Ishige and Mitsukaido district of Joso city in Ibaraki prefecture was attacked by heavy flood due to overflow and dike break of Kinu River in September, 2015. Although relatively higher natural levees adjacent to overflow and dike break sites in Ishige district were inundated with the depth of 1.0 m or less, flood water was soon drained to reach floodplain and back marsh behind and expanded southward. Longer and deeper inundation of more than 1.5 m deep around Shinhakkenbori River in Mitsukaido district was caused because developed natural levees prevented to drain flood water smoothly downstream. As issued evacuation orders were not covering all the inundation area, verification of issuing process and evacuation activities of local residents are necessary. |