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NOAA projects that Boston will see up to 18 days of ‘sunny day’ flooding next year

"High tide flood levels may become the new high tide in some locations."

Water from Boston Harbor floods Long Wharf during high tide in October 2018. Craig F. Walker / The Boston Globe

Federal officials expect Boston to see up to 18 days of ocean flooding next year — and that’s just when it’s sunny out.

The National Oceanic and Atmospheric Administration released a report Wednesday projecting that Boston will see 11 to 18 days of high-tide flooding in 2021, as climate change makes the type of floods previously only caused by storms increasingly common across the country.

Also known as “nuisance” or “sunny day” flooding, high-tide flooding occurs when tides reach anywhere from 1.75 to 2 feet above the average daily high tide, according to the NOAA.

Officials say high-tide flooding can be caused by things as simple as a full-moon tide or a change in prevailing winds or currents. At the same time, it can damage infrastructure and cause disruption (case in point: Boston’s frequently flooded Morrissey Boulevard).

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Across the United States, high-tide flooding increased by about 50 percent in the last 20 years — and 100 percent in the last 30 years — according to the NOAA.

Back in 2000, Boston saw just six days of high-tide flooding; last year it saw 11. By 2030, the city will see between 20 and 30 days of such flooding, the NOAA said. By 2050, the agency says Boston is expected to see between 45 and 95 days of high-tide flooding — potentially more than a quarter of all days in the year.

The projected increase in Boston is more than any other New England location included in the NOAA’s report.

“High tide flood levels may become the new high tide in some locations,” Nicole LeBoeuf, director of NOAA’s National Ocean Service, said at a press conference Wednesday, according to WBUR.

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“For the first time in human history, the infrastructure we build must be designed and constructed with future conditions in mind,” she said.

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