Assessment of land subsidence and future flood hazards for coastal cities of the Gulf of Mexico using time series InSAR.

Sea level rise poses a significant natural hazard to coastal cities, with profound socio-economic and environmental impacts. This study analyzes new measurements of ongoing subsidence in Houston, New Orleans, and Tampa using Sentinel-1A SAR data (2019-2024) and evaluates its impact on future flooding risks. While the overall surface in these cities remains relatively stable, this study has identified multiple previously unrecognized land deformation zones. InSAR time-series deformation rates in the line-of-sight (LOS) direction range from - 42 to 10 mm/year in Houston, - 48 to 19 mm/year in New Orleans, and - 144 to 24 mm/year in Tampa. InSAR-derived velocities are correlated with land cover, with higher subsidence rates observed in vegetated areas compared to developed regions. Geographically weighted regression (GWR) is applied to quantify the spatially varying relationships between subsidence and potential driving factors. The results indicate that both groundwater withdrawal and hydrocarbon-related activities contribute to the observed deformation patterns, although their influence varies across locations. To assess future flood risk, InSAR-derived deformation data are integrated with the SSP 5-8.5 sea level rise scenario. The results show that subsidence increases the inundation area over sea level rise alone by up to 86% in Houston, 5% in New Orleans, and 50% in Tampa. These findings provide valuable insights for disaster risk management and urban planning in coastal regions.