Dredging & Marine Construction

Gulf Coast Replenishment Plans Threaten Fishing, Critics Say

Mardi Gras Pass, an unintended breach in the levee system, could well provide the science that supports claims of fishermen regarding the dire effects of freshwater intrusions into rich coastal seafood harvesting grounds. 

For years, fishers have claimed that two large freshwater diversion canals planned for the Lower Mississippi River would devastate saltwater and brackish-water seafood harvesting. The Louisiana Coastal Protection and Restoration Authority (CPRA) proposes building the channels, one on the east bank of the Mississippi River, and one on the west bank. The channels would use silt suspended in river water to rebuild land along coastal Louisiana. 

For nearly 100 years, flood control levees have prevented silt deposits left during high river from building and restoring coastal Louisiana land. The diversion channels will “reconnect the Mississippi River to the marshes,” claims Chip Kline, CPRA board chairman and director of coastal activities for the state of Louisiana

The breach in the east bank Mississippi River levee near the town of Bohemia, or Mile 44 AHP (Above Head of Passes), occurred on Mardi Gras Day in 2012, and it is being called the “smoking gun” supporting objections to the diversion projects.

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Mitch Jurisich, chairman of the Louisiana Oyster Task Force and a third-generation oysterman, said the levee breach, now called the Mardi Gras Pass, was initially about 40 feet wide, but raging high water currents have widened the breach to 300 feet wide and 100 feet deep, dumping fresh river water into Breton Sound and lowering the salinity of coastal marshes below a level that supports oyster growth.

Oysters require a very limited range of salinity, with a minimum of about five parts of salt per thousand of water to thrive.

Oyster Production Wiped Out

“Breton Sound oyster production is now wiped out,” Jurisich insisted. “Since the Mardi Gras Pass breach, what were once the most productive oyster fishing grounds in the world are gone. Production is zero.”

Further, any land built adjacent to the breach was simply existing land washed from the riverside to the marsh side, Jurisich said. It was not new land derived from river-carried silt.

Situated with the Mississippi River levees to the west and Mississippi coast to the north, Breton Sound was protected from freshwater intrusion lowering its salinity and was also protected by barrier islands from higher-salinity sea water, making it one of the world’s premier oyster harvesting areas. 

Prior to the breach, 70 percent of the total oysters harvested in Louisiana came from “public grounds” east of the Mississippi River where state-owned water bottoms in Breton Sound were open for anyone to harvest oysters, Jurisich said. 

The remaining 30 percent of the oysters harvested came from cultivated “oyster leases” on which oystermen pay the state for exclusive shallow water territorial rights. They are cultivated by the lease-holders moving shells onto their shallow water leases by boat and dumping the shells onto firm bottoms where juvenile oysters are “seeded” to build oyster reefs. 

Oyster leases, mostly on the west side of the Mississippi River, stretch toward the Texas border. About 1.4 million acres of shallow, brackish water along the Louisiana coastline are public oyster seed grounds, and 433,000 acres are leased water bottoms.

Prior to the Mardi Gras Pass breach, oystermen in the public grounds and leases of the near-shore, brackish waters of Breton Sound harvested an annual crop worth from $150 million in a good year, to a low of about $50 million in a poor year, when natural disasters such as hurricanes or the BP oil spill interrupted production or harvesting, Jurisich said.

Fishermen proposed sealing off Mardi Gras Pass. The cost is now estimated at $8 million, although Jurisich said it would have been much less if permitted before river flow scouring created the huge breach.

He said about 80 percent of the east bank inhabitants of the town of East Pointe à la Hache are commercial fishermen. The population has been hard hit. There are now very few seafood harvesting jobs. There is only one gas station left in town, and it’s barely holding on, he said. 

Louisiana Shrimping Also Affected

Louisiana has two inshore shrimping seasons, with brown shrimp harvested from May to July and white shrimp from August until December, said Acy J. Cooper, president of the Louisiana Shrimp Association.

Much of the harvesting is from small, shallow-draft boats where shrimpers leave the dock in late afternoon, drag their skimmer nets throughout the night and bring their catch to the buyers at the dockside “shrimp sheds” in the morning. From there, the shrimp are packaged for shipping, or sold to local consumers.

Offshore, larger “double riggers” drag their trawl nets for longer periods. 

When the diversion canals are operational, the influx of fresh water will send shrimp further out into the bays and Gulf of Mexico, eliminating much of the small boat catch, Cooper said. The CPRA has proposed mitigation measures in its initial environmental impact statement that include providing large ice machines or freezers on the shrimp boats.

