Abstract
Wuhan is an important city in central China, with a rapid development that has led to increasingly serious land subsidence over the last decades. Most of the existing Interferometric Synthetic Aperture Radar (InSAR) subsidence monitoring studies in Wuhan are either short-term investigations—and thus can only detect this process within limited time periods—or combinations of different Synthetic Aperture Radar (SAR) datasets with temporal gaps in between. To overcome these constraints, we exploited nearly 300 high-resolution COSMO-SkyMed StripMap HIMAGE scenes acquired between 2012 and 2019 to monitor the long-term subsidence process affecting Wuhan and to reveal its spatiotemporal variations. The results from the Persistent Scatterer Interferometric SAR (PSInSAR) processing highlight several clearly observable subsidence zones. Three of them (i.e., Houhu, Xinrong, and Guanggu) are affected by serious subsidence rates and non-linear temporal behavior, and are investigated in this paper in more detail. The subsidence in Houhu is caused by soft soil consolidation and compression. Soil mechanics are therefore used to estimate when the subsidence is expected to finish and to calculate the degree of consolidation for each year. The COSMO-SkyMed PSInSAR results indicate that the area has entered the late stage of consolidation and compression and is gradually stabilizing. The subsidence curve found for the area around Xinrong shows that the construction of an underground tract of the subway Line 21 caused large-scale settlement in this area. The temporal granularity of the PSInSAR time series also allows precise detection of a rebound phase following a major flooding event in 2016. In the southern industrial park of Guanggu, newly detected subsidence was found. The combination of the subsidence curve with an optical time-series image analysis indicates that urban construction is the main trigger of deformation in this area. While this study unveils previously unknown characters of land subsidence in Wuhan and clarifies the relationship with the urban causative factors, it also proves the benefits of non-linear PSInSAR in the analysis of the temporal evolution of such processes in dynamic and expanding cities.
Highlights
Unlike the previous Interferometric Synthetic Aperture Radar (InSAR) studies that estimated linear deformation trends and displayed annual average subsidence rates in Wuhan, we here focus on the subsidence patterns observed across the city based on the eight-year-long cumulative displacement
A Persistent Scatterer Interferometric SAR (PSInSAR) analysis of nearly 300 COSMO-SkyMed high-resolution images was used to monitor the large-area surface subsidence affecting the city of Wuhan
The results show that there are many subsidence areas in the main urban areas of Wuhan
Summary
The capital of Hubei Province, is the largest city in central China and one of the most important industrial bases and transportation hubs of the country; it is famous for its “major juncture of nine provinces”. Wuhan has a registered population of 9.08 million and a floating population of 5.1 million [1]. With the relaxation of the settlement policy, the urban population will continue to increase, and so will the demand for housing in the city. The external expansion of the city is inevitable, followed by a new round of urban construction
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