REPAIR THE MARSHLANDS OR REBUILD NEW ORLEANS

Date: Saturday, July 16, 2005

Louisiana is washing away into the Gulf of Mexico.

From 1932 to 2000, the state lost 1,900 square miles, mostly wetlands, to open water. Without intervention, it could lose another 900 square miles by 2050.

At a conference in New Orleans last week, Troy Constance of the New Orleans District of the U.S. Army Corps of Engineers spoke about the Louisiana Coastal Area Ecosystem Restoration Study, which he manages.

It's a joint project between the Corps and the Louisiana Department of Natural Resources, aimed at doing enough relatively small demonstration projects to determine what works and to eventually develop a strategy for long-term, large-scale restoration.

The question is whether they'll get it done in time. When I was there, New Orleans was just cleaning up after Hurricane Cindy, and anticipating the arrival of Hurricane Dennis (which eventually went and bothered Pensacola instead). If you can go look at a map online, this would be a good time; at www.lca.gov, click on "Facts & Info" to see a map of land changes.

The chief danger to New Orleans is a storm surge. Wetlands attenuate the height of a surge, at a rate of about one foot for three miles. But in the Barataria Basin south of the city, 15 miles of marsh have deteriorated, according to the United States Geological Service. A slow-moving Category 5 hurricane could produce a 19- to 21-foot storm surge in Lake Pontchartrain, higher than the levees that protect the city. New Orleans could find itself under 20-25 feet of water.

And because much of the city is below Mississippi River level, you can't just drain the water out, either.

Even if all the people got out safely, the economic loss would be incalculable. And that's not to mention that Louisiana produces 28 percent of America's crude oil and 26 percent of its natural gas. A lot of imported oil comes through Louisiana ports, too.

Louisiana has the largest commercial seafood harvest in the lower 48 states, and a billion-dollar recreational fishing industry as well.

Millions of migratory birds along the Mississippi Flyway rely on the state's wetlands.

How did this erosion happen? Basically, the Mississippi River was separated from the land along its banks. After the Great Flood of 1927, levees were built along the river so it wouldn't overflow its banks during high water. The river basin drains 41 percent of the continental United States, as well as bits of Canada, and from time immemorial, the river has been carrying bits of Montana and Pennsylvania downstream and dropping them on its delta to make more Louisiana. From time to time, the river would change course and start a new delta while the old one began to erode away.

At the beginning of Constance's talk, he said that sediment in the Mississippi has been reduced by about 70 percent. At first I thought he meant that was a good thing, but quite the contrary. It was the sediment that nourished the coastal marshes, not only in building land but providing nutrients.

One technique is to create a small back channel from the river to nearby wetland areas, providing both freshwater and sediment to help them recover. As a bonus, the material dredged from the channel can be used to build land elsewhere. Material dredged from navigational channels is also a resource rather than a nuisance. Small enclosed platforms filled with dirt quickly revegetate with marsh grasses.

How much will it cost? The smaller demonstration projects being done or considered now will come to about $2 billion, in a mixture of federal and state funds. By 2050, the goal is to restore about 500,000 acres.

The total cost might be $14 billion -- but on the other hand, what would it cost to replace New Orleans?

The scientific work and demonstration projects being done in Louisiana will affect restoration projects elsewhere. The Florida Everglades aren't washing away, but intensive drainage there has created some of the same problems caused by a network of drainage ditches and pipelines in Louisiana. The reflooding of the Iraqi marshes, which were drained by Saddam Hussein to put down a rebellion, is also a test laboratory in re-creating an ecosystem.

It's worth noting that this is not your grandfather's Army Corps, whose unofficial motto used to be, "Dam the rivers and damn the consequences."

It's a philosophy of working with nature, not against it, or as the LCA plan says, use restoration strategies "that reintroduce historical flows of river water, nutrients, and sediments to coastal wetlands and that maintain the structural integrity of the coastal ecosystem."

I asked Constance if the shift in philosophy caused any tension within the corps. No, he said; it's happened over a long time and people are comfortable with it.

If you'd like to see all of Constance's Power Point presentation, it's available at ftp://ftp.usace.army.mil/pub/mvn/ Morgan/ but just be warned; it took more than an hour to download. Worth the wait, I think. And if you want to get involved, he'll tell you how.