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

Geohazard chains in watersheds often involve a series of interconnected events, such as landslides that propagate along slopes, intrude into river channels, form landslide dams, and result in dam breaches and outburst flooding. Because the sub-processes within a geohazard chain are coupled, one or more of these events can trigger subsequent ones, leading to larger spatial and temporal scales than isolated disasters. This results in more destructive power and a wider impact area. In this study, a numerical case study focuses on the most recent geohazard chain event: the 2018 Baige landslide in Sichuan Province, China. This event can be divided into several sub-processes based on the coupling order within the chain. The first landslide formed a landslide dam, followed by another landslide at the same location, which overlapped with the first, creating a higher dam. This ultimately led to a larger-scale dam breach and outflow.
To simulate this sequence, a series of validated depth-averaged models for geohazard chains was employed, along with a standard LxF central differencing scheme to retain high resolution and avoid Riemann characteristic decomposition. The landslide propagation was modeled using a visco-inertial friction law. The numerical predictions were verified against field measurements from the literature, demonstrating the feasibility of using μ(K) visco-inertial rheology to simulate large-scale landslides and landslide dam formations. The overtopping failure of the two overlapping landslide dams and the subsequent outburst flooding were successfully simulated using the proposed model. Maximum discharge results indicate the model's capability to capture the interaction between dam breaches and outburst floods. The numerical findings, validated by existing literature, provide a reliable assessment for emergency relief and hazard mitigation. This modeling framework is expected to contribute to improved mitigation strategies for geohazard chains.