Transcript Wetlands and Hurricanes By Wynn W. Cudmore, Ph.D. Northwest Center for Sustainable Resources DUE # 0757239 This project supported in part by the National.

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
1882
2000
10% Forest remaining
Wetlands of the Gulf Coast
Intact wetlands of coastal Louisiana
1.
2.
3.
4.
5.
Louisiana contains over 40% of
wetlands in the lower 48 states
Barrier islands
Brackish wetlands
Swamps
Freshwater marshes
Bottomland forests
New Orleans's
growth has required
draining wetlands
and a complex
system of levees,
pumps and canals
New Orleans, Louisiana 29 April 2008
Historical Development of
New Orleans, Louisiana
Wetlands as buffers to storm surges
Every 2.7 miles
of wetland
lowers storm
surge by one
foot
Barataria Bay, Louisiana
Wetland Loss along
the Louisiana Coast
1999
Over the past few
centuries 25% of
wetlands associated
with the Mississippi
Delta have been lost
to the ocean
1976
Causes of Gulf Coast Wetland Loss
1. Levees and dams direct sediment out into
the Gulf of Mexico rather than to wetlands
Sediment flowing from the
Mississippi River into the
Gulf of Mexico
2. Canals cut into
coastal wetlands
allow saltwater
intrusion
3. Sea level rise
due to climate
change
Oil gas extraction rig among eroding wetlands
in coastal Louisiana
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
Failed levee
Flood damage
New Orleans flooded
Fishing boats on levee
Damage to Hard Rock Casino
The impacts on wetlands from Hurricanes Katrina and Rita (2005)
Katrina transformed
217 square miles of
marsh into open
water
Before
Rita’s impact was less
severe with some
marsh impact west of
the Mississippi River
After
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
Baldcypress (Taxodium distichum)
and water tupelo (Nyssa aquatica)
were mostly unaffected by the storm
Katrina wind damage in Pearl River
Basin, Mississippi – late 2005
Impact of Hurricane Katrina on
Coastal Forests
Before Katrina
Green – intact forests
After Katrina
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 marshbuilding process
Marsh terraces built in Little Vermillion Bay,
Vermillion Parish, Louisiana.
Marsh terraces
Marsh terraces in Vermillion Bay, Louisiana after several growing seasons
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
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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
After
Rita’s impact was less
severe with some marsh
impact west of the
Mississippi River
Before
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