Weights-of-evidence method based on GIS for assessing susceptibility to debris flows in Kangding County, Sichuan Province, China

Assessing susceptibility to debris flows is of great importance for hazard prevention and mitigation. Kangding County, a region with a high occurrence of destructive geological events, was selected as the study area, to evaluate the area’s susceptibility to debris flows using the weights-of-evidence method based on ArcGIS. First, the determination method of training points was revised. The unit cells covered by the debris flow catchments were set as the training points, rather than using one point to represent the debris flow catchment. Then, the landforms, lithology, faults, earthquakes, and river systems were selected as evidential themes for the analysis. The optimum buffer zones cutoff distance of the faults and rivers was determined by the maximum studentized value of the contrast. Finally, the map of the susceptibility to debris flow in Kangding County was obtained by combining the evidential themes. The susceptibility was categorized as low, moderate, and high susceptibility. The low-susceptibility zones cover an area of 6253 km², accounting for 53.93 % of the county area. The moderate-susceptibility zones cover an area of 3323 km², accounting for 28.67 % of the county area. The high-susceptibility zones cover an area of 2018 km², accounting for 17.40 % of the county area. The moderate-susceptibility zones surround the high-susceptibility zones. The assessment results agree well with field data, demonstrating that the revised method is more suitable for debris flow assessment than the previous method. The assessment results can be used as guidelines for policy makers regarding prevention and mitigation of debris flow hazards.