— The sands of the severely eroded county park here are now sweeping across what was marsh behind it. The beach park, in other words, isn’t disappearing, but it’s moving the other way.

The science of shifting sands

The phenomenon is called “island roll over.” The seas push barrier beach sand over what were trees and marsh, moving the beach inland.

Because of that sand, the closed, eroding Folly Beach County Park isn’t losing ground for facilities.

But flat sand covers what used to be wildlife habitats of marsh reeds and a maritime grove. Protecting dunes, even scarps, are gone.

New research: The Charleston County Park and Recreation Commission has asked College of Charleston researchers to document what’s happening, to provide data to assess its proposed groin project, said Director Tom O’Rourke.

Leslie Sautter, associate geology professor, who is doing the work along with colleague Scott Harris and students, said they are establishing baseline data of the volume of sand and its various elevations.

Potential work: The commission could fund an overall monitoring, using techniques such as underwater mapping, for an ongoing survey of park grounds and nearby shorebird key and shoals.

“For our purposes, we’re documenting this beach because it’s changing so rapidly. It’s a very serious situation,” Sautter said. Whether the data shows beach renourishment works or not, it’s important information for developers and coastal engineers worldwide.

No politics: The researchers are not taking a position in the dispute, she said. “We are observing and quantifying. We want to make a very public, open interface for the taxpayers to see what’s going on.”

Bo Petersen

The same could be said of the negotiations over what to do about it. Conservationists had pushed to forge a compromise over a groin for the closed Charleston County park, wanting to get an agreement in place before a pivotal environmental ruling on the project was issued by federal regulators.

The U.S. Fish and Wildlife Service ruling is now in. It largely backs up conservation measures already included in the project by Charleston County Park and Recreation Commission, to protect nearby shorebird habitat and other species.

Regulators are close to deciding whether to permit the commission to erect a $3 million groin — a wood or rock barrier — stretching more than 700 feet, including 200 feet out to sea. The groin would rebuild some beach and protect renourishment sand along what is now largely a duneless, overwashed beach.

The Coastal Conservation League now has little remaining leverage in negotiations besides the threat of a lawsuit that would stymie the project.

The league’s original stand against building the groin has been scaled back over three months. The group now only insists that a coastal scientist who is not part of the project be made part of a project team that determines whether the groin is damaging the valuable Bird Key Stono and Skimmer Flats shorebird grounds nearby. According to permit specifications, significant damage to those grounds would call for the groin to be removed.

The league and the commission now are squabbling over whether S.C. Department of Health and Environmental Control has endorsed the league’s call for an independent monitor.

Catherine Templeton, DHEC director, said the agency wouldn’t prohibit it but that “the parties can agree on whatever they want.”

Commission Director Tom O’Rourke said that falls short of endorsing the idea.

“We have dropped all of our requests except that (the commission) include an independent geologist on the evaluation team,” said Dana Beach, league executive director. “They have refused to do that. They initially said they couldn’t. Now we know they can.”

State coastal policy discourages groins because, while they collect sand upstream of the barrier, they exacerbate erosion downstream.

In December, the league said it would take its permit fight into court if necessary.

Reach Bo Petersen at 937-5744 or @bopete on Twitter .