Wetlands and Hurricanes
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Transcript of Wetlands and Hurricanes
Wetlands and Hurricanes
By Wynn W. Cudmore, Ph.D.Northwest Center for Sustainable Resources
DUE # 0757239
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
2000 10% Forest remaining
1882
Wetlands of the Gulf Coast
Intact wetlands of coastal Louisiana
1. Barrier islands2. Brackish wetlands3. Swamps4. Freshwater marshes5. 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
1976
1999
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 leveeFlood 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
AfterBefore
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 mi2 to 2.0 mi2
Impact of hurricanes on the Chandeleur Islands, Louisiana
July 2001
Pre-Hurricane Lili (2002), Ivan (2004), Dennis (2005), Katrina (2005)
31 August 2005
2 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 forests Red – 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 18-24 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.• 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 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 2005
6 days post-Katrina
9 August 2005
Pre-Katrina
New Orleans –Before and After Katrina
30 August 2005
27 August 2005
New Orleans – Before and After Katrina
31 August 2005
2 days post-Katrina
27 August 2005