Rain score and debris flow occurrence criterion in case of mizunashi river, shimabara

Rain score and debris flow occurrence criterion in case of mizunashi river, shimabara

Creators Shiotsuki Yoshiharu

Creators Yamamoto Tetsuro

Creators Shibasaki Kazuya

Creators Inoue Masayuki

Debris flow occurrence at Mizunashi river of Mt. Unzen, Shimabara, Nagasaki prefecture, is discussed with the various factors obtained from the parameters a, b of rainfall intensity maxima curve. The maximum instantaneous intensity (R0) and the space liquid water content (M10) of the maximum 10 minute rainfall intensity (R10) are recognized important factors as well as the maximum 3 hour rainfall (R180). In case of R0>21.4mm, M10>0.8g/m^3, and R180>38mm, the debris occurrence probability is 90.9%. This paper proposes the rain score P as a new factor representing the rain strength. 8 significant debris occurrences including 5 flooded cases occur without exception in case of P≧5. The criteria are useful for the voluntary disaster prevention activity with the aid of 1-3 hour rainfall amount forecast.

[ISSN]0386-3433

[NCID]AA0086073X