2014 Volume 23 Issue 1 Pages 1-10
Sixty six years ago, Miyata River in Hitachi City was flooded by Kathleen typhoon in September, 1947, and the serious harm was caused by centering on the Hitachi mine company houses. In this paper, the relation between runoff characteristics in small mountainous basin and the occurrence of sediment disaster is discussed dynamically, referring the previous study. The runoff analysis results show the soil layer of mountain slope mostly attained to saturation by the rain which got down intermittently about one week, and the danger of debris flow occurrence was high enough. But the presumed maximum flow discharge by rainfall and debris-flow can't cause the river flood. Then it thinks about the obstruction of the river cross section area due to sediment and washing things such as driftwood and slag at the actual flooding point. There is a possibility to generate the flood in the above mentioned maximum flow discharge, and it is assumed enough from victim's testimony and documentary photography.
