Evaluation of landslide susceptibility in Portland’s West Hills

Diane Moug, Portland State University


Portland’s West Hills in the Tualatin Mountains are home to approximately 22,200 residents and 10,000 households, with supporting roads, utilities, and businesses (2010 Census data). The Tualatin Mountains are covered in wind deposited soils (“loess”) that the Oregon Department of Geology and Mineral Industries (DOGAMI) considers to have a high landslide susceptibility where slopes are sufficiently steep, and a very high landslide susceptibility in existing landslides (Multnomah County 2017). However, there remains uncertainty in Portland’s West Hills whether existing landslides actually have a very high landslide susceptibility, or if the landslide susceptibility reduces after a landslide (Ian Madin, DOGAMI, personal communication). The objective of this project is to determine if landslide hazard in the West Portland Hills is higher in existing landslides than soil that has not failed (i.e. intact soil). This project hypothesizes that differences in soil particle structure, soil density, and soil strength can be measured between loess soil that is part of a landslide mass, adjacent soil that did not slide (i.e. the landslide scarp), and soil at the interface of the intact soil and landslide mass (i.e. the sliding plane). The approach will be to train and assist an undergraduate student, Michelle (“Chelle”) Guckenheimer, to sample soil from different points in three existing landslides in Portland’s West Hills. Chelle will take part in (i) selecting field sites for sampling, (ii) performing field sampling, and (iii) laboratory analysis of soil. The samples will be analyzed with geotechnical methods to measure soil density and measure soil strength in the geotechnical lab with a direct simple shear device.

Project Details

Project Type:
Project Status:
In Progress
End Date:
December 15,2018
UTC Grant Cycle:
NITC 16 Diversity Grant
UTC Funding: