Journal of the Japan Society of Erosion Control Engineering, Vol.57,No.1,p.20-26,2004

The characteristics of an unseasonably heavy rainfall and debris flow disaster in Tsurumi Town, Ohita Prefecture

Masahiro KAIBORI, Hiroshi OHMURA, Tetsuya KUBOTA, Masaru NISHIMURA, Hideo FURUSAWA, Shinpei INOUE

Abstract

Debris flow disaster in the area around Tsurumi Town, Ohita Prefecture, Japan, occurred during a heavy rainfall over 600mm from November 27, 2003to November29, 2003. Antecedent precipitation of more than 300mm, and additional severe hourly rainfall of about90mm were brought onto the area. We have investigated the circumstances of the disaster in Tsurumi Town and confirmed the occurrence of the fluidized phenomena there. While some houses were damaged by debris flows, nobody was killed. Although there is not usually a heavy rainfall in this season, it showed that the debris flow could occur at any time depending on weather and environmental conditions. However, it is very characteristic that the rich forest there has resisted the enlargement of the extent of sediment produce and sediment yield even as a result of this heavy rainfall.
Key words:unseasonably heavy rainfall, debris flow disaster, antecedent precipitation

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