Debris Flow Prevention Countermeasures with Urban Inundation in a Multihazard-Environment

Natural disasters can strike without notice at any time, anywhere. Also these disasters can occur in multiple locations between high and low mountainous areas simultaneously with flooding in urban areas caused by heavy rainfall. However, it is becoming more and more difficult to predict heavy rainfall, and intensive rainfall could become more frequent in the future due to climate change. In order to reduce these impending disasters more effectively, it is necessary to investigate what causes the damage with an integrated model of disasters at once, and to adequately predict rainfall. The main objectives of this study are to evaluate the maximum forecast rainfall by a depth-area-duration analysis, to analyses the debris flow during urban inundation in a real basin, and to estimate the risk evaluation index according to two-dimensional debris flow with two-dimensional urban inundation models. Finally, the establishment of an evacuation time scenario is proposed, and multihazard risk and evacuation route maps combining both disasters are created using a geographic information system. The peak precipitation is estimated at 135mm/hr of torrential rainfall, and the maximum total rainfall is estimated at 544mm of typhoon-related rainfall at Ono, Japan, using depth-area-duration analysis.