EVALUATION OF INUNDATION RISK IN LOWLAND RIVER WITH TOPOGRAPHIC VULNERABILITY USING LARGE ENSEMBLE RAINFALL DATA

Abstract

 This study assessed the latent risk of large-scale flooding and the effectiveness of flood control facilities in low-lying river areas of the Chitose River, a tributary of the Ishikari River. As this river flows through low-lying areas, it is affected by backwater from the main river. To estimate the inundation risk of the Chitose River basin area, a large volume of ensemble rainfall information, acquired by downscaling d4PDF data, was used to estimate climate uncertainty. A case similar to floods observed in the past was confirmed among the 3,000 cases in the d4PDF current climate prediction data. Additionally, a case was found that predicted outflow patterns for both the Chitose River and Ishikari River which exceeded past flood records. These results indicated the latent possibility of inundation damages exceeding those from the past floods for the Chitose River, while acknowledging the effectiveness of flood control facilities.