Prediction of debris flow blocking river hazard chain by the numerical simulation: the Cutou catchment, Wenchuan County, China

On August 20, 2019, a catastrophic debris flow occurred in the Cutou catchment, leading to the formation of a dam in the Min River. This debris barrier triggered a chain of multiple hazards, resulting in widespread flooding of houses upstream and downstream. To understand and assess the impact of this hazard chain, we conducted a comprehensive study using numerical modeling, field survey, the solid material reserve, and the probabilistic method. We began by conducting a detailed investigation of the 2019 event and calibrated the model parameters using survey data. Subsequently, we simulated and analyzed the entire process of hazard chain event, which was divided into four stages by the characteristics of water level. Finally, we developed a comprehensive and efficient approach for hazard assessment using the solid material reserve method and the probabilistic method. This approach enabled us to generate a hazard distribution map for the debris flow chain, providing valuable insights for effective hazard prevention in the Wenchuan area.