InSAR Time Series Analysis to Evaluate Subsidence Risk of Monumental Chandigarh City (India) and Surroundings.

Groundwater depletion is one of the serious geoenvironmental issues causing ground subsidence, which damages buildings, infrastructures, and causes loss of life. The quantitative and qualitative evaluation of groundwater variability requires multiple approaches to measure hydraulic head level and geodetic deformation. In this study, we have made efforts to integrate multiple hierarchical space-borne data, including Gravity Recovery and Climate Experiment (GRACE), Sentinel-1 interferometric synthetic aperture radar (InSAR), and geological and hydrological data, to quantify subsidence in Chandigarh city and its surroundings. First, we conducted New-Small BAseline Subsets (NSBASs) and pointwise persistent scatterer (PS) InSAR techniques in parallel, using three-year Sentinel-1 data showing a vertical subsidence up to 120 mm/year around fluvial sediment deposits. Furthermore, correlation analysis of hydraulic/climatic measurements clearly shows the subsidence associated with the groundwater depletion. The pattern of PS points shows the instability of structures associated with the ground subsidence over the central city areas. The monumental architectures designed by Le Corbusier in the northern sectors are outside of the main subsidence area. In the target area, the magnitude of subsidence and surface deformation due to groundwater depletion depends on the subsurface geophysical environment and the anthropogenic activities within the region and surroundings. The results provided a case of monitoring scheme using multiresolution satellite data about the subsidence and associated consequences due to groundwater depletion.