An American research team has managed to model the geology under New York City using satellite data. His study reveals that the American metropolis is sinking into the ground at a rate of 1 to 2 millimeters per year, which makes it all the more vulnerable to rising waters.
Published on May 8 by a team from the University of Rhode Island in the journal Earth’s Future, this study aims to highlight the impact of buildings, in particular that of skyscrapers, on “subsidence”, i.e. the progressive subsidence of the surface of the earth’s crust under the effect of a mass.
This mass, the researchers have calculated, at least in part: 764 million tons, the total weight of New York buildings. A partial figure that does not take into account infrastructure such as roads, sidewalks, bridges or other city railways.
Nor does it take into account the weight of the approximately eight million people who inhabit the city. Also, the comparison is complex because the urban load has accumulated over a much longer period than the measured subsidence rates, and there are multiple interacting causes.
Alert on the impact of a skyscraper
Moreover, the city is built partly on rocky ground, but also on deposits of silt, sand and clay, which makes it even more fragile in places. The increasing urbanization of the megalopolis, coupled with the drainage and pumping of groundwater, risks further aggravating the phenomenon.
Modeling suggests that subsidence is greater in parts of Brooklyn and Queens, but especially in lower Manhattan, an area that is largely only 1 to 2 meters above sea level. ocean.
“New York is emblematic of expanding coastal cities around the world seen subsiding, signifying that there is a common global challenge of mitigating increasing flood risk,” the researchers write.
“The objective of this study is to warn that each new skyscraper built near a coast, a river or a lake can contribute to increasing the risk of flooding.”
Many cities involved
The New York metropolis is therefore particularly vulnerable to natural disasters due to its geographical location. Especially since the rise in water levels on the North American Atlantic coast is “three to four times higher than the world average”, note the researchers. The water around New York has risen 22 centimeters since 1950.
But “Big Apple” is far from being the only city to suffer from subsidence: Istanbul, Shanghai, Houston, Auckland or Manila are all in the process of subsiding, according to satellite data acquired over six years and published in another study from 2022.
Part of Jakarta also already has its feet in water, and the Indonesian capital could be submerged by 2050. Parts of the city are sinking nearly 11 centimeters a year due to groundwater extraction. Nearly 11 million inhabitants will soon emigrate to a brand new metropolis.
>> Read about it: In Indonesia, the crazy project of a new capital in Borneo
Pierrik Jordan
2023-05-26 04:18:18
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