Some commercial and sports fishermen have long charged that the state’s plan to use diversions of river water to help save Louisiana’s sinking, crumbling southeastern coast will result in an economic apocalypse for their lifestyles.

Flooding brackish estuaries with silt-laden fresh water from the Mississippi River might build new marshes, they say, but it also will evict the species they depend on for a living, leaving thousands jobless and turning thriving communities into ghost towns.

Now the state is trying to find out whether they’re right.

The Coastal Protection and Restoration Authority has begun a study to analyze the effects on the fisheries, the economy and the communities in the receiving basins over the next 50 years if diversions are built, as well as what will happen if nothing is done.

Those findings, the agency says, will help determine whether diversions, long considered essential to coastal restoration, will be built.

“If the results of the study show that the costs of a diversion — not just in construction but also to the economy and to communities — are greater than the benefits from the land it can build, then, yes, we would have to reconsider that project,” said Jerome Zeringue, chairman of the authority and an executive assistant to the governor for coastal activities.

A leader of the concerned fishermen had mixed reaction to the news.

“We’re glad it’s being done, but we wanted this to be done by an independent agency” such as the National Oceanic and Atmospheric Administration, said George Ricks, a charter-boat captain who heads the Save Louisiana Coalition, which opposes diversions.

“Look, we’ve been pushing for this for a long time,” he said. “The real question is: Why wasn’t this done before all the millions that have been spent on design and engineering of these projects?”

Zeringue said the study had always been part of the planning process, but it could not be started before knowing where diversions would be built and how they would be operated. Those key decisions are only now being made by engineering and design teams.

Bren Hasse, who will be leading the study for the authority, said his group would assess effects based on different diversion flow volumes for four projects planned south of New Orleans: Mid-Barataria and Lower Barataria on the West Bank and Mid-Breton and Lower Breton on the East Bank. These four are likely the first ones to be built.

The authority will be working with coastal researchers and economists from the Water Institute of the Gulf, LSU and the RAND Corp.

Zeringue stressed the research would analyze not only impacts to current estuarine species but the effects of other changes caused by the diversions, including land building.

“You have to add in the benefits from improved storm (protection) as a result of building those new wetlands and how that impacts the future costs of flooding,” he said.

“And you also have to add the impacts in the changes in fisheries production. Yes, speckled trout, reds, oysters and blue crabs might move further south. But the areas they might leave won’t be without fish; they will just have different fish. Instead of specks and reds, you might have bass, catfish and sac-a-lait.

“So we have to consider the value of that new production as well.”

Critically, the team also will assess the impacts to fisheries, the economy and communities if nothing is done and the current rate of land loss continues.

Production of many species such as shrimp and fish is proportional to the total acres of marsh, which is still being rapidly lost, Zeringue said. “So you have to look at the costs associated with that loss,” he said.

Zeringue said the analysis underway does not look at the socioeconomic results of trying to use other methods of rebuilding the wetlands.

Groups opposed to the diversions would prefer the state to rebuild wetlands by pumping sediments mined from the river into the basins. The state’s master plan calls for spending almost three times as much on those pipeline projects. Some groups advocate extending pipelines across the basins to rebuild land without dramatically changing the salinity level of the water.

But subsidence likely will require those projects to be repeated in 30 to 40 years. That led the master plan designers to conclude that diversions, while more expensive to construct, are a better bargain for the perpetual land building that will be required to keep the region above the rising Gulf.