Hazard Assessment of Unstable Rock Mass Collapse in Hydropower Station Areas Based on Spatial Motion Characteristics

Pumped-storage power stations are typically built in steep, mountainous terrain, where rock-slope collapse threatens critical infrastructure including powerhouses and dams. Conventional assessments seldom consider the full 3-D kinematics of unstable rock masses. To fill this gap, we present a spatial-motion-based method for evaluating slope-collapse hazard at hydropower sites. Using the planned lower reservoir area of a pumped-storage station in southwestern China as a case study, unmanned-aerial-vehicle photogrammetry was employed to obtain the spatial distribution, geometric features, and topographic attributes of unstable rock masses. These data were used to generate a high-resolution DTM and an orthophoto mosaic.RocPro3D simulated the 3-D trajectories of falling rocks. A comprehensive evaluation model integrating four indicators—rock-mass stability, rockfall kinetic energy, bounce height, and trajectory density—was established to classify hazard levels and propose corresponding protection measures. This assessment framework enables spatially quantitative characterization of hazard parameters and provides a scientific basis for slope-collapse mitigation design in hydropower engineering.