‘Defend, Adapt, Retreat’: Tybee’s plan to grow resilient against sea level rise

Our Changing Climate

TYBEE ISLAND, Ga. (WSAV) ⁠— Tybee Island has, like many coastal communities along the eastern United States, been experiencing gradual sea level rise for decades.

In fact, the National Oceanic Atmospheric Administration’s (NOAA) tide gauge records from nearby Fort Pulaski show about 10 to 11 inches of sea level rise between 1935 to now.

“We see the same thing in North Carolina, where sea levels are rising more rapidly than they are here in Georgia, on the order of 5-6 millimeters per year,” Dr. Clark Alexander, the director and professor of the Skidaway Institute of Oceanography, told News 3.

The Fort Pulaski tide gauge shows a rise of about 3 millimeters per year, Alexander noted.

“We also see a rise down to the bottom of Florida, as well in about the same rate that we see here in Savannah,” he said. 

Three of the top 10 highest tides ever recorded by the Fort Pulaski tide gauge happened in October 2015, according to NOAA — a trend that scientists across the globe are expecting to accelerate in the future. 

“Most of the projections of sea level rise show an acceleration starting to occur sometime in 2030 in most of the models, so we’re getting to the point where in [our] lifetime, we will be able to see whether the rate of sea level rise will be increasing,” Alexander said.

He added that some of the more extreme models show up to 6 feet of sea level rise by the end of the 21st century. 

“You can just imagine what having the sea level come 6 feet higher every high tide would do,” Alexander said.

“It’s probably not something you and I will experience, but it’s something that our children will be dealing with.”

Those possible changes may be at least a decade away, but Tybee has been feeling some of the impacts of sea level rise more recently, from beach erosion to flooding from storm surge brought on by storms and hurricanes as well as inundation from high tide.

The flooding has also resulted in more frequent road closures of Highway 80, the only road on and off the island.

In recent years, the city came to a decision to do something about this pressing problem. 

At one point, the cost of the damage is going to be one that people are not going to be willing to accept.”

Dr. Clark Alexander, director and professor of the Skidaway Institute of Oceanography

In April 2016, with the help of the University of Georgia, Stetson University and the Georgia Sea Grant, officials of Georgia’s most densely developed barrier island agreed on a Sea Level Rise Adaptation Plan to respond to the issues of climate change-related sea level rise over the next five decades.

It was the first plan of its kind in the state of Georgia. 

‘Defend, Adapt, Retreat’

“We’re taking a three-step approach,” Tybee Island City Manager Shawn Gillen told News 3.

That approach involves the “defend adapt and retreat” plan.

“The ‘Defense’ part is what building dunes and renourishing the beach is all about,” Gillen said.

Tybee recently built a new dune from 19th Street to the Tybee Beach Pier.

They brought in 20,000 cubic yards of sand to build up a very strong dune system where, during Irma, there was no dune at all, allowing the area to be overwhelmed by storm surge, Gillen said.

Building dunes was part of the sea level rise study, according to Alan Robertson, the project manager of dune construction for the City of Tybee Island Planning Commission.

“Our dunes on Tybee in the middle of the island are actually quite good, they’re very high and they’re very wide,” Robertson told News 3. 

“But on the south and north ends, as you can see on Gulick, there are either very small dunes or in the middle of the island, no dunes at all.”

In 2018, he said, the city ended up building the first dune on 19th Street, which held off a lot of flooding during Hurricanes Florence and Michael. 

The people on Tybee aren’t going anywhere. This city’s been around for a long time.”

Shawn Gillen, Tybee Island City Manager

Beach renourishment, another key factor in the defense part of the plan, is done every seven to 10 years by the U.S. Army Corps of Engineers.

“They dredge sand from the ocean about a mile off, pour it onto the beach and smooth it out,” Robertson said.

The Corps received $13 million in a supplemental bill that will fund a beach renourishment over the coming winter with about a million cubic yards of sand.

“Right now, the beach is relatively narrow, it had a lot of damage from the hurricanes and tropical storms, but when the Corps finishes their renourishment, it’ll be a gorgeous, large beautiful beach,” he said.

There have also been adjustments to Highway 80, but according to Alexander, raising all of the highway wasn’t considered affordable by those involved in the adaptation plan.

However, the Georgia Department of Transportation did recently raise the road by 8 inches in lower-lying spots between Bull River Bridge and Lazaretto Creek Bridge. 

“[It’s] enough to keep it from flooding during normal tides now, which is great, but doesn’t do much in protecting it from flooding during storm surge,” Alexander said.

Adaptation measures taken by the city include raising houses to be lifted above the floodplain, according to Gillen. 

So far, the city has been approved by the Federal Emergency Management Agency’s (FEMA) Hazard Mitigation Grant Program to be funded for 12 homes to be lifted, and the city hopes that a second grant will fund the lifting of 49 additional homes.

“[Another] piece of that is the backside of the island, where the marsh floods frequently at high tide, and where some of the homes that are going to be lifted are located,” Gillen said.

The city has applied for a grant to study the best way to prevent that area from tidally influenced marsh flooding.

They [also] put flap gates on their storm drain system, so that their storm drain pipes won’t be full of saltwater during high tide, and they’ve raised their water well intakes so they’re still able to pump fresh water during storm events.”

‘Retreat’: The unpopular part of the plan

The third piece of the puzzle — “Retreat” — is the least discussed portion of the plan.

“The people on Tybee aren’t going anywhere,” Gillen said. “This city’s been around for a long time.”

Alexander added that the idea of retreating with sea level rise doesn’t get a lot of attention, in part because it’s not currently considered politically acceptable.

The damages that we’re seeing, although they’re increasing, are not enough to make people start seriously thinking about retreating from the coast,” he said.

“Obviously, that’s going to change as sea levels rise, because every time the sea level goes up by a little bit, that raises your base level, basically.”

That means, according to Alexander, that storm surge will be a little higher, it will reach a little bit farther inland and the waves and the wave damage will be farther inland, as well. 

“At one point, the cost of the damage is going to be one that people are not going to be willing to accept,” he said.

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