Interferometric Synthetic Aperture Radar (InSAR) is a remote sensing technique that uses satellites to measure land surface movement by comparing radar images collected at different time periods. This technique is one of several methods utilized by the Harris-Galveston Subsidence District (HGSD) to measure and monitor subsidence in the region. InSAR allows for the analysis of vertical movement of the land surface throughout the region at a higher spatial resolution. 

In 2019, the HGSD, in partnership with the Fort Bend Subsidence District (FBSD), initiated a research project with subject matter experts at Southern Methodist University to process and analyze land-surface deformation from 1992 through 2023 using multi-temporal InSAR techniques. This research project also investigated subsidence impacts, such as fault reactivation, and localized features, such as hydrocarbon fields and salt domes. The results included spatially and temporally variable land surface deformation data.

More recently, HGSD collaborated with experts at the Conrad Blucher Institute at Texas A&M University-Corpus Christi to develop an application for InSAR analysis as a monitoring tool that will allow for the tracking and detection of land surface deformation over time throughout the region, involving integrating multidisciplinary datasets for a regional, holistic approach to monitoring changes in the land surface. Routine InSAR analyses will enhance subsidence monitoring and provide a better understanding of land surface deformation in Harris, Galveston, and Fort Bend counties as well as portions of adjacent counties, including Brazoria, Wharton, Waller, Montgomery, Liberty, and Chambers counties.  

The District published a new interactive map that provides a more comprehensive view of subsidence in our region by combining InSAR technology and Global Positioning System (GPS) data.

  • The InSAR data is used to visualize changes in land surface over time to see whether the surface is moving toward the satellite (uplift) or away from the satellite (subsidence).
  • The GPS station data is used to determine the station’s position on the ground and provides accurate measurements of localized changes; you can click on each GPS station on the map to view specific data for that station, including the years of monitoring and the total amount of subsidence recorded.