Formation of a typical landslide-debris flow disaster chain induced by rainstorm

Due to global warming, the Qinba Mountain Area in China has experienced frequent extreme heavy rainfall events, transforming isolated geological hazards into multi-hazard chains characterized by cascading and compound disasters. These occurrences often lead to severe casualties and socioeconomic losses. To investigate the formation mechanisms of typical landslide-debris flow disaster chains in this region, this study selected the Gaojiawan disaster chain—a representative case within the study area—for systematic analysis. Using integrated methodologies, including unmanned aerial vehicle (UAV) mapping, geographic information system (GIS) spatial analysis, and a numerical simulation method based on PFC 3D , the entire disaster chain process was reconstructed and investigated. The results show that collision interactions between cascading hazards were found to amplify the affected area and debris flow interactions fundamentally altered deposition mechanisms, transforming localized slope accumulation into integrated mass transport processes. This paper analyzes the transformation of the landslide debris flow disaster chain from the perspective of energy. Additionally, based on the analysis of field investigation and numerical simulation results, the formation mechanism of the Gaojiawan landslide-debris flow disaster chain is summarized into five stages: landslide formation stage, landslide activation stage, slope deposit mixing stage, debris flow formation stage, and low-speed deposition stage. This research elucidates the evolutionary dynamics and underlying mechanisms of landslide-dominated geohazard chains in mountainous regions. The proposed integrated monitoring-modeling framework provides methodological references for theoretical research and risk mitigation of similar disaster chains worldwide.