Mapping and analysis of the Rio Chama landslide and evaluation of regional landslide susceptibility, Archuleta County, Colorado

Abstract

Recent landslides, such as the West Salt Creek landslide in Colorado and the Oso landslide in Washington, have brought to light the need for more extensive landslide evaluations in order to prevent disasters in the U.S.. The goal of this research is to characterize and map the Rio Chama landslide, evaluate conditions at failure, predict future behavior, and apply these findings to create a regional susceptibility model for similar failures. Based on the classification scheme proposed by Cruden and Varnes (1996), the Rio Chama landslide is an active multiple rotational debris slide and flow complex with observed activity since 1952, located near the headwaters of the Rio Chama River in south-central Colorado. Site reconnaissance was conducted in 2015 and 2016 and coupled with laboratory testing of samples and limit equilibrium stability analysis. A hierarchical heuristic model using an analytic hierarchy process was applied to evaluate the susceptibility of the region to failures similar to the Rio Chama landslide. Weights were assigned to parameters based on their influence on landslide susceptibility, and weighted parameters were combined to produce a regional susceptibility map. The causative factors in order of most to least contribution to susceptibility are: slope angle, lithological class, surface waterbody density, stream density, slope aspect, profile curvature, and land use. The regional model accurately and consistently identifies zones as having low, moderate, and high susceptibility to failures similar to the Rio Chama landslide. Discussion of the causative factors and their impact on susceptibility, as well as the implications of each susceptibility zone is presented. The regional model is intended to identify areas susceptible to failures similar to the Rio Chama landslide, allowing appropriate preventative action to be taken.