The land under the largest cities in the United States is slowly sinking, posing a direct threat to millions of residents and critical infrastructure. This was reported by the Washington Post, writes UNN.
Details
According to the media, researchers have mapped the vertical movement of land in 28 of the most populous US cities and found that all cities are sinking to some extent. Twenty-five of them are sinking on two-thirds of their territory. According to a study published Thursday in Nature Cities, about 34 million people (about 10% of the US population) live in subsidence areas.
Among the cities with the most extensive subsidence are Chicago, New York, Houston, Dallas, Columbus, Indianapolis, and Denver. The highest rates - more than 5 mm per year - were recorded in Houston, San Antonio and Washington.
Many of these sinking cities are located inland. Subsidence is usually a major concern in coastal cities, where rising sea levels can easily reach the shore and flood areas. However, researchers say that land subsidence inland can destabilize infrastructure and exacerbate flooding during storms.
Soil subsidence often does not stop at the border of coastal regions. This is a problem that (affects, -ed.) everything, both inland and coastal areas
Despite the fact that subsidence occurs slowly - the effects can noticeably accumulate over the years.
The consequences are already noticeable: subsidence damages runways, stadiums and buildings, changes drainage systems and exacerbates flooding. In particular, during Hurricane Harvey in 2017, 85% of the flooded areas in the Houston area subsided by more than 5 mm per year.
The highest risk of structural damage was recorded in San Antonio: there 1 in 45 buildings are potentially at risk. In Fort Worth - 1 in 143.
Subsidence occurs when the main supporting structure of the earth weakens.
It is reported that the causes of subsidence may vary from city to city.
Along the east coast and the Great Lakes region, the land is mainly slowly sinking due to melting glaciers.
In large cities such as New York, the weight of buildings literally pushes the ground. Concrete jungles also absorb more heat, which can be transferred underground and deform the soil and rocks - as seen in Chicago. The Pacific Northwest is prone to tectonic plate activity, when one plate goes under another and leads to subsidence.
Researchers have found that the most common cause of subsidence in most places is the pumping of groundwater for drinking and agriculture. They determined that groundwater removal was the cause of 80% of subsidence in cities.
In some places, it has been possible to slow down and stop land subsidence using a system that collects water from rain, floods, rivers or treated wastewater and returns it to underground aquifers. Such systems exist in the Coachella Valley in California, Santa Clara and Santa Ana, in the Spanish district of El Carracillo and in Beijing.
Having detailed maps of soil movement, as well as information about its causes, can help in policy development
According to Tahmasebi, the results can also help in developing more effective groundwater management plans or improving urban planning in a way that reduces harm and any danger to human life.
We need to start talking about these solutions right now. This problem will only continue to grow as we move into the future