Disaster mechanism and its deposition area of the Xiaochang gully debris flow in Hanyuan County industrial park

Influenced by the 2013“4•20” Lushan earthquake, geological disasters occurred frequently along the Baiyan River Basin in Hanyuan County. At present, there is a large amount of loose material sources in the Xiaochang gully, posing a significant risk of large-scale debris flows, which severely threaten the factories and mining enterprises in the Hanyuan Industrial Park plant. Therefore, understanding the mechanism of disaster occurrence and its hazard is of great significance for future debris flow prediction, early warning, and prevention engineering design. Combining field investigation, UAV aerial photography, remote sensing interpretation, and RAMMS, this study analyzes the development characteristics of debris flows in Xiaochang gully, simulates the process of debris flow movement and accumulation, and reveals the disaster mechanism of disaster occurrence. The results show that the current dynamic storage of the source in Xiaochang gully reaches 370,000 m3. A wide and gentle channel ( 900 m long, and average width of 60 m ) has naturally formed in the middle reaches of the basin, acting as a natural sedimentation pond, which intercepts small-scale debris flows. Numerical simulation results show that when the rainfall frequency is less than once every 20 years, the main deposition of debris flows occurs in the middle and upper reaches of the gully, and will not directly threaten the industrial park; when the rainfall frequency reaches once every 50 years, the outbreak of large-scale debris flow will impact the industrial park.