In a lush green bayou a little southeast of New Orleans, John Lopez and Howard Callahan are cruising the waterways in an airboat under the hot Louisiana sun on a recent day.
It's an area known as Breton Basin, and Callahan is a local land manager who often helps researchers such as Lopez explore environmental changes in coastal wetlands. The pair head to a concrete and steel structure that separates the bayou from the nearby Mississippi River.
This is the Caernarvon river diversion. Built in 1991, it works like a faucet: When it's open, freshwater and sediment from the Mississippi River — usually hemmed in by the levee system — flow back into what was a dying swamp. Diversions such as this one are meant to free the river to do its original job as it nears the Gulf of Mexico: spread out sediment, create land and provide freshwater to local habitats.
In the past decade, thick, green vegetation has grown up around the diversion, and Lopez says that's a good thing.
"This is what Louisiana's supposed to be," he says. "Not a dying coast, but a living coast."
Now, 10 years after Hurricane Katrina devastated much of the Gulf Coast region, expanded efforts are underway to revitalize this "living coast," Louisiana's original storm protection system. State officials have earmarked billions of dollars to rebuild the marshes and wetlands that create a natural buffer against storms and floods.
Over the past century, man-made canals and natural storm surge pushed too much saltwater into the bayou, killing the swamp. Cypress trees and swamp grasses are what slow hurricanes down and absorb storm surge.
New Orleans is technically 80 miles from the Gulf of Mexico, but with a football field of coastal wetlands disappearing every half-hour, that distance is deceptive, says Kyle Graham, head of Louisiana's Coastal Protection and Restoration Authority.
"Our levee systems aren't designed to have the Gulf of Mexico lapping up against the outside. They're designed to have that amount of marsh, or a marsh-protected fringe in between them and the Gulf of Mexico," he says.
Graham oversees an ambitious plan — $50 billion over 50 years — to rebuild the coast. Compare that to the $14 billion spent since Hurricane Katrina to rebuild the man-made levee system that lines the Mississippi River and protects the city of New Orleans and other areas along the river.
The coastal rebuilding plan prescribes bigger and deeper diversions than Caernarvon, according to the Environmental Defense Fund's Natalie Peyronnin, who helped draft the idea. The alternative — digging up sediment, transporting it and manufacturing land — is too expensive, she says.
"We know the river built the wetlands; we do know that. And we know that the river can rebuild wetlands, and they can rebuild the system on a scale that we can't mechanically do with just dredging," Peyronnin says.
Not everybody wants diversions. George Ricks is one of several sport fishermen worried about the effects of river diversions. More freshwater and less saltwater will upset the balance of local habitats that nurture fish, shrimp, oysters and more.
"When you look at the economic impact of losing our fisheries, and our seafood industries, and our restaurant businesses, because of a lack of seafood, it's not that economically feasible to have diversions instead of dredging," Ricks says.
But diversion advocates say the Gulf of Mexico will eventually push back and restore the brackish water balance. And with Louisiana's coast rapidly disappearing, there are bigger issues at hand, says Peyronnin of the Environmental Defense Fund.
"If we don't use the river to build land, and maintain this wonderful coast, then people are going to have to move away," she says.
Louisiana officials hope to begin construction of multiple river diversions in the next few years. They believe this approach will give Louisiana not just its coast back, but its best chance at surviving the next big hurricane.