Land Subsidence Analysis of the Houston Area Using interferometric synthetic aperture radar (InSAR) and GNSS

The Harris and Galveston Counties have been experiencing a prolonged process of land subsidence since the early 21st century. The Harris-Galveston Subsidence District (HGSD) manages the use of groundwater resources and monitors the subsidence rate using stations from the Global Navigation Satellite System (GNSS). However, the point observations of GNSS stations cannot capture the spatial variability of subsidence on a large scale. Here, we present an approach by combining interferometric synthetic aperture radar (InSAR) data and GNSS data to investigate the surface deformation of this region. We leverage open-access InSAR displacement products at 90 m resolution from Sentinel-1 data produced by JPL's Advanced Rapid and Imaging Analysis (ARIA) Project. Data processing was conducted by creating rate of deformation maps and time series graphs using Mintpy (Miami Insar Time series analysis). The data from the local GNSS network were also used as a reference to a regional subsidence map.
Results show an overall rate of subsidence of -2.0 +/- 0.5 mm/yr, where the high subsidence areas are in the expansion of the city towards the suburbs, with total subsidence between 6-7 cm in the Northwest part of Houston from 2019 to 2021 and 5-6 cm to the east of Houston above the bay area from 2017-2021. The highest subsidence rate is found in the Katy region, a location with oil and gas companies and residential areas. Further investigation and reviews indicate that oil and gas mining and aquifer system compaction is likely to be the primary factors. Meanwhile, some areas also show upliftment: southwest Houston, Bellaire, Hedwig Village, and the Houston Bay area shoreline. Future studies are suggested to compare the ARIA products with other methods, such as SBAS (Small Baseline subset), QPSInSAR (Quasi-Persistent Scattering Interferometry), and MTInSAR (Multi-Temporal INSAR) in order to find best performing InSAR techniques.