Casts + Blasts

As the state of Louisiana is ready to in­vest close to $2 bil­lion on Mis­sis­sippi River sed­i­ment-di­ver­sion projects to re­plen­ish sink­ing and erod­ing wet­lands, ques­tions sur­face about the po­ten­tial ef­fects on the es­tu­ar­ine ma­rine life.

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Be­fore the Mis­sis­sippi River’s ex­ten­sive levee sys­tem was built, sed­i­ment flowed freely into south­east Louisiana’s marshes and swamps when the river over­flowed its nat­u­ral banks. Now, much of the sed­i­ment stays in the river and gets chan­neled into the Gulf of Mex­ico in­stead of spilling out to sur­round­ing wet­lands.

The state of Louisiana plans to build two large sed­i­ment di­ver­sions in Plaque­m­ines Parish as ma­jor tools for es­tu­ary restora­tion, repli­cat­ing the Mis­sis­sippi River’s wider flow of sed­i­ment while keep­ing lev­ees in­tact.

As re­ported by the Times-picayune, the $1.3 bil­lion Mid-barataria Sed­i­ment Di­ver­sion would send as much as 75,000 cu­bic feet per sec­ond of water and sed­i­ment to Barataria Bay dur­ing high-river pe­ri­ods — through a con­trolled open­ing in the West Bank levee near Myr­tle Grove — to re­duce land-loss rates and sus­tain wet­lands dam­aged by the BP oil spill; the $696 mil­lion Mid-bre­ton Sed­i­ment Di­ver­sion would al­low up to 35,000 cu­bic feet per sec­ond of water and sed­i­ment to flow into Bre­ton Sound, in­tro­duc­ing 70 mil­lion tons of sed­i­ment to the basin over 50 years.

Many con­ser­va­tion groups sup­port the di­ver­sions, but both projects are rais­ing con­cerns about the ef­fects on ma­rine life and cer­tain wildlife species. While the long-term im­pacts of the state’s plan to un­leash the Mis­sis­sippi River into its coastal marshes

are the fo­cus of stud­ies and much dis­cus­sion, many of Louisiana’s com­mer­cial and recre­ational fish­ers be­lieve more needs to be done to un­der­stand the ef­fects in the first five years of the projects.

State of­fi­cials re­cently con­ducted a survey that asked peo­ple — mostly in­volved di­rectly in Louisiana’s fish­ing in­dus­try — ques­tions about the state’s plans for the Mis­sis­sippi River di­ver­sions; 98 per­cent of those sur­veyed con­sid­ered it es­sen­tial to fo­cus on the short-term eco­log­i­cal and eco­nomic im­pacts.

How the di­verted river water would change salin­ity in the bays was the big­gest con­cern, fol­lowed by the flow rate of the di­ver­sions and the time of year when they would be opened, since the ex­cess of fresh water could kill oys­ters and drive shrimp, crabs and fish far­ther out into the Gulf of Mex­ico.

“Peo­ple can no longer ques­tion whether the Mid-barataria Di­ver­sion is go­ing to hap­pen,” said Pa­trick Banks with the Louisiana Depart­ment of Wildlife and Fish­eries. “It’s com­ing!” The Trump ad­min­is­tra­tion agreed in Jan­uary to speed up per­mit­ting for the project, but an en­vi­ron­men­tal re­view will still be re­quired.

FRIEND OR FOE: Will plans to di­vert the Mis­sis­sippi hurt the ma­rine life?

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