Paper No. 10
Presentation Time: 10:35 AM


SCHULZ, William H.1, DEUELL, Amelia E.1, COE, Jeffrey A.2, WASKLEWICZ, Thad A.3 and REAVIS, Kathryn J.4, (1)U.S. Geological Survey, MS 966, Box 25046, Denver, CO 80225, (2)U.S. Geological Survey, Denver Federal Center, P.O. Box 25046, MS 966, Denver, CO 80225-0046, (3)Department of Geography, Planning, and Environment, East Carolina University, A-227 Brewster Building, East Carolina University, Greenville, NC 27858, (4)Department of Geography, East Carolina University, A-227 Brewster Building, East Carolina University, Greenville, NC 27858,

Landslides pose significant hazards to human life and property while also substantially modifying hillslopes and sediment supplies in watersheds. Movement of landslides is largely dictated by their basal geometry because it exerts strong control upon stress distributions and hydrology; hence, improved understanding and modeling of landslide processes requires constraining this geometry. Pronounced advances during the past century in direct and indirect means for evaluating the subsurface often enable accurate identification of geologic conditions. Although drilling and subsurface penetration methods have improved, landslide basal shear surfaces are typically very difficult or impossible to identify without direct observation by engineering geologists within large-diameter boreholes or trenches. Even direct observations using these methods provide only spatially isolated observations. Advanced geophysical methods have been developed and are able to provide more spatially continuous subsurface data; however, these methods have proven unable to identify landslide bases absent significant contrasts in material within and below landslides.

Development of light detection and ranging (LIDAR) techniques during the past two decades has revealed ground-surface topography in unprecedented detail. During July and October 2011 and July 2012, we obtained repeat terrestrial LIDAR scan (TLS) data for part of a persistently moving landslide. Previous mapping and photogrammetric studies demonstrated that ground-surface topography grossly mimics landslide basal topography and we developed a simple approach to infer basal topography from the multi-temporal TLS datasets. Our findings suggest that rugged topography in the scan area result both from surface processes and sliding over a basal rupture surface with significant local relief. This approach could be used to infer the basal topography of other landslides and, perhaps, glaciers and tectonic faults. The absolute depths of such features still require identification using other methods, but isolated measurements of these depths could be used to project to depth the basal topography inferred from repeat LIDAR data, thus revealing a much more spatially continuous surface than is typically obtained.