Numerical study on morphology and material spatial distribution of landslide dams in different shaped valleys

Abstract

The characteristics of a landslide dam, including morphology and material spatial distribution, are dependent on its formation conditions and directly affect the dam stability. In this study, a series of numerical modeling tests were performed to reveal the importance of six accessible factors (landslide material, volume, height, slope gradient, width of sliding path, and valley shape) on dam characteristics. Two deposition modes were observed during dam formation: “collisional spreading” mode in U-shaped valleys and “pushing and climbing” mode in V-shaped valleys. The dam height was strongly related to the valley shape and landslide volume, whilst the dam width was highly sensitive to the slope gradient and width of sliding path. The crest surface frontal angle and up/downstream slopes were mainly influenced by slope gradient and landslide material. Due to the different deposition modes, the main factors regulating the material distribution of the dam in the U-shaped valley were the width-to-depth ratio of the valley and landslide height, while in the V-shaped valley, the slope gradient and valley bank slope were the primary parameters. The prediction models considering significant influencing factors were established for evaluating the geometrical and material distribution parameters of a landslide dam. Two case studies (Attabad and Baige landslide dams) are presented to test the prediction models. This study provides a rapid prediction of landslide dam characteristics, which can be used to assess the dam stability.