Atlantic Cities

New York City in Line for Dozens of '100-Year Floods' Every Century

New York City in Line for Dozens of '100-Year Floods' Every Century
Jim Henderson

Good thing New Yorkers have so many sources for cute rain boots – looks like they might need them soon.

If the global climate continues its warming trend, Manhattan could see a drastic uptick of so-called 100-year floods, or those with storm surges around 6.5 feet, according to a new MIT study. These mondo deluges could occur as often as every 3 to 20 years by the end of this century, blasting over the island's seawalls into businesses and subways and causing the kind of mass evacuations last seen with Hurricane Irene.

Worse to imagine, the incidence of 500-year floods, or those that carry in swells towering at nearly 10 feet, could speed up to every 25 to 240 years, say the MIT researchers. The highest surge ever recorded in New York, during the terrifying Hurricane of 1821, was just above that magnitude, at 10.5 to 13 feet (the estimate varies per source). That godawful drenching brought water up to Canal Street and washed away a bridge connecting Harlem to Ward's Island.

The researchers arrived at this grim vision of the future by conjuring 45,000 computer-generated storms and throwing them toward Battery Park. They studied the effects of these tempests in a hypothetical warmer climate caused by unimpeded greenhouse-gas emissions, using estimates devised by the Intergovernmental Panel on Climate Change. The scientists found that from 2081 to 2100 (and beyond), there would likely be more storms and more surges.

New York has been hit by a parade of vicious hurricanes in its history that have shown it to be particularly vulnerable to surges, the most damaging aspect of hurricanes. City planners who pay attention to such studies may be questioning if it's time to add a few feet onto Manhattan's protective seawall, notes MIT:

Carol Friedland, an assistant professor of construction management and industrial engineering at Louisiana State University, sees the group’s results as a useful tool to inform coastal design — particularly, she notes, as most buildings are designed with a 60- to 120-year “usable lifespan.”

“The physical damage and economic loss that result from storm surge can be devastating to individuals, businesses, infrastructure and communities,” Friedland says. “For current coastal community planning and design projects, it is essential that the effects of climate change be included in storm-surge predictions.”

The study is featured in the current issue of Nature Climate Change; you can read more about it here.

Above: People in the flooded Hudson River Park during Aug. 2011's Hurricane Irene. Courtesy of Jim Henderson.

John Metcalfe is a staff writer at The Atlantic Cities. All posts »

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