Assessing Land Deformation in Trivandrum City, Southwest India, Using Time Series InSAR Analysis

Groundwater abstraction is a major anthropogenic factor behind local land subsidence, which increases the risk of floods, loss of biodiversity, and storm damage in coastal areas, especially when combined with the threat of relative sea-level rise (SLR). The heavily populated coastal region of Trivandrum city in Kerala, situated along the southwestern coastline of India, exhibits a high susceptibility to sea surges and has undergone significant climatic fluctuations throughout the Holocene epoch. In this study, we investigate land deformation in Trivandrum City by conducting an InSAR analysis of Sentinel-1 data from 2019 to 2022, coupled with groundwater level data from observation wells. Our primary objective is to ascertain whether Trivandrum is experiencing significant land subsidence. Between 2019 and 2022, Trivandrum City exhibited land uplift at rates ranging from 2 to $9 \mathrm{~mm} / \mathrm{yr}$ without any instances of land subsidence. The southern part of the city experienced a more pronounced uplift than the rest of the city, while a small land subsidence was detected north of Trivandrum City’s border. Available groundwater level trends do not align well with the observed land uplift in Trivandrum City.