GIS-BASED LANDSLIDE SUSCEPTIBILITY ANALYSIS OF WESTERN COLORADO SPRINGS, EL PASO COUNTY, COLORADO

Mass wasting processes occur worldwide. Mass wasting is defined as the down slope movement of rock and regolith near the Earth's surface mainly due to gravity, which includes creep, landslides, debris flows, topples, and rock falls, each with its own characteristic features, and taking place over timescales ranging from seconds to years. Of these, landslides are known to be one of the most hazardous in that they often cause injuries and fatalities. In a typical year in the United States, landslides cause over $2 billion in damages and 25 to 50 deaths. With its western portions located on the foothills of the Rocky Mountains, Colorado Springs, Colorado has proven to be highly susceptible to landslides which cause ongoing destruction of numerous hillside and mesa top developments. The purpose of this study is to perform a GIS-based landslide susceptibility analysis of Colorado Springs using the following GIS-based methods: One Dimensional Infinite Slope Stability Model and a Weighted Overlay Model. Unlike traditional landslide inventory investigations which often require extensive field work, the methods used in this study allow for the minimization of time, expense, and labor required. The weighted overlay model is a subjective method which allows the researcher to place varying degrees of emphasis on the causative factors of a landslide based on the statistical historical records of other landslides and the experience of the researcher. For this study the causative factors include slope angle, cohesion, internal friction angle of material, unit weight of material, depth to water table, and depth to the potential failure plane. The output of the weighted overlay model will be a landslide susceptibility zonation map which indicates areas where a landslide is most/least likely to occur in the study area. The infinite slope stability model separates the study area into an abundance of individual slopes or ‘cells’. A factor of safety is calculated for each cell. The output of the infinite slope stability model will be a landslide susceptibility zonation map which displays the factors of safety throughout the study area. Having created a geodatabase which houses all data related to this project, the two models will be compared with one another. Future work related to this project will be based on the interpretation of the two methods.