Geomorphic signatures of reservoir–slope hazards triggered by the Baihetan Reservoir impoundment, lower Jinsha River, China

Objective Slope instability triggered by reservoir water-level fluctuations represents a prevalent geohazard in mountainous regions and canyons undergoing large-scale hydropower development. Since the 21st century, accelerated hydropower development has necessitated enhanced methodologies for identifying such specific-type geohazard potentials. In recent years, InSAR observations have largely addressed the challenge of identifying large-scale, multi-target deformation; however, due to limitations in real-time monitoring capabilities, this technique cannot detect latent hazards that have not yet manifested as deformations. Therefore, there is an urgent need to establish geomorphic signatures of reservoir-induced slope failures to improve hazard identification specificity. The large-scale impoundment of the Baihetan Reservoir since 2021 has triggered a series of slope instabilities, providing an exceptional opportunity to define the geomorphic signatures. Methods We integrated InSAR observations, geomorphic parameters, and optical imagery. Specifically, we utilize 228 ascending and 234 descending Sentinel-1A datasets (2020–2023) processed with DS-InSAR to identify deformed slopes triggered by reservoir water-level fluctuations. Results The results demonstrate the explanatory power of geomorphic parameters such as toe height, slope, aspect, and roughness in relation to disaster triggers. Furthermore, the analysis reveals correlations between lithological variations, slope structures, precipitation, and reservoir water-level fluctuations. Conclusion The strength of lithology, slope structure, and geomorphometric parameters in the Baihetan Reservoir area, along with their corresponding numerical ranges, form composite geomorphic signatures that can be used to identify hazards associated with reservoir water-level-induced slope instability early on. Additionally, we discovered that, beyond the effects of water-level fluctuations , precipitation events also play a significant role in triggering slope instability in the reservoir area, highlighting the importance of this factor as a driving force. Significance These insights significantly advance risk mitigation strategies for hydropower projects, facilitating optimal site selection and operation of hydropower stations, while providing a reference framework for assessing other slope instability mechanisms.