2006 Volume 59 Issue 2 Pages 5-12
Abstract A deep-seated landslide occurred in the Harihara River basin on the western flank of Mt. Yahazu-lake, the Pliocene volcano, in Izumi City, Kagoshima Prefecture on July 10, 1997. This deep-seated landslide was caused by rising of groundwater level associated with heavy rainfall, the hydrogeomorphological formation of the underground area prone to storage of groundwater, and deeply weathered volcanic rocks. This study aimed to develop a method for potential site prediction of deep-seated landslide. Some indicators for ascertaining such sites were examined based on topographical and geological surveys, along with hydrological observations in four watersheds on the western flank of Mt. Yahazu-lake. It was ascertained that effective indicators for predicting potential site of deep-seated landslide were the patial distributions of gentle slopes, boundaries between aquifer and aquiclude, the change points of stream discharge, electric conductivity, and silica concentrations along a longitudinal stream, and the distribution of springs.