Typhoon Hagibis, which hit Japan directly on October 12, 2019, caused great damage, including the flooding of rivers, across various parts of Japan. The Tama River, which flows north of Kawasaki City, also experienced flooding which exceeded the designed high water level; although it did not cause fluvial flooding, river water flowed into the urban areas through the sewerage system, causing unprecedented inundation damage. This damage was reproduced with the inland flood simulation model. Furthermore, we performed simulations in which the water level, precipitation, and sluice gate operation of the Tama River differed from actual conditions, and compared them with the actual damage. Based on these results, we examined methods for reducing inundation damage, such as improving the operation method of sluice gates, and confirmed their effects.

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