Fake Kelp Holds the Tide Against Erosion of Beach
Every year, the ocean stole more of the beach.
Winter storms ravaged a 10-block section of shoreline, carrying away a mountain of sand. The ocean gradually crept closer to the posh seafront homes on the peninsula near Belmont Shore.
By 1979, former city Public Works Director James T. Pott recalled, the problem was getting out of hand.
“I was called out at some ungodly hour of the night because the owner of a house on the boardwalk was getting seawater splashed on his front windows,” he said.
Long Beach was quickly losing part of its long beach. Pott said he assured the man that the city would try to halt the erosion.
Coastal engineers were hired to find a solution. They suggested such expensive remedies as extending the offshore breakwater or building a sunken rock structure to keep the sand from washing away.
But it was a persuasive salesman, not the engineers, who eventually provided the solution--"synthetic seaweed.”
No Problem for Boaters
And after six years, the ersatz kelp is working so well that the city is about to spend another $7,000 or so to buy more. Erosion began to halt as early as 1984, when Councilwoman Jan Hall announced the early success of the program in a formal paper presented at a conference in Santa Cruz.
“We’re delighted. It’s worked,” Hall said. “It’s something that doesn’t interfere with swimmers and boaters. It has stabilized the beach for a long time.”
Synthetic seaweed acts like the undulating leaves of underwater plants, but does not look anything like them. It is a barrier of plastic or fiberglass sheeting that knocks down large sand particles that normally would be carried out to sea.
A single unit resembles a big paint dropcloth or car cover that has been shredded to create strips, like fingers on a hand. A sleeve is sewn into the bottom, which is filled with sand that serves as an anchor. Ping-Pong balls or plastic foam blocks are sewn in at the top to allow the strips to float upright.
The units--each about five feet high and four feet wide--are sunk in about eight feet of water off the beach. Over time, Hall said, they stop enough sand that the strips become buried. But the strips are still effective because they create mounds on the sea floor. The mounds take the energy out of the big waves that crash ashore, and less sand washes away.
Unlike other beach communities that are completely exposed to the ocean, most of Long Beach’s four-mile strand of sand is protected by a breakwater. Virtually all of Long Beach’s oceanfront has little more than knee-high waves except for the unprotected stretch running from about 60th to 70th places on the peninsula, which divides Alamitos Bay from the sea.
There, the city has waged its years-long battle to keep the sands in place. Photos taken during World War II show that stretch along the peninsula virtually devoid of sand, with huge boulders at the base of the seawall. Between 1957 and 1978, the city estimates it was losing 5 to 10 feet of beachfront a year to erosion.
Wooden jetties running 200 feet into the ocean were constructed after the war along the peninsula to try to stop the erosion, but did little to stabilize the troubled section known as East Beach.
Bulldozers pushed the sand up on the beach during winters to minimize sand loss during storms, and additional sand was dredged from the bay to rejuvenate the beach.
Former city Public Works Director Pott said a number of possible solutions were being considered, some of them quite expensive, when he was visited by a salesman offering the phony seaweed.
“A salesman for this stuff saw an article in the newspaper (about the erosion problem) and said, ‘Boy, have I got a deal for you,’ ” Pott recalled.
A similar installation was being credited with saving the famous lighthouse near Cape Hatteras, N.C., and appeared to be successful in preserving beaches in communities on the banks of Lake Michigan. Pott said he was intrigued enough to take the idea to Hall.
Because the idea was not scientifically proven, “the risk would have been too high for a scared public works director to do himself,” said Pott, now a private engineering consultant based in Long Beach. “Thanks to (Hall) and her dealings with the community, she and the Alamitos Bay Beach Protection Assn. and public works, in concert together and knowing all the risks, decided to proceed.”
First, a dredge restored the beach to its original condition. Then, 1,600 of the artificial kelp units were dropped in three rows, positioned like snow fences by scuba divers. The total cost of the units was $57,500 of $950,000 total spent on the project.
Different Kinds Used
Different kinds of artificial kelp were installed to see which would be most effective, Pott said. Fiberglass cloth was found to resist barnacles and other sea growths that weigh it down and cause it to sink.
Now, city officials are hoping to cut the losses to erosion even more. City Marine Bureau Director Richard L. Miller said the next installation of synthetic seaweed should begin in another month or two.
The beach will be leveled out with dredged material to give the next “planting” of phony seaweed a strong start, he said.
Miller added, however, that the artificial seaweed will not work everywhere. The plastic barriers proved unsuccessful in stopping erosion inside by the bay, presumably caused by suction from the cooling water intakes for nearby electric power-generating steam plants. The sand particles in the bay are too fine to be stopped by the artificial seaweed.
“Mother Nature says this beach is going to have a problem and we’re fighting Mother Nature,” Hall said.