Risk assessment study on landslide-generated impulse waves: case study from Zhongliang Reservoir in Chongqing, China

Landslide-generated impulse waves in reservoirs can overtop and even breach the dam and cause flooding of the downstream area, leading to catastrophic events with hazardous consequences. The Xiaodongcao (XDC) landslide located on the right bank of Daning River in Chongqing, China, at the anti-dip carbonate bank slope 2 km away from the Zhongliang Dam only, has an overall volume of about 1400 × 10⁴ m³. After the reservoir impoundment, the XDC landslide began to topple violently. Based on the survey and monitoring results from this study, the front Donghuatian part, with a volume of 130 × 10⁴ m³, has the highest probability of instability. The front Lanbandeng part, with a volume of 360 × 10⁴ m³, a deformation area, will lead to the worst-case scenario. A fully coupled numerical model of fluid–solid-structure interaction is established to predict the landslide -water-dam interaction dynamic processes, under the four most probable and worst conditions. In the most likely scenario, about 48 buildings of the resettled town would be hit by a 6-m-high flow, causing hazardous consequences. In the worst-case scenarios of high water-levels in this study without considering dam break, 1.09 × 10⁶ m³ of water will overtop the dam, leading to the complete destruction of about 150 buildings. Meanwhile, some measures, such as slope reinforcement, monitoring and early warning, are discussed to reduce the risk of landslide-generated impulse wave in the study area. This study is helpful for geological disaster prevention and mitigation for Zhongliang dam reservoir and provides reference for similar case studies in the world.