Comparison study of active landslides in four giant cascade hydropower station reservoir areas on the Jinsha River, China

Large reservoir impoundment poses exceptionally severe impacts on slope stability across extended spatial and temporal dimensions, threatening hydropower infrastructure and downstream communities. Although this is a topic of great concern, there are still many disputes in the characteristics, deformation laws and mechanisms of reservoir-induced landslides. Therefore, this paper systematically compares reservoir-induced landslides in the four world-class giant cascade hydropower stations for the first time. The investigation is carried out by integrating remote sensing techniques, Interferometric Synthetic Aperture Radar (InSAR), and geostatistical analysis methods, and examines 283 landslides (198 reservoir-induced) across the four cascade reservoirs along China's Jinsha River, specifically Xiangjiaba (XJB), Xiluodu (XLD), Baihetan (BHT), and Wudongde (WDD). The results showed: (1) The reservoir-induced landslides are dominated by large-scale accumulation landslides. And reservoir-induced landslides have similar spatial distribution characteristics, mainly in low-relief topography and gentle slopes near dams, concentrating in seven zones. (2) There are significant differences in elevation difference, slope, stratigraphic lithology and relationship with tectonics of reservoir-induced landslides. Their development in in the elevation difference and slope characteristics is ranked as XJB < XLD < WDD < BHT. Geological control patterns vary among reservoirs: XJB is dominated by Jurassic sandstone-mudstone interbedded lithology; XLD and BHT are under strong lithology-structure coupling, controlled by Ordovician-Silurian-Cambrian and Ordovician-Silurian-Proterozoic lithological assemblages, respectively; and WDD, influenced by Jurassic-Proterozoic lithology and structures, is characterized by weak tectono-lithological coupling. (3) Reservoir operation mode is the most important factor affecting the deformation time, degree and mechanism of reservoir-induced landslides. The most intense deformation occurs during the first impoundment stage, and greater water-level fluctuations increase the degree of induced deformation. Hydrodynamic pressure-type landslides, the dominant type, develop on arc slip surfaces and decrease with submergence; buoyancy weight loss-type landslides show a “first increasing then decreasing” trend with submergence, concentrating on chair-shaped slip surfaces. This paper defines the similar and different characteristics of landslide induced by reservoirs, records valuable data, and provides a clear object for the prevention and control of reservoir-induced landslides.