Spatial-temporal evolution of landslides spanning the impoundment of Baihetan mega hydropower project revealed by satellite radar interferometry

Abstract

Reservoir landslides are the focus of geohazards associated with mega hydropower projects and have been extensively studied by monitoring their post-impoundment deformation. However, how landslide deformation changes before, during, and after impoundment is rarely known. Using satellite radar interferometry, we map 200 active landslides with their time-series deformation spanning the impoundment of Baihetan, the second-largest hydropower project globally. We define the amplitude of seasonal fluctuation (ASF) to analyze the impact of rainfall and water level on seasonal landslide velocities before and after impoundment. Interestingly, although landslides are overall accelerated, a reduction in seasonal fluctuation is apparent after the impoundment. We argue that the project elevated water levels during the dry season, only promoting landslide motion when they were kept stable before impoundment. We also find the 32 newly formed landslides are more likely to develop on slopes with structures related to river flow direction, emphasizing the role of the raised water in triggering new landslides. These findings reveal how landslides respond to mega hydropower projects, facilitating disaster risk management and resettlement policy regulation.