Monitoring and assessing reclamation settlement in coastal areas with advanced InSAR techniques: Macao city (China) case study

In the present study, we have investigated spatial-temporal behaviours of the land subsidence induced by reclamation activities in Macao Special Administrative Region, a coastal city of southern China. An advanced Synthetic Aperture Radar Interferometry (InSAR) technique, referred to as Interferometric Point Target Analysis (IPTA), was applied to retrieve the deformation rate and displacement time series during the period from July 2006 to March 2009. Validated by levelling survey measurements, the InSAR-derived results showed a fairly stable and homogeneous pattern within the land of Macao before 1912, which consists mainly of the three granitic islands of Macao Peninsula, Taipa Island and Coloane Island. In contrast, relatively large deformation rates (between − 15 and − 41 mm year − 1) and local spatial settlement variability were discovered within the latest reclamation areas. A quantitative comparison analysis of the relationship between the observed settlements and the evolution of land reclamation indicated a time-dependent settlement behaviour with respect to the age of the reclamation. Another key result was that differential settlements were detected over short distances in reclamation areas, particularly between the ground surfaces and the adjacent buildings, thus providing valuable information not only for early detection and remedial activities of potential settlement of such buildings but also for the design of future facilities adjacent to the buildings, particularly for that of large infrastructure developments.