Community-based landslide hazard probability and risk assessment: A case in west Hubei, China

Abstract. Small communities living in high mountainous terrains, in Hubei Province are often impacted by landslide hazard. Past work by China Geology Survey focused only on hazard assessment at 1 : 100 000 scales. In this study, we conducted a more-detailed semiquantitative landslide and risk assessment at a community level and scale of 1 : 10 000. We applied the probabilistic method to assess the landslide spatial, temporal and size probabilities while the landslide hazard and risk assessment were considered for four return periods (5, 10, 20 and 50 years) and two size scenarios (landslide volume). The spatial probability by susceptibility mapping with an accuracy of 84 % indicates that Quaternary deposits and weathered eluvium from Ordovician limestone are the two major controlling factors. Most building areas in hazard maps are located at the foot of major slopes where hazard probabilities are very high. We computed the loss of lives and properties for each slope. The result shows that 1530 people and 126 million RMB economics were at risk of being affected by landslides with a 50-year return period and a landslide volume of fifty thousand cubic meters. Meanwhile, the longer the return period, the higher the hazard probability is. Compared with the function by ordinary least square method, classic inverse gamma and power law distribution of landslide magnitude and frequency are not suitable for landslide size probability analysis in the study area. The proposed procedure is proved to be more useful to complement risk assessment on the small scale of 100 000 in west Hubei, China.