CHARACTERISTICS OF FLOOD INUNDATION IN WATARI AREA DUE TO HEAVY RAINFALL IN JULY 2020

Abstract

 The July 2020 torrential rains caused extensive flood damage in the Hitoyoshi and Kuma basins. In the Watari area of Kuma Village, Kuma County, in particular, many houses were damaged by flooding in addition to inundation. In this study, the behavior of downstream flooding, in which the overflowing stream flows together with the river, in the Watari area of Kuma village, was investigated, and the assumed inundation area, including house collapses, was verified. As a result, according to the estimated inundation zones, all areas in the Watari district except for mountainous areas were designated as inundation zones. The most notable area where houses in the village of Chaya in the Watari district were swept away by the flood was the area between the levee and the railroad, which has a large hydrodynamic force. The behavior of the flood flow in the Watari area of the Kuma River was a downstream type of inundation. Calculations without considering the inflow from branch rivers showed that the flooded flow overcame the levee and entered the inner area of the levee from the upstream of the continuous meandering section.