A new study estimates the weight of New York City’s buildings at 1.68 trillion pounds and says that, little by little, they’re sinking into the ground. The Big Apple could ultimately share the same fate as Venice, which is slipping into the Mediterranean Sea at a similar rate. Or it could see a reprise of 2012’s Hurricane Sandy, during which ocean water flooded the city.
Compounding the problem for both Venice and New York City is that the two cities will sink into rising waters – scientists expect sea levels to rise 20 to 60 centimeters by 2050.
The math starts to look dire for lower Manhattan – the area rests 1 to 2 meters above sea level and is currently sinking at a rate of 1 to 4 millimeters. While the paper stops short of predicting when New York City will dip below sea level, it could happen in a matter of decades.
Why Is New York City Sinking?
Much of Manhattan was built on sand and clay and “artificial fill,” which also means garbage and other material. The soils of Brooklyn, Queens and Staten Island also contain large amounts of fill, which seems to accelerate the sinking.
New York City's decline may be due to the weight of its 1.08 million buildings, the study says.
Or it may be sagging in response to the effects of the Last Ice Age. Human pumping of groundwater for drinking and other purposes could be to blame. And we may also be wearing away at the Earth through our endless need to build things and shape the land. The study also points to how the tributaries feeding the East and Harlem rivers can no longer pass along sediment due to development.
Measuring Rising Sea Levels
The researchers from the U.S. Geological Survey and the University of Rhode Island Graduate School of Oceanography reviewed satellite data and found that New York City had dropped an average of about 2 millimeters a year between 2015 and 2020. GPS data showed that the city had sunk an average of 1.5 millimeters a year.
To estimate the effects buildings might have, the team used a pixel-reading algorithm from Microsoft that turns satellite images into 3D models. They further estimated the heights of buildings and assumed that everything was made of reinforced concrete, the most common building material in New York City. Multiplying by an average weight for such walls, they arrived at 1.68 trillion pounds.
The model they designed predicted the greatest sinkage in lower Manhattan and areas of Brooklyn with large amounts of artificial fill.
Will New York City Be Underwater?
The coastline of New York City is constantly being redefined. When glaciers receded from the area 20,000 years ago, their melting moved the waterline inland by 50 miles. By 2050, parts of lower Manhattan could be underwater, assuming the most dire climate predictions come true. Many other cities around the world face a similar or even greater threat.
Jakarta, capital of Indonesia, has already suffered from such flooding that the country is building a new, drier capital. A quarter of the old one could be underwater by 2050.