Quantitative risk analysis of the hazard chain triggered by a landslide and the generated tsunami in the Three Gorges Reservoir area

Abstract

Landslides sliding rapidly into water bodies may trigger tsunamis, which can threaten not only elements at risk on the slopes but also ships and piers on the water bodies. Management of both direct risks from landslides and indirect risks from landslide-triggered tsunamis along navigation channels is thus highly challenging. In this study, a framework, including hazard and risk identification, hazard analysis, consequence analysis, and risk estimation, is proposed for risk analysis of a landslide-triggered hazard chain, through a case study of the Liangshuijing landslide in the Three Gorges Reservoir area, China. Detailed monitoring data of the landslide indicates a significant influence of the reservoir level fluctuation on the landslide stability. Then, the hazards of both the landslide and its triggered tsunami are predicted by landslide stability calculation, run-out analysis, and tsunami propagation simulation according to defined scenarios. The vulnerability of identified static and dynamic elements at risk is quantified based on hazard intensity and their resistance to the hazard. The total risk, estimated by the sum of the direct risk and the indirect risk from the hazard chain, increases during the drawdown period of the reservoir level. Risk maps are designed to present the dynamic indirect risk along the Yangtze River. Systematic risk analysis emphasizes that the indirect risk from the potential tsunami is much higher than the direct risk, which supports the practical mitigation strategy of the landslide. The framework proposed in this study can be helpful to mitigate reservoir landslide risks, and provides a reference through which entire landslide hazard chains can be analyzed.