Studies at odds on removable seawalls as storm waves slam South Carolina beachfront homes
September 18th, 2017
By Bo Petersen
The surf from Tropical Storm Irma swamped past the pillars meant to prop up the experimental removable seawalls that advocates hoped would protect resort homes in the Wild Dunes and Harbor Island communities.
Whether the removed walls would have made a difference, however, remains in dispute as property owners, conservationists and the state wait on the courts to decide their future.
Meanwhile, the research done so far on their effectiveness is inconclusive.
"The walls cause the shoreline to actually move inland towards the buildings they are meant to protect," said attorney Amelia Thompson, with the South Carolina Environmental Law Project.
"Claiming otherwise gives false hope to the desperate people who regrettably own properties built too close to the ocean," she said.
In Wild Dunes on the Isle of Palms, where the slats were ordered removed between the seawall pillars, Irma surf foamed over the sandbags behind and once again swept into the homes and condominiums. The walls could have helped, said Harry Stumpf, the Seascape Villas president.
At the Harbor Island resort on the lip of St. Helena Sound near Beaufort, beachfront homes were further damaged without the walls, as well. But so were others in the neighborhood, said Don Woelke, the island manager.
The horizontal slats for the walls that had been set up in the two communities largely had been removed because of court fights by the time a federal judge in August ordered they had to come down.
The seawalls, or "wave dissipation devices," break up storm waves that cause the worst beach erosion while still allowing water and fine sand through.
The slats were designed to be removed between storms, to allow natural beach flow and to be less an impediment to creatures such as the endangered and threatened species of nesting sea turtles. But the S.C. Department of Health and Environmental Control required the slats to stay put to study their effectiveness.
Three studies were done looking at how well they work — by The Citadel for the walls' designers, by a company hired by DHEC, and then by DHEC staff reviewing the two previous studies. According to the results:
*The Citadel study concluded the walls were a viable alternative to sandbags but were not a "one size fits all" solution. They had limitations as to where they could be used and at times sandbags would need to be used alongside them.
*The company, GEL Engineering, found that while the walls "may cause minimal or insignificant erosion on adjacent properties," they did protect the properties "to some extent."
*DHEC staff concluded the walls didn't stop erosion because sandbags also were needed at the properties. The walls also obstructed public access at high tides times and potentially could impact sea turtle nesting.
The DHEC board ordered the walls to stay put while more study was done. A U.S. District Court judge ordered them removed after a lawsuit filed by the law project contended they impede nesting by sea turtles.
DHEC requested in August to be allowed to leave standing the support pillars, about 100 of them, and allow the slats to be replaced at the nesting season's end. The season ended Aug. 31.
As of Friday, the judge had not ruled.