Deformation process and kinematic evolution of the large Daxiaowan earthflow in the NE Qinghai-Tibet Plateau

Abstract

Intermittently moving earthflows are widespread geomorphological phenomena in mountainous regions. The Daxiaowan (DXW) earthflow in Zhouqu County, Bailong River Corridor of north-eastern margin of the Qinghai-Tibet Plateau, has been active for over a decade. The earthflow covering has an area of ∼1.1 km2 and a length of ∼2.7 km, and it has developed four large secondary landslides and two potential landslides. The slope movements pose great threats to the safety of the local residents and the provincial highway S314 at the toe of the DXW. In this study, we used a combination of interferometric synthetic aperture radar technology, unmanned aerial vehicle photogrammetry, geomorphological interpretation, and field investigations to study the deformation process and kinematic evolution of the DXW between 2007 and 2020. Field investigations of the earthflow revealed distinct source, transport, and compressional zone with different movement attributes. The displacement time-series results indicated that the deformation process of the DXW earthflow could be divided into two stages: steady deformation with cracks propagation and scarps slumping (during 2007–2016); progressive deformation with surges in the rainy season (during 2017–2020). Rainfall was the primary driver of deformation since 2017. The catchment topography generated by the Pingding–Huama fault has caused flowing water to accumulate on the left side of the catchment, as indicated by the Topographic Wetness Index, leading to the reactivation of DXW. This earthflow was initially reactivated from the middle part of the ancient landslide body, characterized by the gradual development from cracks and scarps to four secondary landslides. Our characterization of the mode of evolution of the DXW earthflow potentially improves our understanding of earthflow movement and landslide hazards in the Bailong River Corridor, and it provides a scientific reference for mitigating disasters risks in this and similar areas.