H43E-1663
Estimation Of Landslide Processes And Slope Evolution From LiDAR-Derived DEMs
LiDAR-derived DEMs are making an increasing contribution towards landslide hazard mitigation owing to their increasing availability. They not only produce detailed contour maps and visualized images to create more accurate and complete landslide inventories, but also can be analyzed to understand the surface process of landslides with the notion that their activity relates to fine-scale surface roughness. At present, surface fabric filtering of these DEMs has been used to examine individual landslides, although landslide processes can be better understood when they are considered as a part of hillslope evolution of the area of interest. This presentation introduces the work that the eigenvalue ratio, which represents the 3-dimensional surface roughness, can be used to analyze landslide processes and their influence on hillslope evolution. A case study is presented from a 5 km2 steep (average slope = 36 %) area of Kii Peninsula, Japan, where a 1-m grid LiDAR-derived DEM was used to derive eigenvalue ratios and related terrain attributes. The slopes of the v- shaped valleys are particularly landslide-prone and there is little valley margin except for occasional terraces along the river. Based on a combination of the eigenvalue ratio and field survey, the slopes of the study area were categorized into 4 principal types. Slopes with a filter value of less than 2.50 (roughest) are bedrock-dominant, while those between 2.50 and 2.75 partly represent surface collapses and loosened bedrock, and those between 2.75 and 3.00 are colluvial slopes with large rock materials. Where the value exceeds 3.00 the slopes are inactive or covered with fine colluvial materials. The results imply that more attention should be paid to landslide blocks with a filter value of between 2.50 and 2.75, e.g. by continuous monitoring, as they are at higher risk of entire slope collapse in the near future. The eigenvalue ratio tends to increase and the terrain becomes smoother uphill, indicating that slopes evolve by losing stability from the valley floor. The blocks with a value between 2.75 and 3.00 may in future gain similar slope features to those with a value between 2.50 and 2.75, although how long this transition takes is uncertain. The process has probably been driven by the river eroding the base of hillslopes and striping away earth at high flows. The results suggest that, not only can the current activity of landslides be evaluated, but also their future behavior can be estimated by applying surface fabric filters to an area of interest and considering their spatial distribution. Together with creating detailed landslide inventories, utilizing LiDAR-derived DEMs in this manner will in future contribute to the planning of landslide hazard mitigation programs.
H43E-1664
Predicting The Time And Location For Shallow Landslide Occurrence In Northern Taiwan
The topographic, geological and hydrologic conditions of Taiwan usually induce landslide and debris flow during heavy rainstorms. Poor geological conditions induce a high potential to cause hillslope disasters, and severe rainstorms often trigger slope collapses. The objective of this study is to link a slope-instability analytical procedure to a watershed runoff model for landslide prediction during heavy rainfall periods. The analytical result can provide location and time for shallow landslide occurrences to authorities for disaster warning and evacuation. In this study, hydrologic records and geological information from the Da-Tsu-Keng watershed and Chon-Ho watershed in Taipei County were collected for analysis. By using the hourly rainfall data, the varying of the water table on the hillslope was simulated using a hydrological model, and the temporal water level was then used in the slope instability analysis to predict instability grids within the study areas. The results show that more than 50% area of the study subwatershed was considered having potential for landslide occurrence during a severe typhoon in November 2000. The predicted landslide region and occurrence time matched well with the field investigation data. It is therefore considered promising to apply the proposed analytical procedure for real- time landslide warning to alleviate the loss of lives and property.
