Applying Debris Flow Simulation for Detailed Hazard and Risk Mapping

For houses situated in mountainous regions, evacuation routes during sediment disasters are limited. Thus, in the event of heavy rainfall, it may be difficult for inhabitants to evacuate from disaster areas. Therefore, it is important to understand the risk distribution before debris flow disasters in order to determine safe evacuation planning. Debris flow simulations are useful for the determination of hazard and risk mapping. When considering debris flow behavior and conducting debris flow simulations, there are two critical factors with respect to the debris flow flooding and deposition processes, namely, the scale of debris flow and landform conditions. The focus of this study was on various resolution digital elevation model (DEM) landform data in Japan. Simulations were performed for a residential area in Hiroshima, which was subject to debris flow events in 2014. Based on a comparison of the simulation results obtained using DEM data with a mesh resolution of 5 m, as sourced from the Geospatial Information Authority of Japan, and the results using high-resolution light detection and ranging (LiDAR) DEM data, the houses can be considered to describe the influence area and high risk region situated near the valley exit, in addition to locally dangerous areas and movement of debris flows on roads. To achieve a detailed hazard and risk mapping and determine safe evacuation routes and shelters, the application of high-resolution LiDAR DEM data and consideration of houses is critical.