Coupled model constructed to simulate the landslide dam flood discharge: a case study of Baige landslide dam, Jinsha River

Landslide dam, always triggered by the strong earthquake and heavy rain, is a common natural disaster around the world. In this study, a coupled model was built by combining DB-IWHR model and the two-dimensional hydrodynamic model to simulate the landslide dam flood discharge. We mapped the maximum Baige landslide dam flood inundated area based on Gaofen-1 imagery, and then simulated the process of Baige landslide dam flood discharge using this coupled model. It was proved that, with 80.05% F values, the coupled model was suitable to simulate the process of landslide dam flood discharge. Lastly, multiple scenarios were simulated respectively by setting varying width and depth of spillway. The results of scenarios 1–4 indicated that spillway width presented low sensibility to the peak flow in spillway and the time of its arrival, and similarly to the water depth at river cross-section and the inundated area. Water depth at river cross-section and the inundated area decreased as spillway width increased. Even if spillway width varied at 10 m interval, the average variation of water depth was less than 1.82 m and the variation of inundated area was less than 2.85%. However, the results of scenarios 5–8 indicated that spillway depth was sensitive to the peak flow in spillway and its arrival time, and also to water depth at river cross-section and the inundated area. Water depth at river cross-section and the inundated area increased first and then started to drop with spillway depth kept decreasing. When spillway depth varied at only 2 m interval, the average variation of water depth at river cross-section basically exceeded 2 m and the variation of inundated area was more than 2.85%.