Ever-shifting beaches again in need of sand

High surf at Isle of Palms is scarping the dune line near 7th Avenue, turning the front dunes into a sharp-edged, crumbling cliff.

ISLE OF PALMS — The middle of this barrier island is said to be one of the lucky stretches in the Lowcountry — a beach that is accreting, or gaining sand.

Except high surf is now scarping its dune line, collapsing the front dunes to a sharp-edged, crumbling cliff. Isle of Palms officials have their engineers looking at a possible overall beach renourishment, said Mayor Dick Cronin, possibly within the next five to seven years.

That doesn’t bode well for other efforts to keep sand on popular Lowcountry beaches, as more people swarm Isle of Palms, Sullivan’s Island, Folly Beach and nearby destinations.

The beaches are barrier islands, really not any more than big sandbars sifting and sliding through the surf. Sands erode and pile up downstream, continually reshaping even the most stable stretches. The beach that was there yesterday won’t be tomorrow. The beach you rebuild doesn’t stay put.

That’s a problem not only for the hordes of beachgoers who can find themselves pushed back against the dune line at high tide, but also for the climbing rows of high-dollar beach mansions behind them. The beach is one of the big draws of the booming Lowcountry, and the difficulties and expense of keeping it there is growing just as fast.

Sandbags have been piled in front of more beachfront homes at the beleaguered Wild Dunes resort on Isle of Palms’ north end toward Dewees Inlet. Property owners are looking to move beach sand this fall to stop erosion that is again threatening to undermine the multimillion dollar homes.

It’s a second go at the temporary fix, because an offshore sandbar is taking longer to attach than expected. The attachment too will be a temporary shoring-up of a volatile inlet stretch of those shifting bars and beaches.

Meanwhile, the U.S. Army Corps of Engineers is searching for new sand off Folly Beach, already eyeing its next renourishment after work in 2005 and 2014, amid a number of smaller shoring-up jobs. So much sand has been dredged from the former offshore sites that they can no longer be used.

Seabrook Island just recut Capt. Sam’s Inlet to keep the shifting sands from eroding away its beach, a periodic gouging that disrupts the prized wildlife environs. Kiawah Island is moving sand to shore up its east end by the vaunted Ocean Course golfing mecca, another periodic shoring up job. Edisto Beach is preparing for an overall renourishment in 2016.

The expense of doing it all is skyrocketing: Folly’s cost climbed 200 percent since the 1990s to $30 million for the 2014 work. Federal legislators incrementally are backing away from the renourishment business, no longer willing to pay the lion’s share of that climbing cost.

Beach communities are faced with paying more of the load on their own, and might well be forced to turn to beachgoers for the funds. Even the “accreting” ones; Isle of Palms was designated as “stable to slightly accretional” in the 2009 State of the Beaches report issued by S.C. Health and Environmental Control, the most recent of the reports.

The wild card in what’s happening here is the Charleston jetties. The jetties are rock walls lining the shipping channel that interrupt the predominant north-south flow of sand in the shore current, piling some of it back on Sullivan’s Island and eddying the flow to add to Isle of Palms sand.

That sand otherwise would be headed toward Folly Beach — where the erosion is worse because of its absence. But even the jetties can’t keep the sand in place. The shifting would be taking place whether or not man-made structures and cuts were affecting it.

“Absolutely,” said Nicole Elko of Elko Coastal Consulting. “The Charleston area barrier islands are characterized as mixed energy barrier islands.” Oddly enough, the islands are relatively sand-rich, receiving periodic shots of those sandbars drifting from the inlets with the flow.

“The cycles of erosion and accretion that occur on the bulbous ends as the sandbars are migrating onshore are natural fluctuations that the islands have experienced for millennia with or without man,” Elko said.

The sand shift is so relentless that trouble in one spot can spell trouble for the next. That unexpected erosion in the “accretional” Isle of Palms mid-island area might be caused partly by the Dewees Inlet bars eroding Wild Dunes. Those migrating bars might be disrupting flow patterns of sand in the shore current.

“In the big picture it can factor into what’s going on,” said Steven Traynum of Coastal Science and Engineering, the company working with Wild Dunes. “It all has to do with shoal movements.”

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