A big landslide on the Jinsha River, Tibet, China: geometric characteristics, causes, and future stability

On October 10, 2018, a big landslide occurred on the right bank of the Jinsha River in Baige Village, Polo Township, Jiangda County, Tibet (hereafter called the Baige landslide), which blocked the Jinsha River, forming a barrier lake. Afterward, the landslide dam broke, producing a flood. On November 3, the rear wall of this landslide failed again, also blocking the Jinsha River and creating a bigger barrier lake. Then, by local people, a discharge channel was excavated on the top of the landslide dam, making lake water cross over the discharge channel. As the water flow gradually increased, the landslide dam broke again, producing a more severe flood, resulting in huge economic losses downstream. The purpose of this study is to understand the cause of this landslide and predict the future stability of its head scarp, providing some support for the control scheme in the later stage. A digital orthophoto map (DOM) and a digital elevation model (DEM) of the landslide were created using an unmanned aerial vehicle. Then based on the DOM and DEM, the geometric characteristics of the landslide were described. Multi-phase Planet 5 images were used to infer the development process of the landslide. Finally, the cause of the landslide was analyzed based on the rainfall data and the limit equilibrium calculation. The results show that the Baige landslide was a self-weight creeping event, and its development and trigger were independent of the rainfall. Before the landslide, the slope experienced five stages of evolution: steady deformation, slow deformation, rapid deformation, steady deformation, and rapid deformation. The limit equilibrium calculation indicates that the stability coefficient of the middle section of the head scarp is the lowest, thus which should be cut down as a priority. This study provides a typical example of a self-weight creep type landslide, and an important reference for prediction and prevention of similar large landslides in the Tibetan Plateau, southwestern China.