Although it may seem like a scene from science fiction, it is a reality, large cities in the United States are sinking.
While the global sea level has risen 22 centimeters since 1880, according to the NOAA, a new study published in Nature Cities by researchers from Virginia Tech reveals that the land beneath many American cities is subsiding.
The phenomenon, known as subsidence, was analyzed in 28 major cities, and the results are alarming: at least 20% of the urban area in all of them shows some degree of sinking, and in 25 of the 28, more than 65% of the surface is descending.
Houston, the most extreme case: up to 10 mm per year
Although initially it was thought that sinking mainly affected coastal cities like New York, Los Angeles, or Houston, the study showed that the phenomenon also occurs in inland areas such as Las Vegas, Denver, Nashville, Oklahoma City, and Indianapolis. This indicates that urban subsidence is much more widespread than previously believed.
In Houston, some areas are sinking up to 10 millimeters per year, posing a cumulative risk to urban infrastructure.
Structural impacts and challenges for urban planning
Even minimal displacements can compromise buildings, roads, and transportation networks.
“Even slight drops in the terrain can affect the structural integrity of buildings, bridges, and railways,” warns Leonard Ohenhen, the study’s lead author.
These movements, although imperceptible in the short term, pose urgent challenges for urban planners, engineers, and homeowners.
Why are cities sinking?
The main cause of subsidence in many cities is the intensive extraction of groundwater, which reduces pressure in aquifers and leads to the compaction of fine sediments. “This type of sinking has been observed for decades, but its impact on urban areas is increasingly concerning,” says Susanna Werth, a co-author of the study.
However, there are other geological factors that contribute:
– Glacial rebound: in some regions, the “seesaw effect” of the bedrock after the last ice age generates vertical movements.
– Plate tectonics: in western cities like Portland, Seattle, and San Francisco, tectonic activity also influences sinking.
– Permafrost degradation: in Alaska, the melting of frozen soil accelerates sinking.
– Construction on artificial fill: in Hawaii, certain areas of O’ahu sink up to 25 mm per year for this reason.
A silent phenomenon with visible consequences
Urban subsidence requires constant monitoring and adaptation policies. Although subsidence is measured in millimeters, its cumulative effects can be devastating.
From cracks in structures to more frequent floods, land subsidence exacerbates climate vulnerability and demands integrated responses in territorial planning.
