Effectiveness of investing in flood protection in metropolitan areas: Lessons from 2019 Typhoon Hagibis in Japan

Purpose: This study aims to demonstrate the effectiveness of investment in flood protection by analyzing the flood disaster caused by Typhoon Hagibis in Japan in October 2019. The typhoon severely damaged the central and eastern Japan regions and threatened the Greater Tokyo area. Design/methodology/approach: The paper examines flood risks in the Greater Tokyo area and reviews how the flood protection systems functioned to protect Tokyo from the typhoon. The hydrological data of rainfall and water levels at major rivers and the operation records of flood control facilities are collected and analyzed. Findings: The study’s major finding is that the flood protection system succeeded in protecting the Greater Tokyo area from flooding. Typhoon Hagibis maintained its power until landing because of climate change and caused record-breaking rainfall. In a worst-case scenario, thousands of people could have died and hundreds of billions USD worth of assets could have been lost in Tokyo. Practical implications: The paper describes the actual effects of the flood protection systems, consisting of dams constructed upstream, reservoirs midstream and diversion channels downstream. Thus, this study’s findings directly relate to practical implications for other countries and cities, which face flood risks under a changing climate. Originality/value: The paper highlights the importance of investing in flood protection by examining actual disasters and providing detailed descriptions of flood protection systems.