creek in a bulbous toe. Combining high resolution digital topography from LiDAR, total station surveying, and a sequence of orthorectified historical aerial photographs, we generated displacement vectors of earthflow movement spanning the past 6 decades. The earthflow has a complex history of movement, with rates of activity varying through time and across the different kinematic zones of the earthflow complex. Horizontal movement rates range from 0.2-1m/yr and are greatest in the narrow mid-section of the earthflow, consistent with the dictates of mass conservation. Given direct observations of earthflow width and thickness at the hillslope-channel interface, we estimate the modern sediment flux attributable to mass movement to be 650 +/- 200 m3/yr. To extend our analysis to the millennial scale, we measured inventories of meteoric 10-Be in 4 soil pits down the flow axis, and one pit on unfailed terrain above the headscarp. The 10-Be depth profiles show how adjacent slopes enriched with >15kyr of 10-Be detach from the headscarp as the earthflow margin retrogresses upslope. These slump blocks

  6. Long-term kinematics and sediment flux of an active earthflow, Eel River, California

    Science.gov (United States)

    B. H. Mackey; J. J. Roering; J. A. McKean

    2009-01-01

    Although earthflows are the dominant erosion mechanism in many mountainous landscapes, estimates of long-term earthflow-driven sediment flux remain elusive because landslide displacement data are typically limited to contemporary time periods. Combining high-resolution topography from airborne LiDAR (light detection and ranging), total station surveying, orthorectified...

  7. Triggering conditions and mobility of debris flows associated to complex earthflows

    Science.gov (United States)

    Malet, J.-P.; Laigle, D.; Remaître, A.; Maquaire, O.

    2005-03-01

    Landslides on black marl slopes of the French Alps are, in most cases, complex catastrophic failures in which the initial structural slides transform into slow-moving earthflows. Under specific hydrological conditions, these earthflows can transform into debris flows. Due to their sediment volume and their high mobility, debris flow induced by landslides are far much dangerous than these resulting from continuous erosive processes. A fundamental point to correctly delineate the area exposed to debris flows on the alluvial fans is therefore to understand why and how some earthflows transform into debris flow while most of them stabilize. In this paper, a case of transformation from earthflow to debris flow is presented and analysed. An approach combining geomorphology, hydrology, geotechnics and rheology is adopted to model the debris flow initiation (failure stage) and its runout (postfailure stage). Using the Super-Sauze earthflow (Alpes-de-Haute-Provence, France) as a case study, the objective is to characterize the hydrological and mechanical conditions leading to debris flow initiation in such cohesive material. Results show a very good agreement between the observed runout distances and these calculated using the debris flow modeling code Cemagref 1-D. The deposit thickness in the depositional area and the velocities of the debris flows are also well reproduced. Furthermore, a dynamic slope stability analysis shows that conditions in the debris source area under average pore water pressures and moisture contents are close to failure. A small excess of water can therefore initiate failure. Seepage analysis is used to estimate the volume of debris that can be released for several hydroclimatic conditions. The failed volumes are then introduced in the Cemagref 1-D runout code to propose debris flow hazard scenarios. Results show that clayey earthflow can transform under 5-year return period rainfall conditions into 1-km runout debris flow of volumes ranging

  8. A digital photogrammetric method for measuring horizontal surficial movements on the slumgullion earthflow, Hinsdale county, Colorado

    Science.gov (United States)

    Powers, P.S.; Chiarle, M.; Savage, W.Z.

    1996-01-01

    The traditional approach to making aerial photographic measurements uses analog or analytic photogrammetric equipment. We have developed a digital method for making measurements from aerial photographs which uses geographic information system (GIS) software, and primarily DOS-based personal computers. This method, which is based on the concept that a direct visual comparison can be made between images derived from two sets of aerial photographs taken at different times, was applied to the surface of the active portion of the Slumgullion earthflow in Colorado to determine horizontal displacement vectors from the movements of visually identifiable objects, such as trees and large rocks. Using this method, more of the slide surface can be mapped in a shorter period of time than using the standard photogrammetric approach. More than 800 horizontal displacement vectors were determined on the active earthflow surface using images produced by our digital photogrammetric technique and 1985 (1:12,000-scale) and 1990 (1:6,000-scale) aerial photographs. The resulting displacement field shows, with a 2-m measurement error (??? 10%), that the fastest moving portion of the landslide underwent 15-29 m of horizontal displacement between 1985 and 1990. Copyright ?? 1996 Elsevier Science Ltd.

  9. The process of earthflow propagation: insights from an application of the SPH technique to a case history

    Science.gov (United States)

    Lollino, Piernicola; Giordan, Daniele; Allasia, Paolo; Pastor, Manuel

    2016-04-01

    An intense reactivation of a large earthflow (about 6 million m3 of soil debris) took place in Montaguto (Southern Apennines, Italy) between 2005 and 2006 as a consequence of the retrogression of a sliding process in the source area at the top of the slope. The earthflow run-out was approximately 2-2.5 km long, with the landslide mass thickness approximately ranging between 5 m and 30 m. Relevant damages were produced at the toe of the slope, since important infrastructures hereby located were covered by large volumes of landslide detritum. In the transition area, that is just downslope the source area, the landslide soil mass was channelized and transformed into a viscous soil flowing down through a natural depression channel, with an average displacement rate estimated to range between 3 and 7 m/day. In this work an application of the Smoothed Particle Hydrodynamics method has been carried out in order to simulate both the main features of the earthflow propagation, that is the direction and the thickness of the flowing mass, as well as to investigate some factors of the soil mechanical behavior that might have controlled the earthflow mobility. In particular, two different assumptions concerning the soil rheology, i.e. Bingham visco-plasticity and frictional-consolidating soil, the first complying more with the assumption of a flow-like behavior and the latter with a soil-like behavior of the landslide mass, have been made for comparison purposes. Based on the experiences gained from previous authors concerning the in-situ features of similar earthflow soil masses, these landslides are thought to behave more as a viscous fluid during the very first stages of propagation due to phase transition processes and, later on, to recover a soil-like behavior, therefore characterized by sliding mechanism, due to soil consolidation processes. Field evidences of consolidation processes have indeed been observed in situ in recent years based on pore water pressure monitoring

  10. Characterizing Earthflow Surface Morphology With Statistical and Spectral Analyses of Airborne Laser Altimetry

    Science.gov (United States)

    McKean, J.; Roering, J.

    High-resolution laser altimetry can depict the topography of large landslides with un- precedented accuracy and allow better management of the hazards posed by such slides. The surface of most landslides is rougher, on a local scale of a few meters, than adjacent unfailed slopes. This characteristic can be exploited to automatically detect and map landslides in landscapes represented by high resolution DTMs. We have used laser altimetry measurements of local topographic roughness to identify and map the perimeter and internal features of a large earthflow in the South Island, New Zealand. Surface roughness was first quantified by statistically characterizing the local variabil- ity of ground surface orientations using both circular and spherical statistics. These measures included the circular resultant, standard deviation and dispersion, and the three-dimensional spherical resultant and ratios of the normalized eigenvalues of the direction cosines. The circular measures evaluate the amount of change in topographic aspect from pixel-to-pixel in the gridded data matrix. The spherical statistics assess both the aspect and steepness of each pixel. The standard deviation of the third di- rection cosine was also used alone to define the variability in just the steepness of each pixel. All of the statistical measures detect and clearly map the earthflow. Cir- cular statistics also emphasize small folds transverse to the movement in the most active zone of the slide. The spherical measures are more sensitive to the larger scale roughness in a portion of the slide that includes large intact limestone blocks. Power spectra of surface roughness were also calculated from two-dimensional Fourier transformations in local test areas. A small earthflow had a broad spectral peak at wavelengths between 10 and 30 meters. Shallower soil failures and surface erosion produced surfaces with a very sharp spectral peak at 12 meters wavelength. Unfailed slopes had an order of magnitude

  11. Using COSI-CORR to Quantify Earthflow Movement Rates Over Decadal Time Scales

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    Cerovski-Darriau, C.; Roering, J. J.

    2011-12-01

    Large, complex earthflow systems can evolve over diverse (seasonal to millennial) timescales and thus require a range of tools to document their kinematics. In many areas, extensive archives of historical aerial photographs offer potential for quantifying decadal fluctuations, but tracking individual features has been impractical over significant temporal and spatial scales. Here, we explore recent software that automates landslide mapping and improves feasibility of tracking deformation at these scales. The Co-registration of Optically Sensed Images and Correlation (COSI-Corr) software allows for correlation between air photographs and LiDAR imagery, and tracks surface deformation over a sequence of aerial surveys. To analyze the efficacy for landslides, we focused on a 1km2 area riddled with active earthflows, shallow landslides, and gullying in the Waipaoa River catchment on the North Island of New Zealand. This area is dominated by Late Cretaceous-Early Tertiary clay-rich mudstones and calcite-rich sandstones with highly sheared and more massive units that fail in diverse fashion. Starting in the 1900s, the area was burned and converted to pastureland, and is now heavily grazed by sheep and cattle. Slope deformation in the study area has accelerated due to this history of land use changes. We used aerial photographs from 1956, 1960, 1979, and 1982 to track slide movement. The photos were scanned at 1200 dpi (21 micron), giving a ground resolution between approximately 0.2-1m/pixel (scale of 1:16000 to 1:47000). We rectified the photos with 2010 orthophotos and a corresponding 1m LiDAR DEM and hillshade map using the COSI-Corr interface in ENVI 4.5. They were then sequentially correlated, which automatically identifies surface changes with sub-pixel resolution. Next we generated a vector field displacement map for each time step with 8m grid nodes. The resulting vector maps show velocities ranging from about 1-5m/yr. This corresponds well with previously

  12. GB-InSAR monitoring and observational method for landslide emergency management: the Montaguto earthflow (AV, Italy)

    Science.gov (United States)

    Ferrigno, F.; Gigli, G.; Fanti, R.; Casagli, N.

    2015-12-01

    On 10 March 2010, due to the heavy rainfall that occurred on the previous days, the Montaguto earthflow reactivated, involving the road SS 90 "Delle Puglie", as had happened previously in May 2005 and in September 2009, and reaching the Roma-Bari railway. This determined a special attention of the National Civil Protection Department and a widespread monitoring and analysis program was initiated. A monitoring activity using GB-InSAR (Ground Based Interferometric Synthetic Aperture Radar) system began, in order to investigate the landslide kinematics, to plan urgent safety measures for risk mitigation and to design long term stabilization work. In this paper the GB-InSAR monitoring system results and its applications in the Observational Method (OM) approach are presented. The paper also highlights how the OM based on the GB-InSAR technique can produce savings in cost and time on engineering projects, without compromising safety, and how it can also benefit the geotechnical community by increasing scientific knowledge. This study focuses on the very much active role played by the monitoring activities, in both the design and plan modifications; with a special consideration for the emergency phase.

  13. Probabilistic Risk Assessment in Medium Scale for Rainfall-Induced Earthflows: Catakli Catchment Area (Cayeli, Rize, Turkey

    Directory of Open Access Journals (Sweden)

    H. A. Nefeslioglu

    2011-01-01

    Full Text Available The aim of the present study is to introduce a probabilistic approach to determine the components of the risk evaluation for rainfall-induced earthflows in medium scale. The Catakli catchment area (Cayeli, Rize, Turkey was selected as the application site of this study. The investigations were performed in four different stages: (i evaluation of the conditioning factors, (ii calculation of the probability of spatial occurrence, (iii calculation of the probability of the temporal occurrence, and (iv evaluation of the consequent risk. For the purpose, some basic concepts such as “Risk Cube”, “Risk Plane”, and “Risk Vector” were defined. Additionally, in order to assign the vulnerability to the terrain units being studied in medium scale, a new more robust and more objective equation was proposed. As a result, considering the concrete type of roads in the catchment area, the economic risks were estimated as 3.6×106€—in case the failures occur on the terrain units including element at risk, and 12.3×106€—in case the risks arise from surrounding terrain units. The risk assessments performed in medium scale considering the technique proposed in the present study will supply substantial economic contributions to the mitigation planning studies in the region.

