Multi-scale hazard assessment of debris flows in eastern Qinghai-Tibet Plateau area

Abstract

Process analysis and hazard assessment are essential for the prevention and mitigation of debris-flow hazards in mountainous areas. Many villages and ongoing infrastructure projects in China are vulnerable to large debris flows during heavy rainfall or glacier lake outbursts. Without emergency management planning, such contingencies can lead to extensive loss of life and egregious property damage. In the eastern Qinghai-Tibet Plateau area, debris-flow disasters are a common phenomenon. In this article, we analyzed the spatial distribution, activity and hazard characteristics of debris flows and established a debris-flow database by using geographic information technology. Moreover, we comprehensively analyzed the dynamic process of debris flow at a local scale, the compound effects of debris flows along riverside section and the disaster environment factors of debris flows overall scale of Sichuan-Tibet highway respectively. Accordingly, we built an applicable factor system and a comprehensive framework to quantitatively evaluate debris-flow hazard degree, and then proposed a multi-scale debris-flow hazard assessment method by analyzing typical large-scale debris-flow hazard, debris flows along riverside highway and debris flows in whole traffic corridor, respectively. Especially, with respect to typical large-scale debris-flow disaster, we proposed a dynamic process-based method to analyzed debris-flow hazard by using numerical simulation of debris flow, flood analysis, RS and GIS technology. In view of debris flows along riverside highway, we analyzed debris flow process and determined the hazard evaluation indexes and proposed a quantitative method of hazard assessment for debris flow along riverside highways. Regarding to debris flows along whole road, we proposed a quantitative method to analyze the hazard of debris flows and classified hazard levels in the debris- flow prone area along highways. Finally, these proposed methods were applied in case studies in a local scale (K3404 of G318), Xiqu river section and Sichuan-Tibet highway respectively. The results showed that the calculated risk zones consist with the actual distribution and severity of damage of the debris- flow events, which can provide scientific reference for debris-flow risk management and disaster prevention and mitigation of arterial traffic lines.