America's biggest cities are sinking and scientists know why
"A lot of small changes will build up over time, magnifying weak spots within urban systems and heighten flood risks," Leonard Ohenhen, a former Virginia Tech graduate student and the study’s lead author, said in a statement.
World Water Day 2022: Groundwater may seem invisible to us but it's vital to our health
Scott Rayder, Executive Director at the Alabama Water Institute, explains the importance of clean and accessible water.
BLACKSBURG, Va. – Dozens of American cities are gradually sinking, according to a new study published in the journal Nature Cities.
Researchers from Virginia Tech found that groundwater extraction is the primary driver of this threat, which is affecting communities such as New York, Dallas and Seattle.
Using satellite data, the team mapped vertical land motion in more than two dozen urban areas across the United States, with some areas sinking at rates estimated at between 2 and 10 millimeters per year.
Shifting soil can impact the integrity of roads, buildings and other infrastructure, according to Leonard Ohenhen, the study’s lead author.
"A lot of small changes will build up over time, magnifying weak spots within urban systems and heighten flood risks," Ohenhen said.
HOUSTON, TEXAS - SEPTEMBER 9: The Houston downtown skyline is photographed Monday, Sept. 9, 2024 at Harris County Criminal Courthouse in Houston. (Yi-Chin Lee/Houston Chronicle via Getty Images / Getty Images)
DID THE NATIONAL WEATHER SERVICE CAPTURE A PHOTO OF BIGFOOT DURING A PENNSYLVANIA STORM SURVEY?
The study analyzed data from regions home to approximately 34 million people - only about 12% of the U.S. population.
Cities such as New York, Chicago and Denver are considered to show modest sinking with just around 2 millimeters of change every year, while Houston was characterized as more significant with a recorded change of 10 millimeters per year.
Along the Gulf, some localized areas are sinking faster than others, creating a host of problems. Researchers noted that inconsistent land motion can lead to the formation of structural cracks and the eventual failure of infrastructure.
Other cities with high variability in land movement include Las Vegas and Washington, D.C.
According to the study, as more cities grow, the demand for groundwater rises and when aquifers can't keep up, they often contract and even collapse.
Long-term climate changes also play a role, with droughts reducing groundwater levels and contributing to land subsidence.
A "Do Not Enter" sign is on display as floodwaters wash up the bank during high tide across the Washington Channel from The Wharf amid cherry blossoms in peak bloom near the Tidal Basin on March 23, 2023, in Washington, D.C. (Alex Wong / Getty Images)
DOZENS OF BUILDINGS ALONG SOUTH FLORIDA COASTLINE ARE SINKING, STUDY FINDS
"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, an associate professor at Virginia Tech’s Earth Observation and Innovation Lab. "This risk is often exacerbated in rapidly expanding urban centers."
To gauge how significant of a problem cities face, researchers urged city planners and policymakers to conduct increased land subsidence monitoring.
The latest study builds upon previous research from last year that warned about rising flood risks for dozens of coastal communities - many of which are also grappling with sinking soil.
Annual vertical land motion map (NASA)