Spatial and temporal characteristics and evolutionary mechanism of surface subsidence in Wanqingsha soft soil area in Pearl River Estuary based on SBAS-InSAR

Rapid urbanization has stimulated the human-land conflict in the Pearl River estuary. Several years of land reclamation have induced serious ground subsidence disasters, which seriously constrains the coordinated development of economy, society and ecology. The authors in this study focused on Wanqingsha area in the Pearl River Estuary and selected 24 views of C-band Sentinel-1A uplinked SAR images between December in 2015 and December in 2016. The SBAS-InSAR technique and high-accuracy borehole monitoring data were used to extract spatial and temporal characteristics and evolutionary mechanism of the surface subsidence. The research results indicated that the overall average sedimentation rate in the study area was -9.45 mm/a, and the most significant area is Nansha Port. It showed a pattern of increasing subsidence rate from the interior to the coast, and experienced the trend of point-sheet-surface, slow-fast-steady subsidence. Three typical subsidence centers were Nansha Port, Shazai Village and Nansha Bay. The mechanistic results showed that ground settlement was nurtured and developed in a fragile geologic environment dominated by soft soil development. And it was externally influenced by ground loading and precipitation recharge during the evolutionary process. The study results could provide references for urban planning and development under the background of growing contradiction between people and land, and technical support for monitoring and early warning of ground settlement and disaster prevention and control in the wide area of soft soil where the sea and land intersect.