Advancing reservoir landslide stability assessment via TS-InSAR and airborne LiDAR observations in the Daping landslide group, Three Gorges Reservoir Area, China

The Three Gorges Reservoir Area (TGRA) is highly susceptible to the reactivation of ancient landslides and the emergence of new ones due to the fragile geological conditions and the regulation of water levels. This study integrated multi-source data from space-air-ground-based platforms to investigate the dynamics and stability of the Daping landslide group on the bank of TGRA. Monitoring active landslide deformation is essential to ensure the safety of coastal residents and waterways. The results demonstrate that combining Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) and Distributed Scatterer InSAR (DS-InSAR) methods effectively increases measurement point density and enhances the visibility of displacement. The reliability of using InSAR monitoring results for landslide analysis has been validated through the consistent displacement trends between the InSAR and Global Positioning System (GPS) points with a high correlation (R-2 = 0.968). Spatial-temporal variations in the displacement of the Daping landslide group were observed during the monitoring period, attributable to fluctuating reservoir water levels and rainfall events. Additionally, Light Detection and Ranging (LiDAR)-derived Digital Elevation Model (DEM) from Unmanned Aerial Vehicle (UAV) was employed to reveal the actual micro-geomorphological and topographical features related to landslide movement, such as the bank slump at the toe of the landslide. This bank slump itself is a consequence of water-level fluctuations following the impoundment of TGRA. Numeric simulation was conducted to quantitatively assess the influence of bank slump on the slope's stability, the displacement results of which were consistent with those of GPS and InSAR. The evolution characteristics of the Daping landslide group were summarized as a sequence of events: bending-tensile cracking-sliding failure along weak surfaces and predicted future development. The findings of this study hold significant importance for effective monitoring of slope bodies in reservoir areas, providing valuable insights into potential landslide risks and contributing to overall safety measures.