Landslide Susceptibility Assessment: Deep and shallow-seated landslide susceptibility model, Chambers Creek, Pierce County, WA

Abstract

In wet, glacially overridden regions, landsliding is a common and dangerous natural phenomenon. Thus, attempting to predict these mass wasting events is a vital and useful task. Many landslide models already exist, but the ultimate goal of this Capstone Project was to create a deep and shallow landslide susceptibility model of a segment of the right bank of Chambers Creek Basin. By combining field and computer testing, appropriate material strength values, potential slide plane slopes and depths, a factor of safety analysis, slope and curvature models, a vegetation analysis, and field observations a thorough deep and shallow landslide hazard model was created. According to the data, the highest risk of shallow landsliding is located in the center of the field area, within the Pre-Vashon non-glacial course-grained unit (A2). The highest risk of deep landsliding is located on the eastern extent of the field area, where a concave, protruding section sticks out into the valley (between the western face of the most eastern large landslide complex and where the Pre-Vashon till (C1) reaches the surface). Both models agreed that the lowest risk of both deep and shallow landsliding is located on the western edge of the field area, due to the exposure of the strong underlying Pre-Vashon non-glacial fine-grained unit (C2).