All the largest cities in the United States sink into the ground in places, reveal new satellite data – and 34 million people are affected. However, some cities flow faster and in a much larger area than others.
A study revealed that Houston is the fastest city, with certain areas falling at a rate of 0.4 inches (10 millimeters) per year, while most large cities have localized areas where the earth flows faster than 0.2 inches (5 mm).
Cities flow for various reasons, but the most common cause is the extraction of groundwater. The sinking is a problem because it increases the risk of flooding and threatens buildings and other infrastructure, according to the study, published Thursday, May 8 in the journal Natural cities.
To approach the sinking, the researchers suggested measures such as the attenuation of the floods, the modernization of vulnerable structures and the limitation of the building in the most risky areas.
“Instead of simply saying that this is a problem, we can answer, address, mitigate, adapt”, principal author of the study Leonard OhhenhenA researcher at Columbia Climate School from Columbia University, said in a statement. “We have to go to solutions.”
In relation: Parties of San Francisco and Los Angeles sink into the sea – which means that the rise in sea level will be even worse
The disadvantage of land is often associated with coastal areas, where a combination of flowing land and Ris at sea Can potentially drown cities like New Orleans and San Francisco in the water. However, the subsidence of land is not limited to the coasts and can cause problems in the United States, according to the study.
The new research has explored land sagging in the 28 most populous cities in the country, all of which had populations greater than 600,000 people. Researchers have used remote sensing data collected by the European Space Agency Sentinel-1 Satellites to create high resolution maps of the vertical terrestrial movement.
The cards revealed that in the 28 cities, there was a flow in at least certain parts of each city – a minimum of 20% of the urban area. Twenty-five of the 28 cities had at least 65% of their area area. In the case of Houston, Dallas, Fort Worth, Chicago, Columbus, Detroit, Denver, New York, Indianapolis and Charlotte, the sinking covered 98% of the city.
Houston, Dallas and Fort Worth had the highest proportion of areas (over 70%) flowing at a rate of 0.1 inches (3 mm) per year. Houston was the most affected, with 43% of its land which flowed more than 5 mm per year and 12% jump to 10 mm per year, depending on the study.
Why do cities flow?
The terrain adapts due to natural factors and man -oriented. The soil is never really static, the geological processes constantly keeping in motion. In cities like new York And Nashville, the soil adapts to the loss of massive glacial caps that increased it during the last glacial era approximately 16,000 years ago. This process, called ISOSTATIC ISOSTATIC adjustmentcauses the rise of the land and the descent when it returns to its original pre-glued age form.
However, despite these natural processes, humans are always the greatest contributors to pour urban land, according to the study. The researchers said that 80% of the subsidence of urban land is associated with an extraction of groundwater. Pumping groundwater can have a variety of drive effects. For example, the elimination of water from the aquifers with fine grain sediments creates spaces between these sediments, which can then collapse and compact the earth underneath, pulling the surface down. In Texas, this problem is exacerbated by pumping oil and gas, according to the press release.
Researchers noted that shipwreck problems could be exacerbated by climate change. While the planet warms up, drought Will probably create a greater demand for groundwater and will cause more extraction. In addition, the threat of floods is likely to grow as climate change increases frequency and intensity extreme time, according to the study.
Another problem is that cities are still growing, which means that more people will live on switching land, and therefore there will be more groundwater demand and more pressure on infrastructure. The study revealed that the vertical terrestrial movement has already put 29,000 buildings in risk of high damage.
“While cities continue to grow, we will see more cities developing in substitution regions,” said Ohenhen. “Over time, this collapse can produce constraints on infrastructure that will exceed their security limit.”
