Land subsidence in coastal reclamation with impact on metro operation under rapid urbanization: A case study of Shenzhen

Abstract

With rapid urbanization in coastal cities, the sharp increase in coastal reclamation due to human activity has caused serious land subsidence problems and threatened the safety of urban traffic in reclamation areas, especially in fast developing cities, such as Shenzhen. However, the spatio-temporal distribution of reclamation evolution and land subsidence to assist in metro operations on a regional scale remain under-explored. To fill-in this research gap, an attempt was made to monitor the coastal reclamation dynamics of Shenzhen from 1979 to 2020.The spatial-temporal changes in the reclamation were discussed based on the Landsat 5, 7 and 8 datasets along with urban growth for a 40-year period. Accordingly, the fill height distribution was employed using available global DEM datasets to perform land fill height effect of metro system in the reclamation area. After understanding the spatial-temporal patterns of land reclamation changes, we focused on monitoring the land subsidence in reclamation area using time-series Sentinel-1 Interferometric SAR (InSAR) datasets by SVD and Stacking techniques. 48 scenes were acquired during ascending and descending passes respectively between 8/3/2015 to 8/8/2023 for the study area. The field measurements of metro deformation in reclamation area acquired from investigation data reflects the risk level of metro operational risk of urban traffic. In-depth analysis of reclamation characteristics revealed a direct relationship between urban expansion, land subsidence and metro deformation. A high correlation coefficient of 0.89 was observed between land subsidence variation and the metro deformation measured along metro line 2 and line 11 in reclamation area. Understanding the impact of land subsidence on metro operation is key to refining sustainable urban development in reclamation areas.