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Pawleys Island: Study shows beach stable, but groins need repairs
By Charles Swenson
A study commissioned by the town of Pawleys Island in the wake of winter erosion has found that the beachfront has remained mostly stable in the 15 years since a beach nourishment project.
But the study by Coastal Science and Engineering also found that the field of 23 rock and timber groins that traps sand along two thirds of the island’s beachfront needs work, estimated at between $117,000 and $351,000. The cost varies because the study didn’t look at the condition of the groins below the surface. That needs to be done by a contractor, the study says.
Coastal Science also did the assessments used by the town for its 1998 nourishment project. “This study confirms that the rates of change along the beach have been low,” the study says, about 1 cubic foot a year since that project.
“The good news is you didn’t lose much sand,” said Tim Kana, principal in Coastal Science and the author of the study. “The bad news is you didn’t have enough to begin with.”
Mayor Bill Otis also pointed out that the average disguises differences between the north end of the island, which is widening, and the narrow south end. The southern third of the island needs about 350,000 cubic yards of sand to have “a minimum healthy beach volume seaward of buildings,” the study says. But it notes that all the areas between groins, known as cells, have more sand now than they did before the 1999 nourishment project. That project added about 270,000 cubic yards of sand.
“We were pleasantly surprised that most of the sand was still in the cells,” Kana said.
The island north of Pawleys Pier has gained about 415,000 cubic yards of sand since 1997, the study says. That’s “likely due to natural sand bypassing Midway Inlet,” it says.
The erosion seen along the dunes following the winter storms was not unusual, the study says. “The erosion recently observed relates to ‘profile adjustment’ in the form of onshore-offshore redistribution of sediment. Such adjustment is common along stable beaches with shifts of sand from the dry beach to the wet beach (i.e. profile flattening) after higher wave events such as minor northeasters and a return of sand to the upper beach during normal wave periods,” the study says.
“The whole point of our recommendation is to show that when you have a sand deficit anywhere on the coast, you don’t have that natural sand buffer to come and go with the season,” Kana said. “That’s the problem with Pawleys. There isn’t enough of a sand reservoir at the end of the groins.”
The study also notes that there isn’t enough dune between many of the houses and the beach. When there is a “profile adjustment,” it impacts private property.
“The principal ways to mitigate this situation is to add more sand (ie. renourishment) and, possibly, lengthen the groins to retain greater sand volumes,” the study says.
The study looked at how the length of the groins affected the amount of sand on the beach. It found that 300 feet from the seaward end of the groin to the house line was the optimal distance. To achieve that 11 groins on the south end would need to be lengthened, the study says.
Otis plans to get an estimate on the cost of permits to repair the existing groins. “Every one of our groins needs some repairs – some more than others,” he said. “That’s something we will be talking about.”
Kana agreed that maintaining the groins is an important project, although he also said that erosion rates on Pawleys Island and the Litchfield Beaches are historically low.
The Army Corps of Engineers approved an $8.98 million beach nourishment project for the island’s south end in 2006. Congress has yet to approve funding for the project, which would require a local match. Kana said his estimate of the sand deficit on the south end mirrors the findings in the Corps study.
“Long term, we all need to look at making our beaches more healthy and resilient,” he said. “It takes more sand. That’s why the Corps plan is so important.”