First Line of Defense Against Storms : Nation’s Barrier Islands Are Washing Out to Sea
Chains of islands are strung like beads along America’s coasts--a barrier that absorbs the force of storms and shields the mainland.
But the islands are disappearing. At least 50 barrier islands off Louisiana have washed away over 30 years, exposing delicate marshes and wetlands to direct assault by the Gulf of Mexico.
First Line of Defense
“Barrier islands are like your skin, the first line of defense against infection,” said Robert E. Stewart Jr., director of the National Wetlands Research Center, a branch of the U.S. Fish and Wildlife Service.
However, he said: “It would be enormously expensive to restore them.”
“Something can be done, but it would be very, very expensive,” echoed Jay Warren, a project engineer with the Army Corps of Engineers. “Not only would you have to restore them, but then you have to maintain them.
“We had a study just last year that looked at barrier island maintenance as a way to protect marsh behind the barrier islands and also as a means to reduce storm surge and hurricane damage inland. Even picking up those benefits, the cost was just prohibitive.”
2,700 Miles of Islands
Almost 2,700 miles of barrier islands protect the coasts of 18 states along the Atlantic and the Gulf of Mexico, and all of the islands are threatened. The West Coast has fewer barrier islands, but they also are eroding.
Fire Island, a sliver of sand and expensive cottages just east of New York’s Long Island, is losing beaches on both the seaward and landward sides despite jetties and groins (a rigid structure built out at an angle to the shore) built to save them. A million cubic yards of sand shift along the coasts of both Cape Hatteras and Cape Cod each year.
Texas’ Galveston Island has been protected by seawalls since a hurricane killed 6,000 people in 1900. But its beach eroded after the wall was built--the sort of trade-off made wherever man has moved onto the islands.
Seawalls, jetties, groins and rocks all produce the same result: They direct wave action elsewhere, and the beaches wash away.
Andy Valence is mayor of Grand Isle, Louisiana’s only developed barrier island. A 2,000-foot section of its beach is under a state of emergency as Gulf waters lap at a motel’s pilings and close in on state Highway 1, the only route onto the island. Valence wants to build protective rock jetties and estimates the project will cost about $422,000.
Robert Jones, parish engineer and civil defense director for nearby Terrebonne Parish, predicted that the project would cost 10 times that much and would fail unless the rocks were given a sound foundation and provisions were made to get fresh sand to the beach.
“Unless it’s done right, those rocks are just going to eat themselves into the sand and disappear,” he said.
Jones has earned his air of authority. Five years ago, he defied conventional advice and saved the eastern tip of Isle Derniere, where pounding waves were threatening to cut off two-thirds of a mile.
Island Resists Hurricanes
Isle Derniere, French for Last Island, at 1,800 acres is the largest of Louisiana’s barrier islands. Jones’ repairs have withstood eight hurricanes, absorbing the force of tidal surges that otherwise would have hit coastal communities unchecked.
Jones used all natural materials. Near the area being washed over by waves, he found deposits of especially coarse sand. His crews scooped that sand into a protective dune that topped out at 8 feet above sea level, then filled the holes with finer sand from the Gulf floor.
Next, he hired students to plant sea grass to anchor the sand. “The key to keeping what you’ve got . . . on the island is vegetation,” he said.
“In the first year of its existence, it faced three hurricane surges, and it was completely overtopped by Hurricane Juan,” Jones said. “We had a number of hurricanes every year since then.
Survived Storm Surge
“Hurricane Gilbert (last fall), even though it hit 500 miles away, sent a storm surge here that overtopped every levee in southern Terrebonne Parish. . . . The vegetation held up fine.”
Jones said that the best way to save the barrier islands is to put $10 million in trust for 10 islands, then use the interest each year to restore one. “At the end of 10 years, you’d go back and start over again,” he said.
“You can’t think of it as a one-shot civil engineering problem. That was my major problem to begin with,” Jones said. “I’m used to putting something up in concrete and five years later having it look the same way.
“The first time I went out there after a hurricane, I was very disappointed. The geologists were ecstatic that it survived as well as it did.”