A new satellite-based study reveals that the 28 most populous cities in the United States—including New York City, Chicago, Dallas, and Denver—are gradually sinking at rates of 2 to 10 millimetres (0.08 to 0.4 inches) per year. Researchers at Virginia Tech used high-resolution radar measurements to map this ground subsidence across urban regions. In every city examined, at least 20 percent of the land area was found to be sinking; in 25 of the 28 cities, more than 65 percent exhibited measurable downward movement, posing serious long-term risks to urban infrastructure systems.

As per the Nature Cities report published on May 8, cities in Texas showed the highest subsidence rates, with Houston being the most affected—40 percent of the city is sinking faster than 5 millimetres per year, and 12 percent exceeds 10 millimetres annually. Under the direction of Leonard Ohenhen, the researchers linked almost 80 percent of the urban subsidence to too high groundwater extraction, a process motivated by growing urban needs. While natural geological activity is important as well, human activity is now the dominant driver of land depression.

Experts warned that even small changes can undermine the structural integrity of roads, bridges, rail systems, and other infrastructure. “This hazard grows very slowly, decimates the ground from underneath, and if disasters occur, very few people recognise it in its early stages,” Manoochehr Shirzaei, who is an associate professor at Virginia Tech, said in a statement. The study also highlighted the vulnerability of not only coastal cities but also inland cities, including those located far from the ocean, where land subsidence increases the frequency of flooding and impacts the long-term planning of urban development.

Although it’s never going to be completely prevented, the report recommends more monitoring and legal action. Emphasis should be on improved satellite surveillance, changes in groundwater management, and building strong infrastructure. Left alone, the subsidence can turn into a quiet urban menace, experts stated.