Abstract:  Since the 20th century, the frequency of geological disasters appearing in the form of disaster chains has significantly increased. Currently, there are few researches on the evolution process and impact scope of the disaster chain. In this paper, the evolution process of the disaster chain was illustrated taking the high-level remote landslide debris flow disaster chain in Tiejiangwan, Hongya County, Sichuan Province on April 5, 2021 as an example. The initiation source is high-level collapse, and a large number of falling rock blocks impact and load the rock and soil mass on the lower slope to form a landslide, and then the avalanche debris flow material of the landslide develops into a debris flow towards the Shuangxi River under the influence of rainfall. RAMMS software was used to numerically simulate and analyze the movement process of the debris flow, and its impact range was delineated under different rainfall frequency. The results show that the impact scope covers some scattered farmers in the upstream of Shuangxi Village under the frequency of rainfall in 20 a, the impact area covers the densely populated area of Shuangxi Village under the frequency of 50 a, and the impact area will continue to develop downstream and extend to the residential area of Laozhaohe under the frequency of 100 a. During the disaster chain, the maximum rainfall in the vicinity of Tiejiangwan close to the frequency of 10 a rainfall. It was found that the simulated results of the 10 year return period was consistent with the actual impact range, indicating that the simulation results were reliable.

Key words: disaster chain, debris flow, barrier lake, numerical simulation, high level remote, Tiejiangwan, Hongya County