High tide flooding along the North Carolina coast is expected to increase in coming years

Southport is no stranger to dealing with tidal flooding.

Bordered by the Cape Fear River to the east and the Intracoastal Waterway to the south, the Brunswick County community at the mouth of the river has been in a constant standoff with Mother Nature since its founding in 1792. residents have grown to live with the untimely floods, floods have become more frequent.

Post-storm emergency infrastructure and repair projects in recent years have helped stabilize some riparian areas, and city officials hope recently allocated state funds can provide some relief to the basin’s floodplain. yachts. But Mayor Joe Hatem knows climate change means it will be a constant battle to contain rising waters.

“We are going through a transformation and we want to be ready for that, and we intend to do everything we can with the technology we have to do that,” he said.

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But Southport could soon face a series of new challenges.

The National Oceanic and Atmospheric Administration (NOAA) reported this month that nearly 2/3 of federal tide gauge stations along the US East and Gulf Coasts experienced increased flooding last year, and the rising tides is a sign of what is to come.

Indeed, high tide (HTF) flooding, defined as anywhere between 1.75 and 2 feet above the daily mean high tide, is becoming more common due to years of sea level rise. The latest government estimate predicts that the seas will rise one foot over the next 30 years, as much as the rise measured over the past 100 years.

According to NOAA, the East Coast and Gulf Coast states will experience at least a 150% increase in HTF over the year 2000, limited only by periodic weather and climate events. And this trend will only continue as global warming, linked to temperature changes that are already underway due to the massive release of greenhouse gases since the industrial revolution, accelerates. By 2050, NOAA predicts nationwide high tide flooding to last between 45 and 70 days per year on average.

Some estimates for parts of the North Carolina coast could see even more high tide days. In 2021, the tide gauge near the Cape Fear Memorial Bridge in Wilmington recorded two days of flooding at high tide. That could go from 40 to 65 days of flooding in 2050, according to NOAA. The situation is even more concerning further up the North Carolina coast on the Outer Banks. There, projections show Oregon Inlet will experience 110 to 166 high tide days in 2050. That’s up from just five recorded last year. In Duck, 30 miles north of Oregon Inlet, NOAA projections call for up to 120 high tide days by 2050. The town experienced 11 in 2021.

Tidal flooding continues in downtown Wilmington, NC after Hurricane Matthew JOHN STATON/STARNEWS PHOTO

“Water levels are approaching the edge in many communities,” William Sweet, a NOAA oceanographer, told USA Today earlier this month. “We have flooding on a sunny day, (without) any storms and you start to overwhelm the defences.”

“We can’t protect everything against floods”

As concerning as NOAA’s predictions are, Dr. Larry Cahoon thinks the real situation could be even worse.

The University of North Carolina Wilmington oceanographer said his review of data from the Wilmington tide gauge, supported by a review of water levels recorded at gauges in Beaufort, North Carolina, and Myrtle Beach, shows that regional water levels are increasing more than expected. . Cahoon said that’s because the Gulf Stream, which oscillates near the Carolina coast as it moves north, has warmed itself. This makes the water less dense and allows it to rise higher, pushing even more water towards the coast.

“We’ve seen a dramatic increase in sea level rise,” Cahoon said. “Where does it go from here, I couldn’t begin to tell you.”

Rising seas also allow seawater to push further inland, a situation amplified by high tides. Cahoon said that means more stress on fresh and brackish water habitats, many of which are already suffering from rising salinity, as evidenced by the proliferation of “ghost forests” of dormant or dying trees throughout. of the North Carolina coast and increased erosion in many areas.

It also increases inland flooding, especially when linked to a tropical storm. Cahoon noted that one of the highest water levels ever recorded at the Wilmington tide gauge was during 2020’s Hurricane Isaias, a weak Category 1 storm that happened to follow a path along the coast that allowed its right quadrant – which is the strongest section of a hurricane – to blow all the way to the Cape Fear River.

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“When hurricanes happen, they’re going to do a lot more damage than what we saw just 20 years ago,” Cahoon said.

South Lake Park Boulevard in Carolina Beach is closed due to September 2018 flooding.

High tides, and not just those due to HTF events or storms, also impact coastal infrastructure. Cahoon said seawater can be very destructive, corroding and collapsing utility lines and pipes, undermining stormwater systems when it backs up into sewers, damaging buildings and vehicles and short- circuit electrical systems.

“It’s a very difficult situation that many of our communities face because we can’t protect everything from flooding,” he said. “There is no engineering to get out of it.”

“No quick or easy solutions”

The Cape Fear Public Utilities Authority, which provides water and sewer services to most New Hanover County residents, is already planning to live with higher water levels.

Gary McSmith, the utility’s chief engineer, said resiliency and looking to the future are considered whenever a pump station, pipe or manhole is rehabilitated or replaced.

CFPUA recently raised the pump station on Oak Landing Road near the Intracoastal Waterway in Wilmington.

“Every piece we touch, we’re mitigating those risks,” he said, adding that’s especially true in low-lying areas, like along the riverfront in downtown Wilmington and around the ‘Intracoastal Waterway.

While the long-term future looks daunting, McSmith said there is a silver lining. The seas do not rise a foot in a year, but a few millimetres. This gives officials time to plan what’s to come.

“We believe we have the time to mitigate these risks over time and through wise investments,” McSmith said.

But Cahoon said engineers and technology could do little to protect coastal communities, especially those along the seafront or in low-lying interior areas.

“We have major problems ahead, and there are no quick or easy fixes,” he said. “It’s a red flag that we don’t have as much time as we think, and we better start planning.”

Journalist Gareth McGrath can be reached at [email protected] or @GarethMcGrathSN on Twitter. This story was produced with financial support from 1Earth Fund and the Prentice Foundation. The USA TODAY Network retains full editorial control of the work.

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