Land subsidence risk assessment along metro lines in Shanghai using InSAR monitoring data and optical images

Abstract

Land subsidence, one of the most common geological hazards in urban development, poses a significant threat to the safe operation of urban infrastructure. Conducting risk assessment of land subsidence along metro lines is vital to ensure the safe operation of metro lines and enhance urban safety resilience. Based on monitoring data acquired by Interferometric Synthetic Aperture Radar (InSAR) from 2013 to 2020 and socio-economic data of Shanghai in 2020, an index system suitable for the risk assessment of land subsidence along metro lines was proposed. This system comprises four hazard evaluation factors: maximum cumulative settlement, maximum differential settlement, average annual settlement rate in the past year, and time of opening to traffic. It also includes four vulnerability evaluation factors: population density, gross domestic product (GDP) per unit area, proportion of construction land, and proportion of building area. The risk zoning map of land subsidence along the metro lines was obtained using analytic hierarchy process (AHP), comprehensive index method (CIM), and spatial analysis based on geographic information system (GIS). The zoning results showed that the metro lines were generally located in moderate-risk zones of land subsidence with effective controllability, while high-risk areas were mainly concentrated in four locations: the section between Xidu Station and Jiangchuan Road Station of Line 5, the section between Zhaojiabang Road Station and Dong’an Road Station of Line 7, the section between Songyuan Road Station and Yili Road Station of Line 10, and the section between Yunjin Road Station and Longyao Road Station of Line 11. Optical images were particularly employed to support the assessment results by detecting changes in relevant regions, thereby strengthening and enriching the basis for formulating effective prevention and control strategies for land subsidence.