More days with more coastal flooding coming, NOAA says

Coastal living is baked into Florida culture, but multimillion-dollar second homes along beaches and new developments along estuaries are going to be an endangered species if sea levels rise with the expected quickness to their expected levels over the next decades.

The scientists at the National Oceanic and Atmospheric Administration (NOAA) produced reports referencing data showing record-breaking high-tide flooding caused by sea-level rise over the past year, and which is expected to continue for the foreseeable future.

“As sea level rises, damaging flooding that decades ago only happened during a storm now happens more regularly, even without stormy weather, such as during a full-moon tide or with a change in winds or currents,” said William Sweet, an oceanographer with NOAA’s National Ocean Service. 

High-tide flooding, or sunny-day flooding, happens when waters are 1.75-2 feet above average daily high tide. It’s happening more often — more water, more days. Some of NOAA’s tide gauge stations recorded changes in tides for more than a century. The data isn’t encouraging.

“It shows that U.S. communities saw four days, on average, of high-tide flooding in 2021, just shy of the record of five days set a few years ago,” Sweet said, acknowledging the number of days is accelerating along the Atlantic and Gulf coasts. 

Coming to our rescue: the moon.

“The … presence of La Nina over the last couple of years, together with the downward swing in tide heights from the wobble in the moon’s orbit, have slowed flood frequencies some, but won’t take the foot off the accelerator, if you will,” Sweet said.  

For Fernandina Beach, it’s likely Amelia Island will see close to a foot of sea-level rise in 20 years and nearly 2 feet in 40 years. With that, high-tide flooding days, which now are around four to seven, will multiply. There were six high-tide flooding days in 2021, a few short of the record of nine. The usual number of such days in 2000 was two.

The intermediate forecast puts the number of flooding days around 20 for 2040 and around 90 for 2060. The intermediate-high and high projections both have Fernandina Beach eclipsing the mark of 100 days of regular flooding before 2060.

The eastern Gulf saw an average of four high-tide flooding days in 2021, compared to six for the Southeast Atlantic. Nationally, the expectation is three to seven days this year, which is the same forecast for the Southeast Atlantic and eastern Gulf coasts.

“In terms of where we’re headed for the longer term, with nearly one foot of sea-level rise expected over the next 30 years … these numbers can be put in perspective,” Sweet said. “By 2050, the number of high-tide flood days will rise between 45 to 70 days per year on average, suggesting high-tide flood days will become the new high tide in many locations.”