Scientists studying sea-level rise found that the weight of New York City’s buildings is causing the city to sink.
Using NYC as an example, they caution that new flooding risks can come from building too many high-rises near waterfront.
The sinking caused by heavy buildings is something the researchers say can continue indefinitely.
According to a new study, all of New York City is under pressure due to the weight of its many massive buildings. It’s enough pressure, in fact, that the city is sinking.
In the study, published in Earth’s Future by New England-based scientists investigating sea level rise on coastal cities, the authors found that the “downward pressure exerted by the built environment” of New York City is causing the city to sink up to 2 millimeters per year (and faster in some parts)—a relatively quick sink rate compared to other cities.
With 1.68 trillion pounds of buildings in New York City, that’s a lot of downward pressure.
“New York is emblematic of growing coastal cities all over the world that are observed to be subsiding,” the study authors write, “meaning there is a shared global challenge of mitigation against a growing inundation hazard.”
The increasing risk to sea level rise in New York City, specifically, comes from the sheer weight of the high-rise buildings. The combination of a dropping city and a rising sea increases future flood risks, according to the study.
To calculate the risk to New York City, the researchers studied satellite data to determine the urban load the city has accumulated and its rate of subsidence (fancy word for gradual sinking in of land). This was done across a longer period than subsidence rates had previously been measured. Some of the sink may happen because of the use of artificial fill or soft sediment, but the authors say that building weight plays a key factor.
“Cumulative pressure applied to the ground from large buildings contributes to subsidence not only from initial primary settlement caused by soil compression and reduction of void space, but also through potential secondary settlement cause by creep in clay rich layers that can continue indefinitely,” the study says.
That clay is somewhat notorious for continually giving way under the pressure exerted by the heaviest of buildings.
“Of particular concern,” the study says, “is the possibility of ongoing long-term secondary settlement in densely built areas close to coastlines.”
As major cities around the world are expected to grow disproportionally to rural areas over the next decades, the weight of the world will soon be concentrated even more in specific locations. That weight may become too much to bear in the face of rising seas.
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