1. 1) Japan Meteorological Agency (JMA) : The Weather Events Caused Heavy Rains, Storms and Other Weather Events by Typhoon Hagibis, pp. 1-35, 2019 (in Japanese).
2. 2) Cabinet Office : Damage Situation of Typhoon Hagibis, 2020 (in Japanese).
3. 3) Cabinet Office : Disaster Prevention Information Page, List of Disasters (in Japanese), <http://www.bousai.go.jp/updates/> (viewed on April 20, 2020)
4. 4) Mito City, Hitachinaka City, Hitachi Omiya City, Naka City, Ibaraki Town, Oarai Town, Jori Town, Otawara City, Nasukarasuyama City, Ibaraki Town, Ichikai Town, Nakagawa Town, Ibaraki Prefecture, Tochigi Prefecture, Japan Meteorological Agency, Mito District Meteorological Observatory, Utsunomiya District Meteorological Observatory, Hitachi River National Highway Office : “Naka River Emergency Flood Control Project” based on Typhoon Hagibis ~Aiming at minimizing socioeconomic damage through multiple flood control measures in cooperation with local communities~ [Outline of main measures], pp. 6-8, 2020 (in Japanese).
5. 5) Kanto Regional Development Bureau, Ministry of Land, Infrastructure and Transport : Naka River System River Improvement Plan [Ministerial Management Section], pp. 1-9, 2016 (in Japanese).