A new report from NOAA’s National Ocean Service says coastal communities nationwide saw record-setting high tide flooding in 2019 and that trend is expected to continue into 2021.
Through May 2021 the national high tide flood frequency is expected to accelerate, with U.S. coastal communities seeing an average of two to six days of flooding in the coming year, NOAA scientists said during a teleconference on Tuesday, July 14, on the status of high tide flooding and NOAA’s annual outlook.
By 2030, they said, high tide flooding is likely to be in the range of seven to 15 days and by 2050, between 25-75 days. These long-term outlooks are based on the range of relative sea level rise “more likely” to occur by 2030 and 2050 using projections of the Fourth National Climate Assessment, they said.
“Conditions are changing, and not just in a few locations,” Nicole LeBoeuf, acting assistant administrator for the National Ocean Service. “Damaging floods that decades ago happened only during a storm now happen more regularly, even without severe weather.”
The report made no mention of the cause of rising seas, either by climate change or global warming.
High tide flooding is defined by NOAA as situations where water rises more than half a meter, about 20 inches, above the normal daily high tidemark. Such flooding has increased in recent years because of rising sea levels, which were about 13 inches higher nationally last year than in 1920, according to the National Ocean Service, which compiled the report.
NOAA is projecting that by 2030 the frequency of high tide flooding may double or triple and by 2050 that frequency could be up to 15 times greater, with typical coastal community flooding ranging from 25 to 75 days annually.
According to William Sweet, an oceanographer with NOAA’s Center for Operational Oceanographic Products and Services, the federal agency does not yet have a handle on the overall impact of rising high tide flooding on Alaska.
“We don’t understand how water levels are changing locally,” Sweet said.
The federal agency plans to continue to monitor water levels in Alaska but is not trying to predict local flood risks everywhere, he said.
More information is at tidesandcurrents.noaa.gov/HighTideFlooding_AnnualOutlook.html.
