In the simplest of terms, land subsidence is the gradual sinking of the Earth’s surface due to subsurface movement. In the greater Houston area, groundwater withdrawals have caused subsidence, or land sinking.
Although the process is slower than that of other natural hazards, subsidence has serious consequences. Once subsidence has occurred in our area, it is irreversible. Given our region’s proximity to the coast, any loss of land surface elevation poses significant threats from weather-related events like storm surges and flooding.
To prevent further subsidence, the Harris-Galveston Subsidence District works diligently to reduce reliance on groundwater through groundwater regulation and water conservation.
Illustration of subsidence in a Gulf Coast aquifer as a result of groundwater withdrawals producing a decrease in the potentiometric surface (the groundwater level). Source: Kasmarek, M.C., Ramage, J.K., and Johnson, M.R., 2016, Water-level altitudes 2016 and water-level changes in the Chicot, Evangeline, and Jasper aquifers and compaction 1973–2015 in the Chicot and Evangeline aquifers, Houston-Galveston region, Texas: U.S. Geological Survey Scientific Investigations Map 3365, pamphlet, 16 sheets, scale 1:100,000, http://dx.doi.org/10.3133/sim3365.
HGSD applies a science-based Regulatory Plan that establishes guidelines for groundwater withdrawals through a well-permitting process to reduce reliance on groundwater. The Regulatory Plan is an adaptive management strategy that is regularly reviewed using the best available data to ensure it is effective in preventing further subsidence.
The District also provides water conservation tools and resources to further reduce reliance on groundwater.
HGSD was created by the Texas Legislature in 1975 to prevent further subsidence. HGSD applies a science-based Regulatory Plan that establishes guidelines for groundwater withdrawals through a well-permitting process to reduce reliance on groundwater. The Regulatory Plan is an adaptive management strategy that is regularly reviewed using the best available data to ensure it is effective in preventing further subsidence. The most recent review was completed in 2025.
The goal is to shift our region’s primary water supply from groundwater to sustainable alternative water supplies that do not cause further land subsidence. However, the transition from groundwater to alternative water supplies (surface water, reclaimed water, etc.) is complex and requires regional water planning, which is why the Texas Legislature created Regional Water Authorities to provide local control for these water infrastructure projects. Regional Water Authorities are responsible for facilitating the conversion from groundwater to alternative water supplies to meet HGSD’s Regulatory Plan requirements.
In the 1990s, Regulatory Areas 1 and 2 were converted to surface water to meet the requirements laid out in HGSD’s Regulatory Plan, and they now have significantly improved subsidence rates. Conversion to alternative supplies is an ongoing process in Regulatory Area 3, with full conversion required by 2035.
Considerable supplies of surface water are available through the development of Lake Livingston on the Trinity River, Lake Houston and Lake Conroe on the San Jacinto River, and the Brazos River. The HGSD reviews the availability of freshwater resources as part of the science and research program. An alternative water supply assessment was completed as part of the Joint Regulatory Plan Review, which included an assessment of aquifer storage and recovery, brackish groundwater, and seawater desalination as alternative water supply options.
Our area has experienced the following consequences of subsidence:
- Permanent elevation loss
- Increased flooding
- Damage to infrastructure like roads, bridges, homes, pipelines, and more
- Faulting
One of the most significant instances of subsidence occurred in the Brownwood Subdivision in Baytown, Texas. The Brownwood subdivision originally had over 400 homes built in the 1940s. As a result of large volumes of groundwater withdrawal, the area experienced up to 10 feet of subsidence, leading to some homes being inundated and others experiencing frequent flooding. Brownwood is now mostly underwater and has been turned into the Baytown Nature Center – a habitat for native plants and animals. The Houston History Magazine wrote an article in March 2019 that includes links to original video footage of the site and interviews with the residents of Brownwood.
Brownwood Subdivision in 1944 to 2002. Slide the arrows to see the impact of subsidence.