Estimation of the effects of climate change on flood-triggered economic losses in Japan

Abstract. This study evaluates the effects of climate change on economic losses due to flood-related damage in Japan. Three selected GCM climate data were downscaled using an analytical method that uses observed precipitation data as the reference resolution. The downscaled climate data were used to estimate extreme rainfall for different return periods. The extreme rainfall estimates were then entered into a two-dimensional (2-D) non-uniform flow model to estimate flood inundation information. A novel technique based on the land use type of the flood area was employed to estimate economic losses due to flood damage. The results of the rainfall analysis shows that at present (in 2000), the Nankai region, the area from Wakayama Prefecture to Kagoshima Prefecture and the mountains of the Japan Alps receive very high extreme rainfall. By 2050, in addition to these areas, the rainfall in the Tokai and Koshinetsu regions will be 1.2 to 1.3 times greater than at present. The flood-related economic loss estimation shows that the relationship between increased extreme rainfall and increased potential economic loss due to flood damage has a nearly linear relationship. The overall variations show that the potential economic loss is greater for the SRES-B1, A2 and A1B scenarios for all return periods. These results clearly show that flood-related economic losses in Japan will increase significantly in the future as a result of climate change.