Posted on May 3, 2021
FOLLY BEACH — Federal engineers are testing a new way to battle erosion on this vulnerable barrier island.
The Army Corps of Engineers are taking the sand they suck up while clearing the Folly River, just west of the island, and will use it to create an offshore sandbar just off the north end of Folly Beach. The hope is that the sand will migrate back on to the beach, providing at least some help for an area where sand can disappear quickly.
The project costs $1.2 million and is funded through federal money already appropriated to keep the Folly River clear for boat traffic, said Wes Wilson, the project manager with the Corps.
It mimics a natural process for beach islands. Winter storms like nor’easters scrape sand off the beach and deposit the sediment in sandbars just offshore. In calmer, warmer months, the sand drifts back to the island.
The dredge is out working now for 24 hours a day, and will continue through the end of May, Wilson said. In total, 60,000 cubic yards of sand, or enough to fill 18 Olympic swimming pools, will be deposited in the newly constructed sandbar.
“We’re really encouraged (the Corps is) going to give it a shot,” said Eric Lutz, the director of public works for the city of Folly Beach.
He referred to the process as almost recycling because sand that erodes off the beach already floats south to clog the mouth of the river.
Folly Beach has long had erosion problems, particularly on its northeast edge, because of jetties upstream that keep the mouth of Charleston Harbor clear of drifting material. The same jetties have caused sand to pile up across the harbor at the southern end of Sullivan’s Island, making the shoreline there grow.
Because the Corps constructed those jetties, it now pays a larger-than-normal amount when sharing the cost to dredge sand off the seafloor and put it back onto the beach on Folly, a process known as renourishment. The Corps is now in the midst of revising its 50-year-plan with Folly to keep putting sand back on the beach.
But renourishment is an expensive process, and supplies of offshore sand are depleting.
The island also faces the challenges of climate change and rising oceans. But tidal flooding on barrier islands usually intrudes first on the marshy side that faces the mainland, in this case the edge of the Folly River. Sea rise can scrape away at beach sand, but is less likely to overtop it because of the natural slope of a beach.
The Corps will track the progress of its new project through cameras affixed to the second story of a beach house on the north end of Folly.
The movement of sand will also be measured through the movement of “trackers” — synthetic sand in fluorescent pink and orange that will be mixed in with the sandbar.
Because the trackers are such a small portion of all the sand being used, the Corps can only determine if they drifted to the right place with careful observation. Samples of sand will be taken from multiple spots for the next two years and analyzed in a lab, said Clay McCoy, technical director of the Corp’s Regional Sediment Management Center of Expertise.
As for being able to spot a few fluorescent grains on the beach, “It would be very, very, very unlikely,” McCoy said. “We did a study of this in Brunswick Harbor (in Georgia), but we couldn’t see anything with the naked eye.”