Kazuki YAMANOI and Masaharu FUJITA
During sediment disaster, multi]hazard (e.g. landslide, debris flow, flood, inundation, and strong rainfall) can make evacuation difficult or dangerous. In order to clarify the safety of the evacuation, the estimation of the occurrence timing of each phenomenon is very important. Japan Meteorological Agency and prefectures cooperatively operate the sediment disaster alert system using the snake line and critical line on the two]dimensional plane whose horizontal and vertical axis are the soil water index and cumulative rainfall in60minutes. However, the alert does not contain any information on the kind of hazards or the evacuation possibility. In order to evaluate the risk of the multi]hazard, we have developed the multi]hazard simulator SiMHiS based on the landslide prediction model and water and sediment runoff model in the watershed scale. In this simulator the risk level of the3categories of multi]hazard related to rainfall, landslide, and flood can be obtained spatially and temporally. However, the landslide prediction model in the simulator has a problem with the decreasing process of water content. To solve the problem, before employing the simulator, we modified the numerical model using the theory of saturated seepage flow. In this study, we applied the improved simulator employing the several rainfalls whose maximum intensity and duration are different. The estimated risk level of the hazards was arranged on the same two]dimensional plane used in the sediment disaster alert system in Japan. As a result of the arrangement, the boundary diagram of the probable phenomenon is obtained on the plane at overlaying the critical lines of the flood, landslide and rainfall related hazards. Using the diagram, the kind of hazards and evacuation possibility can be estimated moment by moment. Also, an additional information related to the probable phenomena and evacuation can be supplied with the sediment disaster alert employing the diagram.
Key wordsFsediment disaster, multi]hazard, warning system, evacuation