Sunny day flooding increases at Fort Pulaski, adds height to Tybee road project
Tybee Island, Georgia - Sunny day flooding, most evident locally on U.S. 80 near Fort Pulaski, is getting more frequent in coastal communities nationally as sea level rises, according to a report issued by the National Oceanic and Atmospheric Administration on Wednesday.
NOAA predicts four to eight tidal floods at Fort Pulaski for the period between May 1, 2019, and April 30, 2020. The area saw six high tide floods over the previous 12 months. These events are also referred to as “nuisance” or “sunny day” flooding because they can occur with an unusually high tide without rain or a storm surge.
The tide gauge at Fort Pulaski is among more than 40 locations where the annual rates of high-tide flooding are rapidly increasing, according to NOAA. Annual rates at 25 other locations are also trending upwards but more gradually. These increases suggest a much wetter future for many coastal areas.
“The current projections suggest a lot, let’s say, floodier, future,” said William Sweet, an oceanographer for NOAA’s Center for Operational Oceanographic Products and Services and lead author of the report. He spoke during a national teleconference Wednesday. The report, 2018 State of U.S. High Tide Flooding with a 2019 Outlook, indicates “impacts will soon become chronic without adaptation.”
Fort Pulaski experienced two days of tidal flooding in 2000. That’s expected to rise to 15 to 25 days in 2030 and 40 to 95 days in 2050.
According to the report, a median of five days of high tide flooding occurred nationally within coastal communities in 2018, tying the record set in 2015. Flood days broke records in the Northeast, with a median of 10 days, and in the Eastern Gulf of Mexico at five days, due to a combination of active nor’easter and hurricane seasons combined with sea level rise.
Sea level is currently rising at a rate of about an inch every eight years, Sweet said. It’s the result of both melting glaciers and ice sheets and the expansion of ocean water as it warms. Ocean rise and land subsidence are built into NOAA’s projections, which also use moderate emissions scenarios. Sunny day flooding will be more frequent if carbon emissions are greater than modeled.
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Nicole LeBoeuf, acting director of NOAA’s National Ocean Service, urged action for what she called “an increasingly urgent issue that many coastal communities are grappling with as our seas continue to rise.”
“We cannot wait to act,” she said. “This issue gets only more urgent and complex with each passing day.”
There is some adaptation already in place for U.S. 80, where the Georgia Department of Transportation is finishing a project that included the resurfacing of a more than four-mile stretch from Bull River and Lazaretto Creek bridges.
“This $1.8 million resurfacing project included spot leveling of the lowest-lying stretches along the causeway to minimize road closures due to tidal flooding,” GDOT Spokeswoman Jill Nagel wrote in an email. “The leveling increased the asphalt depth up to 10 inches in some areas, and it raised the roadway center line to an elevation that corresponds to an approximate tide reading of 10.65 feet on the Fort Pulaski tide gauge.”
Nagel said the main paving is finished except for some possible corrective work, but the contractor is still working on hatching and grassing with silt fence removal. The road ended up higher than initially planned.
“We estimated 8 inches, but once out there 10 inches was needed to bring the roadway elevation up to the proper height we needed to prevent flooding,” Nagel wrote.
This fix may be put to the test soon. NOAA predicts tides will be higher than normal in the Southeast this summer from July 31 through Aug. 3 and again from Aug. 28 through Sept. 2, which coincides with the Labor Day holiday. A perigean spring tide, when the moon is either new or full and closest to earth, will be occurring during these periods. Higher than normal high tides and lower than normal low tides will occur.