  14. null Mudflows and Earthflows, null Images

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The slopes above streams and rivers are subjected to a variety of processes that cause them to recede and retreat from the river or stream channel. These processes,...

  15. GB-InSAR monitoring and observational method for landslide emergency management: the Montaguto earthflow (AV, Italy

    Directory of Open Access Journals (Sweden)

    F. Ferrigno

    2017-06-01

    Full Text Available On 10 March 2010, because of the heavy rainfall in the preceding days, the Montaguto landslide (Southern Italy reactivated, affecting both state road 90 Delle Puglie and the Rome–Bari railway. A similar event occurred on May 2005 and on September 2009. As a result, the National Civil Protection Department (DPC started an accurate monitoring and analysis program. A monitoring project using the GB-InSAR (ground-based interferometric synthetic aperture radar system was emplaced to investigate the landslide kinematics, plan urgent safety measures for risk mitigation and design long-term stabilization work.Here, we present the GB-InSAR monitoring system results and its applications in the observational method (OM approach. GB-InSAR is an established instrument for long-term campaigns aimed at early warning and monitoring during construction works. Our paper further develops these aspects in that it highlights how the OM based on the GB-InSAR technique can produce savings in terms of cost and time in engineering projects without compromising safety. This study focuses on the key role played by the monitoring activities during the design and planning activities, with special reference to the emergency phase.

  16. GB-InSAR monitoring and observational method for landslide emergency management: the Montaguto earthflow (AV, Italy)

    Science.gov (United States)

    Ferrigno, Federica; Gigli, Giovanni; Fanti, Riccardo; Intrieri, Emanuele; Casagli, Nicola

    2017-06-01

    On 10 March 2010, because of the heavy rainfall in the preceding days, the Montaguto landslide (Southern Italy) reactivated, affecting both state road 90 Delle Puglie and the Rome-Bari railway. A similar event occurred on May 2005 and on September 2009. As a result, the National Civil Protection Department (DPC) started an accurate monitoring and analysis program. A monitoring project using the GB-InSAR (ground-based interferometric synthetic aperture radar) system was emplaced to investigate the landslide kinematics, plan urgent safety measures for risk mitigation and design long-term stabilization work.Here, we present the GB-InSAR monitoring system results and its applications in the observational method (OM) approach. GB-InSAR is an established instrument for long-term campaigns aimed at early warning and monitoring during construction works. Our paper further develops these aspects in that it highlights how the OM based on the GB-InSAR technique can produce savings in terms of cost and time in engineering projects without compromising safety. This study focuses on the key role played by the monitoring activities during the design and planning activities, with special reference to the emergency phase.

  17. Geomorphic response to historic drought in northern California

    Science.gov (United States)

    Bennett, Georgina; Roering, Joshua; Mackey, Ben; Handwerger, Alexander; Guillod, Benoit; Schmidt, David

    2016-04-01

    California declared a state of drought emergency in early 2014 with a recent study showing that 2012 - 2015 constitutes a drought unprecedented in the state's historical record. Much has been reported on the drought's devastating impacts on water supply, agriculture and wildfire occurrence as well as its possible origins, including the role of anthropogenic climate change. However, its geomorphic impact has been given little attention. We address this gap by assessing the response of earthflows to drought in the Eel River in northern California. Despite their slow-moving nature, earthflows contribute ~50% of erosion in the region and are a constant threat to transport routes, making their behavior important to understand. We used pixel tracking in the program COSI CORR to measure velocities of 98 earthflows for the periods 2009 - 2012 and 2012 - 2015 from 0.5 m resolution Worldview satellite imagery. Putting these measurements in the context of velocities manually measured from aerial photographs dating back to the 1950s indicates that whilst earthflows have decelerated significantly in the ensuing drought this is part of a slowing trend commencing around 2000. We show that decadal earthflow velocities are closely correlated with the Palmer Drought Severity Index (PDSI), which in turn is correlated with North American Land Data Assimilation System (NLDAS)-modeled soil moisture. Slowing of earthflows since 2000 is coincident with a reduction of soil moisture, starting with the 2000 - 2001 drought from which earthflows have not yet returned to their pre-drought values and which set the stage for the slowest mean velocities observed in recent decades during the current drought. It will be important to continue to monitor these earthflows as rains return, particularly given the hypothesis that extreme drying may increase pathways for future runoff into earthflows.

  18. The contribution of large, slow-moving landslides to landscape evolution

    Science.gov (United States)

    Mackey, Benjamin Hunter

    This dissertation discusses the contribution of deep-seated landslides and earthflows to the morphology, erosion, and evolution of mountainous landscapes, focusing on the northern California Coast Ranges. In active landscapes, channel incision is necessary to create relief but also increases stresses in adjacent hillslopes, ultimately leading to slope failure. While conceptually simple, the spatial relationships between channel incision and landsliding have not been well quantified. Along the South Fork Eel River, I mapped the distribution of deep-seated landslides using light detection and ranging (LiDAR) derived maps. Landslide density increases in regions subject to late Pleistocene--Holocene channel incision and particularly in response to lateral incision at the apex of meander bends. Wavelet analysis of channel sinuosity reveals hillslopes are most sensitive to meander wavelengths of 1.5 km. Argillaceous lithology generates abundant earthflow activity along the main stem Eel River, yet spatial and temporal patterns of earthflow movement are poorly understood. I undertook a detailed study of the Kekawaka Earthflow using LiDAR, meteoric 10Be in soil, orthorectified historical aerial photographs, and field surveys. Inventories of 10Be in soil pits increase systematically downslope, indicate an average movement rate of 2.1 +/- 1.3 m/a over the past 150 years, and establish a minimum earthflow age of 1700 years. The Kekawaka earthflow has a systematic history of movement, both spatially, with greatest movement in the narrow transport zone, and temporally, as velocities peaked in the 1960's and have slowed since 1981. I used LiDAR and aerial photographs to map earthflow movement and calculate sediment flux across 226 km2 of the main stem Eel River. From 1944--2006, 7.3% of the study area was active, and earthflows account for an erosion rate of 0.53 +/- 0.04 mm/a, over half the regional average sediment yield. Velocity time series on 17 earthflows suggest temporal

  19. Active landsliding and landscape denudation in response to transient tectonic uplift, Northern California.

    Science.gov (United States)

    Bennett, G. L.; Roering, J. J.; Miller, S. R.; Kirby, E.; Schmidt, D. A.

    2014-12-01

    The northern Californian Coast ranges present a unique area to study landscape response to transient tectonic uplift. Studies have shown that an increase in uplift may be balanced by the rate of landsliding in settings of steady uplift. However, the landsliding response to transient tectonic uplift remains to be elucidated. The Californian Coast ranges are shaped by the northward migration of the Mendocino Triple Junction (MTJ), which geodynamic modeling suggests produces a transient double-humped uplift field. A major research question is whether we can detect a signature of this transient tectonic uplift in landslide activity and document how the channel network communicates this signal to hillslopes. Using air photos and Worldview imagery, we manually mapped more than 2000 earthflows and debris slides in the Eel and surrounding catchments that span the ~400 km-long region. The velocities of active earthflows were estimated by visually tracking features between images spanning 1993 to 2013. We mapped channel steepness from 10m NED DEMs in Topotoolbox 2 and developed a new tool to automatically define knickpoints along the channel network. Earthflows occur almost exclusively in a band of Franciscan mélange oriented along the MTJ transect whilst debris slides are more evenly distributed by lithology. Both earthflows and debris slides are clustered in the Eel catchment around the proposed uplift peaks and are largely absent outside of these zones. Within these areas of high landslide densities, we observe peaks in active earthflows adjacent to peaks in dormant earthflows to the south, suggesting that the signature of earthflow activity remains for a period of time once the uplift peak has passed. Landslide density, mean landslide area, and earthflow velocity all increase rapidly above threshold values of channel steepness and local relief. In the Eel catchment, where the zone of rapid uplift is commencing, landslides, particularly earth flows, are concentrated

  20. Pattern of Landslide Distribution Reflects Degree of Hillslope Adjustment in a Waipaoa River Catchment, New Zealand

    Science.gov (United States)

    Cerovski-Darriau, C.; Roering, J. J.

    2014-12-01

    Using landslide morphology to determine the state of hillslope transience provides a diagnostic tool to identify the extent of landscape adjustment. Here we test for a temporal and spatial progression of landslides reflecting the degree of adjustment for a Waipaoa River catchment (North Island, New Zealand). Following the shift to a warmer, wetter climate after the Last Glacial Maximum (LGM) (~18 ka), the Waipaoa River rapidly incised up to 120 m, leaving perched, low-relief hillslopes unadjusted to that base level fall. In the 16 km2 study catchment—principally comprised of weak mélange—pervasive post-LGM landslides responded to >50 m of fluvial incision by sculpting and denuding >99% of the catchment, but adjustment is not yet complete. Starting ~150 years ago, European settlers deforested ~95% of the landscape, which triggered a sharp increase in hillslope erosion as widespread earthflow complexes and gully systems reactivated and/or expanded in the weak lithology with the loss of vegetation cover. Most of the remaining relict (≥18 ka) landforms are confined to the upper watershed, upholding the proposed upstream progression of hillslope adjustment. Based on previous tephrochronology and surface roughness data, present-day earthflows follow this pattern of younging upstream. Here we analyze the size, location, and distribution of ~500 earthflows (mapped from 2010 lidar and orthophotos) to determine if there is a spatial progression of earthflows reflective of hillslope adjustment and correlated to the previously identified temporal progression. Morphologic evidence from this study indicates the younger earthflows in the upper watershed have smaller areas (6000 ± 600 m2 (mean ± s.e.)), a more elongate aspect ratio (AR=3.6 ± 1.6 (mean ± s.d.)), and are generally (>50%) deposited in axial gullies, whereas downstream earthflows are larger (20000 ± 9000 m2), statistically less elongate (AR=2.3 ± 0.9), and more frequently coupled with the main channel

  1. Caractérisation de la structure interne et de l'état hydrique de glissements argilo-marneux par tomographie géophysique : l'exemple du glissement-coulée de Super-Sauze (Alpes du Sud, France)

    Science.gov (United States)

    Grandjean, Gilles; Pennetier, Céline; Bitri, Adnan; Meric, Ombeline; Malet, Jean-Philippe

    2006-07-01

    Geophysical methods such as seismic surveying and electrical resistivity imaging appear to be well-adapted to investigate and understand landslide mechanisms. They allow direct and non-intrusive measurement of acoustic velocity and electrical resistivity, two fundamental parameters used to define the physical properties of the reworked moving materials. Both methods were applied at the Super-Sauze site in the French South Alps, where a typical example of an intra-material earthflow-mudslide can be observed. Measurements were taken simultaneously along two orthogonal profiles: one 325 m in length is perpendicular to the axis of the earthflow; the other 235 m in length is located along the axis of the earthflow. The results show a correlation between the seismic and electrical resistivity data, confirming that the simultaneous use of both methods gives complementary information about landslide mechanisms. The seismic data provide information on fracture density variations, whereas the electrical resistivity data provide information on water content variations. To cite this article: G. Grandjean et al., C. R. Geoscience 338 (2006).

  2. Preliminary map of landslide deposits, Denver 1° by 2° Quadrangle, Colorado

    Science.gov (United States)

    Colton, Roger B.; Holligan, Jeffrey A.; Anderson, Larry W.

    1975-01-01

    Areas inferred to be underlain by landslide deposits resulting from landsliding, avalanching, block gliding, debris sliding or flowing, earthflows, mudflows, rocksliding, rockfalls, rotational slides, slab or flake sliding, slumping, talus accumulation, and translational sliding. Rock glacier deposits, colluvium, and solifluction deposits are included in some areas. Some till is mapped with landslide deposits because distinguishing these two deposits from one another is difficult: Furthermore, in some areas till has failed by landsliding and other types of mass movements. Movement within the deposits varies from none to rapid; rates of movement may also be variable in any given landslide within the same year. Ages of deposits' range from early Pleistocene to Holocene.

