All 28 of the largest cities in the United States are gradually sinking, which could impact 34 million residents, according to new research.
Researchers at Virginia Tech’s Earth Observation and Innovation Lab utilized satellite-based radar technology to assess sedimentary land subsidence in these major urban areas.
The data revealed that in all examined cities, at least 20% of urban regions sank by a minimum of 2mm per year. In 25 out of the 28 cities, nearly two-thirds of the land exhibited signs of sinking.
“The immediate dangers of land subsidence include heightened vulnerability to localized flooding, potential structural damage to buildings, roads, bridges, and pipelines, as well as disruption of essential services,” stated Assistant Professor Manoochehr Shirzaei from Virginia Tech, as reported by BBC Science Focus.
Shirzaei noted that even slight annual movements can compromise building foundations and distort land enough to create surface cracks.
“In places like Houston and New York, local subsidence is already associated with infrastructure vulnerability and heightened flood risks during storms,” he explained.
This phenomenon of subsidence is largely driven by groundwater extraction. As urban populations grow, the demand for freshwater intensifies.
Water is drawn from aquifers, allowing for the flow of rocks containing water and other geological layers.
However, if water is extracted faster than it can be replenished, the aquifer can become compressed, leading to subsidence of the land above.
“Urban centers built on reclaimed or depositional areas, such as parts of San Francisco and New Orleans, face particular vulnerability,” added Shirzaei.
Studies indicate that cities like New York, Chicago, Seattle, and Denver experience sinking rates of about 2mm annually.
In Texas, certain cities experience sinking rates of around 5mm per year, with specific areas in Houston sinking as much as 1cm annually.
Localized zones in cities such as Houston, New York, Las Vegas, and Washington, DC, are sinking significantly faster than adjacent areas.
“As time progresses, subsidence exacerbates the effects of climate change, especially in coastal regions and flood-prone areas,” warned Shirzaei. “As the land sinks and sea levels rise, the floodplains stretch, and storm surges reach further inland.”
He emphasized that the study offers a “roadmap for aggressive, science-based planning” to assist experts and policymakers in monitoring subsidence and mitigating its impacts.
The 28 most populous cities in the United States include New York, Los Angeles, Chicago, Houston, Phoenix, Philadelphia, San Antonio, San Diego, Dallas, Jacksonville, Austin, Fort Worth, Columbus, Charlotte, San Jose, Indianapolis, San Francisco, Seattle, Denver, Washington, Portland, Las Vegas, Detroit, and Memphis.
This study has been published in Natural City.
Read more:
About our experts
Manoochehr Shirzaei is an associate professor of geophysics and remote sensing at the Faculty of Geo-Science at Virginia Tech. He specializes in geodesy and geophysics, focusing on satellite geodesic theory, inverse theory, signal processing, modeling techniques, and the physics of crustal deformation.
Source: www.sciencefocus.com
