Deformation features of the Shenjiagou landslide before and after the impoundment of the Baihetan Reservoir, Southwest China

At the Baihetan Hydropower Station, the world’s second largest hydroelectric project, reservoir filling began on April 6, 2021. This resulted in a 165-m rise in the reservoir level, leading to potential landslide instability. In this study, we focus on the Shenjiagou landslide, which was exacerbated by the secondary process of water storage at the Baihetan Hydropower Station. We analyzed the deformational features of the landslide before and after impoundment via various data sources, including optical images, field investigations, borehole data, television surveys, interferometric synthetic aperture radar (InSAR), and monitoring data. A cross-wavelet transform was used to analyze the relationship between the reservoir level time series and landslide displacement. The results indicated that the Shenjiagou landslide was an old translational landslide that exhibited continuous deformation prior to the secondary process of water storage. While the reservoir was being filled, the buoyancy effect on the resistant portion decreased the landslide stability, leading to increased deformation, resulting in surface cracks, bank collapses, road damage, and tilted trees. The cross-wavelet transform revealed an in-phase link between the reservoir level time series and landslide displacement. The methods and findings are valuable for understanding the deformational features and processes of landslides in the presence of significant variations in the reservoir level.