Hydrological control shift from river level to rainfall in the reactivated Guobu slope besides the Laxiwa hydropower station in China

• Published in: Remote sensing of environment 2021-11, Vol.265, p.112664, Article 112664
• Main Authors: Shi, Xuguo, Hu, Xie, Sitar, Nicholas, Kayen, Robert, Qi, Shengwen, Jiang, Houjun, Wang, Xudong, Zhang, Lu
• Format: Article
• Language: English
• Subjects: Drawdown; Flooding; Geological hazards; Global positioning systems; GPS; Hydraulic diffusivity; Hydroclimatic controls; Hydroelectric power; Hydroelectric power stations; Hydrology; Impoundments; InSAR; Interferometric synthetic aperture radar; Interferometry; Land degradation; Land use; Landslides; Landslides & mudslides; Movement; Precipitation; Radar; Rainfall; Reservoir water; Reservoirs; River erosion; River levels; Rivers; Rock masses; Rocks; Rockslides; Seasonal precipitation; Shaking; Slopes; Synthetic aperture radar interferometry; The Guobu slope; Triggered landslide; Water levels; Wave erosion
• ISSN: 0034-4257; 1879-0704
• DOI: 10.1016/j.rse.2021.112664

Landslides are common geohazards associated with natural drivers such as precipitation, land degradation, toe erosion by rivers and wave attack, and ground shaking. On the other hand, human alterations such as inundation by water impoundment or rapid drawdown may also destabilize the surrounding slopes. The Guobu slope is an ancient rockslide on the banks of the Laxiwa hydropower station reservoir (China), which reactivated during the reservoir impoundment in 2009. We extracted three-dimensional surface displacements with azimuth and range radar interferometry using European Space Agency's Copernicus Sentinel-1 and German Aerospace Center's TerraSAR-X data during 20152019. The upper part of the Guobu rockslide is characterized by toppling and is mostly subsiding with maximum rates over 0.4 m/yr and 0.7 m/yr in the vertical and horizontal directions, respectively. During filling of the reservoir prior to 2014, there was a long-wavelength in-phase response between rising reservoir level and GPS-observed increased slope movements. After the reservoir water level stabilized from 2015 to 2019, the slide movement became seasonal and we see a correlation between rainfall and landslide movement. These observations suggest that the slide motion is now primarily controlled by rainfall. The spatiotemporal landslide displacements allow us to estimate the hydraulic diffusivity of the rock mass, to be on the order (~1.05 × 10‐7 m2/s) and the thickness of the moving rock mass (~200 m). Our results demonstrate that InSAR is a useful tool for monitoring the rockslide movement as a function of seasonal precipitation. •Map 3D surface motion of Guobu slope using traditional and split-bandwidth InSAR.•Control of the slope stability shifted from river level to rainfall in 2014–2015.•Vertical and horizontal rates are 0.4+ and 0.7+ m/yr respectively during 2015–2019.•The hydraulic diffusivity is ~1.05 × 10‐7 m2/s, in the range for fractured rocks.•The inferred mass movement is ~200-m thick and ~107-m3 in volume.