Emergency risk management for landslide dam breaks in 2018 on the Yangtze River, China

Abstract

In October and November of 2018, the upper reach of the Yangtze River was blocked twice by landslide dams. A large landslide dam on a major river can impound a huge amount of water and trigger catastrophic flooding once it fails, imposing great risk to the downstream communities. Considering the chain of large dams and densely populated cities along the river, there is an urgent need to improve the system resilience of the Yangtze River to the landslide dam break hazard. This study presents a basin-scale emergency risk management framework based on an overtopping-erosion based dam failure model and a 1-D flood routing analysis model. Basin-wide inundation and detailed flood risk analyses are carried out considering engineering risk mitigation measures, which will facilitate the decision-making on future emergency risk mitigation plans. The proposed framework is applied to the landslide dam on the Yangtze River in November 2018. Results show that excavating a 15 m-depth diversion channel could effectively mitigate the flood risk of downstream areas. Further mitigation measures, including evacuation, removal of obstacles in the river, and preparation of certain intercept capacity in downstream reservoirs, are suggested based on the hazard chain risk analysis. The mitigation results in the case prove the effectiveness of the proposed framework. The incorporation of open-access global databases enables the application of the framework to any large river basin worldwide.