  3. Forecasting the behaviour of complex landslides with a spatially distributed hydrological model

    Directory of Open Access Journals (Sweden)

    J.-P. Malet

    2005-01-01

    Full Text Available The relationships between rainfall, hydrology and landslide movement are often difficult to establish. In this context, ground-water flow analyses and dynamic modelling can help to clarify these complex relations, simulate the landslide hydrological behaviour in real or hypothetical situations, and help to forecast future scenarios based on environmental change. The primary objective of this study is to investigate the possibility of including more temporal and spatial information in landslide hydrology forecasting, by using a physically based spatially distributed model. Results of the hydrological and geomorphological investigation of the Super-Sauze earthflow, one of the persistently active landslide occurring in clay-rich material of the French Alps, are presented. Field surveys, continuous monitoring and interpretation of the data have shown that, in such material, the groundwater level fluctuates on a seasonal time scale, with a strong influence of the unsaturated zone. Therefore a coupled unsaturated/saturated model, incorporating Darcian saturated flow, fissure flow and meltwater flow is needed to adequately represent the landslide hydrology. The conceptual model is implemented in a 2.5-D spatially distributed hydrological model. The model is calibrated and validated on a multi-parameters database acquired on the site since 1997. The complex time-dependent and three-dimensional groundwater regime is well described, in both the short- and long-term. The hydrological model is used to forecast the future hydrological behaviour of the earthflow in response to potential environmental changes.

  4. Ambient seismic noise monitoring of a clay landslide: Toward failure prediction

    Science.gov (United States)

    Mainsant, Guénolé; Larose, Eric; Brönnimann, Cornelia; Jongmans, Denis; Michoud, Clément; Jaboyedoff, Michel

    2012-03-01

    Given that clay-rich landslides may become mobilized, leading to rapid mass movements (earthflows and debris flows), they pose critical problems in risk management worldwide. The most widely proposed mechanism leading to such flow-like movements is the increase in water pore pressure in the sliding mass, generating partial or complete liquefaction. This solid-to-liquid transition results in a dramatic reduction of mechanical rigidity in the liquefied zones, which could be detected by monitoring shear wave velocity variations. With this purpose in mind, the ambient seismic noise correlation technique has been applied to measure the variation in the seismic surface wave velocity in the Pont Bourquin landslide (Swiss Alps). This small but active composite earthslide-earthflow was equipped with continuously recording seismic sensors during spring and summer 2010. An earthslide of a few thousand cubic meters was triggered in mid-August 2010, after a rainy period. This article shows that the seismic velocity of the sliding material, measured from daily noise correlograms, decreased continuously and rapidly for several days prior to the catastrophic event. From a spectral analysis of the velocity decrease, it was possible to determine the location of the change at the base of the sliding layer. These results demonstrate that ambient seismic noise can be used to detect rigidity variations before failure and could potentially be used to predict landslides.

  5. Modeling fluxes and form in landslide-prone terrain

    Science.gov (United States)

    Roering, J. J.; Booth, A. M.; Stock, J. D.

    2011-12-01

    Landslides dramatically alter the Earth's surface over short timescales. The mass transfer associated with a limited number of slope failures can dominate the sediment budget of a region for decades or longer. The initiation, failure geometry, and runout of individual landslides depend on a range of factors and cannot be predicted from current models. Given these realities of landslide behavior over human timescales, it is challenging to reasonably represent these processes in landscape evolution models. Here, we evaluate the ability of two landslide models, both of which are formulated to apply at geomorphic timescales, to generate topographic patterns and sediment flux rates observed in natural landscapes. Episodic debris flow activity is ubiquitous in steep, low-order mountainous catchments and generates valley networks with low concavity. A physically-based model for debris flow incision (Stock and Dietrich, GSA Bull, 2006) proposes that incision rates depend on the frequency, volume, and velocity of debris flows as well as the density of trigger sites and the state of bedrock weathering in low-order valleys. Valley slope angles are predicted to decline with drainage area according to how these properties vary spatially. We calibrated the model for a well-studied small catchment in the Oregon Coast Range using cosmogenic radionuclide erosion rates and then analyzed the slope-area signature of low-order valleys across much of the Central Oregon Coast Range to explore spatial variations in baselevel lowering. This endeavor shows that baselevel lowering rates vary significantly due to patches of resistant bedrock, drainage reorganization, and tectonic forcing. In regions with weak sedimentary bedrock, earthflows can reduce hillslope gradients, promote gullying, and dominate sediment yield through their downslope translation. A one-dimensional, physically-based model for earthflow-prone hillslope evolution (Booth and Roering, JGR, in press) incorporates earthflow

  6. Comparison of Natural Dams from Lava Flows and Landslides on the Owyhee River, Oregon

    Science.gov (United States)

    Ely, L. L.; Brossy, C. C.; Othus, S. M.; Orem, C.; Fenton, C.; House, P. K.; O'Connor, J. E.; Safran, E. B.

    2008-12-01

    Numerous large lava flows and mass movements have temporarily dammed the Owyhee River in southeastern Oregon at various temporal and spatial scales. These channel-encroaching events potentially play a significant role in creating and maintaining the geomorphic features of river canyons in uplifted volcanic terranes that compose a significant part of the western U.S. Abundant landslides and lava flows have the capacity to inhibit incision by altering channel slope, width, and bed character, and burying valley- bottom bedrock under exogenous material; or promote incision by generating cataclysmic floods through natural dam failures. The natural dams vary in their source, morphology, longevity and process of removal, which in turn affects the extent and duration of their impact on the river. The 3 most recent lava flows filled the channel 10-75 m deep and flowed up to 26 kilometers downvalley, creating long, low dams that were subject to gradual, rather than catastrophic, removal. In the last 125 ka, the Saddle Butte and West Crater lava dams created reservoirs into which 10-30 meters of silt and sand were deposited. The river overtopped the dams and in most reaches eventually cut a new channel through the adjacent, less resistant bedrock buttresses. Terraces at several elevations downstream and upstream of the West Crater dam indicate periods of episodic incision ranging from 0.28 to 1.7 mm/yr., based on 3He exposure ages on strath surfaces and boulder-rich fluvial deposits. In contrast to the lava dams, outburst flood deposits associated with landslide dams are common along the river. The mechanisms of failure are related to the geologic setting, and include rotational slump complexes, cantilevered blocks and block slides, and massive earthflows. Most large-scale mass movements occur in reaches where the Owyhee canyon incises through stacks of interbedded fluviolacustrine sediments capped with lava flows. The frequently observed association of landslides and flood

  7. Caesium-137 as Indicator of Present Mass-Movement and Erosion Processes

    Science.gov (United States)

    Supper, R.; Baron, I.; Winkler, E.; Motschka, K.; Jaritz, W.; Moser, G.; Carman, M.

    2012-04-01

    After the Chernobyl atomic accident in April 1986, notable parts of Eastern, Northern and Central Europe were contaminated by Caesium-137 (137Cs). This radioactive isotope with 30.17 years half-life is completely of anthropogenic origin. After the accident it was transported through the atmosphere for long distances and contaminated the soil surface variably in the vast areas. Although much of the 137Cs content has already decayed, notable amounts can still be detected. The Department of Geophysics of the Geological Survey of Austria conducted in 2009 an airborne multi-sensor geophysical survey over three prominent landslides in Austria and Slovenia as a test study for the application of airborne geophysics for landslide investigations. Besides elelectromagnetic (subsurface resistivity) and passive microwave (soil moisture) measurements, a gamma ray survey was done; natural radioactive isotopes such as Potassium, Thorium, and Uranium were mapped. This paper deals only with the Caesium-137 distribution. The Gschliefgraben test site (N Austria) is a complex of active and dormant earthflows, landslides and rockfalls in a 4 km long valley at the foot of Northern Calcareous Alps within Ultrahelvetic and Rhenodanubian flysch rocks. The last major reactivation occurred in 2007 and 2008. Also the Sibratsgfäll test site (W Austria) is a complex of shallow and deep-seated landslides and earthflows in sedimentary rocks of the Helvetic Zone, Liebenstein Nappe, Feuerstätte Zone and the Rhenodanubian Flysch. Here the major recent reactivation occurred in May 1999 affecting the villages of Sibratsgfäll and Rindberg. The Stoze landslide (NW Slovenia) occurred in November 2000 and is situated in dolomitic to clayey and marly Upper Triassic rocks, in Quaternary glacial moraine sediments and slope debris. The Caesium-137 maps were compared to landslide inventory maps, airborne laser-scan DTMs and up-to-date orthophotos. In all of the test sites, the 137Cs minima correlated well

  8. 4D very high-resolution topography monitoring of surface deformation using UAV-SfM framework.

    Science.gov (United States)

    Clapuyt, François; Vanacker, Veerle; Schlunegger, Fritz; Van Oost, Kristof

    2016-04-01

    During the last years, exploratory research has shown that UAV-based image acquisition is suitable for environmental remote sensing and monitoring. Image acquisition with cameras mounted on an UAV can be performed at very-high spatial resolution and high temporal frequency in the most dynamic environments. Combined with Structure-from-Motion algorithm, the UAV-SfM framework is capable of providing digital surface models (DSM) which are highly accurate when compared to other very-high resolution topographic datasets and highly reproducible for repeated measurements over the same study area. In this study, we aim at assessing (1) differential movement of the Earth's surface and (2) the sediment budget of a complex earthflow located in the Central Swiss Alps based on three topographic datasets acquired over a period of 2 years. For three time steps, we acquired aerial photographs with a standard reflex camera mounted on a low-cost and lightweight UAV. Image datasets were then processed with the Structure-from-Motion algorithm in order to reconstruct a 3D dense point cloud representing the topography. Georeferencing of outputs has been achieved based on the ground control point (GCP) extraction method, previously surveyed on the field with a RTK GPS. Finally, digital elevation model of differences (DOD) has been computed to assess the topographic changes between the three acquisition dates while surface displacements have been quantified by using image correlation techniques. Our results show that the digital elevation model of topographic differences is able to capture surface deformation at cm-scale resolution. The mean annual displacement of the earthflow is about 3.6 m while the forefront of the landslide has advanced by ca. 30 meters over a period of 18 months. The 4D analysis permits to identify the direction and velocity of Earth movement. Stable topographic ridges condition the direction of the flow with highest downslope movement on steep slopes, and diffuse

  9. Influence of Anthropogenic Land-Use Change on Hillslope Erosion in the Waipaoa River Basin

    Science.gov (United States)

    Cerovski-Darriau, C.; Roering, J. J.

    2015-12-01

    European settlement of the North Island, New Zealand resulted in deforestation of >90% of the landscape followed by conversion to pastureland. The resulting loss of vegetation cover triggered a sharp increase in hillslope erosion as widespread earthflow complexes and gully systems developed on the weak marine sedimentary lithologies in the Waipaoa River basin. However, the rate and volume of hillslope degradation due to land-use change has not been quantified. Using a 1955-2013 decadal sequence of aerial photographs for a ~16 km2 sub-catchment, we mapped the spatial extent of active landslides and then created a 'turf index' to relate the amount of ground disruption to average downslope velocity. The sub-catchment is predominately comprised of a weak mélange of highly sheared mudstone and riddled with pervasive earthflows that often span from ridgetop to the channel, dissected by gullies. We separated the landslides into three turf classes based on the spectral signature of the landslide, which relates to the style of ground disruption. Based on the movement of trees and other features, we assigned velocities to each class. The resulting three landslide categories are: 1) little to no disrupted ground that averaged ≤1 m/yr, 2) a mix of disrupted ground and intact blocks that averaged 2-5 m/yr, and 3) no intact blocks or vegetation that averaged ≥5 m/yr. We then calculated the average annual sediment flux based on the corresponding turf index, landslide depth, and length along the channel or gully. Using an average toe depth of 4.4 ± 1.3 m (avg ± sd) determined from field measurements of 37 earthflows, we calculated a sub-catchment averaged erosion rate of up to 23 mm/yr (for 1955). Despite evidence that >99% of the terrain is covered by post-LGM landslides, only 38% is active in 1955 (and that proportion is decreasing through time—seemingly correlated with localized reforestation). Compared with long-term (post-18 ka) erosion rates from this catchment (1

  10. Response of middle-taiga permafrost landscapes of Central Siberia to global warming in the late 20th and early 21st centuries

    Science.gov (United States)

    Medvedkov, Alexey A.

