A groundbreaking study from Columbia University has revealed a concerning trend quietly reshaping America’s biggest cities: land subsidence. According to the research, all 28 of the most populous U.S. cities are experiencing sinking terrain, often at rates invisible to the naked eye.
Using ultra-high-resolution satellite data, researchers measured vertical land movement down to as little as 1 millimeter—a precision beyond the reach of typical satellite technology. The findings were startling: in 25 of the 28 cities studied, at least two-thirds of their land is sinking, affecting approximately 34 million residents.
At the heart of the issue is intensive groundwater extraction, which the study attributes as the primary driver behind 80% of the observed subsidence. When aquifers are overdrawn, fine-grained soils compress, leading to the gradual collapse of pore spaces underground. This is particularly severe in places like Houston, where 40% of the area is sinking more than 5 mm annually, and some neighborhoods are dropping up to 5 cm each year. Roughly 12% of the city’s population lives in zones surpassing the 10 mm per year threshold.
Other fast-sinking urban areas include Dallas, Fort Worth, Las Vegas, San Francisco, and even parts of Washington, D.C. Satellite observations also flagged terrain shifts around New York’s LaGuardia Airport, suggesting subsidence hotspots across various geographic landscapes.
However, not all ground movement stems from human activity. Cities such as New York, Philadelphia, and Chicago are still undergoing a slow rebound from the last Ice Age, when vast glaciers depressed the land. This natural process, known as post-glacial isostatic adjustment, continues to influence urban landscapes 20,000 years later.
Adding to the complexity is the sheer weight of infrastructure. A 2023 study proposed that New York City’s towering skyline is itself a contributing factor to localized subsidence. In Miami, older structures built adjacent to new high-rises are showing signs of uneven settlement, prompting further investigation.
Lead researcher Leonard Ohenhen issued a sobering warning: “As cities continue to grow, we will see more cities expand into subsiding regions. Over time, this subsidence can produce stresses on infrastructure that will go past their safety limit.”
He emphasized that even seemingly minor changes in ground elevation can accumulate to produce significant damage: “A lot of small changes will build up over time, magnifying weak spots within urban systems and heightening flood risks.”
The study highlights that subsidence can compromise infrastructure long before obvious signs appear, making it a hidden but pressing urban hazard. Unlike flood events where danger is immediately visible, the gradual downward shift of land can silently undermine buildings, roads, and utilities—often without detection until severe damage has occurred.
Among the hardest-hit are eight major U.S. cities, including New York, Los Angeles, Houston, and Phoenix, where more than 60% of the nation’s subsidence-affected population resides. Alarmingly, these cities have experienced over 90 major floods since 2000, suggesting that sinking land may be exacerbating flood severity and frequency.
Ohenhen concluded, this is not just a matter of observation—it’s a call to action: “As opposed to just saying it’s a problem, we can respond, address, mitigate, adapt. We have to move to solutions.”
