The 28 largest cities in the United States are facing a growing problem: they are sinking.
This phenomenon, affecting coastal and inland areas, compromises buildings, bridges, roads, and other infrastructures, putting 34 million people at risk.
### What is the cause of sinking?
The excessive pumping of groundwater is the main reason for this problem. When water is extracted faster than nature can replenish it, aquifers collapse, and the soil loses stability.
### A satellite study revealing the magnitude of the problem
Researchers have used advanced satellite radar to analyze ground displacement in the country’s most populous cities.
The study, published in Nature Cities, shows that:
– 20% of the urban area in each city is sinking.
– In 25 cities, 65% of the territory is affected.
– More than 29,000 buildings are in high-risk areas of structural damage.
## Houston: the most affected city
The most concerning case is Houston, where:
– 40% of the city is sinking more than 5 mm per year.
– Some areas are sinking up to 5 cm annually.
– Areas in Texas are experiencing up to 10 mm of sinking per year.
The effects of this phenomenon become evident when cracks appear in buildings, roads deform, and light poles tilt.
## Cities with differential sinking
Some cities have varying subsidence rates, affecting the alignment of infrastructure foundations.
### Critical cases in the U.S.:
– New York, Washington D.C., and Las Vegas: exhibit extreme variations in sinking.
– San Antonio and Austin: in San Antonio, 1 in 45 buildings is at high risk, while in Austin, the ratio is 1 in 71.
## Other factors contributing to city sinking
While water extraction is the main cause, other elements exacerbate the situation:
– The removal of ice layers thousands of years ago.
– The weight of buildings in cities like Miami and Manhattan.
– Intensive construction in urban areas.
## Consequences and strategies to mitigate sinking in the long term
– Increased risk of flooding in cities with inadequate drainage.
– Impact on transportation infrastructure.
– Danger to residents’ safety.
Experts recommend:
– Improve groundwater management to reduce extraction.
– Implement advanced satellite monitoring to detect risk areas.
– Modify building codes to address the problem.
## A call to action
Geophysicist Manoochehr Shirzaei, a study co-author, states: “With smart monitoring and appropriate policies, we can slow down or even stop sinking and protect our cities for the future.”
With efficient urban planning, it is possible to mitigate the effects of sinking before the damages become irreversible.
