Characteristics and mechanism of high-vegetation-coverage recurrent debris flow disaster chain: Insights from a case in the Qinling Mountains, China on July 19, 2024

On July 19, 2024, a recurrent landslide-debris flow disaster chain was induced by extreme rainfall in Mao’ergou, Qinling Mountains, Shaanxi Province, China, resulting in catastrophic damage to agricultural land, residential infrastructure, and transportation networks. This event exemplifies high-vegetation-coverage (HVC) and cycle-recurring patterns, which are characterized by concealed source material and complex activation mechanisms under extreme rainfall. Through integrated UAV-based remote sensing, multi-source geospatial data fusion, and field geomorphological mapping, this study deciphers the spatiotemporal characteristics and recurrence mechanisms of vegetation-masked geological hazard chains governed by geomorphology-source material-hydrology (GM-SM-H) coupling. Some key findings reveal: (1) The steep topography provided a topographic basis for energy conversion; the last debris flow accumulation and the source material generated by new landslide were synergistically activated under extreme rainfall; (2) A GM-SM-H-driven avalanche-like feedback loop initiated an avalanche-like feedback loop of material accumulation and energy amplification via “scraping (slope failure)-erosion (channel confinement)-entrainment (alluvial fan saturation)” mechanisms. This study provides a representative case study for the risk assessment, prevention, and control of geological disaster chains in the Qinling Mountains and similar (HVC) mountain regions worldwide.