Spatiotemporal evolution and surface response of land subsidence over a large-scale land creation area on the Chinese Loess Plateau

For Yan'an (China) and many other cities on the Loess Plateau, development is limited by a severe lack of available land. To support the city's sustainable development, the Yan'an New District (YND) was constructed in 2012 through a mountain excavation and city construction (MECC) project. However, rapid land creation and urbanization have caused extensive anthropogenic land subsidence, which may impose new constraints on YND development. This study investigated the spatiotemporal development pattern and long-term temporal response of land subsidence related to land creation in the YND. First, 95 Sentinel-1 images acquired from 2016 to 2019 were analyzed with the small baseline subset (SBAS) interferometric synthetic aperture radar (InSAR) method to reveal the long-term displacement rates and spatiotemporal displacement patterns in the YND region. The interrelationship between the spatiotemporal variations in ground subsidence and the land creation history was also discussed. Then, an exponential model was employed to characterize the InSAR time series to assess the long-term displacement trends and temporal response of the land-subsidence process related to land creation. The results suggest that the observed long-term subsidence patterns in the land creation area showed an exponentially decaying trend with the fill compaction process. The newer and thicker the loess fill foundation was, the greater the subsidence rate and the smaller the decay trend over the same observation time, indicating slower stabilization relative to the compaction of the filling loess. The spatial variation in the significant land subsidence zone gradually shifted toward the newly formed fill area as the land creation area expanded. In addition, the ground displacement response estimates highlighted that most of the Qiaoergou subsidence zone in the YND will continue to sink for approximately 7.2 years following the InSAR observations used here. These findings have important implications for disaster mitigation and urban planning in similar large-scale land creation areas.