H43E-1665
Analysis of the effects of geological and geomorphological factors on earthquake triggered landslides using artificial neural networks (ANN)
The occurrence of landslide is the result of the interaction of complex and diverse environmental factors. The geomorphic and geologic features, rock types and vegetative cover are important base factors of landslide occurrence. However, determining the relationship between these factors and landslide occurrence is very difficult using conventional mathematical analysis. The use of an advanced computing technique for this kind of analysis is very important. Artificial neural network (ANN) has recently been included in the list of analytical tools for a wide range of applications in the natural sciences research fields. One of the advantages of using ANN for pattern recognition is that it can handle data at any measurement scale ranging from nominal, ordinal to linear and ratio, and any form of data distribution (Wang et al., 1995). In addition, it can easily handle qualitative variables making it widely used in integrated analysis of spatial data from multiple sources for predicting and classification. This study focuses on the definition of the relationship between geological factors and landslide occurrence using artificial neural networks. The study also focuses on the effect of the DTMs (e.g. ASTER DTM, ALSM, digitized from paper map and digital photogrammetric measurement data). The main aim of the study is to generate landslide susceptibility index map using the defined relationship using ANN. Landslide data in the Chuetsu region were used in this research. The 2004 earthquake triggered many landslides in the region. The initial results of the study showed that ANN is more accurate in defining the relationship between geological and geomorphological factors and landslide occurrence. It also determined the best combination of geological and geomorphological factors that is directly related to landslide occurrence.
H43E-1666
Can Anything be Done to Improve the Geomorphological Value of off-the-Shelf DEM Products?
Elevation models are a fundamental requirement for distributed, process-based modelling in hydrology and geomorphology. The increased accessibility of high resolution elevation data makes them an easily accessible and potentially powerful tool in many studies. However, the quality of these data are closely linked to the processes used to derive them. These processes are rarely explicit and can be difficult to untangle. The associated errors often propagate into geomorphic variables in a highly non-linear fashion. This study examines the processes of DEM generation, the associated error and its effect on geomorphic variables in relation to modelling shallow landslide processes. Using data collected from digital photogrammetry and Airborne Interferometric Synthetic Aperture Radar (IfSAR), we show that for the same raw data, processing techniques can alter vertical precision in the elevation model by an order of magnitude. We calculate the hydrogeomorphic variables: slope, contributing area, topographic index and probability of slope instability from DEMs with different error properties to demonstrate the resulting variablilty. Based on these results we make a series of recommendations for minimising uncertainty in the DEM generation process with specific reference to airborne IfSAR and digital photogrammetry.
H43E-1667
Investigating Spatial Interpolation of Light Detection and Ranging Data for Analyzing Fluvial Geomorphic Properties of Streams
Streams are intricate components of the landscape system that vary across temporal and spatial scales while transporting and storing water, sediment, energy, nutrients as well as aquatic and terrestrial species from one part of the system to another. Such changes have traditionally been captured with extensive expert assessment and/or remote sensing analysis (i.e. photo interpretation). In collaboration with the Vermont Agency of Natural Resources River Management Program, this study aims to enhance the capabilities of traditional remote sensing studies by incorporating Light Detection and Ranging (LiDAR) data in the geomorphic assessment of fluvial channels to quantify stream adjustment properties and gain insight into a stream's state of dynamic equilibrium with greater accuracy than traditional methods. A series of 18 digital elevation models (DEM) were generated using three interpolation methods (inverse distance weighting (IDW), natural neighbor (NN), and ordinary kriging), varying raster grid cell sizes (1, 2 and 3m) and different amounts of LiDAR data (bare earth data alone and bare earth with additional reflective data that reduce the mean point spacing) and compared with survey data (n = 689) to determine the optimal interpolation parameters for an agricultural study area, a portion of Allen Brook watershed in northern Vermont. Through analytical comparison, 1m IDW with the additional reflective data was the optimal method for minimizing error metrics but 1m NN (with additional reflective data) was best for retaining maximum elevation range, computational simplicity, and identifying small stream channels.