    2016-11-01

    In this paper, regional features of a climatogenic response of the middle-taiga permafrost landscapes of Central Siberia, as well as corresponding transformations of the exodynamic processes, are considered. Lithological-geomorphologic and landscape- geocryological data are analyzed with large amounts of actual data and results of monitoring surveys. Specific features of an ecotone localization of middle-taiga permafrost landscapes and their typical physiognomic characteristics are described. A comprehensive investigation of representative key sites makes it possible to discover the response of different types of permafrost landscapes to regional climate warming. A rapid increase in the active layer depth, slower creep, transformations of the moving kurums, intensive solifluction, and a local replacement of solifluction by landslides-earthflows are revealed within ecotone landscapes of the cryolithozone.

  11. Geomorphological features and monitoring of a large and complex landslide near Avigliano urban area (South Italy

    Directory of Open Access Journals (Sweden)

    F. Sdao

    2005-01-01

    Full Text Available This paper reports the results of geological and geomorphological surveys and the first results of a still in progress GPS monitoring campaign, taken on a large and ancient landslide located near Avigliano town (Basilicata region, South Italy. The landslide occurs on structurally complex clayey-marly terrains and it is classifiable as a multiple and complex roto-translational-earthflow landslide. In the last years this landslide has been affected by frequent reactivations that have been the cause of grave damages to the urban structures in the area. During January 2004, in order to monitor the present kinematics of the landslide body, a GPS network was installed. Until today several GPS surveys have been carried out. The results of GPS data analysis show centimetres level motions going on the landslide. The final goal of the research will be to define a hazard evaluation and an evolution model of the landslide, using the integrated information coming from GPS and geomorphological surveys.

  12. ADVICE: A New Approach for Near-Real-Time Monitoring of Surface Displacements in Landslide Hazard Scenarios

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    Giorgio Lollino

    2013-06-01

    Full Text Available We present a new method for near-real-time monitoring of surface displacements due to landslide phenomena, namely ADVanced dIsplaCement monitoring system for Early warning (ADVICE. The procedure includes: (i data acquisition and transfer protocols; (ii data collection, filtering, and validation; (iii data analysis and restitution through a set of dedicated software; (iv recognition of displacement/velocity threshold, early warning messages via SMS and/or emails; (v automatic publication of the results on a dedicated webpage. We show how the system evolved and the results obtained by applying ADVICE over three years into a real early warning scenario relevant to a large earthflow located in southern Italy. ADVICE has speed-up and facilitated the understanding of the landslide phenomenon, the communication of the monitoring results to the partners, and consequently the decision-making process in a critical scenario. Our work might have potential applications not only for landslide monitoring but also in other contexts, as monitoring of other geohazards and of complex infrastructures, as open-pit mines, buildings, dams, etc.

  13. Development of a New Zealand SedNet model for assessment of catchment-wide soil-conservation works

    Science.gov (United States)

    Dymond, John R.; Herzig, Alexander; Basher, Les; Betts, Harley D.; Marden, Mike; Phillips, Chris J.; Ausseil, Anne-Gaelle E.; Palmer, David J.; Clark, Maree; Roygard, Jon

    2016-03-01

    Much hill country in New Zealand has been converted from indigenous forest to pastoral agriculture, resulting in increased soil erosion. Following a severe storm that hit the Manawatu-Wanaganui region in 2004 and caused 62,000 landslides, the Horizons Regional Council have implemented the Sustainable Land Use Initiative (SLUI), a programme of widespread soil conservation. We have developed a New Zealand version (SedNetNZ) of the Australian SedNet model to evaluate the impact of the SLUI programme in the 5850 km2 Manawatu catchment. SedNetNZ spatially distributes budgets of fine sediment in the landscape. It incorporates landslide, gully, earthflow erosion, surficial erosion, bank erosion, and flood-plain deposition, the important forms of soil erosion in New Zealand. Modelled suspended sediment loads compared well with measured suspended sediment loads with an R2 value of 0.85 after log transformation. A sensitivity analysis gave the uncertainty of estimated suspended sediment loads to be approximately plus or minus 50% (at the 95% confidence level). It is expected that by 2040, suspended sediment loads in targeted water management zones will decrease by about 40%. The expected decrease for the whole catchment is 34%. The expected reduction is due to maturity of tree planting on land at risk to soil erosion. The 34% reduction represents an annual rate of return of 20% on 20 million NZ of investment on soil conservation works through avoided damage to property and infrastructure and avoided clean-up costs.

  14. ADVICE: a new approach for near-real-time monitoring of surface displacements in landslide hazard scenarios.

    Science.gov (United States)

    Allasia, Paolo; Manconi, Andrea; Giordan, Daniele; Baldo, Marco; Lollino, Giorgio

    2013-06-27

    We present a new method for near-real-time monitoring of surface displacements due to landslide phenomena, namely ADVanced dIsplaCement monitoring system for Early warning (ADVICE). The procedure includes: (i) data acquisition and transfer protocols; (ii) data collection, filtering, and validation; (iii) data analysis and restitution through a set of dedicated software; (iv) recognition of displacement/velocity threshold, early warning messages via SMS and/or emails; (v) automatic publication of the results on a dedicated webpage. We show how the system evolved and the results obtained by applying ADVICE over three years into a real early warning scenario relevant to a large earthflow located in southern Italy. ADVICE has speed-up and facilitated the understanding of the landslide phenomenon, the communication of the monitoring results to the partners, and consequently the decision-making process in a critical scenario. Our work might have potential applications not only for landslide monitoring but also in other contexts, as monitoring of other geohazards and of complex infrastructures, as open-pit mines, buildings, dams, etc.

  15. Engineering geologic assessment of the slope movements and liquefaction failures of the 23 October 2011 Van earthquake (Mw= 7.2)

    Science.gov (United States)

    Karakaş, A.; Coruk, Ö.; Doğan, B.

    2013-04-01

    On 23 October 2011, a Mw = 7.2 earthquake occurred in the Van Province in eastern Turkey, killing 604 people. The earthquake was triggered by a thrust fault due to a compression stress in the region, and caused extensive damage over a large area. Many structures in the earthquake region collapsed, and the damage spread from the city of Van to the town of Erciş, in a distance of 60 km. The earthquake generated several slope movements and liquefaction failures in the region, and this study evaluates these processes from the perspective of engineering geology, and presents field and laboratory results related to these processes. Attenuation relationships were used for estimation of peak ground accelerations (PGAs), and an empirical liquefaction evaluation method employing ground accelerations was used to define threshold accelerations initiating the liquefaction. The results demonstrate that landslides were widespread and more frequently observed in the field in comparison with earthflows and rockfalls. Flow-type liquefaction and lateral spreading was found to be widespread and more common than the liquefaction-related settlement. The minimum threshold acceleration value for the initiation of soil liquefaction was calculated to be 188.87 cm s-2 (~0.19 g) in the earthquake region. Laboratory results indicated that the soil liquefaction was closely associated with grain size. The slope instabilities, liquefaction and associated ground failures occurred mainly in rural areas, and their impact on structures was quite low as compared to the human loss and structural damage by the earthquake.

  16. Landslide Mapping in Vegetated Areas Using Change Detection Based on Optical and Polarimetric SAR Data

    Directory of Open Access Journals (Sweden)

    Simon Plank

    2016-04-01

    Full Text Available Mapping of landslides, quickly providing information about the extent of the affected area and type and grade of damage, is crucial to enable fast crisis response, i.e., to support rescue and humanitarian operations. Most synthetic aperture radar (SAR data-based landslide detection approaches reported in the literature use change detection techniques, requiring very high resolution (VHR SAR imagery acquired shortly before the landslide event, which is commonly not available. Modern VHR SAR missions, e.g., Radarsat-2, TerraSAR-X, or COSMO-SkyMed, do not systematically cover the entire world, due to limitations in onboard disk space and downlink transmission rates. Here, we present a fast and transferable procedure for mapping of landslides, based on change detection between pre-event optical imagery and the polarimetric entropy derived from post-event VHR polarimetric SAR data. Pre-event information is derived from high resolution optical imagery of Landsat-8 or Sentinel-2, which are freely available and systematically acquired over the entire Earth’s landmass. The landslide mapping is refined by slope information from a digital elevation model generated from bi-static TanDEM-X imagery. The methodology was successfully applied to two landslide events of different characteristics: A rotational slide near Charleston, West Virginia, USA and a mining waste earthflow near Bolshaya Talda, Russia.

  17. Long-runout landslide occurred in snowmelt period at the Higashi-kubiki Hill, Niigata, Japan: effects of snowpack on behavior of landslide movements

    Science.gov (United States)

    Kimura, Takashi; Hatada, Kazuhiro; Maruyama, Kiyoteru; Noro, Tomoyuki

    2013-04-01

    The mountain areas and the western part of Japan, along the Japan Sea, have over 1.0 m snow accumulation in every winter. For this reason, snowmelt-induced landslides occur frequently in these regions. If a landslide occurs particularly in early snowmelt period, abundant snow potentially causes the landslide to travel long distance. However, because there have been few literatures reported details of landslide movements in deep snow condition, our understanding of landslide movements affected by snow is still limited. This work reports movements and topographies of the Kokugawa landslide, occurred in early snowmelt period at the Higashi-kubiki Hill, Niigata, and discusses the effects of snowpack on behavior of landslide movements. On 7th March 2012, a snowmelt-induced landslide occurred at gentle slope (10-20° ) of the Higashi-kubiki Hill, adjacent to the Takada floodplain, Niigata, Japan, and destroyed eleven houses. Geology of the site consists of Neogene marine mudstone and Early Pleistocene conglomerate, while the slope surface is covered by loose materials (7-8m thick) composed of old colluvial deposits and spoil of gravel extraction in the 1980s. The Kokugawa landslide occurred initially as a rotational slide, which continued to enlarge until the afternoon of 8th, then it tuned into earthflow. The estimated earthflow volume was 750,000 m3. Although the outer part of the sliding mass spread out and deposited at the foot of hill, 350-500 m downward from the top of the scarp, the main body of the sliding mass continued to move rapidly (approximately 15 m/h) without spread out after reaching flat paddy field. When the landslide occurred, about two meters snow covered the site. Snow on the paddy field was pushed by the sliding mass and swelled up several meters above the snow surface level. The swelled snow formed moraine-like snowpack of 5-20 m width. The sliding mass including the snowpack reached houses 250 m apart from the foot of hill on morning of 10th, and

  18. Efficient near-real-time monitoring of 3D surface displacements in complex landslide scenarios

    Science.gov (United States)

    Allasia, Paolo; Manconi, Andrea; Giordan, Daniele; Baldo, Marco; Lollino, Giorgio

    2013-04-01

    prediction of the temporal evolution of the landslide, e.g. through the failure forecast method; (vi) publication of the results on a dedicated webpage. Here we show the results gained in the area of Montaguto (southern Italy, ca. 100 km northeast from Naples), where a large-scale earthflow reached the bottom of the valley and severely damaged the SP90 provincial road, as well as the national railroad [2]. We discuss how the use of ADVICE has speed-up and facilitated the understanding of the landslide evolution, the communication of the monitoring results to the partners, and consequently the decision-making process in a critical landslide scenario. [1] Manconi, A., P. Allasia, D. Giordan, M. Baldo, G. Lollino and A. Corazza, Near-real-time 3D surface deformation model obtained via RTS measurements. In Procedings of World Landslide Forum 2, October 3-9, 2011, Rome, Italy. [2] Giordan, D., P. Allasia, A. Manconi, M. Baldo, G. Lollino, M. Santangelo, M. Cardinali and F. Guzzetti, "Morphological evolution of a large earthflow: the Montaguto landslide southern Italy", Geomorphology, in press.

