Risk Evaluation of Landslide Disaster Occurrence Using Quantification of Soil Moisture Considering Snowmelt

Abstract

 This study was conducted to assess the risk of slope failure disaster using soil moisture estimated based on the long-term water cycle of a catchment basin. In recent years, landslide disasters caused by heavy rainfall and rapid snowmelt have occurred in many areas in Japan. Such disasters are expected to increase in frequency in snowy areas because of climate change. This study examines a soil water index (SWI) and soil water storage (SWS) by assessment of the water level of a tank model with input values of rainfall and snowmelt. Then the soil water content was conceptualized. The soil water content was estimated at each location of a slope failure disaster. Then the estimated values were examined by comparison with snake lines to assess the risk of disaster occurrence. Estimation of SWI and SWS for the disaster locations revealed that occurrence conditions of the slope failure disasters were assessed appropriately. Results clarified that the disasters occurred when the soil water storage was at its maximum value and that the slope failure was triggered by rainfall and snowmelt. For periods of prolonged high soil water content, this study showed the possibility of predicting the slope failure disaster risk by inputting appropriate weather data into a hydrol-ogical model that incorporates rainfall and snowmelt.