H43E-1668
Characterising the Geomorphology of Forested Floodplains Using High Resolution Terrestrial Laser Scanning
Forested floodplain environments represent the undisturbed land cover of most temperate and tropical river systems, but they are under threat from human resource management (Hughes et al., 2005, FLOBAR II Project report). A scientific understanding of forest floodplain processes therefore has relevance to ecosystem conservation and restoration, and the interpretation of pre-historic river and floodplain evolution. Empirical research has highlighted how overbank flows are relatively shallow and strongly modified by floodplain topography and the presence of vegetation and organic debris on the woodland floor [Jeffries et al., 2003, Geomorphology, 51, 61-80; Millington and Sear, 2007, Earth. Surf. Proc. Landforms, 32, doi: 10.1002/esp.1552]. In such instances flow blockage and diversions are common, and there is the possibility of frequent switches from sub-critical to locally super-critical flow. Such conditions also favour turbulence generation, both by wakes and by shear. Consequently, the floodplain terrain (where we take ‘terrain' to include the underlying topography, root structures, and organic debris) plays a key role in modulating the processes of erosion and sedimentation that underpin the physical habitat diversity and hydraulic characteristics of complex wooded floodplain surfaces. However, despite the importance of these issues, as yet there are no formal, quantitative, descriptions of the highly complex and spatially diverse micro- and meso-topography that appears to be characteristic of forested floodplain surfaces. To address this gap, we have undertaken detailed surveys on a small floodplain reach within the Highland Water Research Catchment (HWRC: see http://www.geog.soton.ac.uk/research/nfrc/default.asp), which is a UK national reference site for lowland floodplain forest streams. This involved the deployment of a Leica ScanStation terrestrial laser-scanner from 14 setups and ranges of less than 30 m to acquire an extremely high resolution, accurate (185 million xyz observations, with absolute mean registration errors of 2 mm) 3-d point cloud model of the floodplain. These raw data were processed using a combination of Leica CYCLONE and bespoke filtering algorithms to construct a multi-resolution DTM of the forested floodplain at hitherto unprecedented detail (median point density ~4500 pts m-2). A key point is that the extreme precision and point density permit relevant features of the terrain (micro-topography, protruding roots, branches and stems, and surficial debris) that contribute to the floodplain roughness, to be readily and directly be incorporated in the DTM as topographic features. To characterise the morphology of the floodplain surface we have used the DTM to analyse a range of floodplain morphometric indices, in particular focusing on derivative surface roughness metrics (including roughness height) which are relevant in the parameterization of flow resistance. These are analysed at the floodplain scale to show the spatial distribution of roughness, and at a patch scale selected from a simple classification of floodplain surface. The analysis demonstrates spatial variability in roughness metrics at both scales, which have implications for parameterising flow resistance in models of wooded floodplains.
H43E-1669
Flow routing algorithms and landslide modelling
The physical processes governing shallow landslide triggering can be ascribed to hydrological and geomechanic forcings. Modelling shallow landslide triggering via hydrogeomorphic spatially distributed model requires to extract for any location in the river basin the geomorphic and hydrologic attributes. The Digital Elevation Models allow an easy quantification of several morphologic and hydrologic landscape properties e.g. primary attributes such as slope, aspect, plan and profile curvature, flow path lengths and secondary attributes such as topographic index and drainage area per unit contour length. Although all of these attributes are used when assessing the hydrological forcings to shallow landslide triggering, it has to be stressed that the flow direction and accumulation algorithm plays a significant role in the accurate physical representation of those water-driven slope instability phenomena. In this study three flow direction algorithm (D8, D8-LTD and Dinf) are applied in conjunction with three DEM correction techniques for the treatment of pits and flat areas, in order to determine the terrain attributes needed as input for the hydrogeomorphic model Shalstab. Quantitative results corresponding to the implementation of the different hydrogeomorphic terrain analysis algorithms on different case studies provide an objective framework for testing the accuracy and performance of the different schemes in relation to the DEM-based hydrogeomorphic prediction of shallow landslides.