  19. Distributed Fiber Optic Sensors For The Monitoring Of A Tunnel Crossing A Landslide

    Science.gov (United States)

    Minardo, Aldo; Picarelli, Luciano; Zeni, Giovanni; Catalano, Ester; Coscetta, Agnese; Zhang, Lei; DiMaio, Caterina; Vassallo, Roberto; Coviello, Roberto; Macchia, Giuseppe Nicola Paolo; Zeni, Luigi

    2017-04-01

    Optical fiber distributed sensors have recently gained great attention in structural and environmental monitoring due to specific advantages because they share all the classical advantages common to all optical fiber sensors such as immunity to electromagnetic interferences, high sensitivity, small size and possibility to be embedded into the structures, multiplexing and remote interrogation capabilities [1], but also offer the unique feature of allowing the exploitation of a telecommunication grade optical fiber cable as the sensing element to measure deformation and temperature profiles over long distances, without any added devices. In particular, distributed optical fiber sensors based on stimulated Brillouin scattering through the so-called Brillouin Optical Time Domain Analysis (BOTDA), allow to measure strain and temperature profiles up to tens of kilometers with a strain accuracy of ±10µɛ and a temperature accuracy of ±1°C. These sensors have already been employed in static and dynamic monitoring of a variety of structures resulting able to identify and localize many kind of failures [2,3,4]. This paper deals with the application of BOTDA to the monitoring of the deformations of a railway tunnel (200 m long) constructed in the accumulation of Varco d'Izzo earthflow, Potenza city, in the Southern Italian Apennine. The earthflow, which occurs in the tectonized clay shale formation called Varicoloured Clays, although very slow, causes continuous damage to buildings and infrastructures built upon or across it. The railway tunnel itself had to be re-constructed in 1992. Since then, the Italian National Railway monitored the structure by means of localized fissure-meters. Recently, thanks to a collaboration with the rail Infrastructure Manager (RFI), monitoring of various zones of the landslide including the tunnel is based on advanced systems, among which the optical fiber distributed sensors. First results show how the sensing optical fiber cable is able

  20. The high resolution topographic evolution of an active retrogressive thaw slump compiled from a decade of photography, ground surveys, laser scans and satellite imagery

    Science.gov (United States)

    Crosby, B. T.; Barnhart, T. B.; Rowland, J. C.

    2015-12-01

    Remote sensing imagery has enables the temporal reconstruction of thermal erosion features including lakes, shorelines and hillslope failures in remote Arctic locations, yet these planar data limit analysis to lines and areas. This study explores the application of varying techniques to reconstruct the three dimensional evolution of a single thermal erosion feature using a mixture of opportunistic oblique photos, ground surveys and satellite imagery. At the Selawik River retrogressive thaw slump in northwest Alaska, a bush plane collected oblique aerial photos when the feature was first discovered in 2004 and in subsequent years. These images were recently processed via Structure from Motion to generate georeferenced point clouds for the years prior to the initiation of our research. High resolution ground surveys in 2007, 2009 and 2010 were completed using robotic total station. Terrestrial laser scans (TLS) were collected in the summers of 2011 and 2012. Analysis of stereo satellite imagery from 2012 and 2015 enable continued monitoring of the feature after ground campaigns ended. As accurate coregistraion between point clouds is vital to topographic change detection, all prior and subsequent datasets were georeferenced to stable features observed in the 2012 TLS scan. Though this coregistration introduces uncertainty into each image, the magnitudes of uncertainty are significantly smaller than the topographic changes detected. Upslope retreat of the slump headwall generally decreases over time as the slump floor progresses from a highly dissected gully topography to a low relief, earthflow dominated depositional plane. The decreasing slope of the slump floor diminishes transport capacity, resulting in the progressive burial of the slump headwall, thus decreasing headwall retreat rates. This self-regulation of slump size based on feature relief and transport capacity suggests a capacity to predict the maximum size a given feature can expand to before

  1. Hybrid-SAR Technique: Joint Analysis Using Phase-Based and Amplitude-Based Methods for the Xishancun Giant Landslide Monitoring

    Directory of Open Access Journals (Sweden)

    Tengteng Qu

    2016-10-01

    Full Text Available Early detection and early warning are of great importance in giant landslide monitoring because of the unexpectedness and concealed nature of large-scale landslides. In China, the western mountainous areas are prone to landslides and feature many giant complex landslides, especially following the Wenchuan Earthquake in 2008. This work concentrates on a new technique, known as the “hybrid-SAR technique”, that combines both phase-based and amplitude-based methods to detect and monitor large-scale landslides in Li County, Sichuan Province, southwestern China. This work aims to develop a robust methodological approach to promptly identify diverse landslides with different deformation magnitudes, sliding modes and slope geometries, even when the available satellite data are limited. The phase-based and amplitude-based techniques are used to obtain the landslide displacements from six TerraSAR-X Stripmap descending scenes acquired from November 2014 to March 2015. Furthermore, the application circumstances and influence factors of hybrid-SAR are evaluated according to four aspects: (1 quality of terrain visibility to the radar sensor; (2 landslide deformation magnitude and different sliding mode; (3 impact of dense vegetation cover; and (4 sliding direction sensitivity. The results achieved from hybrid-SAR are consistent with in situ measurements. This new hybrid-SAR technique for complex giant landslide research successfully identified representative movement areas, e.g., an extremely slow earthflow and a creeping region with a displacement rate of 1 cm per month and a typical rotational slide with a displacement rate of 2–3 cm per month downwards and towards the riverbank. Hybrid-SAR allows for a comprehensive and preliminary identification of areas with significant movement and provides reliable data support for the forecasting and monitoring of landslides.

  2. Monitoring of an active landslide in chaotic clay shales (Emilia Romagna region, Northern Apennines)

    Science.gov (United States)

    Squarzoni, Gabriela; Bertello, Lara; Guerriero, Luigi; Berti, Matteo

    2017-04-01

    Sassi Neri landslide is located in the Farini area (North Apennines), about 40 kilometers southwest of Piacenza city. The geology of the area is quite complex, with strongly tectonically deformed shales (Palombini Shales formation) thrusting over an arenaceous-pelitic flysch (Bettola Flysch formation). Starting from '50s, the landslide has been subjected to many reactivations developed as earthflows, the last one in the period between November 2013 and January 2014. The landslide is about 700 m long with a maximum width of about 200 m and a slip surface lying at a depth varying from 5 m to 15 m (Pizziolo et al 2014). In early fall 2016, Sassi Neri landslide seemed starting to move again; hence, a monitoring system has been installed in order to study the landslide's displacements and displacement rates and their correlation with rainfall events, pore water pressure and shear wave velocity (Vs) variations. The monitoring system consists of: 1) a CR1000 datalogger (Campbell Scientific), 2) a charge controller STECA SOLSUM 88F, 3) two time lapse cameras (Brinno TLC200 pro), 4) a pore water pressure sensor (buried at a depth of almost 1 meter), 5) a rain gauge and 6) four vertical polarized geophones at 4.5 Hz. The geophones are placed at intervals of 2 m and are acquiring the ambient seismic noise (passive mode) with a sampling frequency of 300 Hz for 2min every hours and all the data are collected in a Flash Memory Drive (SC115). The information about the displacements are collected analyzing the time-lapse video and using the free software Tracker. Preliminary collected data are presented here and their possible correlation is analyzed.

  3. Behaviour of mudflows realized in a laboratory apparatus and relative numerical calibration

    Science.gov (United States)

    Brezzi, Lorenzo; Gabrieli, Fabio; Kaitna, Roland; Cola, Simonetta

    2016-04-01

    Nowadays, numerical simulations are indispensable allies for the researchers to reproduce phenomena such as earth-flows, debris-flows and mudflows. One of the most difficult and problematic phases is about the choice and the calibration of the parameters to be included in the model at the real scale. Surely, it can be useful to start from laboratory experiment that simplify as much as possible the case study with the aim of reducing uncertainties related to the trigger and the propagation of a real flow. In this way, geometry of the problem, identification of the triggering mass, are well known and constrained in the experimental tests as in the numerical simulations and the focus of the study may be moved to the material parameters. This article wants to analyze the behavior of different mixtures of water and kaolin, which flow in a laboratory channel. A 10 dm3 prismatic container that discharges the material into a channel 2m long and 0.16 m wide composes the simple experimental apparatus. The chute base was roughened by glued sand and inclined with a 21° angle. Initially, we evaluated the lengths of run-out, the spread and shape of the deposit for five different mixtures. A huge quantity of information were obtained by 3 laser sensors attached to the channel and by photogrammetry, that gives out a 3D model of the deposit shape at the end of the flow. Subsequently, we reproduced these physical phenomena by using the numerical model Geoflow-SPH (Pastor et al., 2008; 2014) , governed by a Bingham rheological law (O'Brien & Julien, 1988), and we calibrated the different tests by back-analysis to assess optimum parameters. The final goal was the comprehension of the relationship that characterizes the parameters with the variation of the kaolin content in the mixtures.

  4. Comparison of various remote sensing classification methods for landslide detection using ArcGIS

    Science.gov (United States)

    Escape, Carmille Marie; Kristia Alemania, Maneka; Luzon, Paul Kenneth; Felix, Raquel; Salvosa, Sheena; Aquino, Dakila; Narod Eco, Rodrigo; Mahar Francisco Lagmay, Alfredo

    2014-05-01

    landslide areas because of the high contrast of barren soil and earthflows to grass/forest and urban areas. It identified 88% of the previously pinpointed landslides. On the other hand, the manually reclassified NDVI showed a better delineation of the landslide area and detected 82% of the landslides.

  5. Submarine creeping landslide deformation controlled by the presence of gas hydrates: The Tuaheni Landslide Complex, New Zealand

    Science.gov (United States)

    Gross, Felix; Mountjoy, Joshu; Crutchle, Garethy; Koch, Stephanie; Bialas, Jörg; Pecher, Ingo; Woelz, Susi; Dannowski, Anke; Carey, Jon; Micallef, Aaron; Böttner, Christoph; Huhn, Katrin; Krastel, Sebastian

    2016-04-01

    Methane hydrate occurrence is bound to a finite pressure/temperature window on continental slopes, known as the gas hydrate stability zone (GHSZ). Hydrates within sediment pore spaces and fractures are recognized to act like a cement, increasing shear strength and stabilizing slopes. However, recent studies show that over longer strain periods methane hydrates can undergo ductile deformation. This combination of short term strengthening and longer term ductile behavior is implicated in the development of slow creeping submarine landforms within the GHSZ. In order to study this phenomenon, a new high-resolution seismic 3D volume was acquired at the Tuaheni Landslide Complex (TLC) at the Hikurangi margin offshore the North Island of New Zealand. Parts of TLC have been interpreted as a slow moving landslide controlled by the gas hydrate system. Two hypotheses for its slow deformation related to the presence of methane hydrates have been proposed: i) Hydrofracturing, driven by gas pressure at the base of the GHSZ, allows pressurized fluids to ascend toward the seafloor, thereby weakening the shallow debris and promoting failure. ii) The mixture of methane hydrates and sediment results in a rheology that behaves in a ductile way under sustained loading, resulting in slow deformation comparable to that of terrestrial and extra-terrestrial rock glaciers. The 3D dataset reveals the distribution of gas and the extend of gas hydrate stability within the deformed debris, as well as deformation fabrics like tectonic-style faulting and a prominent basal décollement, known to be a critical element of terrestrial earth-flows and rock glaciers. Observations from 3D data indicate that the TLC represents the type example of a new submarine landform - an active creeping submarine landslide - which is influenced by the presence of gas hydrates. The morphology, internal structure and deformation of the landslide are comparable with terrestrial- and extra-terrestrial earth flows and

  6. Repeated remobilisation of submarine landslide debris on an active subduction margin interpreted from multibeam bathymetry and multichannel seismic data

    Science.gov (United States)

    Mountjoy, J. J.; Barnes, P. M.; McKean, J.; Pettinga, J. R.

