Spatiotemporal prediction of land subsidence and its response patterns to different aquifers in coastal areas

Overexploitation of underground fluid resources is an important factor causing land subsidence, seriously threatening the development of coastal cities and the personal and property safety of residents. Due to the unreasonable exploitation of groundwater for a long time, Guangrao has become the most serious area of land subsidence in Shandong Province. The study analysed spatial and temporal evolution characteristics of settlement in the region during the last 5 years (2017–2021) and discussed the response patterns of land subsidence to groundwater level changes in different aquifers. Sentinel-1 satellite data and the short baseline (SBAS) method were used to reveal the sedimentation evolution pattern in Guangrao from 2017 to 2021. MODFLOW was used to simulate dynamic changes in groundwater flow fields to obtain more accurate and reliable gridded water level data. Geographically weighted regression (GWR) model was used to explore the spatial correlation between land subsidence and groundwater level changes in each aquifer in Guangrao. The results showed that the maximum cumulative land subsidence in the study area was 502 mm, with two subsidence centers. The GWR model of the study area was established by studying the effects of the first confined aquifer (AⅠ), the second confined aquifer (AⅡ), and the third confined aquifer (AⅢ) on different settlement zones and their spatial correlation. Positive and negative correlations existed between the water level changes of each aquifer and different subsidence zones. The changes of water level in AⅠ and AⅢ were the primary controlling factors, affecting most of the subsidence areas in Guangrao. The research results not only quantify the spatial response pattern between aquifers and land subsidence, but also provide a basis for the rational allocation of water resources and scientific prevention and control of land subsidence in coastal areas.