H43E-1670
Investigating the spatial variability of hillslope flow velocities in the Width-Function
The width function (WF) i.e. the fraction of points/area at the same distance to the outlet measured along the downhill flow path is an important river basin and stream network parameter for hydrogeomorphic applications. Weighted WF, obtained rescaling the hydrologic travel distances with the corresponding surface flow velocity strengthens the physical concept with particular regard to the implementation of the rainfall-runoff WF-based instantaneous unit hydrograph (WFIUH). The basic assumption for obtaining the rescaled WF of assigning a different velocity to hillslope cells as respect to channel cells has already proven to positively enforce the geomorphic physical concept improving the timing and the behavior/shape of the river basin hydrologic response. In this context the natural spatial variability of hydraulic conditions (velocity) within the different hydrogeomorphic features has never been broadly investigated. Aim of this work is to investigate the impact of WF rescaled using spatial distribution of hillslope flow velocities linked to the different terrain morphologic (slope, curvature) and land use properties (vegetation, soil type).
H43E-1671
Morphometrics, Erosion Processes and the influence of Climate on Upland Soil-Mantled Landscapes
Hillslope morphology reflects processes of sediment transport and offers key insight into controlling mechanisms on landscape evolution. Here, we examine how climate influences landscape form, using remotely sensed data from an upland soil-mantled region of the Sierra Nevada, California. Previous work in this field area has quantified rates of landscape lowering by cosmogenic 10Be and dominant processes of soil transport by fallout radionuclides and field measurements including incidence of tree throw, burrow density, root density and soil surface exposure. Here, we examine high resolution Light Distance and Ranging (LiDAR) and coarser scale Shuttle Radar Topography (SRTM) data for four distinct climate zones along the western front of the southern Sierra Nevada range. We quantify slope and curvature distributions and metrics of surface roughness, ruggedness, drainage density and relief. Furthermore, we couple hillslope profiles with calculated denudation rates and soil transport processes to examine climate modulated control of erosion and weathering on landscape morphology. Our morphometric examination demonstrates the sensitivity of variables such as hillslope curvature to distinct processes of soil transport across the climate gradient.
H43E-1672
Improved Fluvial Geomorphic Interpretation Derived From DEM Differencing
Technological advances over the past two decades in remotely-sensed and ground-based topographic surveying technologies have made the rapid acquisition of topographic data in the fluvial environment possible at spatial resolutions and extents previously unimaginable. Consequently, monitoring geomorphic changes and estimating fluvial sediment budgets through comparing repeat topographic surveys (DEM differencing) has now become a tractable, affordable approach for both research purposes and long-term monitoring associated with river restoration. However, meaningful quantitative geomorphic interpretation of repeat topographic surveys has received little attention from either researchers or practitioners. Previous research has shown that quantitative estimates of erosion and deposition from DEM differencing are highly sensitive to DEM uncertainty, with minimum level of detection techniques typically discarding between 40% and 90% of the predicted changes. A series of new methods for segregating reach-scale sediment budgets into their specific process components, while accounting for the influence of DEM uncertainty, were developed and explored to highlight distinctive geomorphic signatures between different styles of change. To illustrate the interpretive power of the techniques in different settings, results are presented from analyses across a range of gravel-bed river types: a) the braided River Feshie, Scotland, UK; b) the formerly gravel-mined, wandering Sulphur Creek, California, USA; c) a heavily regulated reach of the Mokelumne River, California, USA that has been subjected to over 5 years of spawning habitat rehabilitation; and d) a restored meandering channel and floodplain of the Highland Water, New Forest, UK. Despite fundamentally different process suites between the study sites, the budget segregation technique is in each case able to aid in more reliable and meaningful geomorphic interpretations of DEM differences.
