From water to wetlands
Pipeline Projects Build New Marsh

IN THE UNITED STATES PIPELINE SEDIMENT TRANSFER is a relatively new tool for wetland restoration, but in coastal Louisiana it’s already been successful.

Since 1994, Breaux Act projects using piped sediment have created more than 3,000 acres of new land. Some experts say we’ve only scratched the surface of the technique’s potential.

“Conceivably, we could use this technology to offset all of our land loss,” says coastal oceanographer Dr. Joe Suhayda. “We could stop the loss of Louisiana’s coast.”

The success of three pipeline transport projects — at Bayou LaBranche, at West Bay, and on Timbalier Island— illustrates the technique’s land-building potential.

Billy Hicks, USACE Billy Hicks, USACE

A Successful Start

As Interstate 10 travelers sweep past the southern shore of Lake Pontchartrain, they look out over one of the Breaux Act’s first success stories: the lush, green wetlands near Bayou LaBranche.

Just a decade ago, the area was open water — the result of more than 150 years of subsidence, flooding and erosion that began when railroad construction in the 1830s altered the flow of water through the wetland. By the 1990s, only a narrow strip of marsh separated the ponds from Lake Pontchartrain.

The Bayou LaBranche Wetland Creation project, located just east of the Bonnet Carre Spillway near New Orleans, involved dredging sediment from the bottom of Lake Pontchartrain, then pumping it through a 7,500-footlong pipeline to the open water area. In four weeks, nearly 2.7 million cubic yards of sediment were placed to create 300 acres of land.

“With the Bayou LaBranche project, it was immediately obvious we would be able to use this technique to create marsh,” says Gregory Miller, project manager with the U.S. Army Corps of Engineers. “Because LaBranche is one of the most visible Breaux Act projects, people who remember the area as open water can view these wetlands, and see that it’s possible to literally build land.”

Pipeline, Diversion Restore Marsh

West Bay embodies one of the ironies of wetland loss: though only a few yards from the sediment-rich waters of the Mississippi, the marsh subsided and converted to open water.

To restore the marsh, the West Bay Sediment Diversion project, located about five miles from the river’s Head of Passes, required dredging a 440-foot-wide, 25-foot-deep channel from the river to the bay, and pumping the dredged material into the bay’s open water area.

“The goal of the project was to create a diversion through which sediment-laden water would flow naturally to the marsh during high river stages, creating land over the course of 20 years,” Miller explains. “But by pumping in the dredged material from the channel, we were able to restore 200 acres right away.”

Marsh creation in West Bay will continue, Miller says, as sediment dredged from the river to maintain the navigation channel is used to build more wetlands. Over the long term, however, the diversion itself will nourish and continue building marsh.“This project shows how well piped sediment complements other restoration methods. It jump-started the land-building process, and the river will do the rest.”

Fortifying Barrier Islands

Louisiana’s barrier islands, the coast’s first line of defense against hurricanes, are eroding even more rapidly than the inland marshes they protect.

“In the past, the Mississippi River directed sediment toward barrier islands, but today the river sends sediment off into the gulf,” explains Beverly Ethridge, environmental scientist with the Environmental Protection Agency. “As storms wash away sand from these islands, there is nothing to replace it.”

Timbalier Island, a narrow strip of land south of Terrebonne Bay, had suffered extensive hurricane damage. “We knew this barrier island would vanish within 50 years if it didn’t receive new sediment,” says Patty Taylor, EPA project manager.

In the Timbalier Island Dune and Marsh Restoration project, 4.6 million cubic yards of sand were pumped to the island from three miles out in the gulf. The project was the first to use sand from so far offshore, says Taylor, who explains that sand dredged from the gulf is superior to that harvested closer to land.

“The high quality sand performed even better than expected,” says Chris Williams, project manager for the Louisiana Department of Natural Resources. “We were able to complete the project $3.5 million under budget while creating more land than was originally intended, for a total gain of approximately 400 acres.”

The Timbalier Island project is another example of the potential of pipeline transport, Suhayda says.

“Pipeline transport is unique among restoration techniques in that it can truly restore land, rather than merely slow the rate of loss,” Suhayda says. “Within weeks, open water can become land.