治水面から見た被害の概要と着目点

Abstract

This manuscript reports the summary of flood damages and each focusing points that the flood control research group in the Disaster Prevention Research Institute, Kyoto University. Selected focus points are as follows: 1) the north side of the Chikugo River was a disaster inexperienced area so far, 2) a large amount of driftwood occurred due to forest collapse and river bank erosion in Hita's forestry area, 3) large amount of sediment discharged from the weathered granite area, 4) it is showing the form of complex disaster of flood, sediment and driftwood, 5) in small rivers without dam, floods flowed out as it is in a short period and caused disasters, 6) out of many irrigation ponds, some expanded disaster damages because of pond collapses, whereas, without collapses, some reduced damages downstream by trapping driftwood and sediment, 7) some Sabo dams trapped not only sediment but also some driftwoods 8) In the dam reservoir, Terauchi dam has played an enormous role by controlling three elements of flood, sediment and driftwood, and large flooding possibly occurred downstream without dam. Based on the characteristics of such damage, we reported from the viewpoints of extreme value statistics of rainfall and runoff/flood analysis, integrated analysis of slope failures and floods in heavy rainfall, flow path

bed fluctuation due to sediment discharge and flood damage characteristics, sediment and flooding analysis in the down-stream area, the driftwood trapping effect and the downstream flood risk mitigation effect in the dam.