Combined numerical investigation of the Yigong rock slide-debris avalanche and subsequent dam-break flood propagation in Tibet, China

On April 9, 2000, a long run-out landslide occurred in Yigong, Bomi county, Yarlung Zangbo Grand Canyon, China. The displaced materials traveled approximately 10 km with an elevation difference of 3 km, and finally generated a barrier lake at the toe of the mountain. The landslide and the collapse of the associated landslide dam killed 30 people, left more than 100 people missing, and destroyed several bridges. A combined debris avalanche-dam break flood simulation was performed in this study to better understand the long run-out mechanism and behaviors of such an event. The dynamic model DAN3D was used to simulate the run-out process of the sliding mass, while the Computational Fluid Dynamics software FLOW-3D was used to simulate the duration of landslide dam break and subsequent outburst flood propagation. Output data from the DAN3D simulation were used as input parameters for landslide dam modeling in FLOW-3D. Simulated results indicated that the duration of the landslide movement was estimated at 300 s with a maximum velocity of 90 m/s. Also, the maximum flow of the outburst flood at the Tongmai bridge was approximately 130,000 m 3 /s. The observed phenomena and measured data in situ verified the validity of the numerical simulation. It is expected that the work conducted in this study could help improve the understanding of the chain disaster of the rock slide-debris avalanche and subsequent dam-break flood.