A predictive model for the geometry of landslide dams in V-shaped valleys

Landslide dams are formed mostly in V-shaped valleys, with poor stability and a high risk of failure. Once landslide dams fail, they may cause floods or debris flows that endanger lives, property, and infrastructure downstream. Therefore, it is important to evaluate the stability immediately once a landslide dam is formed. The geometry of a landslide dam is the most critical to its stability assessment. However, the complex terrain and geomorphological conditions in the disaster area often make field surveys difficult. Aerial photography and satellite imagery technology are usually limited by poor weather conditions, which bring severe restrictions to the timely acquisition of the geometry of a landslide dam. In this paper, a discrete element simulation model was proposed and verified by two experiments, and then a series of numerical simulations were performed to investigate the geometry and formation process of landslide dams under different topographic factors including the motion path dip-angle, the river bed inclination, and the angle between valley slopes (valley angle). The results show that the geometry and formation process of landslide dams are significantly affected by the topographic factors. According to the results of comprehensive numerical analysis, a simple predictive model for landslide dam geometry in V-shaped valleys was established, and two landslide dams with data collected from early events were employed to validate the predictive model. Based on the easily accessible topographical factors, the proposed model accomplished the fast prediction of landslide dam geometry. This research provides a vital basis for the stability evaluation of landslide dams and can be used for the disaster emergency response before the dams break.