Extreme rainfall-related accelerations in landslides in Danba County, Sichuan Province, as detected by InSAR

Abstract

Landslides are frequent mountainous geohazards induced by multiple factors, such as extreme rainfall, river erosion, and intense anthropogenic activities. On 17 June 2020, a rainstorm hit Danba County, Sichuan Province, and triggered the catastrophic Aniangzhai landslide. The impact of this rainstorm on landslide kinematics in this region has seldom been investigated. We used a time-series interferometric synthetic aperture radar (InSAR) analysis to map the active slopes in Danba County using one ascending (2015–2021) and one descending (2018–2021) Sentinel-1 dataset. A total of 36 landslides (63.1 km2) were detected along riverbanks. The time series of eastward and vertical displacements during 2018–2021 were retrieved by integrating the ascending and descending Sentinel-1 datasets. The maximum eastward and vertical displacement rates obtained are 229 and −75 mm/yr, respectively. Seasonal accelerations are correlated with concentrated rainfall. We suggest that the 2020 rainstorm and the abundant precipitation during the water year 2020 altered the long-term displacement trends of active landslides. We further constrained the volumes of the Niela and Gaoding landslides in the order 3.6–6.9 × 107 m3 and 5.4–6.0 × 108 m3, respectively, using 2D displacement rates and mass conservation equations. Our results demonstrate that multi-temporal and multi-orbit InSAR measurements can provide insights into the evolution and mechanism of landslides.