Impacts of Extreme Landslide Dam Event on the Yarlung Tsangpo Basin: Fid-Bau Portal

Impacts of Extreme Landslide Dam Event on the Yarlung Tsangpo Basin

Shen, Danyi / Shi, Zhenming / Peng, Ming

The Yarlung Tsangpo River Grand Canyon is the most precipitous place in the Yarlung Tsangpo River, has a length of 504.6 km, a slope of 0.155%, and a valley bottom elevation difference of 2,755 m. Evidence shows the Yarlung Tsangpo River as well as its tributaries are frequently blocked by landslides, avalanches, and debris flow. The breaching of some large landslide dams, such as the 2000 Yigong landslide dam and the 2018 Gyalha landslide dam, resulted in huge floods and impacted large downstream areas. This paper reports a method to analyze the breaching flood of landslide dams in different locations on the Yarlung Tsangpo River Grand Canyon. The method can be divided into two steps: first, a physical model is used to predict the breach outflow rate of the landslide dam at the prone points in the basin; second, hydraulic software is used to simulate breach outflow rate and flood routing process downstream of the dam. A digital model is composed of the Yarlung Tsangpo River and two of its tributaries are built for this purpose. The results show that the simulated peak discharge at dam sites and corresponding outflow rate along rivers agree well with field observations. The peak outflow rate is amplified when breaching floods of landslide dams on the mainstream and its tributaries are overlapped. The method proposed in this paper can be effectively applied to breaching flood evolution of landslide dams.