Modeling susceptibility to landslides using the weight of evidence approach: Western Colorado, USA

The Paonia–McClure Pass area of Colorado is well known for active mass movements. We examined 735 active shallow movement features, including debris flows, debris slides, rock slides and soil slides, in this area. Identification of the hazardous areas is a fundamental component of disaster management and an important basis for promoting safe human occupation and infrastructure development in landslide prone areas. Bayes' theorem, based on the weight of evidence (WOE), was used to create a map of landslides that could be hazardous. The modeling was accomplished by employing a geographical information system (GIS) and a statistical package.Seventeen factors that cause landslides were measured and weighted using the WOE method to create a map of areas susceptible to landslides. The maps of weighted factors were summed on a pixel-by-pixel basis after performing chi-square tests to determine factors that are conditionally independent of each other. By combining factors that represent topography, hydrology, geology, land cover, and human influences, six models were developed. The performance of each model was evaluated by the distribution of the observed landslides. The validity of the best map was checked against landslides, which were not entered in the analysis. The resulting map of areas susceptible to landslides has a prediction accuracy of 78%.