Wave-Control Devices Tested at Louisiana’s Shark Island

By AMY WOLD, The Advocate | July 29, 2014

Shark Island in Iberia Parish is the testing ground for three unusual devices meant to help keep Louisiana shorelines from retreating under the relentless waves eating away at the state’s coast.

If the devices being used in the project prove successful over the three-year testing phase, they could give state and federal coastal-restoration agencies new tools to protect areas where traditional rock structures aren’t suitable.

The story of these experimental techniques started when engineers working to restore coastal areas under the Coastal Wetlands Planning, Protection and Restoration Act found they didn’t have any tried-and-true materials other than rock to help keep shorelines in place in areas like a seven-mile stretch of shoreline in St. Mary Parish.

On that part of the coast, the soil is soft, and there are many pipelines and other underground utilities. The result is that rocks are not suitable.

Tommy McGinnis, a coastal resource scientist with the state Coastal Protection and Restoration Authority, said soft soils are a common problem around the state for restoration projects.

Artificial oyster reefs are being tested in areas around the coast, but they haven’t been in place long enough to determine their effectiveness, he said.

“So we started looking at alternatives,” said Loland Broussard, a civil engineer with the U.S. Department of Agriculture’s Natural Resources Conservation Service. “We were hard-pressed to find any.”

A fruitless search for something that could provide protection to the shoreline wouldn’t impact underwater pipelines and would stand up to very soft soils led Broussard to propose that CWPPRA run a demonstration project to try to generate some new options.

CWPPRA projects need to be done with proven technologies because the agency is required to do 20 years of maintenance on anything it builds, Broussard said.

If something that has not been tested is tried along a shoreline and it fails, the program is on the hook for not only removing that material but also finding some way to replace it. In a program with limited funding, that kind of risk is not worth it, Broussard said.

The search for something new began four years ago as the NRCS threw out a wide net asking for possible solutions. The service received 17 formal proposals for projects that later were narrowed down to four. One of those proposals didn’t materialize, but the three other test projects were constructed and put in place in Iberia Parish late last year and early this year.

The $6 million that CWPPRA approved for the overall project paid for installation and will also pay for monitoring over the three-year life of the project. Officials will watch how the structures knock down wave action and how effective they are in keeping the current shoreline in place.

Each of the test sites covers 500 feet of the shoreline and just a bit off the shore.

One of the options looks like artificial oyster reefs that have been used elsewhere along the coast’s shorelines, but this one is shaped like a pyramid.

The second idea involves attaching a flat panel to pilings in about 4 feet of water to help reduce the wave action on shore.

The third installed product looks like a freeway buffer used to close off a lane during construction, but it is made of a Styrofoam-filled concrete shell.

NRCS will monitor the shoreline impacts over the three years while CPRA will monitor wave action in front and behind each structure.

Was this article valuable?

Here are more articles you may enjoy.