URBAN RECONSTRUCTION AND VARIATIONS IN POTENTIAL FLOOD ECONOMIC LOSS DUE TO A MEASURE TO PROPOTE RESIDENCE RELOCATION UNDER POPULATION DECLINE

Abstract

 Under the global warming condition, intensification of heavy rainfalls are anticipated and it is difficult to realize a flood resilient-society by only structural counter measures (e.g., levee, dam). Flood management on the premise of inundation is indispensable. In Japan, future population decline is predicted and surplus lands will be created in lower flood risk areas. It is expected that the damage of flood disaster will be reduced by utilizing surplus lands in low-risk areas. In this study, based on inundation simulation results, potential flood economic losses were estimated for Kakehashi River basin in Ishikawa Prefecture, Japan. For the condition of population decline, relocation of households and firms were simulated by a computable urban economic (CUE) model. When households and firms relocate under a population decline, the potential flood economic losses were reduced by 14.1%. When relocation from high-flood-risk areas to surplus lands in low-risk areas were promoted in CUE model by changing ratios of urbanization promotion area, the flood economic losses were reduced by 16.4%. In the past study for the Kakehashi River basin, the flood economic losses could be reduced by about 40% when the relocation to the low-risk surplus lands is the maximum. These results indicate that relocation to low-flood-risk areas will not proceed simply by relying on economic principles. Effective relocation measures are indispensable to maximize the utilization of surplus lands and realize flood-resilient society.