Journal of the Japan Society of Erosion Control Engineering, Vol.56,No.3,2003

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The debris flow disasters caused by localized rainfall of seasonal rain front in Kyusyu region in July, 2003 (prompt report)

Hideaki MIZUNO, Nobuo SUGIURA, Hideki TERADA, Taro UCHIDA, Toshiyuki HARAMAKI, Masatoshi SOKABE, Wataru SAKURAI, Haruo NISHIMOTO, Nobutomo OSANAI, Nagazumi TAKEZAWA, Yasuhiro DOI

Abstract
Debris flows occurred in Kyushu region due to localized rainfall which was caused by a seasonal rain front from 18th to 20th July, 2003, causing 20 dead person, 7 injured person and 63 damaged houses. Authors made investigations at Hougawachi]Atsumari district, Minamata city, Kumamoto Pref. and Sanjyou1]choume, Dazaifu city, Fukuoka Pref., where were damaged by debris flows. In both cases, the debris flows were initiated by landslides. In order to estimate the volume of sediment discharge and velocity, authors surveyed geometry in both site. The volume of sediment discharge plunging into the village of Hougawachi]Atsumari district was estimated from about 98,000m3 to 107,000m3, and the velocity of debris flow was estimated from about 2.9m/s to 23.5m/s. The volume of debris flow plunging into the village of Sanjyou 1 choume district was estimated about12,000m3. And the velocity of debris flow was estimated from about 4.2m/s to 14.3m/s.

Key words:seasonal rain front, debris flow, hillside failure