New York City could see 'once-in-a-lifetime' floods every 5 years

Over the next three decades, New York City could be in danger of getting hit with storms that occurred once every 500 years, every 5 years, according to a new study. (REUTERS/Eduardo Munoz)

Over the next three decades, New York City could be in danger of getting hit with storms that occurred once every 500 years, every 5 years, according to a new study.

The study, performed by researchers at several universities and published Monday in the Proceedings of the National Academy of Sciences, primarily blames the predicted change on sea-level rise caused by global warming.

"This is kind of a warning," said Andra Garner, a Rutgers University scientist and study co-author. "How are we going to protect our coastal infrastructure?"

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The findings were based on analysis from multiple models, taking into account factors such as sea levels rising and differing paths in future hurricanes.

While New York City, which has an estimated population of 8.5 million according to the U.S. Census Bureau, may see a rise in the number of storms that hit the area, many of the models showed that the storms are likely to swing further off-shore, due in part to climate change. This means that storm surge heights aren't likely to increase substantially through 2300.

But because of rising sea levels, floods of 7.4 feet or more, which occurred roughly once every 500 years before 1800, and occur roughly every 25 years now, could happen once every five years between 2030 and 2045.

The researchers made no recommendations on what public officials or others should do to prepare.

"The idea is this kind of study we hope will provide information that people making those kinds of decisions can use," Garner said. "We know that when Sandy hit in 2012, of course, subways, tunnels flooded, power was knocked out, parts of the city were just really devastated so studies like this provide some warning."

Scientists from Penn State University, Massachusetts Institute of Technology, Princeton University, Nanyang Technological University in Singapore, the University of Massachusetts Amherst and the Woods Hole Oceanographic Institution also participated in the study.

The researchers said there is scientific consensus that global sea level will rise in the coming centuries, although it is not certain how much. They cautioned that sea-level rise at New York City could exceed 8 feet by the end of the century if, in a high-emissions future, the West Antarctic ice sheet rapidly melts.

Between the year 2000 and 2030, the study expects sea-levels around New York City to rise between 5 inches and 11 inches. The study examined sea level rise through the year 2300.

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"I think the study is valid, but year 2300 is a long way off," said Billy Sweet, an oceanographer for the National Oceanic and Atmospheric Administration who was not involved in the research. "What is more certain is the amount of sea level rise likely to occur in the next 50 to 100 years or so and that storm surges from nor'easters and hurricanes will continue to pose a risk for New York City."

Hurricane Sandy devastated the oceanfront coastline and caused catastrophic flooding in New York and cities in New Jersey on Oct. 29, 2012. It was blamed for at least 182 deaths and $65 billion in damage in the U.S. Included in that $65 billion is $8.4 billion in payouts for flood damage from the federal insurance program, according to the Insurance Information Institute.

State and city officials in New York say they are planning numerous projects to guard against future flooding, including fortifying utilities and transit facilities, and note other projects are still in the design stage.

Follow Chris Ciaccia on Twitter @Chris_Ciaccia. The Associated Press contribued to this report