Donít rush to judgement: Causes of erosion

Experts still arguing over why Louisiana coast is disappearing

Kelly Connelly, LaPolitics News Service

July 15 at 6:30 am  | Mobile Reader | Pring this storyPrint 

Damage to the wetlands in the Terrebonne and Barataria basins might be caused in part by oil and gas companiesí navigational canals, but it was exacerbated by the disconnection of new sediment from the Mississippi River via Bayou Lafourche.
Damage to the wetlands in the Terrebonne and Barataria basins might be caused in part by oil and gas companiesí navigational canals, but it was exacerbated by the disconnection of new sediment from the Mississippi River via Bayou Lafourche.
South Lafourche Levee District

To raise awareness for one of Louisiana’s first politically spurred campaigns against coastal land loss, former Gov. Mike Foster took a publicity team into open water off of St. Mary Parish, cast a line and showed the crew his GPS, which showed them on solid ground.

Fishermen might be aware of the tangible loss of wetlands throughout the coast, but greater public perception can at times lag behind.

“It’s hard for people to see the problem unless you fly airplanes or helicopters or spend a lot of time out there,” Foster said at the time. “But that’s probably why this is such a difficult subject. It’s so broad, so big and so hard to see.”

The state’s coastal scientists have been trying to get a grasp on the causes of coastal land loss since the 1960s. According to Dr. Robert Twilley, now the executive director of LSU’s division of SeaGrant (a research branch of the National Oceanic and Atmospheric Administration), public perception of the problem doesn’t always match up with that of the scientific community — but campaigns like Foster’s help align the two groups.

“The real sense in the larger public came when people started talking about it in political circles,” and putting tax money behind their initiatives, Twilley said.

He pointed to the program pushed by former U.S. Rep. John Breaux, the Coastal Wetlands Planning, Protection and Restoration Act, that sent national dollars to Louisiana for projects and education programs.

Most recently the issue has resurfaced in the larger public consciousness thanks to the lawsuit filed against 97 oil and gas companies by a New Orleans levee board, the Southeast Louisiana Flood Protection Authority-East.

But policymakers, officials, scientists and the public have varying opinions about whether to blame oil and gas companies for the damage.

Twilley puts the burden on the U.S. Army Corp of Engineers, which completed the system of levees along the Mississippi River in 1935.

“This is a delta, and it’s a delta built by the river,” Twilley said. “The connection of the river and how we manage the river with the plight of the wetlands was up front and center from the very beginning.”

Before the levees were built, every year when the river would flood, it would build land with the sediment the floods carried. But when the river was walled off, that natural nourishment ceased, allowing sea level rise and the process of sediment compression called subsidence more influence on the system.

“It’s what we call abandoning,” Twilley said. “When the river abandons its wetlands in a delta, it’s toast. That’s what drives most of what we’ve seen at the scale of what we’ve seen.”

Researchers have attributed damage to a slew of other causes:

• The state’s historic logging industry dug canals to navigate through the marsh, as did oil and gas companies.

• Hurricanes quickened erosion.

• Nutria ate plant matter that held land together.

• Even the wake caused by recreational fishermen’s boats increases wave action that slowly destabilizes soil.†

Twilley said he thinks all other causes of damage to wetlands have been exacerbated by the river’s levees. Despite the tangible damage, he said, there hasn’t been much change in management of the river.

But John Barry, the director of the nonprofit Restore Louisiana Now, has a different take on the problem. Barry, who was kicked off of the New Orleans levee board for political reasons, is the face of the SLFPA-E lawsuit.

“Are levees a factor? Of course they’re a factor. Are they the only factor? Absolutely not,” Barry told a meeting of the Rotary Club of Houma in March.†

Barry said the argument Twilley and many other scientists make isn’t entirely valid for everywhere in the state because there are areas that the river’s floodplain didn’t reach.

“If it were only the levees, there would be no land loss in the Western part of the state,” Barry argued.

Barry and Twilley agree that both the oil and gas industry and the levees are elements of the problem, but disagree on how heavily each weigh.†

Science hasn’t been able to pin down a percentage of what causes did what damage. One study claims as high as 76 percent of damage was done by the oil and gas industry. Barry cited a 36-percent figure to a legislative committee in May.

Twilley sticks with a smaller number: 11 percent. Twilley said that’s how much of the ground that used to be wetland was dug up for navigational channels. But those canals caused collateral damage in other ways.

“Navigation systems move salt,” for example, which can kill grasses and loosen soil to allow it wash away more easily, he said.

When oil companies dug those canals, they often built the unearthed soil up along the side of the canal, creating “spoil banks.” Those banks hampered the way water moves through the grass.

“So now the water cannot get in, in the same way that leveeing the river affected the hydrology of the wetlands,” Twilley said. “What percent of wetland loss is due to that? Who knows.”

One study showed that the land is sinking in some areas to fill in space created by extracted oil and gas.

“How much of that can you attribute to our total amount? What percent is it? We could sit here and argue all day long about that,” Twilley said.

There’s just as much disagreement on how to fix the coast, but Twilley said the state indisputably needs more of two things: sediment and money.

Twilley said it’s going to take more political action to get either of those.

He advocates for sediment diversions, projects in the state’s plan for coastal management that divert the Mississippi at strategic points to reconnect the river and wetlands.

Many fishermen fear that the diversions will permanently damage habitat.

The lawsuit against the oil companies, Twilley said, distracts from public conversation on that topic and what he considers to be a more-viable option to fund the state’s plans ≠— making use of the oil and gas lease payments that the federal government splits with the state.

Twilley thinks the state should be getting a bigger share.

“We need to manage the river for the sediment that it has, and we need to manage the money that is already flowing,” he said. “Sediment is coming down and money is going up. Both are moving; we just have to capture it.”

Twilley thinks the best chance the state has to capture that money is to get the oil and gas industry in its corner.

“Get oil and gas to take all its political clout that gets it nearly anything it wants in Washington,” Twilley said, “and bring back another $500 million, and then we’re good, but we want you to acknowledge that there was an inequity.”†




View other articles written Kelly Connelly, LaPolitics News Service

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