    2008-12-01

    EM300 multibeam and multichannel seismic data reveal a 230 square kilometre submarine landslide complex which exhibits many of the characteristic features of equivalent terrestrial creeping earthflow complexes. Slope failures are sourced from the shelf edge/upper slope of the Poverty Bay reentrant on the active Hikurangi subduction margin of New Zealand where tectonic deformation, via major thrust faults with slip rates of c. 3-4 mm/yr, exerts a controlling influence on seafloor physiography. Individual landslides within this submarine complex are up to 14 km long over a vertical elevation drop of 700 m. Debris streams are in excess of 2 km wide with a debris thickness of 100 m. While multibeam data is limited to c. 10 m resolution, the scale of submarine landslide features allows us to resolve internal debris detail equivalent to terrestrial landslide examples using terrestrial techniques (e.g. airborne lidar). DEM derivative surface roughness techniques are employed to delineate the geomorphic expression of features including active and abandoned lateral shears, and contractional and extensional deformation of the landslide debris. From these interpretations multiple internal failures are recognised along the length of the landslide debris. Debris deformation is also imaged in high fold multichannel seismic data and correlated to the imaged surface geomorphic features, providing insight into the failure mechanics of the landslides. Failures initiate and evolve within the quasi-stable prograding sediment wedge built onto the upper slope during lowstand sealevels. Landslides within the greater complex are at different stages of development providing information on their spatial and temporal evolution headward and laterally along the transition from shelf to upper slope margin. We infer that failures are triggered and evolve in response to sealevel rise, and/or the frequent occurrence large earthquakes along the margin.

  7. Geodinâmica e perigosidade natural nas ilhas dos Açores

    Directory of Open Access Journals (Sweden)

    António de Brum Ferreira

    2005-12-01

    Full Text Available GEODYNAMICS AND NATURAL HAZARDS IN THE AZORES ISLANDS. The central islands of the Azores archipelago exhibit significant volcanic and seismic activity. The most important tectonic structure responsible for this activity seems to be the leaky transform Terceira Rift, a branch of the Azores triple junction separating the Eurasia and Africa plates. In historical time (since the XV century, the most frequent volcanic eruptions were of the hawaiian and strombolian types, but the level of explosivity has occasionally reached subplinian magnitude, as it happened in the Fogo (1563 and Furnas (1630 volcanoes (hydromagmatic eruptions in the calderas. As in other volcanic regions of the world, effusive volcanism is not particularly dangerous in the Azores islands; explosive activity, however, can be catastrophic (ignimbrites formed in some islands over the last millennia. Still, throughout historical time, earthquakes have been the most dangerous natural phenomena in the Azores, sometimes bringing about tragic consequences: in 1757, an earthquake struck the São Jorge island, killing one thousand people (20% of the total population. But the most catastrophic seismic event of all occurred in the island of São Miguel in 1522: an earthquake triggered an earthflow that submerged the capital (Vila Franca do Campo and killed nearly all of its inhabitants (several thousands. Whether or not they are triggered by earthquakes, mass movements are most common along the coast of the islands: huge falls and rotational slides are attested for by the so-called fajãs, detrital platforms on the foot of cliffs that are several hundred meters high; in death-defying fashion, some of these platforms are actually inhabitated.

  8. Assessing landslide susceptibility, hazards and sediment yield in the Río El Estado watershed, Pico de Orizaba volcano, Mexico

    Science.gov (United States)

    Legorreta Paulin, G.; Bursik, M. I.; Lugo Hubp, J.; Aceves Quesada, J. F.

    2014-12-01

    This work provides an overview of the on-going research project (Grant SEP-CONACYT # 167495) from the Institute of Geography at the National Autonomous University of Mexico (UNAM) that seeks to conduct a multi-temporal landslide inventory, analyze the distribution of landslides, and characterize landforms that are prone to slope instability by using Geographic Information Systems (GIS). The study area is the Río El Estado watershed that covers 5.2 km2 and lies on the southwestern flank of Pico de Orizaba volcano.The watershed was studied by using aerial photographs, fieldwork, and adaptation of the Landslide Hazard Zonation Protocol of the Washington State Department of Natural Resources, USA. 107 gravitational slope failures of six types were recognized: shallow landslides, debris-avalanches, deep-seated landslides, debris flows, earthflows, and rock falls. This analysis divided the watershed into 12 mass-wasting landforms on which gravitational processes occur: inner gorges, headwalls, active scarps of deep-seated landslides, meanders, plains, rockfalls, non-rule-identified inner gorges, non-rule-identified headwalls, non-rule-identified converging hillslopes and three types of hillslopes classified by their gradient: low, moderate, and high. For each landform the landslide area rate and the landslide frequency rate were calculated as well as the overall hazard rating. The slope-stability hazard rating has a range that goes from low to very high. The overall hazard rating for this watershed was very high. The shallow slide type landslide was selected and area and volume of individual landslides were retrieved from the watershed landslide inventory geo-database, to establish an empirical relationship between area and volume that takes the form of a power law. The relationship was used to estimate the total volume of landslides in the study area. The findings are important to understand the long-term evolution of the southwestern flank stream system of Pico de

  9. Geologic map of the Vail West quadrangle, Eagle County, Colorado

    Science.gov (United States)

    Scott, Robert B.; Lidke, David J.; Grunwald, Daniel J.

    2002-01-01

    This new 1:24,000-scale geologic map of the Vail West 7.5' quadrangle, as part of the USGS Western Colorado I-70 Corridor Cooperative Geologic Mapping Project, provides new interpretations of the stratigraphy, structure, and geologic hazards in the area on the southwest flank of the Gore Range. Bedrock strata include Miocene tuffaceous sedimentary rocks, Mesozoic and upper Paleozoic sedimentary rocks, and undivided Early(?) Proterozoic metasedimentary and igneous rocks. Tuffaceous rocks are found in fault-tilted blocks. Only small outliers of the Dakota Sandstone, Morrison Formation, Entrada Sandstone, and Chinle Formation exist above the redbeds of the Permian-Pennsylvanian Maroon Formation and Pennsylvanian Minturn Formation, which were derived during erosion of the Ancestral Front Range east of the Gore fault zone. In the southwestern area of the map, the proximal Minturn facies change to distal Eagle Valley Formation and the Eagle Valley Evaporite basin facies. The Jacque Mountain Limestone Member, previously defined as the top of the Minturn Formation, cannot be traced to the facies change to the southwest. Abundant surficial deposits include Pinedale and Bull Lake Tills, periglacial deposits, earth-flow deposits, common diamicton deposits, common Quaternary landslide deposits, and an extensive, possibly late Pliocene landslide deposit. Landscaping has so extensively modified the land surface in the town of Vail that a modified land-surface unit was created to represent the surface unit. Laramide movement renewed activity along the Gore fault zone, producing a series of northwest-trending open anticlines and synclines in Paleozoic and Mesozoic strata, parallel to the trend of the fault zone. Tertiary down-to-the-northeast normal faults are evident and are parallel to similar faults in both the Gore Range and the Blue River valley to the northeast; presumably these are related to extensional deformation that occurred during formation of the northern end of the

  10. UAV-based landslide deformation monitoring - first results from Corvara landslide

    Science.gov (United States)

    Thiebes, Benni; Tomelleri, Enrico; Mejia-Aguilar, Abraham; Schlögel, Romy; Darvishi, Mehdi; Remondino, Fabio; Toschi, Isabella; Rutzinger, Martin; Zieher, Thomas

    2016-04-01

    In recent years, unmanned aerial vehicles (UAVs) have been more frequently utilised to study geomorphological and natural hazard processes, including gravitational mass movements such as landslides. UAVs can be equipped with different sensors, e.g. photo cameras and laser scanners, and the data that can be achieved can substantially improve the monitoring and understanding of the involved natural processes. One of the main advantages of UAVs is their flexibility that allows for carrying out assessments of large areas in short periods of time and at much lower costs than other platforms, e.g. airplanes or helicopters. Thereby, UAVs represent an interesting technique to complement more traditional monitoring methods. Here we present some first results of the EUREGIO-funded LEMONADE project that is concerned with the combination and integration of novel and traditional landslide monitoring techniques. We carried out a series of UAV flights over a particularly active part of the Corvara landslide and acquired aerial imagery for quantitative assessments of the retrogressive enlargement of the landslide over recent years. Additional field surveys including terrestrial laser scanning, and UAV-based photogrammetry and laser scanning are scheduled for summer 2016. The Corvara landslide is a large complex earthflow in the Italian Dolomites that has been investigated by a wide range of methodologies over the past years. The landslide is characterised by movement patterns of greatly varying magnitude, ranging from annual rates of a few cm to more than 20 m. The current and past monitoring activities concentrated on GPS measurements as well as multi-temporal differential radar interferometry utilising artificial corner reflectors. Thereby, primarily punctual displacement data were achieved and spatial information on topographic and geomorphic changes were consequently sparse. For our photogrammetry study, we utilised a SoLeon octocopter equipped with a Ricoh GR 16.2 Megapixels

  11. Surficial Geologic Map of Mesa Verde National Park, Montezuma County, Colorado

    Science.gov (United States)

    Carrara, Paul E.

    2012-01-01

    Mesa Verde National Park in southwestern Colorado was established in 1906 to preserve and protect the artifacts and dwelling sites, including the famous cliff dwellings, of the Ancestral Puebloan people who lived in the area from about A.D. 550 to A.D. 1300. In 1978, the United Nations designated the park as a World Heritage Site. The geology of the park played a key role in the lives of these ancient people. For example, the numerous (approximately 600) cliff dwellings are closely associated with the Cliff House Sandstone of Late Cretaceous age, which weathers to form deep alcoves. In addition, the ancient people farmed the thick, red loess (wind-blown dust) deposits on the mesa tops, which because of its particle size distribution has good moisture retention properties. The soil in this loess cover and the seasonal rains allowed these people to grow their crops (corn, beans, and squash) on the broad mesa tops. Today, geology is still an important concern in the Mesa Verde area because the landscape is susceptible to various forms of mass movement (landslides, debris flows, rockfalls), swelling soils, and flash floods that affect the park's archeological sites and its infrastructure (roads, septic systems, utilities, and building sites). The map, which encompasses an area of about 100 mi2 (260 km2), includes all of Mesa Verde National Park, a small part of the Ute Mountain Indian Reservation that borders the park on its southern and western sides, and some Bureau of Land Management and privately owned land to the north and east. Surficial deposits depicted on the map include: artificial fills, alluvium of small ephemeral streams, alluvium deposited by the Mancos River, residual gravel on high mesas, a combination of alluvial and colluvial deposits, fan deposits, colluvial deposits derived from the Menefee Formation, colluvial deposits derived from the Mancos Shale, rockfall deposits, debris flow deposits, earthflow deposits, translational and rotational landslide

  12. Progressive Landslides in Uplifted Volcanic Plateaus: Persistent Loci of Channel Perturbation

    Science.gov (United States)

    Safran, E. B.; Anderson, S. W.; Mills-Novoa, M.; Othus, S.; Ely, L.; House, P. K.; O'Connor, J. E.; Grant, G.; Fenton, C.; Beebee, R. A.

