QUANTIFYING LAND SUBSIDENCE IN COASTAL TEXAS USING GEOPHYSICAL AND REMOTE SENSING OBSERVATIONS

Land subsidence and sea level rise are well-known, ongoing problems that are negatively impacting the entire Texas coast. As subsidence poses problems to all coastal communities, infrastructure, and wetland habitats, it is important to determine the rates, locations, and factors controlling this phenomenon. In this study, two independent techniques were used to quantify rates of land subsidence in the Texas Coastal Bend region: temporal gravity and Interferometric Synthetic Aperture Radar (InSAR). Temporal (bi-monthly) gravity measurements have been collected (from October 2020 till now) at six locations along the Coastal Bend of Texas: Packery Channel, Bob Hall Pier, Port Aransas, Rockport Harbor, Nueces Bay, and the Lexington. Collected gravity data were then corrected for tide and drift effects and converted to height variations. InSAR data (Sentinel-1) and techniques (persistent scatterers) were used to generate land subsidence rates during the period from October 2016 to July 2019. InSAR-derived rates were validated and calibrated against those extracted from the available 13 Global Positioning System (GPS) stations. Results indicate that: (1) land subsidence rates in the Texas Coastal Bend exhibit both spatial and temporal variabilities, and (2) land subsidence in the Texas Coastal Bend can be attributed mainly to hydrocarbon and groundwater extraction, sediment compaction, as well as vertical movements along growth faults. Additional temporal gravity measurements and longer InSAR time series are currently being collected and processed to refine the observed land subsidence rates.