Study on the formation and geometries of rainfall-induced landslide dams

Recently, the occurrence of landslide dam problems has been aggravated due to the effects caused by climate change and the further expansion of land use in mountainous areas. Knowledge of landslide dam formation and its geometry is very necessary to accurately evaluate dam stability and hence provide good predictions for disaster preparedness. In previous studies, landslide dam formation was considered as a separate issue; its link with slope failure was ignored, and thus their description and interpretation are still inadequate. Previous models also were limited to evaluate landslide dam shape in 2 dimensions (2D). Through a series of experiments, this study aims to analyze the effect of different slope failure mechanism on the formation of landslide dam. This study also integrated 2D seepage flow model, 2D slope stability model, landslide dam-geometry evaluation model in a single unit and proposed a new method to estimate the landslide dam shape in lateral direction (3D). The experimental results indicated that in the sudden failure, the failed mass can quickly block the river width, making a high impact in regard to dam construction. In retrogressive failure, the shape of dam was formed layers by layers which slowly span to the other side of river and to both up and downstream direction. The results also showed the failed volume and river bottom slope are the two most essential factors that dominate the shape of landslide dam. The simulation results including the failure surface, landslide volume and shape of landslide dam in lateral direction were comparable with those observed from the experiments.