New York City Faces Increasing Risk of Flooding from Climate Crisis, Study Warns

“New York City faces an increasing risk of flooding from sea level rise, subsidence and increasing intensity of storms from natural and man-made sources,” according to the recently published study by the United States Geological Survey in the journal Earth’s Future.

Hurricane Sandy caused seawater to flood parts of the metropolis as early as 2012. In 2021, the heavy rains from Cyclone Ida caused the sewage system to overflow, flooding parts of the city again.

“Clear Threat to Coastal Cities”

According to studies, climate change could mean more hurricanes in the New York area in the future, and sea level rise on the US east coast could be three to four times higher than anywhere else in the world. According to the findings of the study, the water on the coast of New York has risen by around 22 centimeters since 1950.

Global sea levels are expected to rise by 200 to 600 millimeters by 2050. The researchers warn that this represents a “clear threat to coastal cities”. In New York City, 8.4 million people are threatened by the floods in different ways. As coastal cities grow around the world, the combination of urban densification and rising sea levels is leading to an increased risk of flooding.

Heavy buildings increase the risk of flooding

Because the tall and heavy buildings in New York City also increase the risk of flooding. Using modeling and estimation, the United States Geological Survey research team estimated the total weight of the city’s 1,084,954 buildings at 764 million tons — roughly equivalent to the weight of 140 million elephants, according to the Guardian.

This enormous weight presses on various materials in the city’s soil. While many of the largest buildings stand on solid bedrock such as slate, there is also a mix of other materials that have been built over, contributing to a subsidence effect. In many parts of the US east coast, the effect would also occur naturally as the country responded to the retreat of glaciers after the end of the last ice age, the Guardian writes.

Subsidence also depends on soil type

According to the research team, the specific subsidence rate also depends on the soil types. Loamy soil and artificially filled areas would have a subsidence potential of 7.5 to 60 centimeters due to development, with an average of a good 29 centimetres. Coastal areas with softer subsoil are much more affected. Other soils are less prone to give in to the load, with average values ​​of six to twelve centimetres.

“There’s nothing to panic about, but it’s an ongoing process that increases the risk of flooding,” the Guardian quoted Tom Parsons, a geophysicist at the US Geological Survey who led the study. The softer the ground, the greater the pressure that emanates from the buildings. “It wasn’t a mistake to put up such big buildings in New York, but we just have to keep in mind that every time we build something there, the ground gets a little bit more compressed.”

Raise awareness of urban planning

The aim of the research contribution is to raise awareness that “each additional high-rise building that is built on coasts, rivers and lakes could contribute to the future risk of flooding and damage limitation strategies may be required,” the researchers said.

After Hurricane Sandy, 90 percent of buildings in flood-prone areas were not built to flood-prone standards, and abstraction of groundwater could lead to further lowering.

The East River and Harlem River bring little sediment to New York Harbor because of tributary fill-up. This makes the city more vulnerable to flooding from north-easterly winds and hurricanes. Lower Manhattan is likely to be particularly affected: the southern tip of the central district is just one to two meters above sea level.