Landslide dams are caused by large-scale slope collapse. Predicting their failure is important because hazardous flooding may result downstream when landslide dams burst. Accurate prediction of a landslide-dam formation which means height and length via landslide maps that show two-dimensional figure but does not consider landslide depth is needed for a countermeasure against the sediment disaster caused by landslide dam. In this study, past landslide dam failures were investigated. Relationships between landslide dam formation and the topographical and geological characteristics of the region were established to improve landslide dam analysis for more accurate prediction of dams' structural integrity.
Norio HARADA and Yoshifumi SATOFUKA 1 正会員 三井共同建設コンサルタント株式会社(〒552-0007 大阪市港区弁天1丁目2番1-1000号) 2 正会員 工博 立命館大学教授(〒525-8577 滋賀県草津市野路東1-1-1)Debris flow can be trapped in a steel-grid sabo dam, due to the blockade of coarse woody debris without large stones. In addition, the permeable width of the barricade is not determined by the grain-size accumulation rate, but rather by the grain-size frequency. Information on the grain-size distribution characteristics in mountain streams is needed before construction of the dam. In this study, to identify the ideal structure for controlling sediment runoff, we experimented with the structure of the dam to show how the capture rate is affected under different conditions. The capture effect was evaluated for several grain-size distributions of real mountain stream beds to determine the relationship between grain size and the capture rate.
Recently, climate change has resulted in an increasing number of heavy rainfall events. Heavy rainfalls tend to cause large-scale landslides and create large landslide dams. Large landslide dams retain a large amount of water and often burst causing floods and catastrophic damage in the downstream area. Therefore, the study of landslide dam deformation is essential for predicting potential floods to implement effective flood risk management. To understand the landslide dam deformation process and dam outflow discharge characteristics, we carried out field experiments of landslide dam erosion by overtopping flow. In the field experiments, we observed the landslide dam deformation process directly. In a third experimental case, small slope failure occurred and we found that small slope failure affects the outflow discharge. In addition, we developed a numerical model to simulate landslide dam erosion by overtopping flow. To improve the prediction of the outflow discharge, we incorporated the inertial debris flow model, the side bank erosion model, and the slope collapse model into our numerical model. The resulting proposed model is tested by comparing the results of simulation with observation. The numerical model is capable of predicting outflow discharge by landslide dam burst.
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