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Spring/Summer 2009 Vol. 9 Number 1

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Aerial of flooded neighborhood in New Orleans after Hurricane Katrina, photo by Jocelyn Augustino/FEMA A Harbor in
the Tempest

Protecting the
Crescent City

Hurricane Katrina. The words alone stir up powerful images of devastation — entire neighborhoods submerged underwater, people stranded on rooftops and in the city, and levees blasted by floodwaters. But more than anything, the words are connected with pain and suffering for the citizens who are still trying to rebuild their lives and communities.

In Katrina’s aftermath, Americans wondered how the system of levees and floodwalls designed to protect New Orleans could have failed. To help answer this question, the U.S. Army Corps of Engineers created the Interagency Performance Evaluation Task Force (IPET) to carry out a large-scale investigation into the failure of the New Orleans hurricane-protection system and to provide advice on strengthening the system. Subsequently, the National Research Council and National Academy of Engineering were asked by the U.S. Department of the Army to evaluate IPET’s progress and reports.

For more than three-and-a-half years, the study committee examined IPET’s work, as well as held meetings in New Orleans to listen to concerned citizens. From examining IPET’s reports and other evidence, the study committee determined that levees and floodwalls surrounding New Orleans cannot provide absolute protection against over-topping or failure in future extreme events such as a hurricane — no matter how large or sturdy the structures are. They should be viewed as ways to reduce risks from hurricanes and storms, not as complete protection. As with many structures built to protect against flooding, the New Orleans hurricane-protection system promoted a false sense of security that regions behind the structures FEMA Urban Search and Rescue team in area impacted by Hurricane Katrina,photo by Jocelyn Augustino/FEMAwere absolutely safe for habitation and development.

Settlement in areas most susceptible to flooding should be discouraged, the report says. Moreover, voluntary relocation of people and neighborhoods from vulnerable areas should be considered as a viable public policy option. If relocation is not feasible, an alternative would be to elevate the first floor of buildings to at least the 100-year flood level.

Although some of the report’s recommendations to enhance hurricane preparedness have been widely acknowledged for years by experts in fields such as natural hazards mitigation and urban planning, many have not been adequately implemented. Rebuilding the New Orleans area and the levees and floodwalls to their pre-Katrina state would leave the city and its inhabitants vulnerable to similar disasters, the report notes.

The committee also recommended that officials establish a comprehensive evacuation program that is well-designed and tested; includes improved local and regional shelters that would make evacuation less imposing; and enhances the efficiency of evacuations by locating facilities for the ill and elderly away from hazardous areas.

As further assistance to helping protect the city, a separate National Research Council report released in January found that replacing Federal Emergency Management Agency flood maps with ones that contain high-accuracy and high-resolution land surface elevation data could help avoid significant loss of life, destroyed property and businesses, and repairs to infrastructure, not just in New Orleans but throughout the whole country.

Better flood maps would provide more reliable measures of flood hazards, enabling structures to be insured at appropriate levels and more targeted land-use regulations, the report says. Moreover, coastal region flood maps, like those used near New Orleans, could also be improved by updating current models and using two-dimensional storm surge and wave models.  — Jennifer Walsh

 The New Orleans Hurricane Protection System: Assessing Pre-Katrina Vulnerability and Improving Mitigation and Preparedness. Committee on New Orleans Regional Hurricane Protection Projects; Water Science and Technology Board, Division of Earth and Life Studies; Board on Infrastructure and the Constructed Environment, Division on Engineering and Physical Sciences; and National Academy of Engineering (2009, 58 pp.; ISBN 0-309-13833-7; available from the National Academies Press, tel. 1-800-624-6242; $21.00 plus $4.50 shipping for single copies).

The committee was chaired by G. Wayne Clough, secretary of the Smithsonian Institution. The study was funded by the U.S. Department of the Army.

 Mapping the Zone: Improving Flood Map Accuracy. Committee on FEMA Flood Maps: Accuracy Assessment and Cost-Effective Improvements, Board on Earth Sciences and Resources and Water Science and Technology Board, Division of Earth and Life Studies (2009, 136 pp.; ISBN 0-309-13057-3; available from the National Academies Press, tel. 1-800-624-6242; $32.00 plus $4.50 shipping for single copies).

The committee was chaired by David R. Maidment, professor of civil engineering and director of the Center for Research in Water Resources, University of Texas, Austin. The study was funded by the Federal Emergency Management Agency and National Oceanic and Atmospheric Administration.

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Copyright 2009 by the National Academy of Sciences