    2007-12-01

    The semi-arid uplifted volcanic plateaus of the southern interior Columbia River basin contain over 300 large landslides or landslide complexes, ranging in area from several tenths of a km2 to several tens of km2. The distribution of these landslides is dominated by the outcropping of key stratigraphic contacts between coherent, volcanic cap rock atop weak sedimentary or volcaniclastic units in areas of >100 m local relief. The morphologies of many of these landslide complexes suggest a progressive mode of mass movement, with rubble-capped failure slices arrayed downslope at intervals of 10s to 100s of meters and deep tension cracks separating incipient failure blocks from the intact headscarp. Field evidence from the Owyhee River in southeastern Oregon indicates that individual landslide complexes can persist for millions of years. In one reach, for example, remnants of a 1.9 million year old intracanyon lava flow are inset against ancient landslide blocks. In the same location, cosmogenic isotope dating of boulders on a likely dam-burst flood deposit reveal a channel-blocking mass movement that may be as young as Holocene in age. The persistence of these landslide complexes has important implications for channel evolution, as it suggests that, in some environments, sediment supply may be chronically elevated at point sources. On the basis of GIS-based mapping of regional landslides and on field study of individual landslide complexes, we hypothesize that: 1) this sediment supply becomes increasingly dominated by fine-grained material as channels progressively incise into the weak units underlying coherent lava caps; and 2) the mass movements that impinge on the channels become correspondingly more earthflow-like. Loci of persistent landsliding are also subject to episodic variations in channel width due to physical constrictions caused by impinging failure masses. The discrete localization of large landslide complexes by particular stratigraphic and topographic

  13. A methodological approach to comparing pros and cons of delocalizing villages: socio-economic and technical issues

    Science.gov (United States)

    Guadagno, Eleonora; Iovine, Giulio G. R.; Petrucci, Olga; Forciniti, Pinuccia R.

    2014-05-01

    On 7th March 2005, prolonged rainfalls combined with snowfalls activated a wide complex rock slide-earth flow that partly destroyed the village of Cavallerizzo at Cerzeto (Calabria, Southern Italy). Superposed tectonic units made of Palaeozoic metamorphic rocks, overlain by Miocene-Quaternary clastic terrains, crop out in the study area. The main scarp of the landslide developed by a recent normal fault, striking N-S along the western margin of the Crati graben and extended ca. 25 km. In its lower part, the phenomenon evolved in two main earth-flow bodies that extended along minor drainages and then merged along the S. Nicola torrent. The sector affected by the instability actually belongs to a large-scale slope movement: the 2005 activation was in fact only a paroxysmal episode of a long history of slope deformations, noticed in the area since the XVIII century. Warning signs had been recorded for weeks before the collapse, and the threatened area had been put under monitoring by CNR-IRPI. When the movement accelerated, people had already been alerted and evacuated (329 out of 581 inhabitants of Cerzeto were sheltered in nearby villages), thus neither victims nor injured were recorded. As a whole, 124 buildings were severely damaged or destroyed, the main road was interrupted. Immediately after the 7th March 2005 event, the national Department for Civil Protection decided to evaluate the feasibility of delocalizing Cavallerizzo to another site. At this purpose, CNR-IRPI was asked to analysing the "geological suitability" of 3 different sites (Pianette, Amatine, and Colombra), pre-selected by the same Municipality of Cerzeto in accordance to the Civil Protection; the results of the study were completed in early Summer 2005. Between October 2007 and December 2011, a new settlement was realized by the Italian Government, and the houses were delivered to people once living at Cavallerizzo. In the last years, the socio-economic effects of the delocalization of

  14. Geoelectric monitoring of the Bagnaschino landslide (Italy)

    Science.gov (United States)

    Jochum, Birgit; Supper, Robert; Ottowitz, David; Pfeiler, Stefan; Kim, Jung-Ho; Lovisolo, Mario

    2013-04-01

    Landslides are one of the major natural threats to human lives, settlements and infrastructure. Permanent geoelectrical monitoring using the GEOMON4D instrumentation in combination with high resolution displacement monitoring by means of the DMS system was performed at an active landslide area in Italy (Bagnaschino). These sites are part of a geoelectrical monitoring network of the Geological Survey of Austria, which currently comprises six permanently monitored landslides in Europe. The Bagnaschino site represents a landslide/earthflow reactivated within an old landslide mass. The old landslide is situated on the slopes of the Val Casotto about 4 km SE of Torre Mondovì (NW Italy). Evident indications of deep-seated gravitational deformation suggest that the current slopes are in a condition of limit-equilibrium and are predisposed to slow instability, triggered most probably by rain and/or snow melting and river erosion at the foot. The recent landslide was activated during 1994 rainfall event. It covers an estimated area of 150,000 m² and comprises a displaced material of 1.2 million m³. It endangers a regional road and potential formation of a dam. For the purpose of early warning a DMS monitoring column with 60 m length was installed in October 2008. Total displacement recorded by DMS during the events between 2008 and 2010 was 600 mm. Subsequently, the GEOMON4D geoelectric monitoring system was installed there in 2010. Resistivity measurements are performed along a 224 m long profile, which is oriented parallel to the main movement direction. Its midpoint is next to the DMS station. One set of data comprising around 4000 gradient-type measurements is taken every 4 hours. For power supply a combination of a fuel cell and a solar panel is used. Within the observation interval one distinct displacement event was monitored. This event was accompanied by a decrease of electric resistivity. In addition to our standard analysis of resistivity data (e.g. time

  15. La extensa zona de deslizamientos de la escarpa oriental de la Pampa de Salamanca, Chubut, entre los 45°00´S y 45°45´S The extensive zone of slides on the eastern erosion scarp of Pampa de Salamanca, Chubut

    Directory of Open Access Journals (Sweden)

    E.F. González Díaz

    2004-12-01

    Full Text Available Durante la ejecución del mapa geomorfológico de la provincia del Chubut, se identificó entre las latitudes de los 45°00´S y 45°45´S y a lo largo de unos 70-75 km, una extensa faja de deslizamientos adyacente y prácticamente paralela a la escarpa oriental de la Pampa de Salamanca. Los deslizamientos, con marcado predominio de deslizamientos rotacionales, perturban el tramo superior de la secuencia sedimentaria terciaria. En los niveles arcillosos de la Formación Chenque (= Formación Patagonia, se localizarían las superficies de despegue o corte (shear para su ocurrencia. Diferencias entre sus rasgos morfológicos, tipológicos y el promotor sugerido permiten proponer cuatro zonas (I, II, III y IV de deslizamientos. La tipología aquí propuesta es provisoria, siendo sólo una base de futuras elaboraciones. Cronológicamente se diferenciaron dos conjuntos de deslizamientos: unos antiguos, más extensos y de mayor volumen, con marcadas evidencias de erosión y aquellos modernos, más reducidos, que con excelente conservación de su morfología primaria, son producto de posteriores removilizaciones acontecidas en sectores de los antiguos, que se expresan esencialmente bajo la forma de flujos (corrientes de tierra o earthflows y más ocasionalmente como deslizamientos rotacionales secundarios (slumps. Entre los de mayor edad, los de la zona I, son definidos como afines en general a un deslizamiento rotacional con una fase distal de flujo; ocasionalmente habrían superado los límites del actual acantilado marino. A pesar de esta primera apreciación, no se descarta su consideración como ejemplos de expansiones laterales (lateral spreads. Los de la zona II, son definidos como deslizamientos rotacionales múltiples retrogradantes. Aquellos de la zona III integran un conjunto de deslizamientos con un marcado control estructural (N50°E, en sus desprendimientos. La zona IV, compone una estrecha y continua faja adyacente a la Pampa de

  16. Rainfall and Seasonal Movement of the Weeks Creek Landslide, San Mateo County, California

    Science.gov (United States)

    Wieczorek, Gerald F.; Reid, Mark E.; Jodicke, Walter; Pearson, Chris; Wilcox, Grant

    2007-01-01

    Introduction Many different types of landslide occur in the Santa Cruz Mountains of San Mateo County, Calif. (Brabb and Pampeyan, 1972); most slope movement is triggered by strong earthquakes, heavy rainfall, or shoreline erosion. In this area, shallow landslides of loose soil and rock, which may transform into debris flows, commonly occur during individual storms when rainfall exceeds a threshold of intensity and duration (Cannon and Ellen, 1985; Wieczorek and Sarmiento, 1988; Wilson and Wieczorek, 1995). In contrast, deeper rotational and translational slides (Varnes, 1978) typically begin to move only after days to weeks or months of heavy rain. Once started, they can continue to move for months during and after a heavy rainfall season, for example, the Scenic Drive landslide at La Honda, Calif. (Jayko and others, 1998; Wells and others, 2005, 2006). Although the rainfall characteristics triggering rapid, shallow landslides have been documented (Wieczorek, 1987; Cannon and Ellen, 1988), the rainfall conditions leading to repeated deeper-seated slope movements are less well known. The Weeks Creek landslide (Adam, 1975), near the western crest of the Santa Cruz Mountains north of La Honda in San Mateo County (fig. 1), consists of a large prehistoric section containing a historically active section; both sections have earthflow morphologies. The entire landslide mass, which extends about 1,000 m westward from an elevation of 220 m down to an elevation of 120 m, is about 300 to 370 m wide (Cole and others, 1994); The prehistoric section of the landslide is about 30 m deep and approximately 10 million m3 in volume (Cole and others, 1994). The smaller, historically active portion of the Weeks Creek landslide (fig. 1) is only approximately 500 m long, 200 m wide, and 13 m deep (Cole and others, 1994). Near the landslide, the Santa Cruz Mountains consist of tightly folded, Tertiary sedimentary bedrock materials of the Butano sandstone and San Lorenzo Formations (Eocene

  17. Monitoring the Lavina di Roncovetro (RE, Italy) landslide by integrating traditional monitoring systems and multiple high-resolution topographic datasets

    Science.gov (United States)

    Fornaciai, Alessandro; Favalli, Massimiliano; Gigli, Giovanni; Nannipieri, Luca; Mucchi, Lorenzo; Intieri, Emanuele; Agostini, Andrea; Pizziolo, Marco; Bertolini, Giovanni; Trippi, Federico; Casagli, Nicola; Schina, Rosa; Carnevale, Ennio

    2016-04-01

    Tha Lavina di Roncovetro landslide is located in the Enza Valley (Reggio Emilia, Italy). It extends from the top of Mount Staffola down to the Tassobbio River. Since the clay fraction is dominant, it follows that the landslide can be considered as a fluid-viscous mudflow, which can reach a down flow maximum rate of 10 m/day. The landslide started between the middle and the end of the XIX century and since then it has had a rapid evolution mainly characterized by the rapid retrogression of the crown to the extent that now reaches the top of Mount Staffola. In the last 20 years, about 100,000 m3 of bedrock descended from the main scarp into the landslide body. The total volume of the landslide is inferred to be of ~ 3×106 m3. In the frame of EU Wireless Sensor Network for Ground Instability Monitoring - Wi-GIM project (LIFE12 ENV/IT/001033), the Roncovetro landslide is periodically monitored by traditional monitoring systems and Unmanned Aerial Vehicle (UAV) survey. In addition, an airborne LIDAR survey and a photographic acquisition from a small aircraft were carried out on April 2014 and October 2014, respectively. The traditional monitoring system consists of a terrestrial laser scanning (TLS) survey and a robotized total station (RTS). TLS acquisitions have focused on the upper and more active sector of the earthflow and were carried out since May 2014. By comparing TLS data taken at different times, the general deformational field of the landslide can be reconstructed and the displacements affecting the retaining structures built on the landslide crown quantified. The time resolution of both TLS and RTS acquisition is about 6 per year. . Three high-resolution photogrammetric surveys performed using an UAV were carried out on November 2014, July 2015 and January 2016. Starting from the acquired photos and applying photogrammetry and Structure From Motion (SFM) algorithms integrated in the Photoscan Agisoft software, the high-resolution 3D models of the

  18. La extensa zona de deslizamientos de la escarpa oriental de la Pampa de Salamanca, Chubut, entre los 45°00´S y 45°45´S

    Directory of Open Access Journals (Sweden)

