Prediction and risk assessment of Magantang landslide generated waves in Shuibuya Reservoir, Qingjiang River, China.

The Magantang Landslide is located in the Qingjiang Shuibuya reservoir in Hubei Province, China. The landslide has developed multiple fissures due to the reservoir impoundment, which reduces the slope stability and threatens residents' lives and properties in the reservoir area. In this study, we applied the software Geostudio to carry out the steady and seepage stability analysis of the Magantang landslide under the influence of reservoir water level fluctuations and extreme rainfall. The study identifies the potential sliding velocity range for unstable landslides, based on multiple similar events, and selects four velocities within this range for analysis. We use the Tsunami Squares to simulate wave generation and inundation caused by the landslide impacting water and assess the potential hazard risk in the reservoir area. The results show that (1) The Magantang landslide is in a stable state as a whole, but the reservoir water drawdown and heavy rainfall will reduce the stability of the slope; (2) If the landslide fails at velocities of 6.5 m/s, 10.5 m/s, 14.4 m/s, and 17.8 m/s, the initial wave heights are 7.44m, 10.6m, 13.17m, and 17.83m respectively, washing the opposite shoreline to a maximum inundation of 9.91m, 12.56m, 15.63m, and 20.76m respectively. Within a range of 5 km, wave heights decrease sharply; (3) Tsunami Squares simulations show that the major risk area under the most unfavorable scenario distributed 8 km upstream and downstream of the landslide along the Qingjiang River, the runup wave would impact ten houses and one substation. The results have not only laid the foundation for the theoretical study of reservoir landslide tsunami disasters but also provided practical suggestions for actual disaster prevention.