2022 Volume 10 Issue 1 Pages 213-227
Typhoon Hagibis 2019 recorded the highest precipitation in history, in several areas of East Japan. Levee breaching occurred at 7 places in the Arakawa River system. The risk of downstream migration should be discussed when conducting river channel management. For this purpose, it is necessary to understand the inundation between the river and the flood plain. Therefore, the effects of the levee breaching of the Tokigawa River and the timing on flood volume were considered as a first step.
It was suggested that the levee at the junction section of the Tokigawa River and the Oppegawa River gradually scoured, considering the change in water-level hydrograph by changing the levee breaching timing. In addition, it can be considered that the left levee breaching at the Tokigawa River at 6.5 KP occurred after 10:00 PM on October 12th, noting the change in flood volume by changing the levee breaching timing. The inundation on the right side of the Tokigawa River in the section managed by Saitama Prefecture was caused by the inundation from the Kasumi-tei (open levee); therefore, the levee breaching at the 1.4 KP right levee had little effect on the inundation level.
