Mapping Subsidence over the Houston Region from Space
The Harris-Galveston Subsidence District, in cooperation with the Fort Bend Subsidence District, the Brazoria County Groundwater Conservation District, the Lone Star Groundwater Conservation District, the University of Houston, and the Brazosport Water Authority maintains a subsidence monitoring network that is constantly evolving and requires consistent investment. The network, initiated in 1994, currently extends across the Houston-Galveston region, across Harris, Fort Bend and surrounding counties, in an effort to represent the breadth and scope of subsidence in the region.
Since 2019, the Subsidence District has sponsored research conducted by Southern Methodist University (SMU) that utilizes a novel methodology to evaluate land-surface deformation (subsidence) in the region. This study, spawned from their original research that showed subsidence in southern Montgomery County was caused by exploitation of the Jasper aquifer, will investigate the combined effects of climate changes on coastal subsidence to enhance understanding of the deformation process.
Study Details
SMU is developing subsidence maps from 1992 to 2023 by integrating data obtained from multi-temporal Interferometric Synthetic Aperture Radar (InSAR), a remote sensing technique using data collected from orbiting satellites, to quantitatively evaluate subsidence over specific periods of time across the region.
After successfully implementing InSAR mapping in the Houston-Galveston region in 2019, this new project will harness the complimentary capabilities of the Subsidence District’s subsidence monitoring network and SAR imagery to develop these historical deformation maps.
Combining SAR and GPS data improves the Subsidence Districts’ understanding of subsidence in terms of rates, geographic distribution, and temporal variability. These annual subsidence maps will provide a scientific basis to minimize undesired geohazards over the region. This method of subsidence monitoring provides land-surface deformation about every meter throughout Harris, Galveston, Fort Bend, and surrounding counties. The density of this data will inform the Districts on the occurrence of subsidence between the GPS monitoring stations.
Considering the substantial area the Districts cover, the incorporation of remote sensing techniques to monitor subsidence throughout the region will provide a more resolute picture of land-surface deformation.
InSAR is a remote sensing technique that uses satellites to measure changes in land-surface elevation.
Benefits of Remote Sensing
Remote sensing can be accomplished through the use of InSAR methods or Light Detection and Ranging (LiDAR) methods. When combined with the data collected from the subsidence monitoring network, remote sensing can provide coverage between the GPS stations.
InSAR has demonstrated its capability in measuring regional or local ground deformation caused by land subsidence, landslides, earthquakes, and volcanoes among others. In contrast to the ground-based measurements, the InSAR technique has the ability of measuring deformation with a centimeter- to millimeter-level vertical precision over a large area.
In addition to the multi-temporal InSAR technique, GPS and extensometer measurements, hydraulic data, and drilling information will be analyzed to better understand the deformational history and mechanisms in this region.
References
Qu F, Lu Z, Kim J-W, Zheng W. Identify and Monitor Growth Faulting Using InSAR over Northern Greater Houston, Texas, USA. Remote Sensing. 2019; 11(12):1498. https://doi.org/10.3390/rs11121498
Feifei Qu, Zhong Lu, Qin Zhang, Gerald W. Bawden, Jin-Woo Kim, Chaoying Zhao, Wei Qu, Mapping ground deformation over Houston–Galveston, Texas using multi-temporal InSAR, Remote Sensing of Environment, Volume 169, 2015, Pages 290-306, ISSN 0034-4257, https://doi.org/10.1016/j.rse.2015.08.027.
Project Schedule
- Project Initiation: January 2020
- 2019-2021 Final Report: October 2022
- 2022-2023 Final Report: TBD