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 socioeconomic and environmental impacts. Coastal areas along the Gulf of Mexico are particularly vulnerable due to the combined effects of rising sea levels and ongoing land subsidence driven by groundwater withdrawal, hydrocarbon extraction, sediment compaction, and mining activities. Traditional GPS-based approaches to monitoring surface deformation are limited in spatial coverage and are costly to maintain. This study addresses these limitations by applying the SBAS-InSAR technique using Sentinel-1A SAR data from 2019 to 2024 to measure land subsidence in three major Gulf Coast cities — Houston, New Orleans, and Tampa — and to assess future flood risks by integrating InSAR-derived deformation data with sea level rise projections under the SSP5-8.5 scenario. Geographically Weighted Regression (GWR) is further applied to quantify the spatially varying relationships between subsidence and its driving factors across the three study areas.

The findings reveal significant and spatially variable subsidence across all three cities, with InSAR-derived deformation rates reaching −42 mm/year in Houston, −48 mm/year in New Orleans, and −144 mm/year in Tampa, alongside several previously unrecognized deformation zones. Vegetated areas consistently exhibit higher subsidence rates than developed regions across all three cities. Groundwater withdrawal emerges as the dominant driver of subsidence in Houston and Tampa, while in New Orleans multiple factors contribute, including hydrocarbon extraction, shallow sediment compaction, and peat oxidation. When land subsidence is combined with projected sea level rise under the SSP5-8.5 scenario, the total inundated area by 2100 is projected to reach 1,056.9 km² in Houston — an 86% increase over sea level rise alone — 166.5 km² in New Orleans, and 207.6 km² in Tampa. These results demonstrate that subsidence substantially amplifies coastal flood exposure beyond what sea level rise projections alone would indicate, and that its spatial patterns differ markedly across cities, underscoring the need for locally tailored flood risk assessments and mitigation strategies.