Title

Geographic Information System Based Mapping of Slope Stability with Uncertain Parameters

Document Type

Presentation

Journal/Book Title/Conference

AGU Fall Meeting

Location

San Francisco, CA

Publication Date

12-6-1998

Abstract

The infinite plane slope stability model with wetness (pore pressure) obtained from a topographically-- based steady state hydrology model has been used to map a terrain stability index quantifying the potential for shallow transitional landsliding based upon topography. The topographical parameters this procedure uses are slope and specific catchment area (upslope area per unit contour width) computed from grid digital elevation data. To compute stability, this procedure also uses parameters quantifying friction angle, cohesion, and the ratio of steady state recharge rate to soil profile transmissivity. The results are sensitive to the selection of these parameters, which are uncertain. In this paper we extend the infinite plane slope stability model - steady state hydrologic model coupling to account for this parameter uncertainty, with parameters specified as uniform probability distributions between lower and upper limits. Instead of using a factor of safety, terrain stability is mapped with a stability index defined as the probability of stability over the probability distributions of the parameters. Stability classes are defined in terms of this stability index and may be visualized as regions in the slope-specific catchment area domain. This procedure has been implemented as an extension to the ArcView Geographic Information System (GIS). The methodology uses an interactive visual calibration to adjust parameter bounds. This visual calibration is done by simultaneously referring to 1) a stability index map which includes observed landslides, 2) a plot of specific catchment area verses slope (of observed landslide and non landslide points) where lines distinguish zones categorized into the different stability classes, and 3) a table giving summary statistics. The software is available on the Internet at http://hydrology.usu.edu/dtarb/.

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