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Abstract

The Jinsha River basin in the upper reaches of the Yangtze River in China is prone to strong geological activities, with numerous large-scale landslides along its banks that can potentially trigger a cascade of flood hazards. Recent seismic events such as the Wenchuan and Luding earthquakes have heightened the likelihood of landslide collapses along the slopes of the Jinsha River, thereby increasing the risk of a large-scale landslide-dam-break-flood hazard chain. Among these landslides, the ancient Woda landslide is currently in a state of slow deformation, and if reactivated, it can potentially obstruct the river and trigger catastrophic outburst floods. This study uses the integrated continuum method to simulate the dynamic processes associated with large-scale slope failures and the formation of landslide dams. Furthermore, the outburst flood resulting from the dam breach is modeled by combining the dammed lake flow model and the shallow water equation, allowing for the simulation of long-distance flood propagation. The findings indicate that the Woda landslide has the potential to create a dam of approximately 68.1 m in height, with a corresponding dammed-lake volume of about 7.10 × 108 m3. The peak flow rate of the resulting outburst flood can reach 4.4 × 104 m3/s, leading to an extensive impact zone reaching 140 km downstream. This flood inundates several downstream villages, towns, and even the Sichuan-Tibet Railway which is under construction. Moreover, the study reveals that the resistance coefficient of landslides significantly influences the entire hazard chain evolution process. Lowering the resistance coefficient of landslides leads to a considerable increase in the height of the landslide dam, amplification of the peak flow rate of the outburst flood, and an elevated risk for downstream elements situated at greater distances.