A review of multistate dynamics numerical simulation for high-altitude and long-runout geohazards

High-altitude and long-runout geohazards encompass a range of surface processes involving single or cascading geological processes such as rockfalls, landslides, debris flows, and mudflows. Characterized by complex dynamics, high mobility, and large volumes, these hazards pose serious risks to infrastructure and human safety in affected regions. A thorough understanding of their dynamic mechanisms and accurate numerical modeling are therefore critical for effective hazard prevention and mitigation. Drawing on extensive field investigations conducted by our research team, this paper classifies high-altitude and long-runout geohazards into four principal types: granular flows, liquefaction-induced flows, dense inertial flows, and turbidity currents. We systematically review recent advances in the study of these hazards, focusing on both internal dynamic mechanisms and external dynamic effects. Furthermore, a comprehensive review of prevailing numerical simulation methods is provided. On this basis, we propose a dynamic theoretical framework incorporating multistate transitions and multiphase coupling for high-altitude and long-runout geohazards, and three critical shifts are outlined for advancing numerical simulation in geohazard dynamics: (1) from "adapting geological phenomena to numerical algorithms " to "adapting numerical algorithms to geological phenomena"; (2) from “empirically calibrated, generalized calculations” to “computations grounded in actual physical and mechanical processes”, (3) from “small-scale computations for scientific research” to “practical-scale simulations for engineering”, offering novel insights for improving hazard prevention and mitigation strategies.