River sediment can be key to rebuilding coastal marsh

NEW ORLEANS — Getting sediment out of the river and into the marsh and barrier islands can be costly, but can also be the most effective way to quickly build coastal restoration projects in areas that are rapidly deteriorating, according to speakers at a conference Monday.

Outlining three of these types of projects was among presentations delivered at the State of the Coast: Preparing for a Changing Future conference in New Orleans.

The three-day conference organized by the Coalition to Restore Coastal Louisiana in partnership with the state Coastal Protection and Restoration Authority brings together researchers, policy makers and nonprofit organizations for updates on the status of coastal restoration and protection efforts in Louisiana.

One of the presentations on the conference’s opening day highlighted three ways river sediment can be used to help with restoration and protection efforts.

Although projects that will divert sediment and water from rivers are in development, they are designed to hopefully build land over time.

“Natural deltaic building processes take time,” said Paul Tschirky, senior coastal engineer with the Moffatt and Nichol engineering firm’s Baton Rouge office. “In some areas, we have severely degraded marsh and you don’t have that time.”

By using material that is dredged for navigation purposes or dredging river bottoms and then transporting that material by pipeline, the land can be built quicker in some areas. In other areas, sediment from river bottoms can be transported to areas that are too far away from river sources to get much benefit from future diversions.

Tschirky explained the work being done now to plan for and design a long distance pipeline that would take sediment from the Mississippi River and run it to areas north of Barataria Bay for restoration projects. The work involves the state as well as Plaquemines, Jefferson and Lafourche parishes. A pipeline corridor would help connect areas that are already approved for marsh creation projects.

“There’s a real opportunity here for synergy to combine those,” Tschirky said of the restoration projects. “The main constraint is dollars.”

In a similar project that was approved for construction in May, sediment from the Mississippi River will be mined and then shipped to Scofield Island to add material to the island which has a historic rate of erosion of 16.5 feet per year, said Jason Lanclos, restoration engineer supervisor with the state Coastal Protection and Restoration Authority.

The island, located about 11 miles west of Venice, will ultimately have 610 acres built with 240 of those being dune and beach material from the river and a 370-acre marsh platform from material dredged offshore, Lanclos said.

One of the project’s goals is to see how the quality of Mississippi River sand holds up on barrier islands as compared to the previous use of limited offshore sand deposits.

Another aspect of using river sediment is putting material dredged for navigation purposes by putting the sediment into nearby marsh areas. A program that was authorized in the federal Water Resources Development Act 2007

Bill Hicks, project manager with the beneficial use of dredge material program with the Corps of Engineers, said the program would involved federally maintained waterways. The program would pay the cost of anything above what the current dredging program pays for, such as transporting dredged material into marsh areas, he said.

Initially, any project that would use the dredged material would need to be within 15 miles of the dredging work, he said. Currently, the corps is drafting a cost share agreement with the state and are hoping to have that ready by June or July this year, Hicks said.