SUSCEPTIBILITY ANALYSIS OF FACTORS CONTROLLING RAINFALL-TRIGGERED LANDSLIDES USING CERTAINTY FACTOR METHOD

Chun'an county is located in southeast China, where is a typical region with extensive occurrence of rainfall-triggered landslides. Based on the results of detailed field investigation of geohazard in Chun'an county, this study applies GIS and Certainty Factor (CF) method to analyze the susceptibility of 9 landslide controlling factors. They include elevation, slope gradient, aspect, curvature, lithology, distance to fault, distance to roads, land use and vegetation. The results from CF analysis show that (1) stratigraphy of Cambrian, Sinian, Carboniferous and Cretaceous, and lithology of the intrusive rock group, red sandstone rock group, carbonatite mixed clasolite rock group, and carbonatite rock group are more susceptible to landslide. The affection of fault to landslide susceptibility in this study area decreases with the increasing of the distance to fault.(2) the areas relatively more susceptible to landslide occurrence include the areas with slope gradient between 10°~35°, aspects of south-facing in south and southeast direction, elevation between 100 and 200m, concave slope and straight slope, vegetation with non-forest, economic forest, tea and bamboo forest. The quantity of occurred landslides reaches to its peak in areas with slope gradient in a range from 30°and 35°.(3) the land use types with extensive anthropogenic activities such as residential land, cultivated land, transportation land and garden are prone to landslides. The controlling factor of distance to roads has less influence on landslide susceptibility and there is no significant correlation between them. This study will facilitate determination of categories with associated numerical intervals of each controlling factor, which is the fundamental in rainfall-triggered landslide susceptibility assessment and spatial prediction.