The Mississippi River Delta is one of the richest places on earth. This sprawling wetlands environment supports the most productive commercial fishery in North America, provides a port for one of the biggest oil and gas refinery complexes in the United States and harbors a diverse population of wildlife. But over the years, the delta has been carved up like a jigsaw puzzle into a labyrinth of control structures designed to ease navigation, provide flood protection and secure access for oil and gas exploration and extraction. The structures have had another, unintended impact: the wetlands are slowly drying up. Experts believe the wetlands will continue to deteriorate unless Mother Nature is re-engineered back into the equation.
The hurricanes that swept across coastal Louisiana and bordering states last August left their mark on the marsh. The 8-meter storm surge from the Gulf of Mexico washed in salt water and lifted up mats of marsh grasses and folded them back over one another like an accordion.
As he scoops out a sample of the muddy soil, coastal ecologist John Day says the mounting layers of peat, root matter and dense gray clay are what holds the Delta together and keeps it from sinking. "This is a history of the last 100 years of this site probably, and as you see as it sinks, it has to build up. If it wasn't building up and the wetlands became more and more flooded, they would have turned into open water," he says and adds that because they were growing and because of the living thick fibrous root mat they grow up."
But coastal development and flood protection systems like levees and dams and canals are killing the wetlands at the rate of 65 square kilometers a year. Put another way, an area about the size of a football field is drying up every half hour.
Day says saving the wetlands begins with putting that water back. That's what the FreshWater Diversion at Caernarvon has been doing. Day and his colleagues at Louisiana State University have been monitoring the project for over a decade. "We know that when that water flows in here, this is a very healthy area," he says. "Wetland loss stopped in this area. And, the wetland plants are very productive here. There is a big fishery here too."
Here's how it works: Water from the Mississippi is diverted through floodgates cut into the levee. The water runs down through culverts under a highway, into a canal and eventually into the marsh. On this day the floodgates - controlled from a station on top of the levee -- are wide open.
"You can actually put a lot of water through here," says Day. "You can put 8,000 cubic feet per second through this structure, and we've found that that stabilizes land loss for probably 500 square kilometers of marshlands over here. Fresh water compacts salt water. It provides nutrients, which makes the grasses grow more. It provides sediments which gives a stronger soil and all those things enhance the growth rate of the marshes."
Day would like dozens more such water diversions built along the river, but admits the process is slow. It took more than 25 years and considerable political and economic wrangling to get the Caernarvon project built and put into operation.
Another marsh restoration project of a different sort is located along the levee at the Gore sewage pumping station a few kilometers down the highway from Caernarvon.
This area -- once covered by a dense cypress swamp -- is largely a dead zone now of bare, lifeless tree trunks, laid waste by saltwater intrusion. Day says the wetland could be brought back if it were nourished with, of all things, treated sewage. "It's treated for pathogens so that there is no bacteria and it is checked for toxic materials and you really have fresh water with some levels of organic matter and nutrients," he says. "If you put this out here that will fertilize this swamp and keep it healthy and this is an example of that."
Day says the idea might take a little getting used to, but as communities along the Gulf Coast consider how to rebuild the dozens of sewage treatment plants destroyed by last year's storms, the option looks more appealing. With a wave of his hand, Day gestures toward the only patch of swamp that remains because of freshwater effluent from the pump station and oxidation pond. "You know you can get cypress seedlings. Just go out and plant them, protect them from herbivores until they get 10 or 12 feet high (3 or 3.5 meters) and then they will grow," he says. "There is no problem there. It's been done. We know how to do that, too. I think that we just need to get on with it."
For decades Day has studied more than a dozen such projects. Day says the idea is to use effluent as a marsh-building resource instead of letting it flow back into the river. Marshes, he says, are natural barriers against storm surges. And he believes that more coastal communities must adopt strategies to protect themselves from the even more intense storms predicted for the future.