Analysis on disaster characteristics and prevention measures of the post-fire debris flow in Dianchichang gully, Xichang of Sichuan Province

Post-fire debris flow is a special torrent containing a large amount of loose material, which is closely related to forest fire. Its characteristics are significantly different from the conventional debris flow. Therefore, conventional debris flow prevention experience is not completely applicable to it. After the fire that broke out on March 30 in Xichang, debris flow occurred frequently in burned area, seriously threatening the safety of local people's lives and property. It is necessary and urgent to study the characteristics of debris flow after fire and put forward comprehensive prevention and control measures. This study takes Dianchichang gully in Xichang, Liangshan Yi Autonomous Prefecture, Sichuan Province as a typical case. Analyzed the characteristics of burned area and watershed. Studied the characteristics of post-fire debris flow disaster. And proposed the corresponding prevention and control measures. The results show that the burned area covered 83.37%, seriously burned areas accounted for 33.47%, resulting in widely spread ash layer. Slope provenance accounted for 69.83%. Post-fire debris flow occurred one month after the forest fire, and a total of 5 debris flows occurred in the first rainy season. Moreover, the threshold of debris flow starting rainfall is small and the occurrence of debris flow increases rapidly. The post-fire debris flows in the study site are characterized by high frequency and sudden occurrence. Accordingly, the corresponding prevention and control measures were propound as follows. The rapid emergency treatment measures include clarifying dead wood on slope surface, vegetation restoration, and building of simple barrier dams in gully. Medium-term governance measures are debris dams in gully and grit basins. And long-term prevention measures are a combination of forest fire prevention and vegetation protection. This scheme has been implemented in Dianchichang gully. Since the completion of these projects, the effects of comprehensive treatments have been preliminarily proved effective for the mitigation of this type of special debris flow. It can provide reference for post-fire debris flow prevention in the future.