Numerical Modeling of Overtopping-Induced Breach of Landslide Dams

Abstract

Landslide dams have a high risk of overtopping failure compared to that of artificial dams. In this study, based on dam morphological characteristics, field investigations, and model tests, a numerical calculation method for overtopping-induced landslide dam breach is proposed. Highlights of the method include consideration of surface erosion rather than headcut erosion as well as a wide variety of dam deposits used to simulate the dam breach process. Variations in soil erodibility with depth as well as erosion mode (one- and two-sided breach) are also considered in the proposed dam breach model. Two landslide dam breaches, Tangjiashan and Xiaogangjian, are examined as case studies to test the proposed model. A comparison of the calculated and measured results shows that the relative errors in peak discharge, final breach width, and time to peak of the two breach cases are all within ±10%. Sensitivity analysis shows that the aforementioned parameters are more or less sensitive to soil erodibility and erosion mode, with soil erodibility being more important than erosion mode. Three other typical landslide dam breach models are compared to the proposed model for the Tangjiashan landslide dam case. All four models can reasonably simulate the breach process, but the proposed model has the smallest relative errors.