Abstract
This study examined the flooding disaster resulting from the heavy rainfall that was associated with Typhoon No. 10 in northern Iwate Prefecture in August 2016. Meteorological data for Typhoon No. 10, which landed in the Tohoku district on the Pacific Ocean-side of Japan, was obtained from the Japan Meteorological Agency. The typhoon lasted for 11 days and caused extensive damage in the Tohoku district, particularly in Iwaizumi town and Kuji city, which were severely damaged by flooding of the Omoto and Kuji rivers. We conducted field investigations from November 18 to 21, 2016 and collected data from disaster section in Kuji city hall and Iwate Prefecture. In the residential and commercial districts of Kuji city, an area of approximately 0.63 km2 was inundated after an embankment overflowed, causing one fatality and flooding of 2,258 houses. Flooding was increased by the presence of numerous trees in the floodwaters; the trees collected at bridges and interfered with the flow of the Kuji River. By partially blocking the river, water levels rose and the embankment was ruptured causing flooding. Flooding in the Kuji River was severe because a river master plan had not been developed for the river.
In the Omoto and Shizu subcatchment, the number of fatalities and missing people in six districts of Iwaizumi town was 19 and 2, respectively. In addition, 419 houses and businesses were flooded and 1.23 km2 of farmland was inundated. As in the Kuji River, trees that were transported down the river from areas upstream collected at bridges and impeded the flow of water, causing water levels to rise and river embankments, which had not been sufficiently maintained, to overflow.
