Land subsidence (2004-2013) in Changzhou in Central Yangtze River delta revealed by MT-InSAR

Land subsidence in Changzhou City in the central Yangtze River Delta of China poses a serious threat to the safety of the environment and infrastructures. Excessive groundwater withdrawal, rapid urbanisation and industrial activities contribute to land subsidence in this area. In this study, we used the multi-temporal InSAR (MT-InSAR) technique to describe the spatiotemporal characteristics of land subsidence in Changzhou. Twenty-five ENVISAT ASAR and 29 TerraSAR-X images acquired from 2004 to 2013 were used to determine the rate and temporal evolution of land subsidence. We used the ERA-Interim model instead of spatiotemporal filtering in traditional MT-InSAR to mitigate the atmospheric phase screen. The InSAR-derived results were evaluated by comparing data from three time series methods and different bands (C and X bands), and accuracy was validated through levelling surveys and GPS measurements. For three regions, a distinct subsidence pattern was observed in major industrial areas with a maximum subsidence rate of up to -39.9mm/year. We also characterised the spatiotemporal variations of land subsidence in major industrial areas in Changzhou. The deformation of large-scale man-made linear features, namely high-speed railways, highway networks and a bridge, was analysed. The spatiotemporal characteristics and possible reasons for the observed subsidence were discussed to provide a reference for future urban development planning in Changzhou.