Detailed numerical modeling for breach hydrograph and morphology evolution during landslide dam breaching

Landslide dams are common geological disasters in mountainous areas and can pose severe threats to the lives and property of downstream people. In this study, a three-dimensional numerical simulation method was developed to calculate the breaching behaviors and morphological evolution of landslide dams under complex terrain. An explicit finite volume method (FVM) was adopted by solving the Reynolds-averaged Navier-Stokes (RANS) equations and equilibrium suspended and bed load transport equations. The renormalization group (RNG) k-epsilon turbulence model and volume of fluid (VOF) method were combined to describe the hydraulic features of the dam-break flow. The collapse mechanism of breach side slope sliding was considered during the landslide dam breaching. The model was verified by a benchmark experiment case and then applied to study the breach mechanisms and process of the "11.03" Baige landslide dam. Herein, the actual topography of the Baige landslide dam was reconstructed using rapid spatial information processing technology. The comparison showed that the calculated breach hydrograph was consistent with the measured data. Also, the calculated free surface elevation, flow depth, and average flow velocity at each key monitoring point contributed to the mutual corroboration of the breach mechanisms in the field measurements and numerical modeling. Furthermore, the calculated breach morphologies were in accordance with the measured actual topographies at different cross-sections along the Baige landslide dam. After comparing with the typical landslide dam breach models, the model performance showed that the numerical simulation method in this study enhanced the understanding of the dynamic process during landslide dam breaching.