Estimation of the mitigation and the landuse control for climate change based on the flood analysis in Japan

Abstract

 This study evaluated the impact of flood damage caused by climate change and the effects of mitigation and adaptation measures. Using the two-dimensional unsteady flow model and the Flood Control Economic manual (by Ministry of Land, Infrastructure, Transport and Tourisum), the inundation depth and economic damage were calculated. In order to estimate the flood damage at the end of the 21st century, the rainfall in the future climate was obtained using 5 GCMs, and the future inundation depth and economic damage were obtained using these as input values. In addition, we focused on land use control as an adaptation measure, and examined the effect of reducing the amount of damage and the cost-benefit ratio (The social discount rate is 4.0%). It was estimated that the mitigation from RCP8.5 to RCP2.6 at the end of the 21st century would reduce the expected annual flood damage by 246.5 billion yen / year. It was estimated that adaptation measures by land use control, which regulates areas flooded by 3 m or more during floods with a return period of 200 years, would reduce expected annual damage by 26% in the current climate. The estimated cost-benefit ratio was 0.684 for the mitigation measures, while the cost-benefit ratio for land use control was estimated to be about 0.019.