15-05-2025
28 American Cities Are Literally Sinking Into the Earth
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Major U.S. cities are experiencing some degree of subsidence, a.k.a. sinking.
It's not just major coastal cities like New York, Los Angeles, and Houston; landlocked cities like Las Vegas, Denver, Nashville, and more are showing signs of sinking.
Causes range from groundwater extraction to plate tectonics.
It's a well-known fact that sea levels around the world are slowly rising. According to the U.S. National Oceanic and Atmospheric Administration (NOAA), sea levels have risen some eight to nine inches around the world since 1880, and show no sign of stopping. That's concerning enough on its own, considering that 40 percent of the U.S.'s population lives near coastlines. But American cities—along with cities around the world—are facing yet another problem that's only exacerbating this concerning side effect of climate change: They're sinking.
In a new study led by scientists at Virginia Tech, a research team tracked the subsidence (a.k.a. sinking) rate of 28 major U.S. cities across the country and found that at least 20 percent of the urban area of all of the cities was sinking to some degree. In 25 of those 28 cities, more than 65 percent of the land area was sinking to varying degrees. The most extreme example is Houston, Texas, where scientists discovered that some areas of the city were sinking as much as 10 millimeters per year. The results of the study were published in the journal Nature Cities.
Obviously, the image of cities slowly sinking paints a picture of places like Houston, New York, and L.A. simply slipping into the sea. But the implications of this higher-than-expected subsidence rate comes with a much more complex list of nearer-term practical problems for both city planners and average homeowners.
'Even slight downward shifts in land can significantly compromise the structural integrity of buildings, roads, bridges, and railways over time,' Leonard Ohenhen, a former Virginia Tech graduate student and the lead author of the study, said in a press statement.
The cause of the sinking varies from city to city. The leading cause of subsidence is groundwater extraction, which eventually leads to compaction of soil and sediments and—you guessed it—the net result of slowly sinking land. However, other causes can also be pretty impactful. Some parts of the country, for example, are still experiencing the extraordinary see-sawing of bedrock caused by the retreat of glaciers during the tail of the Pleistocene epoch. Meanwhile, out West in cities like Portland, Seattle, and San Francisco, plate tectonics can claim some of the blame.
'Sustained groundwater extraction lowers pore pressure in aquifer systems, leading to compaction of fine-grained sediments, which results in land subsidence that can be detected from satellites,' Susanna Werth, a co-author of the study from Virginia Tech, said in a press statement. 'Such land subsidence has been observed across the U.S. for many decades, but its increasing relevance in urban areas is especially hazardous.'
Ohenhen and his team are part of that observational history. Just last year, they published a study in the journal Proceedings of the National Academies of Sciences about the rapid subsidence of cities along the East Coast. However, this new study shows that not only is the phenomenon more widespread than originally understood, it's also not contained to coastal cities. Las Vegas, Denver, Oklahoma City, Nashville, Indianapolis, and many landlocked metropolitan areas also show signs of sinking.
While this study only focused on the contiguous United States, the country's two most far-flung states—Alaska and Hawai'i—are also struggling with increased subsidence. For Alaska, the main culprit is permafrost degradation. And regarding Hawai'i, a study published earlier this year showed that some areas of O'ahu are sinking as much as 25 millimeters per year due to some industrial sectors having been built atop artificial fill.
None of this means that the U.S. is about to become some legendary, water-filled Atlantis. But understanding the rate at which cities are sinking—and the rate at which sea levels are rising—can help city planners, water resource managers, and average homeowners prepare for the slowly sinking future ahead of us.
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