Spatiotemporal features of reclamation subsidence based on multitemporal interferometric synthetic aperture radar: a case study in the southeast Greater Bay Area

The uneven ground settlement caused by the reinforcement and compaction of filling materials across the Guangdong–Hong Kong–Macao Greater Bay Area (GBA) has continuously threatened infrastructure and the lives and properties of the local people. We utilize a dataset comprising 71 Sentinel-1A images from 2017 to 2023. Applying the small baseline subset interferometric synthetic aperture radar technique, we investigate and analyze the surface deformation of the southeast GBA and its underlying causes and mechanism. The results indicate that the deformation is mainly concentrated over the Hong Kong International Airport and the waterfront areas of southeast GBA, with maximum deformation rates reaching 20 mm/year. Dynamic changes in tidal water levels cause periodic minor vertical deformations in reclaimed areas, with a correlation coefficient greater than 0.61 between them. Within reclaimed areas of the southeast GBA, except for the natural consolidation of soft soils, changes in tidal water levels also play a significant role in ground subsidence, a finding that has been rarely studied or mentioned in previous research, which should be taken into local government’s consideration and measurements. Generally, the study area can be divided into three risk levels, i.e., low-risk, medium-risk, and high-risk zones amounting to 1.87%, 0.11%, and 0.01%, respectively.