Wetlands and Hurricanes By Wynn W. Cudmore, Ph.D. Northwest Center for Sustainable Resources DUE # This project supported in part by the National Science Foundation. Opinions expressed are those of the authors and not necessarily those of the Foundation.

Wetlands and Hurricanes Hurricane Gustav 25 August – 1 September 2008

The Gulf Coast Louisiana, Mississippi, Alabama and Florida

The Lower Mississippi River Basin is probably the most human-impacted large water basin in the world: Logging of forested wetlands Conversion to agriculture Altered hydrology Extirpation of megafauna Fragmentation of the Mississippi River delta Only about 3.7% of the original wetlands in the basin remain in a natural condition Largest intact wetland is the Atchafalaya Swamp % Forest remaining 1882

Wetlands of the Gulf Coast

Intact wetlands of coastal Louisiana 1. Barrier islands 2. Brackish wetlands 3. Swamps 4. Freshwater marshes 5. Bottomland forests Louisiana contains over 40% of wetlands in the lower 48 states

New Orleans, Louisiana 29 April 2008 New Orleans's growth has required draining wetlands and a complex system of levees, pumps and canals

Historical Development of New Orleans, Louisiana

Wetlands as buffers to storm surges Barataria Bay, Louisiana Every 2.7 miles of wetland lowers storm surge by one foot

Wetland Loss along the Louisiana Coast Over the past few centuries 25% of wetlands associated with the Mississippi Delta have been lost to the ocean

Causes of Gulf Coast Wetland Loss Sediment flowing from the Mississippi River into the Gulf of Mexico 1.Levees and dams direct sediment out into the Gulf of Mexico rather than to wetlands

Oil gas extraction rig among eroding wetlands in coastal Louisiana 2. Canals cut into coastal wetlands allow saltwater intrusion 3. Sea level rise due to climate change

Barrier islands also protect the Gulf Coast Chandeleur Islands

Hurricane Katrina 28 August 2005 Category 5 hurricane One day before landfall

Hurricane Katrina 29 August 2005 Landfall as a Category 3 storm

Katrina’s impact New Orleans flooded Failed levee Damage to Hard Rock Casino Fishing boats on levee Flood damage

The impacts on wetlands from Hurricanes Katrina and Rita (2005) Katrina transformed 217 square miles of marsh into open water Rita’s impact was less severe with some marsh impact west of the Mississippi River After Before

Mississippi Delta - Before and After Katrina 31 August 2005 Post-Katrina 9 August 2005 Pre-Katrina

Impacts of Katrina on the barrier islands Land area of Chandeleur Islands decreased from 5.6 mi 2 to 2.0 mi 2

Impact of hurricanes on the Chandeleur Islands, Louisiana July 2001 Pre-Hurricane Lili (2002), Ivan (2004), Dennis (2005), Katrina (2005) 31 August days post-Hurricane Katrina

Hurricanes as agents of renewal Katrina wind damage in Pearl River Basin, Mississippi – late 2005 Baldcypress (Taxodium distichum) and water tupelo (Nyssa aquatica) were mostly unaffected by the storm

Impact of Hurricane Katrina on Coastal Forests Before Katrina After Katrina Green – intact forestsRed – storm-damaged forests

Wetland restoration as a strategy Wetland restoration will require an increase in the sediment load of the Mississippi River Current sediment load is 50% lower than historic levels Sustaining current levels of wetlands will require an additional billion tons of sediment per year Future wetland loss seems inevitable

The “Coast 2050” Wetland Restoration Plan Diverts a portion of the Mississippi River to deliver more sediment to wetlands south of New Orleans Levees below New Orleans opened to increase sediment and freshwater flow into marshes Close the Mississippi Gulf Outlet Oil and gas channels to be filled Sediment builds and wetland grasses replanted as needed Barrier islands replenished with dredged material

Marsh terraces as a conservation practice Earthen terraces are constructed to reduce wind and wave energy in shallow open water Facilitate establishment of submerged aquatic vegetation Each terrace is approximately 1000 feet long, 40 feet wide at the base and 10 feet wide at the top Surface of the terrace is 2 feet above water level and planted with native vegetation Arranged in “V”-shaped patterns in shallow, open water

Marsh terraces Marsh terraces captured vegetation and soil displaced by Hurricane Rita The resulting increase in elevation may assist in the marsh- building process Marsh terraces built in Little Vermillion Bay, Vermillion Parish, Louisiana.

Marsh terraces in Vermillion Bay, Louisiana after several growing seasons Marsh terraces

Marsh terraces as a conservation practice Earthen terraces are constructed to reduce wind and wave energy in shallow open water Facilitate establishment of submerged aquatic vegetation Each terrace is approximately 1000 feet long, 40 feet wide at the base and 10 feet wide at the top Surface of the terrace is 2 feet above water level and planted with native vegetation Arranged in “V”-shaped patterns in shallow, open water Create habitat for fish and wildlife species

Hurricanes and Gulf Coast Wetlands – a summary The Gulf Coast is vulnerable to damage from hurricanes due to its location, elevation and loss of wetlands and barrier islands Wetlands and barrier islands provide significant protection against major storms Wetlands have decreased in area due to natural and human-caused events Hurricanes result in the loss of additional wetlands and barrier islands, some of which is likely permanent Wetland restoration will require additional sediment input, which the current system cannot provide The “Coast 2050” wetland restoration plan proposes to alter the hydrology of the Mississippi River Delta to reverse wetland loss

Photo Credits IAN Image Library (ian.umces.edu/imagelibrary/): Tim Carruthers Louisiana State University Hurricane Katrina and Rita Cooperative Clearinghouse.Hurricane Katrina and Rita Cooperative Clearinghouse. Marine Photobank: David Helvarg, Blue Frontier Campaign, ESA Envisat NASA/courtesy of nasaimages.org Jesse Allen, Earth Observatory, using data provided courtesy of Laura Rocchio, NASA Landsat Project Science Office NASA Earth Observatory NASA/GSFC/LaRC/JPL, MISR TeamMISR Team Image Science & Analysis Laboratory, Johnson Space Center GOES Project Science Office National Oceanic and Atmospheric Administration/Department of Commerce: Dr. Terry McTigue, NOAA Fisheries U.S. NAVY USDA Natural Resources Conservation Service: Lynn Betts, U.S. Geological Survey: National Wetlands Research Center

Additional Slides The following slides are provided as additional evidence of the impacts of Katrina on wetlands

The impacts on wetlands from Hurricanes Katrina and Rita (2005) Katrina transformed 217square miles of marsh into open water Rita’s impact was less severe with some marsh impact west of the Mississippi River Before After

Mississippi Delta – Before and After Katrina 4 September days post-Katrina 9 August 2005 Pre-Katrina

New Orleans – Before and After Katrina 30 August August 2005

New Orleans – Before and After Katrina 31 August days post-Katrina 27 August 2005