H43E-1673
The Comparison of Hydrologic Distributed Models Computed Using Different Digital Elevation Data. An Example in the Umbria Region, Central Italy
The demand for hydrologic prediction tools that utilize information on spatial variations in precipitation and land surface characteristics drive the development of spatially distributed hydrologic models. Several studies have found that spatially distributed hydrological models are sensitive to digital elevation models (DEMs) resolution and vertical accuracy. DEM is a crucial input in hydrologic models. Spatially distributed features, such as number of stream reaches, Strahler order, total length of the stream network and watershed area depend on DEM resolution and quality. This study evaluates the effect of three different DEMs on the spatial distribution of the number of stream reaches (Strahler order), of Horton's parameters variations, of the total length of the stream network and of the watershed area. These components are the main input for hydrologic modelling. Their structure (i.e. number of features) and spatial attributes (length and area) have considerable effect on modelling process and final output. The analysis is carried out in the Umbria region (central Italy) using three different DEMs derived from ASTER data, SRTM data, and a 25m resolution DEM derived from the interpolation of contour lines obtained from 1:25.000 scale topographic maps. The study analyzes the relationship between mean slope and mean elevation for computed watersheds and compares values of the derivatives for each pair of DEMs. Where blue lines derived from topographic maps are available, will be compared with the stream network computed automatically using different algorithms from the three DEMs. The aim of this part of the work is to illustrate how several methods- algorithms of channel extraction (D8, RHO8, LTD) are sensitive both to grid size and different morphological signature proper of each data set. The synthetic drainage networks are also classified in terms of stream ordering. The final overall results will help to translate the error in elevation data set into the error in hydrologic model input and in predictions of the output (i.e. discharge and time lag).
H43E-1674
Creating and coupling a high-resolution DEM with a 1-D hydraulic model in a GIS for scenario-based assessment of avulsion hazard in a gravel bed river
This paper explores the development and assimilation of a high resolution topographic surface with a one- dimensional hydraulic model for investigation of avulsion hazard potential on a gravel bed river. A detailed LiDAR- based channel and floodplain surface model is created to define the geometry parameter required by the 1D hydraulic model HEC-RAS. The ability to extract dense and optimally located cross-sections is presented as a means to optimize HEC-RAS performance. A number of flood scenarios are then run in HEC-RAS to determine the inundation potential of modeled events, the post-processed output of which facilitates calculation of spatially explicit shear stress and level of geomorphic work (specific stream power per unit bed area) for each of these. Further enhancing this scenario-based approach, the DEM is modified to simulate a LWD jam and active-channel sediment aggradation to assess impact on innundation, shear stress and stream power under previously modeled flow conditions. The high resolution DEM facilitates overlay and evaluation of modeled scenario results in a spatially explicit context containing considerable detail of hydrogeomorphic and other features influencing hydraulics (bars, secondary and scour channels, levees). This offers advantages for: (i) assessing the avulsion hazard potential and spatial distribution of other hydrologic and fluvial geomorphic processes; and (ii) exploration of the potential impacts of specific management strategies on the channel.
H43E-1675
Spatial distribution of unmonitored inland water discharges to the sea
We develop a modelling methodology and investigate how spatial data on catchment surface characteristics may be used for quantifying relative coastal discharge contributions of streams and diffuse submarine groundwater discharge along the coastlines of unmonitored near-coastal catchment areas. The methodology is applied to two small Swedish coastal catchments areas using a high-resolution (10m times 10m) digital elevation model as a basis, considering also two different ways to estimate evapotranspiration and its spatial variation within the catchments. Despite considerable differences between the characteristics of the two catchment areas, their relative coastal distribution results are similar, with about 80% of the total coastal discharge occurring through focused flows in visible and permanent streams, whereas the remaining 20% is diffuse and may occur through submarine groundwater discharge (SGD), small transient streams or both at different points in time. Evapotranspiration differs between the two used models, which results in relatively uncertain local flux values within the diffuse flow fields. The large focused stream flows and the mean values and total sums of diffuse flows (such as SGD) along some considerable coastline length, however, are constrained by the catchment-scale hydrological balance and considerably more robust and certain to estimate than the spatially variable small local fluxes within the diffuse flow fields.
