new research concluded that New York City is sinking in part because of the extraordinary weight of its soaring buildings, which aggravates the threat of flooding that the rise in sea level imposes on the metropolis.
The Big Apple is sinking an average of 1 to 2 millimeters a year, although parts of the city are sinking twice as fast, researchers say.
“A highly concentrated population of 8.4 million people faces in varying degrees to the risk of flooding in New York City”, said the researchers in the study published in the journal Earth’s Future.
This subsidence aggravates the impact of sea level rise, which is accelerating at a rate of approximately twice the world average due to the melting of glaciers and the expansion of sea water due to global warming.
Waters bordering New York City have risen about 8 inches since 1950 and major storm flooding could be up to four times more frequent than today by the end of the century, due to the combination of sea level rise and hurricanes enhanced by climate change.
The ground of New York City
The surficial geology of this city is a complex glacial terrain that, according to the study authors, includes sediments, sand, clay deposits, glacial moraines, beach deposits and rock outcrops.
The enormous weight of the buildings pushes down this mixture of materials. Although most large buildings rest on solid bedrock, such as shale, the mixture of other sands and clays on which they were built contributes to this collapse.
“The cumulative pressure applied to the ground by large buildings contributes to subsidence not only through initial primary settlement caused by soil compression and reduction of void space, but also by possible secondary settlement caused by creep in clay-rich layers, which may continue indefinitely“, explains the study.
A weight equivalent to 140 million elephants
The study authors calculated the mass of 1,084,954 buildings in the city’s five boroughs and combined it with soil type and soil conditions. All of these structures, including the famous Empire State Building, weigh about 760 billion kilograms, which is equivalent to about 140 million elephants.
New York currently ranks third in the world in terms of coastal flood risk.
Growing urbanization, the authors add, is likely to exacerbate subsidence through groundwater extraction and building density, which, combined with the acceleration of sea level rise, implies an increased risk of flooding in coastal cities.
Recent severe flooding in the Big Apple
Two recent hurricanes have already caused casualties and severe damage to the city: “In 2012, Hurricane Sandy forced seawater into the city, while heavy rains from Hurricane Ida in 2021 caused the drainage systems to collapse due to the amount of runoff in an essentially paved city”, explain the researchers.
“There is no immediate need to panic, but there are a continuous process that increases the risk of flooding”, said Tom Parsons, geophysicist at theUS Geological Surveywho conducted the research.
2023-05-27 03:00:00
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