Spatio-Temporal Characterization of a Reclamation Settlement in the Shanghai Coastal Area with Time Series Analyses of X-, C-, and L-Band SAR Datasets

Abstract

Large-scale reclamation projects during the past decades have been recognized as one of the driving factors behind land subsidence in coastal areas. However, the pattern of temporal evolution in reclamation settlements has rarely been analyzed. In this work, we study the spatio-temporal evolution pattern of Linggang New City (LNC) in Shanghai, China, using space-borne synthetic aperture radar interferometry (InSAR) methods. Three data stacks including 11 X-band TerraSAR-X, 20 L-band ALOS PALSAR, and 35 C-band ENVISAT ASAR images were used to retrieve time series deformation from 2007 to 2010 in the LNC. An InSAR analysis from the three data stacks displays strong agreement in mean deformation rates, with coefficients of determination of about 0.9 and standard deviations for inter-stack differences of less than 4 mm/y. Meanwhile, validations with leveling data indicate that all the three data stacks achieved millimeter-level accuracies. The spatial distribution and temporal evolution of deformation in the LNC as indicated by these InSAR analysis results relates to historical reclamation activities, geological features, and soil mechanisms. This research shows that ground deformation in the LNC after reclamation projects experienced three distinct phases: primary consolidation, a slight rebound, and plateau periods.

Characterizing and Monitoring Ground Settlement of Marine Reclamation Land of Xiamen New Airport, China with Sentinel-1 SAR Datasets

“…Therefore, it can be concluded that the magnitude of ground deformation after land reclamation at Xiamen New Airport is closely correlated to the completion time of land reclamation projects, i.e., significant deformation occurred in newly reclaimed areas, and the deformation rate decreased as time went by. Such a deformation pattern is in good agreement with that of other land reclamation areas, such as Lingang New City in Shanghai, China [7]. In addition, the results reveal that most areas (e.g., Region A in Figure 8a) of the second phase of land reclamation are in a state of severe deformation, with the deformation rate in the vertical direction greater than −93 mm/year from January 2017 to October 2018.…”

“…P9 in Figure 11a was in the subsidence stage before August 2017, afterward turning to uplift. Such a phenomenon was also observed in other land reclamation cases [7], which can be explained by the well-known compression mechanisms of hydraulic fill. Generally, ground deformation associated with land reclamation is induced by primary consolidation and long-term second compression of alluvial clay deposits beneath the reclamation [10,16].…”

“…Then, it moves on to the second stage, which is a slight rebound after long-term compression, such as in P9. Finally, land subsidence is in a stable state after long-term changes, such as in P1 [7]. Therefore, we can infer that the P9 uplift was caused by the rebound of reclamation fill materials after long-term compression.…”

“…Furthermore, the eight points had different deformation evolutions. The subsidence trend at P1 slowed down in November 2017 and then turned into a relatively mild subsidence pattern, which suggested that the reclaimed land entered a long-term slow compression phase [7]. However, subsidence at P4, P7, and P8 still showed a large subsidence trend, which indicated that the newly reclaimed land had just been completed and would enter the phase of primary consolidation [10].…”

“…Therefore, land reclamation activities have been performed in many countries around the world, including the USA [1], Singapore [2], the Netherlands [3], Japan [4], China [5], and other countries [6]. However, because land reclamation usually involves dumping uncompacted filling materials over unconsolidated marine sediments [7], the settlement process of reclamation foundation has become a problem of great public The function area of the airport mainly includes the flight area, the terminal area, and the supporting area, and the runway is about 3800 m in length [23]. The engineering geology of Xiamen New Airport can be divided into five layers from top to bottom, that is, sand-mixed silt (Q m 4 ) with a thickness of around 7.86 m, silt and silt mixed with sand (Q m 4 ) with a thickness of around 7 m, silty clay and clay (Q al 3 ) with a thickness of around 2.1 m, silty sand (Q al 3 ) with a thickness of around 4.9 m, and residual clay (Q el ) with a thickness of around 3.1 m. Two Landsat-8 remote sensing images of the airport were acquired on 26 March 2014 and 13 March 2018, which are shown in Figure 2a,b, respectively.…”