Editor’s note: This is the final segment of a three-part series on the importance of restoring the state’s barrier islands.
More than 20 state-managed barrier island restoration projects have been undertaken over the past two decades, re-creating 9,300 acres of sandy, sea-facing beach and back-island marsh on the Louisiana coast.
The projects have gotten a lot bigger than they were back in the 80’s.
"But we're using the same principles," said Darin Lee, a coastal resource scientist who manages Coastal Protection and Restoration Authority's (CPRA) barrier island projects.
First step: find a sand source. Early restoration projects would use the dredge-and-barge method, which can be time consuming and expensive, depending on the distance between the island and the sand source. Sand is an abundant material but finding the right type in vast quantities isn't easy.
In 2012, the CPRA turned to the Mississippi for the first time. Sand was dredged from the river and sent through a pipeline from Buras to Scofield Island, a fast-dissolving barrier island near the river's mouth.
The 22-mile-long pipeline had to duck under and jump over several hurdles, including two hurricane levees, two highways and a busy shipping canal. A headache for engineers and builders, the project's total cost was nearly $57 million for 510 acres of restored beach and dune.
The restoration of neighboring Pelican Island was, in contrast, accomplished with sand dredged from the Gulf. It ended up costing about $10 million less than Scofield and restored 76 more acres.
Offshore sand is now the primary source of material for rebuilding barrier islands, but it, too, has challenges. The first one is locating good Gulf sand under all that Mississippi mud.
"Finding sand for our uses takes a lot of searching," Lee said.
The CPRA reviews geologic data collected over the past century to find large sand deposits under heaps of mucky river sediment. They zero in on their quarry with a combination of sonar readings and sediment sampling.
The richest sand sources are ancient barrier islands - ones that sank under the waves after the river retreated or changed course. Ship Shoal, the main sand supplier for the Whiskey and Caminada restorations, was a barrier island 7,000 years ago, around the time humans invented the wheel.
Then comes the second challenge: getting through all of the oil and gas pipeline that lay in a tangle across the seafloor.
"There's a ton of oil and gas infrastructure on Ship Shoal," Lee said. "Even if we wanted to, we couldn't dig up the whole shoal. We have to find blocks that are useable."
Pipeline maps aren't always reliable, so to avoid breaking through a pipe with a dredge, the CPRA and its contractors must use high-powered metal detectors to get the exact locations of undersea obstacles.
Once a sandy sweet spot is found, a dredge digs in, vacuums up the sand and pumps it through a pipe to the restoration site.
Oil and gas infrastructure can also make offloading the sand difficult. The restoration of East Timbalier Island in Lafourche Parish was mired by an extensive network of active and abandoned oil wells and pipelines, much of it buried and poorly mapped. Already expensive, the project's budget swelled by over $2 million dollars as workers navigated what project manager Kenneth Bahlinger called "a spiderweb of lines."
At a dredging summit last year, coastal engineering consultant Steve Dartez classified the Whiskey Island project as Louisiana's "biggest," Scofield as the "baddest" and Caminada Headland as the "bestest."
While not strictly a barrier island, Caminada serves the same protective role on the coast. Its restoration wasn't as big as Whiskey in the sheer volume of sand, but it was the first to tap into Ship Shoal, located nearly 35 miles from the headland. It tops Whiskey in money spent, totaling more than $216 million, and it covers more ground, some of which is easily visible to the public.
Elmer's Island, on the project's east edge, is a popular state wildlife refuge - even more popular now that it's covered in a thick coating of fine sand. It shields not just 13 miles of marsh, but Port Fourchon, a hub of oil shipping in the northern Gulf, and Highway 1, the only hurricane evacuation route for Grand Isle and other communities.
The Caminada project had another surprise benefit - becoming one of the nation's biggest nesting colonies for least terns, a shore bird threatened by habitat loss. The birds swarmed in just after the project was completed last year, dropping thousands of eggs across the new beach.
"Build it and they'll come," said Erik Johnson, the Audubon Louisiana’s director of bird conservation.
The big barrier island buildup has come to a close, at least for now. Only 3 percent of the state's $50 billion Coastal Master Plan is earmarked for barrier islands. Four projects are on the docket - the restoration of Rabbit Island in Cameron Parish and West Grand Terre and Queen Bess islands in Jefferson Parish.
The largest project, likely to cost $150 million, is a series of island upgrades in the Terrebonne Basin.
The state's focus is now largely on upkeep. With the natural forces that built and restored barrier islands crippled by dams and levees, the state will need to keep the islands alive by artificial means. That will require regular dredging and sand pumping to replace material chewed away by waves and storms and swallowed by subsidence and rising seas.
Mississippi River sediment diversions - a major element of the master plan - could give barrier islands a boost. The Mid-Barataria and Mid-Breton diversions, totaling $2 billion in cost, would funnel some sediment toward the island's backsides, but there's concern the diversions could backfire, according to Suhayda. The complex water chemistry in protected bays makes them effective marsh builders. Their balanced mix of saltwater and freshwater has the effect of binding passing river sediment together. These larger sediment clumps sink rather than float away. Allow too much freshwater, Suhayda warns, and the saltwater is pushed out, and the sediment with it.
Another concern: maintaining the supply of sand. Ship Shoal can't keep giving forever, and many nearshore sand sources have been exhausted.
"The availability of beach-compatible sand has become increasingly scarce," Dartez said.
Coastal managers may have to seek out distant reserves or rely more heavily on sediment dredged from the Mississippi.
Money is also a constraint. The BP settlement was a one-time deal. Barring another big disaster-induced windfall, the state will need to find reliable sources of money for expensive repairs and rebuilds. This isn't a far-future concern. The lifespan of each of the multi-million-dollar restoration projects is a touch more than a house cat's - 20 years, maybe less. That means Caminada may need another 13-mile, 8.8 million cubic yard coating of sand by 2037.
"In 20 years, we'll be back where we were," Lee said. "But if we have a stormy decade, we might not get 20 years.”
Posted on Fri, August 3, 2018
by By TRISTAN BAURICK, NOLA.com | The Times-Picayune