Flooded areas along the Akiyama River were investigated after Typhoon Hagibis in 2019. The areas that experienced severe flood damage and the two levee failures that occurred were all areas where the river became narrower, and both levee failures occurred upstream of the foot of a bridge. The particularly severe damage to the levee on the right bank of the Kairiku Bridge in Akasaka-cho might have been the result of multiple compounding factors, including its location on the outer bank of a

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... and risks, such as the angle at which the girders were built relative to the downstream current. The times when the levee failures occurred were determined through interviews with residents of the damaged areas, and a numerical analysis that took each of the relevant conditions into account indicated that the severe damage to downtown Sano City might have been caused not only by the flooding that resulted from the overflow from the Akiyama River and failures of the levees, but also by multiple compounding factors including the effects of the flooding from nearby rivers, such as the Kikusawa River.