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Winter/Spring 2006 Vol. 6 No. 1

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Mapping Louisiana's Future

Louisiana barrier island on Gulf of Mexico, photo courtesy National Oceanic and Atmospheric Administration

A Long and Broad View Needed to Guide Wetland Restoration

As efforts get under way to rebuild New Orleans and mend the damage wreaked by hurricanes Katrina and Rita on the Gulf Coast, drawing a map of what coastal Louisiana will look like decades from now should be one of the first steps in any large-scale restoration of its vanishing marshes and barrier islands, says a new report from the National Research Council.

Wetlands along the state's coast have been disappearing at the rate of several square miles a year, mainly because much of the Mississippi River sediment needed to support them has been trapped upstream by levees and other barriers, or has been routed offshore by flood-control measures. Moreover, the reduction in sediment buildup has prevented the Mississippi delta from keeping pace with sea level rise and natural subsidence.

The report was requested in 2004 by the Louisiana governor, who specifically asked the Research Council to review a study by the state and the U.S. Corps of Engineers that proposes five major wetland restoration projects. A Research Council committee found most of these projects to be scientifically sound, but given the size of the watershed in question and the continuing rapid decline of wetlands, concluded that a much more strategic approach addressing the system as a whole is needed.

Marshlands in Louisiana, ©Philip Gould/Corbis

The current project proposals are designed for completion in the near term -- which is all the federal Office of Management and Budget provided funding for. The committee said this near-term focus precludes more-promising projects that have not yet been fully designed, and the study itself indicates that its projects will only reduce wetland losses by about 20 percent a year. Nevertheless, all but one of the near-term projects should move forward because they will support a broader approach to wetland restoration in the future. The exception is a proposal to build a stone retaining wall along an outlet that provides a shortcut for ships between the Mississippi and the Gulf of Mexico. Despite a price tag of more than $100 million, it will only cut land loss by 0.2 square miles a year. In addition, the Corps is studying whether to even continue maintaining the outlet as a channel for large vessels.

Another idea under discussion is diverting some of the Mississippi's flow to create a so-called Third Delta that will allow the river to reach the Gulf southwest of New Orleans, renourishing wetlands there with badly needed sediment. The committee said consideration should be given to an alternative or companion to the Third Delta that would deliver even greater amounts of sediment but travel through less-developed areas, perhaps making it more feasible.

Projects such as this, where homes and businesses may need to be relocated, will obviously require significant public involvement. Explicit maps depicting what the Louisiana coastline will look like with or without various wetland restoration projects should be circulated among all interested parties.

"It's unlikely that the entire coast can be restored, so decisions need to be made about where restoration is most needed," said committee member Jeffrey Benoit, former director of the National Oceanic and Atmospheric Administration's Office of Ocean and Coastal Management, and now a consultant in Arlington, Va. Once a map has been agreed upon, integrated projects can be designed to achieve it.

As the economic impact of Katrina and Rita becomes clearer, it will be possible to better judge the potential national economic benefits of Louisiana's coastal restoration, the committee noted. And although it's too early to say what role, if any, the missing wetlands played in amplifying the effects of the hurricanes, enough is known about the ability of wetlands to lessen the impact of coastal storms and hurricanes that their restoration should be part of national efforts to reduce hurricane hazards.   -- Bill Kearney

Drawing Louisiana's New Map: Addressing Land Loss in Coastal Louisiana. Committee on the Restoration and Protection of Coastal Louisiana, Ocean Studies Board, Division on Earth and Life Studies (2006, approx. 206 pp.; ISBN 0-309-10054-2; available from the National Academies Press, tel. 1-800-624-6242; $33.00 plus $4.50 shipping for single copies).

The committee was chaired by Robert G. Dean, professor of civil and coastal engineering, University of Florida, Gainesville. The study was funded by the state of Louisiana and the U.S. Army Corps of Engineers.

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Copyright 2006 by the National Academy of Sciences