Rates of Natural Subsidence along the Texas Coast Derived from GPS and Tide Gauge Measurements (1904–2020)

Abstract

This study investigated the rate of natural subsidence along the Texas coast using multidecadal to century tide gauge (TG) and global positioning system (GPS) data sets. The rates of land subsidence and sea level rise are aligned to the Gulf of Mexico (GOM) Reference Frame 2020 (GOM20), which is tied to the stable portion of the Gulf Coastal Plain. GOM20 provides a robust reference for ruling out regional ground movements associated with regional tectonics and glacial isostatic adjustment (GIA) and highlighting natural subsidence in the Gulf Coast Aquifer region. According to this study, the mean sea level rise rate within the GOM was $2.6\mathrm{mm}/\mathrm{year}$ with respect to GOM20 from the 1970s to the 2010s. Present land subsidence along the Texas coast is dominated by the natural subsidence varying from $0.7\mathrm{mm}/\mathrm{year}$ in the central coastal area (Port Mansfield, Corpus Christi, and Rockport) to $1.6\mathrm{mm}/\mathrm{year}$ in the southern coastal area (South Padre Island) to $1.5–3.5\mathrm{mm}/\mathrm{year}$ in the northern coastal area (Freeport, Galveston Island, Texas City, and Sabine Pass). The average natural subsidence rate along the 600-km Texas coastline is $1.4\mathrm{mm}/\mathrm{year}$ with respect to GOM20. Four scenarios (lowest, medium-low, medium-high, and highest) for future coastal submergence were developed by integrating the natural subsidence and sea level rise along the Texas coast with the global sea level scenarios. Our analysis projects that the average submergence along the Texas coastline from 2020 to 2100 will be greater than 0.3 m, and likely between 0.6 and 1.2 m, but is unlikely to exceed 2.0 m.