H43E-1676
Damage asymmetry from hydro-geomorphic signals along the trifurcation area of the San- Jacinto Fault
An important earthquake research topic is the question of whether there are geological controls on rupture propagation direction. A persistent preferred propagation direction should produce asymmetric damage structure that is recorded in the volume of rock surrounding a fault, and there may be geomorphic manifestations on active faults that can be recognized and analyzed in a quantitative fashion. The San-Jacinto Fault (SJF) is one of the most active faults in southern California, with well expressed geomorphology, a fast geologic slip rate, and a strong GPS strain signal. We use standard morphometric analysis to detect the damage asymmetry across a part of the SJF in the trifurcation area where the Clark, Coyote-Creek and Buck-Ridge segments meet. The analysis is done at two scales: 1. Small scale DEM with 30m per pixel resolution derived from SRTM data. 2. Large scale DEM with 1m per pixel resolution derived from LIDAR data, covering the fault at ~1 km width. The geomorphic analysis is done using the GIS software ArcMap and the TauDEM tool box. We compare several morphometric parameters (drainage density, stream frequency, texture ratio, bifurcation ratio, ruggedness number, hypsometric integral) for drainages on both sides of the fault. North of the trifurcation point, the north-east side of the fault is more damaged, in agreement with Dor el at (2006) and Lewis et al (2005), but south of the trifurcation the situation is reversed. A number of factors can affect the results of the morphometric analysis, including the proximity of several fault strands, a restraining bend on the main strand, and different lithologies on the two sides of the fault. The current results are not conclusive since the morphometric analysis depends on various additional factors, such as different slopes, rates of erosion, vegetation, etc., that were only partially accounted for. Nevertheless, these preliminary results on reversed damage asymmetry suggest that large earthquakes on the SJF tend to nucleate in the trifurcation area and propagate from there to the NW and SE.
H43E-1677
Assessment of a Near-Global 30-meter Resolution DEM Derived from the Publicly Available SRTM Data Set for Use in Orthorectification of Satellite SAR Imagery
The Shuttle Radar Topography Mission (SRTM) utilized an interferometric synthetic aperture radar (InSAR) flown onboard the space shuttle Endeavour to obtain high resolution elevation data of Earth's land surface. Virtually all land surface between +/- 60 degrees latitude was mapped. Regions within these bounds contain some data gaps but this represents less than 0.2 % of the coverage. Standard publicly-available data sets from SRTM include a 3 arc-second (~90 meter) resolution Digital Elevation Model (DEM) with absolute average global vertical accuracy of approximately 4 to 5 meters. A 1 arc-second (~30 meter) resolution DEM has also been developed, but only the portion of the data set covering the United States is publicly available. The finished version of these products has been edited for pixel-level errors and delineation of coastlines and water bodies, although some data voids are still present. Utilizing such DEMs of appropriate resolution in a common framework with satellite synthetic aperture radar (SAR) data allows robust ortho-rectification and geo-referencing of the SAR data sets. We have derived a 1 arc-second resolution DEM over the entire domain of the SRTM coverage using a 3- dimensional interpolation scheme applied to the 3 arc-second SRTM DEM. Development of this product involves (1) translation of SRTM products into the WGS84 datum, (2) interpolation of the lower resolution DEMs to 1 arc- second, and (3) assembly of the global-scale 1 arc-second DEM. We assess effectiveness of this interpolation scheme through comparative statistical analysis of the 3 arc-second finished product, the 1 arc-second finished product, and the 1 arc-second interpolated product over selected test regions within the USA where all products are available. Comparisons are also made to standard GTOPO30 products for regions inside and outside of the USA. Comparisons are presented for regions representative of gentle and complex terrain. Ortho-rectification of SAR data such as those obtained from the Japanese Earth Resources Satellite (JERS) and ALOS PALSAR allows for an accurate representation of these data, providing crucial information accounting for effects of topography on geophysical retrievals. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract to the National Aeronautics and Space Administration.
