The June 2020 Aniangzhai landslide in Sichuan Province, Southwest China: slope instability analysis from radar and optical satellite remote sensing data

Zhuge Xia,Mahdi Motagh,Tao Li,Sigrid Roessner

doi:10.1007/s10346-021-01777-4

Abstract

A large, deep-seated ancient landslide was partially reactivated on 17 June 2020 close to the Aniangzhai village of Danba County in Sichuan Province of Southwest China. It was initiated by undercutting of the toe of this landslide resulting from increased discharge of the Xiaojinchuan River caused by the failure of a landslide dam, which had been created by the debris flow originating from the Meilong valley. As a result, 12 townships in the downstream area were endangered leading to the evacuation of more than 20000 people. This study investigated the Aniangzhai landslide area by optical and radar satellite remote sensing techniques. A horizontal displacement map produced using cross-correlation of high-resolution optical images from Planet shows a maximum horizontal motion of approximately 15 meters for the slope failure between the two acquisitions. The undercutting effects on the toe of the landslide are clearly revealed by exploiting optical data and field surveys, indicating the direct influence of the overflow from the landslide dam and water release from a nearby hydropower station on the toe erosion. Pre-disaster instability analysis using a stack of SAR data from Sentinel-1 between 2014 and 2020 suggests that the Aniangzhai landslide has long been active before the failure, with the largest annual LOS deformation rate more than 50 mm/yr. The 3-year wet period that followed a relative drought year in 2016 resulted in a 14% higher average velocity in 2018–2020, in comparison to the rate in 2014–2017. A detailed analysis of slope surface kinematics in different parts of the landslide indicates that temporal changes in precipitation are mainly correlated with kinematics of motion at the head part of the failure body, where an accelerated creep is observed since spring 2020 before the large failure. Overall, this study provides an example of how full exploitation of optical and radar satellite remote sensing data can be used for a comprehensive analysis of destabilization and reactivation of an ancient landslide in response to a complex cascading event chain in the transition zone between the Qinghai-Tibetan Plateau and the Sichuan Basin.

Highlights

Landslides are widespread geological hazards in mountainous regions worldwide
The undercutting effects on the toe of the landslide body, which played a vital role in the toe erosion and Landslides reactivation of this ancient landslide body, are clearly visible in the optical data
The toe erosion was triggered by overflow of a dammed lake, created due to heavy rainfall and the resulting debris flows coming from the Meilong valley to the Xiaojinchuan River, and was influenced by the discharge of the surplus water from a nearby hydropower station to reduce the flood pressure

Summary

Introduction

Landslides are widespread geological hazards in mountainous regions worldwide. Landslide processes are complex and often comprise different process types. To monitor landslide disasters and build effective early warning systems (EWSs), the adopted technical means should meet at least the following requirements: Adequate regional coverage and temporal sampling capacity, sufficient measuring accuracy related to the velocity of the monitored processes, and good cost performance. Ground-based methods, such as continuous GNSS for landslide monitoring, are difficult to set up and implement in mountainous and remote areas (Akbarimehr et al 2013). Optical and radar satellite remote sensing plays a promising role in driving innovation in large-scale detection, monitoring, and assessment of landslide hazards and can be quite useful to incorporate in the framework of multidisciplinary disaster risk reduction (DRR)

Results

Discussion

Conclusion