Geological Primary Cause for Debris flow Hazard at the Harihara River Areain Izumi City, Kagoshima Prefecture

Debris flow and flashwater caused by the heavy rain attacked the farmers residences in Izumi City, Kagoshima Prefecture on 10th, July, 1997. Direct cause had been estimated as a failure of slope near the Harihara river. Authors doubted the possibility of slope failure, because the rainfall didn't exceed usual heavy rain record. On the field survey carried out on three days after of debris hazard, authors found the exsistence of fault at the concaved slope failure spot. Topographical analysis and geological survey were carried out on si tu. Finally, the primary cause for the debris flow hazard was forcussed as the existence of lateral movement fault. In this paper, noticed fault is discribed according to the North Kagoshima earthquake in 1996.