Numerical investigation on the landslide dam formation in landslide-river interaction

Abstract

Landslides occur in valleys always interact with the rivers. The sliding materials are likely to deposit in the river and form a landslide dam that impedes the river water flow, threatening human lives and properties both upstream and downstream. It is thus essential to investigate the formation mechanisms of landslide dams during landslide-river interaction. In this study, a multi-phase depth-averaged model is adopted to systematically explore the key factors that influence landslide dam formation, including the landslide volume, river discharge, landslide discharge, initial solid concentration and internal friction angle of landslide material. It is found that the landslide volume is always the key on landslide dam formation. The river water plays a critical role on retarding the inertia dynamic of landslide and accelerating the deposition process. One interesting finding is that the river blockage condition is insensitive to both the river and landslide discharge rates while the river flow depth is a more direct factor that controls river blockage. The two material properties on landslide dam formation (i.e., the initial solid concentration and internal friction angle) are represented by the enhanced flow mobility. After a landslide dam forms, the lasting impact of river water leads to the evolution of landslide deposit in the river. The kinetic energy ratio of landslide deposit to river water is linearly correlated with the solid concentration of deposit. The in-depth study on landslide formation mechanisms provides a solid basis for the evaluation of landslide hazard chain and risk mitigation.