    E.F. González Díaz

    2004-12-01

    Full Text Available Durante la ejecución del mapa geomorfológico de la provincia del Chubut, se identificó entre las latitudes de los 45°00´S y 45°45´S y a lo largo de unos 70-75 km, una extensa faja de deslizamientos adyacente y prácticamente paralela a la escarpa oriental de la Pampa de Salamanca. Los deslizamientos, con marcado predominio de deslizamientos rotacionales, perturban el tramo superior de la secuencia sedimentaria terciaria. En los niveles arcillosos de la Formación Chenque (= Formación Patagonia, se localizarían las superficies de despegue o corte (shear para su ocurrencia. Diferencias entre sus rasgos morfológicos, tipológicos y el promotor sugerido permiten proponer cuatro zonas (I, II, III y IV de deslizamientos. La tipología aquí propuesta es provisoria, siendo sólo una base de futuras elaboraciones. Cronológicamente se diferenciaron dos conjuntos de deslizamientos: unos antiguos, más extensos y de mayor volumen, con marcadas evidencias de erosión y aquellos modernos, más reducidos, que con excelente conservación de su morfología primaria, son producto de posteriores removilizaciones acontecidas en sectores de los antiguos, que se expresan esencialmente bajo la forma de flujos (corrientes de tierra o earthflows y más ocasionalmente como deslizamientos rotacionales secundarios (slumps. Entre los de mayor edad, los de la zona I, son definidos como afines en general a un deslizamiento rotacional con una fase distal de flujo; ocasionalmente habrían superado los límites del actual acantilado marino. A pesar de esta primera apreciación, no se descarta su consideración como ejemplos de expansiones laterales (lateral spreads. Los de la zona II, son definidos como deslizamientos rotacionales múltiples retrogradantes. Aquellos de la zona III integran un conjunto de deslizamientos con un marcado control estructural (N50°E, en sus desprendimientos. La zona IV, compone una estrecha y continua faja adyacente a la Pampa de

  19. 3D landslide motion from a UAV-derived time-series of morphological attributes

    Science.gov (United States)

    Valasia Peppa, Maria; Mills, Jon Philip; Moore, Philip; Miller, Pauline; Chambers, Jon

    2017-04-01

    Landslides are recognised as dynamic and significantly hazardous phenomena. Time-series observations can improve the understanding of a landslide's complex behaviour and aid assessment of its geometry and kinematics. Conventional quantification of landslide motion involves the installation of survey markers into the ground at discrete locations and periodic observations over time. However, such surveying is labour intensive, provides limited spatial resolution, is occasionally hazardous for steep terrain, or even impossible for inaccessible mountainous areas. The emergence of mini unmanned aerial vehicles (UAVs) equipped with off-the-shelf compact cameras, alongside the structure-from-motion (SfM) photogrammetric pipeline and modern pixel-based matching approaches, has expedited the automatic generation of high resolution digital elevation models (DEMs). Moreover, cross-correlation functions applied to finely co-registered consecutive orthomosaics and/or DEMs have been widely used to determine the displacement of moving features in an automated way, resulting in high spatial resolution motion vectors. This research focuses on estimating the 3D displacement field of an active slow moving earth-slide earth-flow landslide located in Lias mudrocks of North Yorkshire, UK, with the ultimate aim of assessing landslide deformation patterns. The landslide extends approximately 290 m E-W and 230 m N-S, with an average slope of 12˚ and 50 m elevation difference from N-S. Cross-correlation functions were applied to an eighteen-month duration, UAV-derived, time-series of morphological attributes in order to determine motion vectors for subsequent landslide analysis. A self-calibrating bundle adjustment was firstly incorporated into the SfM pipeline and utilised to process imagery acquired using a Panasonic Lumix DMC-LX5 compact camera from a mini fixed-wing Quest 300 UAV, with 2 m wingspan and maximum 5 kg payload. Data from six field campaigns were used to generate a DEM time

  20. Integrated landslide monitoring: rainfalls, pore water pressures and surface movements

    Science.gov (United States)

    Berti, M.; Casula, G.; Elmi, C.; Fabris, M.; Ghirotti, M.; Loddo, F.; Mora, P.; Pesci, A.; Simoni, A.

    2003-04-01

    Rainfall-induced landslides involving clay-rich soils are widely represented in the Apennines. They cover up to 30% of the slopes forming the relief constituted by chaotic clayey units and are typically subject to repeated reactivations of the movement which are often triggered by a series of discrete failures located in the upper part (headscarp). Failures and movement can then propagate downslope and reactivate the whole landslide deposit which displays a typical elongated body, limited depth and a fan-shaped toe as a result of successive slow earth-flow like movements. An experimental monitoring programme was designed and is currently operating on the Rocca Pitigliana landslide whose characteristics well represent the above described type of movements. Its last parossistic movement date back to 1999 and, since then, remedial works were realized on behalf of local authorities. They basically consist of surficial and deep drainage works located on the landslide body. Experimental activities focus on the main headscarp whose morphology and sub-surface water circulation scheme were unaffected by the interventions. The monitoring approach includes measuring rainfalls and pore-pressure responses in both saturated and unsaturated soils. Surficial movements are continuously measured by means of GPS permanent stations and by wire extensometers which allow real time control of headscarp activity. Main aim of the monitoring activities is to provide experimental data, which can be used to test various existing hydrologic models and to identify triggering conditions. Since the ‘70s, many hydrologic models have been proposed to describe the pore water pressure distribution within the soil and its response to precipitation. The topic has recently drawn growing attention because of the recognized importance in landslide triggering but still experimental data are very much needed in order to obtain and validate capable predicting tools. This is mostly due to the multiple and

  1. Geoelectrical monitoring of landslides: results from the sites of Laakirchen (Austria) and Rosano (Italy)

    Science.gov (United States)

    Guardiani, Carlotta; Amabile, Anna Sara; Jochum, Birgit; Ottowitz, David; Supper, Robert

    2017-04-01

    One of the main precursors for landslide activation/reactivation is intense and prolonged precipitation, with consequent pore water pressure rise due to infiltration of rainfall that seeps into the ground. Monitoring hydrological parameters such as precipitation, water content and pore pressure, in combination with displacement analysis for early warning purposes, is necessary to understand the triggering processes. Since the reduction over time of electrical resistivity corresponds to an increase of water content, electrical resistivity monitoring can help to interpret the modifications of slope saturation conditions after heavy rainfalls. In this study, we present the results of the ERT monitoring data from two landslide areas, Laakirchen (47.961692N, 13.809897E) and Rosano (44.662453N, 9.104703E). During March 2010, a shallow rotational landslide was triggered by snow melting and intense rainfall in Laakirchen, in the vicinity of a newly constructed house. Laakirchen landslide was monitored by geophysical/geotechnical measurements from September 2011 to June 2013. In December 2004, Rosano landslide reactivation affected rural buildings: slope deformations caused mainly damages to properties, infrastructures and lifelines. Rosano landslide has been defined as a composite landslide, with a general dynamic behavior that can be regarded as a slow earthflow. The installation of the monitoring system took place in July 2012 and the data acquisition lasted until April 2015. These sites are part of the geoelectrical monitoring network set up by the Geological Survey of Austria for testing the self-developed GEOMON4D geoelectrical system, in combination with complementary geotechnical monitoring sensors (rain gauge, automatic inclinometer, water pressure and water content sensors) to support the interpretation of the electrical response of the near surface (R. Supper et al., 2014). The measurements were funded by the TEMPEL project (Austrian Science Fund, TRP 175-N21

  2. Consideration notes on the critical rainfall threshold to predict the triggering of pyroclastic flows

    Science.gov (United States)

    Scotto di Santolo, A.

    2009-04-01

    This paper reports the results of a theoretical analysis carried out designed to evaluate meteoric events that can be defined as critical since they are capable of triggering landslides in partially saturated pyroclastic soils. The study refers to analyses of the pyroclastic covers in the area of Campania, Italy, which is often affected by complex phenomena that begin as rotational or translational slide or fall and evolve into rapid landslides as earth-flows (debris or mud as function of grain size distributions). The prediction of triggering factors is of extreme importance for the implementation of civic protection schemes, given the dynamic features that characterize these phenomena during their evolution. The study highlights the fact that it is impossible to define the criticality of a meteoric event by means of empiric laws that correlate the mean intensity of rainfall and the "mean" duration of the event. However, it is possible to identify the criticality of a meteoric event in partially saturated soils, by means of a more complex approach which is physically conditioned. The rainfall is critical if it is capable of causing the rainwater to filter into the subsoil into "weak" layers where there is an increase in the specific volume with a significant reduction of the suction and resistance to the shear of the terrain (Fredlund et al., 78). This study focuses exclusively on seepage, regardless of the resistance of the soil, by analyzing, among various aspects, the phenomenon using a simplified subsoil model. For this study, it is assumed that the rainfall is critical when it is capable of saturating the soil cover for a predefined summit thickness Zc. For the purposes of this study, value Zc could be given an arbitrary value. This has been assumed to be 1m, considering that the experimental evidence has shown that rapid flows, at least when triggered, prove to be superficial. The other hypotheses are: • 1D infiltration, • Rigid solid skeleton;

  3. The Influence of the Deep Critical Zone under Hillslopes on Hydrologic, Geomorphic, and Ecological Processes

    Science.gov (United States)

    Dietrich, W.; Rempe, D. M.; Oshun, J.

    2012-12-01

    events, local pore pressures in the fractured bedrock differ greatly across the landscape. Our current research site in Northern California is developed primarily on argillite under a mixed canopy of mature evergreen forest. The critical zone systematically thickens toward the divide, and despite erosion rates of 0.2 to 0.4 mm/yr, the depth to fresh bedrock at the hilltop exceeds 20 m. No overland flow or lateral flow through the soil occurs; instead all runoff is from groundwater perched on the very low permeability fresh bedrock at the base on the critical zone. Twelve wells record the spatial pattern of this perched water table, and reveal widely varying response to storm inputs. The groundwater runoff sustains ecologically significant low flow during the nearly 6 months of no precipitation in adjacent creeks. The forest, despite being within meters of the perched groundwater, does not rely as the primary source of water, even at the end of summer. Instead, rock moisture in the unsaturated part of the critical zone is exploited by trees. Rare storms may cause the perched water table to reach the soil and destabilize it, while the transition from weathered to fresh bedrock at the base of the critical zone may eventually define the plane of failure for deep-seated earthflows which are common in the area.

  4. Progress and challenges in the understanding of long term evolution of deep-seated gravitational slope deformations

    Science.gov (United States)

    Pánek, Tomáš

    2017-04-01

    Deep-seated gravitational slope deformations (DSGSDs; Agliardi et al., 2001) is a generic term for slow moving (mm year-1) rock-mass movements that encompass the entire mountain slopes or valley flanks occurring in a wide spectrum of terrestrial and extraterrestrial settings (Mège and Bourgeois, 2011). Current progress in mapping technologies, geophysics, modelling and monitoring has provided valuable insights into the distribution, internal structure, mechanics and recent movements of DSGSDs. However, amidst all this progress, long-term (≥102 years) temporal dynamics remains one of the least explored aspects of DSGSDs (Pánek and Klimeš, 2016). Based on both the in-depth review of published studies from all around the world and several detailed geochronological investigations in the Carpathians, the Crimean peninsula and the Taurus Mts, this paper accents recent progress in the understanding of the lifespan, long-term rates and potential catastrophic accelerations of DSGSDs. Major concern is paid to the differences between glaciated and non-glaciated mountain landscapes. Outcomes of this review can be summarized as follows: (i) DSGSDs occurring outside the limits of Quaternary glaciations reveal more complex and generally longer lifespans. (ii) Despite traditional views, the dating results show that immediate chronological response of DSGSDs to glacier withdrawal is rather rare. On the contrary, there tends to be a significant (millennial) time-lag due to a complex interaction of paraglacial processes. (iii) Some DSGSDs (or their parts) may originate episodically and relatively fast, which is in contradiction to traditional definitions. (iv) Recurrent catastrophic collapses of slopes (e.g. rock avalanches, rockfalls, earthflows) are frequently sourced within DSGSDs bodies, irrespective of whether localized within glaciated or non-glaciated areas. Although a boom in geochronological methods has significantly improved our knowledge of the temporal dynamics of