HR: 10:35h
AN: H42B-02 INVITED     [Abstracts]
TI: Coupling a Soil Moisture Model and a Slope Stability Model to Predict Landslides in the Himalayas
AU: * Gabet, E J
EM: manny.gabet@mso.umt.edu
AF: Dept of Geology, University of Montana, Missoula, MT 59812 United States
AU: Burbank, D W
EM: burbank@crustal.ucsb.edu
AF: Dept of Geological Sciences, UC Santa Barbara, Santa Barbara, CA` 93110 United States
AU: Putkonen, J K
EM: putkonen@u.washington.edu
AF: Dept of Earth and Space Sciences, University of Washington, Seattle, WA 98195 United States
AU: Pratt-Sitaula, B A
EM: pratt@crustal.ucsb.edu
AF: Dept of Geological Sciences, UC Santa Barbara, Santa Barbara, CA` 93110 United States
AB: Landsliding of the hillslope regolith is an important source of sediment to the fluvial network in the unglaciated portions of the Himalayas of Nepal. These landslides can produce abrupt increases of up to 3 orders of magnitude in the fluvial sediment load in less than a day. An analysis of 3 yr of daily sediment load and daily rainfall data defines a relationship between monsoonal rainfall and the triggering of landslides in the Annapurna region of Nepal. Two distinct rainfall thresholds, a seasonal accumulation and a daily total, must be overcome before landslides are initiated. To explore the geomorphological controls on these thresholds, we develop a slope stability model, driven by daily rainfall data, which accounts for changes in regolith moisture. The pattern of rainfall thresholds predicted by the model is similar to the field data, including the decrease in the daily rainfall threshold as the seasonal rainfall accumulation increases. Results from the model suggest that, for a given hillslope, regolith thickness determines the seasonal rainfall necessary for failure, whereas slope angle controls the daily rainfall required for failure. The magnitude and frequency of predicted landslides are compared to data from other regions.
DE: 1807 Climate impacts
DE: 1810 Debris flow and landslides
DE: 1815 Erosion
DE: 1826 Geomorphology: hillslope (1625)
SC: Hydrology [H]
MN: Fall Meeting 2005