“It just doesn’t make sense,” Cooper said, because ice machines and freezers are not suitable for a boat less than 35 feet long, and many, if not most, inshore boats are smaller.

Unlike oysters, Cooper explained the shrimp can move to waters with higher salinity. The issue, though, is the brackish estuaries that will be eliminated by fresh water from diversion canals are the nursery ground for the shrimp at the bottom of the food chain. 

Once the shrimp move out, other species up the food chain also will move, including speckled trout and redfish, which attract both commercial fishermen and the lucrative market of recreational fishermen. 

Sediment Diversions Planned

As one of the “tools in the toolbox,” the CPRA proposes the sediment diversion canals for rebuilding coastal Louisiana land using suspended sediment flowing with Mississippi River water into the brackish marshes, Kline said, adding other coastal restoration methods are also employed.

The CPRA is proposing building the nation’s largest freshwater diversion, which will flow fresh river water into the remaining brackish oyster grounds west of the Mississippi River through what is being called the Mid-Barataria Sediment Diversion. 

If built, fishermen say the Mid-Barataria Sediment Diversion would mimic the devastation brought on by Mardi Gras Pass to the east side of the river. 

The Mid Barataria Sediment Diversion on the west bank is planned for Mile 61 AHP, just below the Alliance Refinery, and is designed to flow 75,000 cfs. of Mississippi River water into brackish marshes during high river. During lower river levels, the flow would be reduced. 

The proposed Mid-Breton Sediment Diversion Canal on the east bank of the Mississippi River is planned to be situated below Wills Point at about Mile 68 on the Mississippi River. The permit request of river water flow was recently downsized and is currently designed to have a maximum flow of 50,000 cfs. into Breton Sound during high river. 

By comparison, during high river, Mardi Gras Pass now flows about 35,000 cfs. of fresh river water into small bays that feed into Breton Sound. Even with low river, as much as 20,000 cfs. of water flows through Mardi Gras Pass, Jurisich said.

When the river level approaches 5 feet on the Carrollton gauge in New Orleans, the diversion channels would be shut down. Kline said this pause in the flow of fresh water from the diversion canals will allow salinity to temporarily rise a bit in Breton Sound and Barataria Bay.

Even if successful in depositing sediment into the marshes, sediment diversion projects will not create much “land” as is normally understood, but will mostly build sand bars that may appear above the waterline only at low tide, Cooper said. Sediment cannot be deposited above the level of the water, he said. 

Cooper said that in 1982, a freshwater diversion was constructed near the Head of Passes. This diversion created very little land, he said, but sediment clogged up South Pass, with the channel having only 2 feet of water in places, according to the Local Notice to Mariners at the time.

Crew boats servicing oil platforms east of the Mississippi River and fishermen could no longer divert their course from the main shipping channel of Southwest Pass into South Pass until it was recently dredged.

What had been open waters for shrimping was no longer accessible because the water had become too shallow for safe navigation. But it was not dry land suitable for walking on or cattle grazing, he said.

Sportsman’s Paradise In Jeopardy

Louisiana license plates proclaim the state a Sportsman’s Paradise. Recreational and commercial saltwater fishermen come because they can catch speckled trout and redfish feeding along the oyster beds and brackish, shrimp-laden estuaries, Jurisich said, in addition to fin fishing further offshore. 

The annual Grand Isle Tarpon Rodeo is one of the nation’s oldest offshore sport fishing events.

Areas of Breton Sound were known as the “Iron Banks” because decades of natural brackish water oyster growth left expansive oyster reefs along with shell-laden islands where fin fish feed. 

Jurisich said freshwater outflow from the two sediment diversion canals proposed by the CPRA would create massive influx of fresh water into the brackish marshes, turning them into freshwater bays and forever changing the natural habitat.

“There was frequently a ‘city of boats,’ both recreational and commercial fishermen, who would ‘limit out,’ catching their legal limit of speckled trout and redfish in the area of the Iron Banks,” he said. “Those fishermen were not looking for carp and catfish. They can catch those inshore. If the diversion canals are built, the recreational saltwater fishing industry will take a huge hit.” 

“We have seen what happened to the oyster industry on the east side of the Mississippi River with the Mardi Gras Pass breach 10 years ago,” Jurisich concluded. “What happens when we double the water flow on the west side?”