Numerical study of 2018 Baige landslides induced geohazards chain and dynamic proesses

Geohazards chain in watershed contains a landslide, which contributes to the propagation on the slope, intruding into river channels forming a landslide dam, a subsequent dam breach, and outburst flooding. Since the sub-process belonging to one chain are all coupled, one or several sub-processes can be the triggering factors of the subsequent one. They can generally own a larger space and time scale than that of a single disaster resulting in greater destructive power and amount of impact area. In this study, the most recent geohazard chain event that happened in the 2018-Baige landslide in Sichuan province, China is adopted for a numerical case study. This event can be divided into several sub-processes according to the coupling order within the chain process. The first landslide generates a landslide dam followed by another landslide and landslide dam sharing the same location. The second landslide overlapped with the first one forming a higher landslide dam. A larger-scale dam breach and resulting outflow occurred eventually. For solving this, a series of validated depth-averaged containing models for geohazards chain is adopted to simulate the whole coupling sub-processes, as well as, the standard LxF central differencing scheme is adopted for retaining high resolution and avoiding Riemann characteristic decomposition. The numerical study simulates the landslide propagation process using a viscos-inertial friction law. The numerical prediction is verified by values from field measurement in the literatures, indicating the feasibility of the (K) viscos-inertial rheology in simulating the large-scale landslide and the landslide dam formation. The overtopping failure process of the two overlapping landslide dams and the outburst flooding is numerically modeled by the proposed model. The results of maximum discharge illustrate the proposed model for landslide dam failure can simulate the interaction process of dam breach and outburst flood. The numerical results, validated by the literature provide reliable assessment and emergency relief support of the actual event. This proposed modeling framework is expected to improve mitigation strategies for geo-hazard chain hazards.