New York City is sinking by 1-2 millimeters per year under the weight of its own skyscrapers: the ground deformationwhich in the long run could increase the risk of floods, has been mapped by comparing satellite data with subsurface geology models. The study is published in Earth’s Future by a team of experts from the University of Rhode Island led by geologist Tom Parsons.
The researchers calculated the cumulative mass of more than one million buildings in New York City to be about 764 million tons. They then divided the city into a grid of squares 100 meters on each side and converted the mass of the buildings into downward pressure, taking gravity into account. However, the weight of roads, sidewalks, bridges and railways was not considered.
These data have been entered into models that reproduce the complex geology of the subsoil, made up mostly of sand, silt, clayey sediments and rocky outcrops. The experts were thus able to ascertain that the Big Apple rests on a rather variegated substrate that reacts differently to the weight of the buildings. The soils richer in clayey sediments and artificial fillings are more prone to the phenomenon of subsidence (i.e. sinking), with an average value of 294 millimeters measured in the lower part of Manhattan; more elastic soils manage to recover after the construction of the buildings, while the more rocky substrate to which many skyscrapers are anchored does not move much.
By comparing these data with satellite measurements of ground height, the researchers have developed a new and more detailed map of subsidence in New York.
The purpose of the study, explain the authors, “is to raise awareness that every new high-rise built in coastal, river or lakefront areas could contribute to future flood risk”.
Source: Ansa
I am a journalist with over 6 years of experience working in the news industry. I currently work as an author for Global Happenings, and my coverage focuses on Technology news. I have written for various publications, including Reuters, The New York Times and The Guardian.
