Numerical simulation for deformation of landslide dam by overtopping water

Fumiaki AKAZAWA and Yoshifumi SATOFUKA

Heavy rainfall and strong earthquakes cause large]scale landslides and create large landslide dams in mountain rivers. When it retains a large amount of water and bursts, it may cause inundation and catastrophic damages in the downstream area. Therefore, the study of landslide dam deformations is essential for predicting flood potential and flood risk. To predict the flood risk of a landslide dam, we developed a numerical model to simulate the landslide dam erosion by overtopping. The model calculates the process of overtopping erosion in two]dimensions. To improve the prediction of the outflow discharge, we incorporated the inertial debris flow model proposed by Takahashi et al. (2002), the side bank erosion model, and the slope collapse model. We verified the model results by comparing them with the experimental results of Takahashi et al. (1993). The comparison showed that the model is capable to predict the outflow discharge of a landslide dam collapse by overtopping. In addition, we examined the effects of side bank erosion on the dam erosion process, and showed that the side bank erosion affects the overtopping erosion and outflow discharge.