Landslide hazard rating for the Oregon coast range

Burroughs, E.R., Jr. 1985. Landslide Hazard Rating for the Oregon Coast Range. Proceedings of Symposium Sponsored by Committee on Watershed Management, Irrigation & Drainage Div., ASCE. Denver, CO: ASCE Convention, April 30-May 1, 1985. 132-139.

Keywords: slope stability, landslide

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Abstract: The landslide hazard rating system for shallow soils on steep terrain over hard sandstone has three components: ground water response to precipitation, soil shear strength (including root strength), and a factor of safety model. Ground water rise over a hyperbolic-shaped bedrock surface in debris avalanche terrain is empirically derived as a function of easily measured site characteristics. Data on soil shear strength (ø and c) are based on triaxial tests on samples from sites with a high potential for translational failure. Root strength is the sum of the residual strength of Douglas-fir roots as they decline with time after clearcutting and the passive resistance to sliding of an alder soil-root mass. Driving and resisting forces are calculated for a three-dimensional block using estimated ground water rise for a selected design storm, soil shear strength, and estimated root strength.

Moscow FSL publication no. 1985a