Mechanism of rainfall inundation caused by the 2019 Typhoon Hagibis in Iwate Prefecture coastal zone, Japan

Abstract

This study aims to clarify the mechanism of rainfall inundation caused by the 2019 Typhoon Hagibis in Iwate prefecture coastal zone, Japan, using probable one-hour rainfalls estimated for the 2 periods of 1976-2005 and 1989-2018. The differences between rainfalls by the 2019 Typhoon Hagibis and the ten-year return level of one-hour rainfall (P10) of 1976-2005, which is generally assumed as the discharge standard of drainage system in Japan, at Fudai village, Iwaizumi town, Miyako city, and Yamada town were in the ranged of 40.7 mm–106.6 mm for maximum three-hour rainfall during the 2019 Typhoon Hagibis, and the estimated massive rainfall inundations. On the other hand, massive rainfall inundations were also observed at Kamaishi city, although the amount of water overflow from the existing drainage system was only 3.5 mm for a maximum of three-hour rainfall during the 2019 Typhoon Hagibis. These were caused by water overflow at narrow sections in the streams and drainage systems by huge sediment and large wood and debris from landslides dammed up, and by damming up rainfall inundation at coastal levees for tsunami. In addition, P10 at all study areas were increased by 8–24% from 1976-2005 to 1989-2018, which corresponded with increasing frequency of P10 of 1976-2005 by 1.4-2.1 times. Thus, increasing frequency of rainfall inundations in the Iwate prefecture coastal zone is expected in the future.

DOI

10.2208/journalofjsce.10.1_195

Published in

Journal of JSCE

Year of publication

2022

Type

Journal article

Language

EN

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