H43E-1678
Quality Assurance of Airborne Lidar Bathymetry Products for Shoreline Mapping
Accurate and consistent shoreline determinations play a major role in coastal management and are necessary for federal and state boundaries. Delineations along this dynamic margin are dependent upon the stage of tide and are demarcated by tidal datums such as Mean High Water (MHW) and Mean Lower Low Water (MLLW). Current shoreline mapping is dominated by passive-sensor aerial and satellite imagery in the visual and infrared part of the spectrum. The limitations of this passive-sensor technology include the requirement of day-time acquisition, optimal weather conditions, and variations introduced by individual operator interpretation that lead to shoreline products with results that cannot be reproduced. Airborne lidar bathymetry (ALB) is an active remote- sensing technology utilized world-wide for coastal-zone applications to measure bathymetry and topography. This study investigates ALB technology as a potential tool for supporting shoreline mapping. Data for this study was acquired by the United States Army Corp of Engineers (USACE) during a survey of Gerrish Island, ME and Portsmouth Harbor, NH using a SHOALS-3000 system. Shoreline determinations from the USACE lidar dataset are obtained by a newly-devised computerized process using various algorithms that distinguish land and water. This work aims to assess the environmental sensitivity of the algorithms and determine if the reliability of the shoreline determination is affected by changes in seafloor composition. The study area includes a variety of shoreline types such as rocky, sandy, and human-altered. The algorithm-derived land-water interfaces are compared and analyzed with each other and against the reference shoreline constructed from the orthorectified aerial imagery simultaneously collected with the ALB data. The results are reviewed to assess the consistency of the shoreline vector in representing actual shoreline features as a function of algorithm and shoreline composition. The evaluation includes analysis of the resolution, accuracy, reliability, and quality of the shoreline determinations.
H43E-1679
Spatial Analysis of Drumlin Orientations
Patterns in the orientations of drumlins may hold insight into their formation, but have received limited attention in the literature. Conventional statistical methods can not be applied to orientation data, so techniques for circular statistics must be used. Specifically, we use geographically weighted techniques as in Brunsdon and Charlton (2006) to assess the spatial structure in the orientations of the Chautauqua drumlin field. The field is located in North Western Pennsylvania and Western New York State and contains 755 drumlins, mapped from a 10m DEM, in an area of approximately 2500 square kilometers (Norton and Lanier, 2007). We also consider regression trees for a circular response, as in Lund (2002), to build predictive models for the orientations using both the drumlin locations and other morphometric characteristics to explain the spatial variability of these subglacial landforms.
H43E-1680
Slope deposits and saprolites in the mid latitudes – the example of the prospection of the shallow subsurface of a slope in the Bavarian Forest, Germany, as a basic study for understanding surface water runoff, interflow and ground water storing on slopes
This study aims the three-dimensional prospection of the shallow subsurface applicating the combination of geomorphological, pedological and geophysical methods. This dataset will suit the purpose of modelling hydrological processes like surface water runoff and interflow within the slope and floodplain sediments in low mountain ranges. Slope geomorphology and slope sediments as well as the underlying saprolites are discussed to play a crucial role in all kinds of solved and particular material flows. The investigation area, the Otterbach Valley, is divided into significant units under the consideration of relief and lithology. In consideration of the 3rd order river catchment, the relief parameters of the slopes are recorded by a total station survey (LEICA TC 600) which are displayed in a high-resolution digital terrain model. Percussion drilling is used to determine the pedological and sedimentological composition of the subsurface. Furthermore the stratigraphy serves as a calibration tool for interpreting the geophysical signals. On upper and middle slope regions, refraction seismic and ground penetrating radar (GPR) measurements were carried out to differenciate between the periglacial layers, underlying saprolite and granitic bedrock. Saprolite is a profound weathering product of the in situ granites in the Bohemian Massif foothills. It acts as an important potential reservoir for slopewater and is therefore a significant criterion considering interflow modelling. The total water discharge in the slope area is measured by TDR probes which are situated in each stratigraphic layer. The floodplain is investigated by the application of the electrical resistivity tomography (ERT) because of the hydrological conditions in order to demonstrate the alluvial deposits, gravel, saprolite and granitic bedrock. The aim of the hydrological model is to map the quantity and quality of slope sediments in low mountain ranges. Therefore, the study helps for a better understanding of flood occurrences, intensities and frequencies. Furthermore it contributes more information to the discussion of the composition of periglacial layers.