A Coastal Star Special Report:
Hurricane shows just how fragile our shores are
Dunes vs. Sea walls: Stopping sand loss is a complicated business
By Cheryl Blackerby
“Permanent solutions” was the continuing theme at coastal community meetings, where residents faced multimillion-dollar bills for beach replacement sand after Hurricane Sandy. What, they asked, could stop the sand loss and the need for expensive and frequent beach renourishment?
But a permanent solution may be elusive, say experts, because beaches are not permanent.
Coastlines are constantly moving with the moon, the tides, the littoral drift, and the certain storms on future horizons.
“Beaches are a very dynamic habitat,” said Michael Stahl, a senior environmental analyst for the county’s Department of Environmental Resources Management. “Littoral drift, or longshore current, is the natural movement of sand along the beach, driven by wave energy.”
But in the final analysis a year after the disastrous ocean surges of Hurricane Sandy, there was indeed a surprising beach defense that stood the test of Sandy — sand dunes, nature’s own fortification of barrier islands.
In Palm Beach County, as well as New York and New Jersey, long-established sand dunes with native vegetation saved beaches and the houses behind them.
The well-developed dunes at the Municipal Beach and neighboring oceanfront houses in Delray Beach generally withstood the hurricanes of 2004 and 2005 as well as Hurricane Sandy and protected houses and A1A.
Far-sighted officials started pumping sand onto the beach and building dunes in 1973 as a desperate measure after the ocean crept up to and often washed over A1A.
But the crucial second step in the dune development came in 1984 when the city called in Robert Barron, owner of Robert Barron Coastal Management and Consulting, to plant sea oats and other native beach vegetation.
“We planted a 6-foot strip of sea oats the entire length of public beach, 6,840 feet, for $22,000. Today, that strip has expanded on its own to 100 to 150 feet wide, and has captured sand and widened the beach,” Barron said.
The slender 5-foot-tall sea oat is a powerful force of nature underground. Plants form networks of interlocking roots 5 feet deep and hundreds of feet long — a sand stabilizer that would be difficult for engineers to replicate.
In addition to sea oats, Barron planted 20 species of native vegetation that has grown to over 60 native species. “It’s taken on a life of its own,” he said.
Barron is now working as a consultant in Miami Beach and planting native species on dunes on 8.6 miles of beach. He is using Delray Beach’s Municipal Beach as a model for that project.
But there are places — including beaches on Singer Island, Palm Beach and South Palm Beach — where dunes and even beach renourishment are not options because the beaches are adjacent to “hard bottom” exposed rock or coral.
Dunes do release sand, indirectly creating a secondary benefit: Dunes act as “feeders,” losing sand into the water, which often comes back on shore as beach.
“That shoreline is protected and designated as essential fish habitat,” said Stahl. “If you heap sand on the shore, it will eventually cover the hard bottom.”
But on most beaches, dunes are the preferred first line of defense, Stahl said. “Certainly any kind of soft approach like beach renourishment and dunes are much better options for shoreline stabilization simply because you’re adding material the beach is comprised of. Anywhere we can build a dune project, that’s preferable.”
DELRAY BEACH: Years of nurturing and building up the dune in Delray Beach shows how a healthy dune can absorb the shock from a storm like Sandy and protect the property built behind it. 2012 photo by Tim Stepien/ The Coastal Star