Regional susceptibility, possibility and risk analyses of landslide in Ulsan Metropolitan City, Korea

The three steps of landslide hazard analysis such as susceptibility, possibility, and risk were performed to study area, Ulsan, using GIS. The susceptibility is a function of the probability of potential landslide occurrence and landslide-related factors. The possibility depends on the impact factor such as rainfall, earthquake and human activity and on the susceptibility. The risk depends on vulnerable objects such as people and property, and on the possibility. For the analyses, the topographic, geologic, soil, forest, meteorological, and population and facility database were constructed using GIS. Landslide susceptibility was analyzed using the landslide-occurrence factors by probability method that is summation of landslide occurrence probability values per each factors range or type. For landslide possibility analysis, the rainfall frequency map that was extracted from meteorological database was added to the susceptibility map, because most of the landslides in Korea occurred by heavy rain. For landslide risk analysis, the population and facility density maps that were created from the population and facility database were added to the possibility map.