Prediction of Floods Caused by Landslide Dam Collapse
Yoshifumi Satofuka*1, Toshio Mori*2, Takahisa Mizuyama*3,
Kiichiro Ogawa*4, and Kousuke Yoshino*5
*1College of Science and Engineering, Department of Civil Engineering, Ritsumeikan University, Noji-higashi 1-1-1, Kusatsu-city, Shiga 525-8577, Japan
*2Sabo Frontier Foundation, SABO-Kaikan Annex 6F, 2-7-4, Hirakawacho, Chiyoda-ku, Tokyo 102-0093, Japan
*3Graduate School of Agriculture, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan
*4Asia Air Survey Co., Ltd., Manpukuji 1-2-3, Asao-ku, Kawasaki-city, Kanagawa 214-0004, Japan
*5Asia Air Survey Co., Ltd. on loan to Incorporated Administrative Agency, Public Works Research Institute, Minamihara 1-6, Tukuba-city, Ibaraki 305-8516, Japan
Landslide dam formation and deformation strongly affect water and sediment runoff. When a large-scale landslide dam collapses due to overflow erosion, peak flood discharge may exceed inflow discharge by several times. Such an abrupt flow discharge increase by a dam burst may cause serious damage downstream. We propose a one-dimensional model for river-bed variation and flood runoff consisting of a two-layer model for immature debris flow and a bank erosion model. We applied this model to the Nonoo landslide dam in Japan’s Miyazaki Prefecture, formed by typhoon Nabi in September 2005, and China’s Tangjiashan landslide dam formed in the Wenchuan earthquake in May 2008. The model reproduces the observed flood runoff processes in the two areas. Calculated results suggest that peak flood discharge diminishes when water accumulating behind the landslide dam is small, and excavating the landslide dam crown effectively reduces flood discharge.
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