South Carolina’s environmental agency says it plans to end the use of experimental plastic seawalls that are being tested as a potential way to stop beach erosion.
The Department of Health and Environmental Control (DHEC) board on Thursday voted on the first step to remove the “Wave Dissipation Systems” (WDS) from testing locations on the Isle of Palms in Charleston County and Harbor Island in Beaufort County. The decision was made after agency staff presented data from a study by The Citadel suggesting the WDS system was not able to slow severe erosion on those beaches — and may have even been making it worse.
However, the board did decide to keep the seawalls in place for another 60 days to give affected property owners a chance to respond. They board plans to make a final decision at its February meeting.
“I feel bad for the property owners,” Chairman Allen Amsler said in the meeting. “Obviously this isn’t going to be a very good future investment. But what is the option? It doesn’t seem to be a really good option to fight Mother Nature.”
South Carolina has had a ban on seawalls for nearly 30 years, but legislators in 2014 gave a temporary exemption for The Citadel to study the WDS walls. The plastic walls use removable pipes with the idea of blunting the force of waves while still preventing sand from washing away. However, DHEC staff said two years of evidence instead indicates the walls prevent sand from naturally building up behind the WDS and are instead pushing the wave force towards other unprotected areas of the beach at the end of the wall. Their report also noted “scouring” caused as sand piled along the wall and caused trenches to appear along the beach after high tide that had not existed before the WDS installation.
“What we’re seeing overall in the study, when you get into the details of the data, it’s showing the structure is not working during erosive times when you want something in there to try and protect your property,” DHEC Office of Coastal Research Management (OCRM) wetland permitting manager Blair Williams told the board.
The staff findings were drastically different from The Citadel’s report. The college had advocated using the walls after initial success along the Isle of Palms, but DHEC wanted it used in other locations for more complete data. Lead Citadel researcher Tim Mays said regulators insisted the walls remain in the same place, while he recommended their adjustment every two months depending on circumstances.
“It is the opinion of the project’s principal investigator that OCRM has always had the overall mindset (regarding a study) that the system should be built and then the research team should just step back and watch what happens over the next year,” he wrote. “This approach is not applicable to sandbags and should not be applied to the WDS.”
However DHEC went more in-depth with the collected data than The Citadel’s report, hiring a third-party engineering group to review the walls. The report recommends replenishing the beach with massive amounts of sand on a regular basis instead of relying on the wall.
Environmental groups have sued DHEC, seeking a judge’s order to take down the walls immediately. The lawsuit filed on behalf of the South Carolina Wildlife Federation and the state Sierra Club chapter argued the walls violate federal law by preventing endangered sea turtles from nesting along the dunes. However, DHEC said its own research did not find evidence the walls were significantly affecting sea turtle nests, noting no decline in nesting along the Isle of Palms and Harbor Island than before the WDS was installed.