Analyzing the multi-hazard chain induced by a debris flow in Xiaojinchuan River, Sichuan, China

Abstract The damage caused by a single natural hazard can be amplified in time and space to form a disaster chain. One such chain was induced by a debris flow that occurred on June 17, 2020 along the Xiaojin River on the eastern Tibetan Plateau of China. The debris flow dammed the Xiaojin River, and subsequent dam breaches instigated a multi-hazard chain that flooded many towns upstream; moreover, the flooding reactivated an ancient landslide downstream, the Aniangzhai landslide. To understand the failure mechanism and risk of such events, a combination of in-situ investigation, remote sensing analysis, and simulation were performed. Field investigations and high-resolution images confirmed that two potential sliding masses detached from the slope, with a overall volume of approximately 30 million m3. To understand the overall disaster chain and evaluate the effects linked to these potential sliding masses, the multi-hazard chain was systematically analyzed using various data and approaches, Finding shows that the reactivation of the Aniangzhai landslide are resulted from the continuous down-cutting and erosion by outburst flooding. Finally, the hypothetical scenarios analyses were completed with respect to the landslide dam and resultant flooding. Integrated studies of disasters based on such a systematic approach can be applied to future analysis of similar hazard chains.