Author(s): Hayata Yanagihara; Tao Yamamoto; So Kazama

Linked Author(s): Hayata Yanagihara, So Kazama

Keywords: Urban flood disaster; Flood simulation; Economic loss; Drainage by gravity to rivers

Abstract: In urban areas, there are concerns that inland flood damage will increase due to climate change. It is necessary to quantitatively evaluate the spatial risk of inland flooding in order to consider the direction and priority of adaptation measures. This study estimated the damage cost caused by inland flooding throughout Japan based on the distribution of extreme precipitation and identified insufficient areas of flood protection for high risk. The inundation depth and the damage cost were calculated using the two-dimensional unsteady flow model and the Manual for Economic Evaluation of Flood Control Investment published by the Ministry of Land, Infrastructure, Transport and Tourism. In inundation analysis, we set up two inundation scenarios (natural drainage scenario and poor drainage scenario) with or without drainage by gravity to rivers. The natural drainage scenario corresponds to inland flooding caused by the elevation, while the poor drainage scenario corresponds to inland flooding caused by poor drainage to rivers. As a result, the expected damage cost was estimated to be 491 billion JPY/year in the natural drainage scenario. The damage cost was the largest in Kanagawa prefecture, followed by Shizuoka prefecture, Aichi prefecture, Osaka prefecture, and Okayama prefecture. On the other hand, the expected damage cost was estimated to be 7,896 billion JPY/year in the poor drainage scenario. The damage cost was the largest in Tokyo Metropolis, followed by Osaka prefecture, Aichi prefecture, Hokkaido prefecture, and Saitama prefecture.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022214

Year: 2022