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Study Reveals That 34 Million Live on Unstable Land — Soil Sinks in Cities Like New York, Chicago, and Other Major Metropolises in the U.S.
The sidewalks crack, the posts lean, and the walls crack. For many residents, these are signs of natural wear and tear. But in several cities in the U.S., the problem is more serious: the soil is sinking.
And, according to a new study published in the journal Nature Cities, this is happening in all 28 most populous cities in the U.S.
Millions Live on Unstable Land
The research indicates that the phenomenon, called subsidence, affects 34 million Americans. This sinking of the soil occurs slowly, often without being noticed. The main cause is not earthquakes or erosion, but rather the excessive withdrawal of water from the U.S. underground aquifers.
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With the help of satellites, researchers detected that in 25 of the 28 largest American cities, over 65% of the urban area is sinking. And in cities like New York, Chicago, Detroit, and Dallas, this rate exceeds 98%.
Houston Leads Urban Sinkage
The most severe case is Houston, where 42% of the area is sinking more than 5 millimeters per year. In some neighborhoods, the rate exceeds one centimeter per year. It may seem small, but that represents about 30 centimeters over three decades — enough to compromise entire buildings.
The sinking does not only occur in peripheral areas. It affects urban zones with critical infrastructure. LaGuardia Airport in New York is sinking. The same is true for parts of San Francisco and even East Potomac Park in Washington, D.C.
Water Shortage, Soil Collapse
The main cause identified by the study is the excessive use of groundwater. The withdrawal of this water reduces the pressure that keeps the soil stable.
When this pressure decreases, the ground begins to compact. In some cases, the collapse can be irreversible, especially in aquifers confined between layers of clay and rock.
The study reveals a direct link between the drop in groundwater levels and soil sinking in at least 13 cities.
The most concerning examples are in New York, San Diego, Houston, and Memphis. In New York and San Diego, 76% of the vertical movement of the soil can be explained by these changes in water pressure.
Geology Also Influences the Rate of Sinking
The local geology also plays a role. In San Diego, the aquifers are highly permeable, accelerating the process. In Washington, D.C., the bedrock offers more resistance. Even so, it does not guarantee complete protection.
Over 29 Thousand Buildings in Risk Zones
The impact is concrete. More than 29,000 buildings are in areas of high or very high risk due to subsidence.
Many are subject to what is called differential soil movement — when one side of the structure sinks more than the other. This can cause cracks, affect foundations, and compromise bridges, roads, and houses.
In cities like Austin, Fort Worth, and San Antonio, the structural risk is even more pronounced. In these places, between 1 in every 45 and 1 in every 143 buildings are under threat. Even a minimal tilt, of just a few millimeters per year, can have serious consequences over time.
Silent and Often Invisible Damage
The study highlights that the problem varies greatly between cities and even between neighborhoods. The composition of the soil, construction methods, and foundation types make a difference. However, the risk exists and, according to the authors, is being underestimated.
Recent cases of collapses alert to the fragility of urban infrastructure. But, often, the damage caused by subsidence goes unnoticed until it becomes severe. The study suggests that this process may be silently weakening various constructions across the country.
There Are Ways to Act and Avoid the Worst Scenarios
The good news is that part of the problem can be managed. Although some causes are natural, much of the subsidence has its origin in human actions. This means that measures can be taken.
The first step is to improve groundwater management. This includes limiting pumping, promoting conscious use, and investing in aquifer recharge technologies. In some places, it is possible to store surface water underground during rain periods.
Planning for the Future with Data and Adaptation
Another essential measure is to map risk areas. Satellite data helps, but more detailed local studies are fundamental. They allow for better soil assessment and adaptation of building plans according to risk.
It is also necessary to adapt U.S. cities. In flood-prone regions, soil sinking can exacerbate the effects of rain and tides. Elevating infrastructure, prohibiting construction in certain areas, and improving drainage systems can help mitigate impacts.
Call for Immediate Action
The study concludes with a clear warning: subsidence needs to be taken seriously. Urban planners and authorities must consider this factor in all decision-making stages. Otherwise, the damages could multiply and become irreversible.
With information from ZME Science.
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