Empirical Modeling on the Spatial Variation of Soil Thickness in Mountain Slopes for Large Scale Landslide Hazard Mapping with GIS Application

Abstract

Soil thickness is one of the important parameters in the stability of mountain slopes. However, determination of its spatial distribution especially for large scale landslide hazard assessment is cumbersome, costly and time consuming. To address the problems of laborious field investigation, efforts have been done by many researchers to arrive at a reasonable prediction of this parameter over large areas. This study aimed to establish an empirical correlation model of the soil thickness with the slope angle. The data were gathered from 3o sampling points and 6o probed points within the study area with Pliocene-Pleistocene geology. The corresponding slope map was generated through a processed Digital Elevation Model (DEM) in Geographic Information System (GIS) platform particularly the ArcGIS software. Slope angles were confirmed in the site through actual measurement using the clinometer. The soil thickness was measured from the ground surface down to the interface of soil and the weathered bedrock. The regression analysis revealed that the soil thickness in the study area has good correlation to the slope angle with R2 of 0.9284. The resulting empirical model was validated from ten different sites with similar geology.