Abstract:

To achieve scientific prevention and control of avalanche disasters in the southeastern Tibetan Plateau, a dynamic deduction and assessment model for avalanche hazard chains was developed, focusing on a high-frequency avalanche site along National Highway G219. A foundational geospatial dataset was first constructed using high-resolution digital elevation models, multi-source remote sensing imagery, and field survey data to support numerical modeling. Building upon snowpack instability mechanisms and physical kinematic theory, a multi-factor-driven model was established to quantify key physical parameters of avalanche processes, including flow trajectories, dynamic characteristics, and deposit morphologies. The SEEP/W model was then employed to evaluate the internal seepage stability of avalanche-induced natural dams under different water-level gradients. Finally, the Hydrologic Engineering Center's River Analysis System (HEC-RAS) hydrodynamic model was used to simulate the post-breach flood propagation, calculating critical variables such as downstream water levels and flow velocities. Results reveal that the dynamic modeling method proposed in this study can quantitatively characterize the evolution of the hazard chain: avalanches in this region are characterized by dense snowpack, high flow velocities, and strong impact forces, with deposited material prone to obstructing adjacent rivers and forming temporary dammed lakes. These provisional dams exhibit poor structural stability and are highly susceptible to rapid breaching, generating destructive floods that pose severe inundation threats to downstream infrastructure and nearby settlements.

Key words: southeastern Tibetan Plateau, avalanche-dammed lake-flood, hazard chain, dam-break flood, dynamic modeling