28 U.S. Cities Are Sinking – But One Is Sinking at an Alarming Rate

A new alarming report reveals that 28 U.S. cities are sinking, showing signs of geological subsidence that could affect buildings and infrastructure sooner than expected. While some of this is natural, 80% is the direct result of human activity.

Satellite Measurements Reveal Land Shifts Across U.S. Cities

A large team of researchers, including geoscientists from Virginia Tech and Columbia University, used satellite-based radar measurements to assess areas of land movement and found that, from coast to coast, there was significant movement in both large and small cities. In 25 of the 28 cities, at least 65% of the urban area is sinking.

“Even slight downward shifts in land can significantly compromise the structural integrity of buildings, roads, bridges, and railways over time,” said Leonard Ohenhen, former Virginia Tech graduate student and the study’s lead author.

However, one place stands out from the others: Houston, Texas. The large southern city is facing serious problems overall, but the study revealed that 42% of its land area is sinking by more than 5 mm (0.2 inches) each year, with 12% subsiding by more than 10 mm (0.4 inches) annually. While this might not seem like much if you look at only 12 months of data, over a decade, 10 mm of subsidence represents a significant structural threat to the built environment, especially if the sinking is uneven.

“Unlike flood-related subsidence hazards, where risks manifest only when high rates of subsidence lower the land elevation below a critical threshold, subsidence-induced infrastructure damage can occur even with minor changes in land motion,” the researchers noted in the study.

Texas Cities Facing Severe Subsidence

Texas has the three cities with the fastest sinking rates among the 28, with Fort Worth and Dallas behind Houston. This is not a surprise, given the state’s climate, rapid growth, intensive groundwater use for both the population and agriculture, as well as oil and gas extraction.

The three cities sit on clay-rich soil, which naturally expands when wet and shrinks quickly when dry, making the land beneath these urban areas particularly prone to subsidence. Additionally, pumping groundwater lowers underground water pressure, which causes clay soils to contract and compact – which, as you can guess, is bad news for what’s above the surface. The weight of infrastructure and drought conditions further impact these clay-rich soils.

While Houston is still sinking, it is nothing compared to past patterns when unregulated groundwater pumping caused the city to subside nearly 5 cm (2 inches) per year at its peak. This led to a major overhaul of the system to mitigate damage.

Other cities high on the list of 28 include Chicago, New York, Seattle, Denver, and Detroit. Overall, these urban areas house about 34 million people. Scientists are concerned because, unlike natural disasters like hurricanes or floods, subsidence is less immediately impactful, making it easier (and cheaper) to ignore.

“The latent nature of this risk means that infrastructure can be silently compromised over time with damage only becoming evident when it is severe or potentially catastrophic,” said Manoochehr Shirzaei. “This risk is often exacerbated in rapidly expanding urban centers.”

Cities of Concern: LaGuardia Airport and Las Vegas

Other areas of concern for researchers included the region around New York’s LaGuardia Airport, where the land was sinking more rapidly than elsewhere in the state, and parts of Las Vegas, Washington, D.C., and San Francisco.

And it’s not just infrastructure that is at risk; any loss of land makes the area more vulnerable to flooding – an extreme weather event that is expected to increase as the planet warms. New York, Chicago, LA, Phoenix, Houston, Philadelphia, San Antonio, and Dallas have collectively experienced over 90 flooding events since 2000.

Last month, another study delved into the geological processes behind North America’s subsiding problem, which is worth a read if you aren’t yet disaster-weary.

Global Examples: China, Venice, and Mexico City

However, the U.S. is not alone, with China facing the same issue, as well as Venice – which has lost around 23 cm (9 inches) – and Mexico City, where some areas are sinking at an alarming rate of around 50 cm (1.6 feet) each year.

But as Houston’s mitigation measures show, intervention is key. The scientists from the latest study point out that measures such as land raising, better drainage, and even constructing artificial wetlands can reduce the impact of floodwaters.

“Instead of just saying it’s a problem, we can respond, address, mitigate, adapt,” said Ohenhen. “We need to move to solutions.”

The researchers are the latest group of scientists urging lawmakers and policymakers to act now rather than wait for the consequences down the line.

“Targeted mitigation through strategic dam planning, managed aquifer recharge, and resource extraction policies may be useful to control, pause, or even reverse subsidence,” they wrote. “Ultimately, a robust and sustainable mitigative and adaptive framework should encompass continuous monitoring, stakeholder collaboration, and flexible management plans.”

The full list of the 28 cities, in order from the most rapid ground changes, is:

1. Houston, TX
2. Fort Worth, TX
3. Dallas, TX
4. Chicago, IL
5. New York, NY
6. Denver, CO
7. Seattle, WA
8. Columbus, OH
9. Indianapolis, IN
10. Charlotte, NC
11. Detroit, MI
12. San Antonio, TX
13. Las Vegas, NV
14. Washington, D.C.
15. Nashville, TN
16. San Francisco, CA
17. Portland, OR
18. San Diego, CA
19. Philadelphia, PA
20. Austin, TX
21. Oklahoma City, OK
22. Phoenix, AZ
23. El Paso, TX
24. Boston, MA
25. Los Angeles, CA
26. Memphis, TN
27. San Jose, CA
28. Jacksonville, FL

Read the original article on: New Atlas

Read more: Study Finds the Wealthiest 10% Account for Two-Thirds of Global Warming