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  • America's Wetland Foundation

    Strong Coast Strong Texas


    The Louisiana Coastal Marsh:
    natural hurricane damage protection slipping from our fingertips

    T. Colleen Morgan, Yale School of Forestry and Environmental Studies

    Coastal wetlands in Louisiana - known as America's WETLAND serve as much more than wildlife habitat and nursery for the multitude of fisheries that feed Gulf coast seafood lovers. The salt marshes and swamps that make up the massive Mississippi River deltaic plain and surround the  city of New Orleans function as a barrier between the infrastructure of the ports of southern Louisiana and hurricane storm surge.

    Tropical storms are extremely common in the Gulf of Mexico, and they often carry with them 15- to 30-foot-high mounds of swirling waves. Since hurricanes gain their energy by being over water, it follows that they lose their energy over land, which causes friction and therefore dissipates the surge. Using the methods and sites from a U.S. Army Corps of Engineers study done in the 1960's, Drs. Paul Kemp, Hassan Mashriqui and others from the Louisiana State University's Hurricane Center have calculated the height of the storm surge in western Louisiana during Hurricane Rita, which hit that region about three weeks after Katrina passed by New Orleans and came on land in Mississippi. They determined that a healthy wetland attenuates storm surge at an average rate of one foot per four square miles. In the areas of the state where the wetlands have degraded, subsided and turned into open water in many places, primarily in the southeastern region around the delta, the attenuation rate has increased to an average of eight square miles for every foot of storm surge.

    Therefore, since wetlands cut down hurricane storm surge, they serve as protection from hurricane damage. In theory, during a storm, every square mile of wetlands of coastal Louisiana buffers every industrial facility, every home, every warehouse and every port. Moreover, the Louisiana Offshore Oil Port (LOOP), which imports nearly 15 percent of the nation's crude oil, and the extensive oil and natural gas production off the Louisiana coast funnels raw material through thousands of miles of pipelines buried in the marsh - an extensive network including more than 10,000 miles of pipelines moves 20 percent of the nation's crude oil and 33 percent of its natural gas. The 19 refineries in Louisiana, which represent nearly 50 percent of the nation's refining capacity also use pipelines to move their product to the fleet of petrochemical facilities in the state and all over the country.

    The coastal wetlands of Louisiana are subsiding at an alarming rate - many say about a football field of marsh disappears every half-hour; U.S. Geological Survey estimates that 1,900 square miles of wetlands have disappeared since the 1930s. The causes for this environmental degradation are complex: they include the complete separation of the Mississippi River from the wetland complex that it once fed with distributaries and spring floods that deposited sediment in the wetlands, and the extensive network of canals that were dredged throughout the coastal marsh areas for navigation changed the hydrologic regime, caused vegetation stress and death, and salt water intrusion into once-freshwater swamps. Many thousands of acres of former cypress stands are now standing dead "ghost swamps."

    With funding from the federal government, the state began a wetlands restoration program and concurrently initiated a process to develop a comprehensive plan for restoring the entire coast. This planning process, initiated in 1995 and called Coast 2050, involved multiple stakeholders and several years of public meetings. When this plan was published in 1998, the U.S. Army Corps of Engineers continued the process with the Louisiana Coastal Area (LCA) Ecosystem Restoration Study, which was essentially a feasibility study. It included a range of types of projects in all the coastal regions.

    Although there are different camps that have strong opinions about how restoration should be done, the plan includes two primary prescriptions: large-scale diversions of the river to bring freshwater, nutrients and sediments back into the wetlands, and using an extensive pumping system to take sediments dredged from the mouth of the river and transport them to coastal areas for marsh building projects. The LCA Study found that carrying out the plan would cost approximately $14 billion over 30 years, but before the study could be published, the Bush Administration's Office of Management and Budget (OMB) had the USACE scale it back to a five-year, $2 billion plan. This document was before the National Research Council when Hurricane Katrina hit on August 29, 2005.

    Since the hurricanes, wetlands restoration has become a high priority for Louisiana residents, as their buffering capacity works in conjunction with, and protects, well-functioning levees. The funding for such a project, however, is the challenge, so Governor Kathleen Babineaux Blanco has committed future royalties from offshore oil revenues to wetlands restoration. Two bills have been approved by Congress -- both propose to provide Louisiana with the revenue sharing it would need to move forward with this comprehensive restoration plan.  We hope that Congress will reach a compromise between the two bills that will provide Louisiana with its fair share of OCS revenues need to protect its coast.

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