Land Subsidence in Fort Bend County, TX
A story map showing information and data on subsidence in Fort Bend County
What is land subsidence?
Land subsidence, also known as ground subsidence, is when the land begins to sink.
What causes it?
Land subsidence is caused by the removal of ground water or other material, such as building water pumps and mining (Holzer & Galloway, 2005).
This story map will focus on groundwater subsidence.
Aquifers manage to replenish their reservoirs naturally. The natural ground water recharge is principally a result of rainfall (Kumar & Seethapathi, 2002).
This recharge is dependent on the amount and duration of rainfall that the regions collect (Kumar & Seethapathi, 2002).
For certain regions, this may be an issue with the limited rainfall that is received throughout the year. Also, with the effects of climate change, some regions may be recharging less throughout the years, causing a larger imbalance of the recharge rate and the extraction rate of groundwater (Collados-Lara et al., 2020).
Is it Dangerous?
Yes! Land subsidence is a hidden threat since the effects occur slowly over time and reveal its damaging effects unexpectedly.
It is also becoming a problem in the areas surrounding Houston, which includes Fort Bend County.
This image provided by the USGS shows the approximation of land levels for those years labeled. Subsidence has caused the area to sink 6.2 ft from 1988 - 2016.
How is it dangerous?
Subsidence causes permanent inundation of land, aggravates flooding, changes topographic gradients, ruptures the land surface, and reduces the capacity of aquifers to store water (Holzer & Galloway, 2005).
The flooding of Hurricane Harvey was also aided by subsidence.
Subsidence also disrupts:
- Collector drains and irrigation ditches.
- Alter the flow of creeks and bayous (causing frequent flooding).
- Damage roadways, bridges, building foundations, and other infrastructure. (USGS, N.D.)
How is Fort Bend County affected and why?
Fort bend county is sitting on top of three aquifers, the Chicot, Evangeline, and Jasper aquifer. However, only the Chicot and Evangeline are being used to extract groundwater.
The aquifers have been the primary source of water for municipal supply, commercial and industrial use, and irrigation in the Houston-Galveston region since the early 1900s. (USGS, N.D.)
The chart here reflects that by 2017, the entire state of Texas used 74% of groundwater obtained from aquifers, for irrigation.
Groundwater has been extracted from the Chicot and Evangeline aquifers since the 1880’s, where about 1 to 2 million of gallons per day (mgd) turned to about 167 mgd by 1972 (Gabrysch & Bonnet, 1977).
Land subsidence d in Fort Bend county between 1943 and 1964 exceeded 1 foot (Wesselman, 1972).
A study calculated that the subsidence rate of about 10 to 25 mm/year occurred in the City of Sugar Land, a city located inside of Fort Bend county, where there were no water regulations in place until recently in 2010 (Yu et al., 2014).
The .gif image below shows the average changes in land from 1906-1978 and 1906-2016 in feet. You can see the large amount of changes that the data from 1906-2016 shows, where subsidence affected certain areas more than other. The labeled numbers here shows the amount of subsidence that occurred in feet since the year 1906.
This data was obtained from the Harris-Galveston Subsidence District.
The slideshow below uses GPS data located within Fort Bend County and this data is important because you can see how much the land rises or sinks as a result of subsidence.
Here, green coloration shows a rise in the land while the red shows areas that have sunk for the year. The contour lines were added to give a visualization on the surface changes.
Clink on the arrow located to the right and see the level of changes occurring!
Scientists have been able to map out land subsidence changes in Harris county.
Here, the darker blue areas have been affected the most by subsidence followed by the red areas, and lastly the brighter yellow.
Kasmarek, et al., 2016
What can you do to help?
There's a lot that you can do at home to help conserve water usage!
The Harris-Galveston Subsidence District is a great place to start and learn about being smarter!
You can learn about conserving water, school programs, grant programs, watering your yard, and more!
A few things you can do right now include using shower heads that reduce water usage, be mindful of running water, doing laundry when you have full loads, and fixing water leaks as soon as possible.
Thank you so much for taking your time and reading through this material! I hope you found it insightful and are able to help conserve water to reduce any subsidence impacts here at home.
Sesame Street: Water Conservation
