SEDIMENT DISASTER RISK ASSESSMENT FOR DEBRIS FLOW INUNDATION AREAS AND ITS APPLICATION TO TOWN PLANNING

Abstract

 We conducted a numerical simulation of debris flow in Yagi 3-chome, Asaminami-ku, Hiroshima City, where a devastating sediment disaster occurred in July 2014, to examine the effect of houses and other structures on the flow characteristics of debris flow, as well as the spatial distribution of sediment disaster risk in debris flow inundation areas, and proposed a method for utilizing the numerical simulation of debris flow for safe town planning. Based on the state of housing land in 1974, when housing development began to progress in the upstream of the debris flow valley in Yagi 3-chome, we performed a risk assessment using the results of the numerical simulation of debris flow based on the presence or absence of houses and the location of newly constructed houses, and were able to visually grasp the risk areas due to debris flow. Unlike field surveys, this type of assessment can be completed in a relatively short time, and is therefore considered to be a useful tool in the planning stage of sediment disaster mitigation measures in town planning.