Breaux Act Newsflash - USGS Reports Preliminary Wetland Loss Estimates from Hurricanes
***********************************************************************USGS Reports Preliminary Wetland Loss Estimates for Southeastern Louisiana
from Hurricanes Katrina and Rita
Hurricanes Katrina and Rita transformed some 100 square miles of marsh to
open water in southeastern Louisiana, according to preliminary estimates by
U.S. Geological Survey (USGS) based on an analysis of Landsat satellite data
from September and October.
Future observations of Landsat imagery over the upcoming year will allow
scientists at the USGS National Wetlands Research Center (NWRC) in Baton
Rouge and Lafayette, La., to determine how much of the loss is permanent and
how the marsh recovers. Although this early analysis of wetlands does not
take into account some marsh recovery, indications are that much of the loss
may be permanent. Some of the new areas of open water will likely become new
lakes.
Most of the loss east of the Mississippi River is attributed to the effects
of Hurricane Katrina's storm surge, although Hurricane Rita's surge appears
to have rearranged some of the wrack, or marsh debris, left behind by
Hurricane Katrina in the upper Breton Sound area.
Substantial marsh loss, primarily from Katrina, occurred east of the
Mississippi River in St. Bernard and Plaquemines parishes. Approximately 39
square miles of marsh around the upper and central portions of Breton Sound
were converted to open water by ripping of the marsh or by marsh
submergence. Large compressed marsh features several thousand feet long are
evident in Breton Sound. Most of the loss was concentrated in an area
bounded by the Mississippi River levee to the west, the Delacroix Ridge to
the east, and State Highway 300 to the north. Follow-up imagery and aerial
photography will be used to determine if some of the submerged marshes
reemerge over time.
An additional 47 square miles of marsh were lost throughout the
Pontchartrain, Pearl River, Barataria, and Terrebonne basins. The active
Mississippi Delta also incurred approximately 14 square miles of loss. The
lower Pearl River basin contains numerous marsh rips south of Highway 90.
Direct impacts from Hurricane Rita were not as severe as Hurricane Katrina's
impacts in southeastern Louisiana. For example, rips in marshes from Rita
were not nearly the size of rips from Katrina in upper Breton Sound although
they are noticeable in the Barataria and Terrebonne basins. Rita's surge
caused new tears in fresh and intermediate marshes within Barataria and
Terrebonne basins and reactivated older hurricane scars attributable to
Hurricane Lili (2002) in western Terrebonne and the East Cote Blanche Bay
area.
Rita's surge caused detectable marsh loss west of the Mississippi River to
the Texas border that could not be attributable to Katrina based on analysis
of satellite imagery obtained a week after Katrina's landfall, but prior to
Rita's landfall.
Now that the compounded effects of the storms on southeastern Louisiana have
been analyzed, NWRC scientists are analyzing Landsat imagery to quantify
Rita's impacts in southwestern Louisiana.
To perform satellite analysis, USGS scientists in Louisiana used remote
sensing technologies and geographic information systems. They compared land
and water areas identified by using Landsat 5 Thematic Mapper satellite
imagery. Landsat data from November 11, 2004 were compared to data acquired
on September 7, 2005, September 16, 2005, October 9, 2005, October 18, 2005,
and October 25, 2005 to identify potential wetland loss.
The imagery was collected by the USGS National Center for Earth Resources
Observation and Science in Sioux Falls, S.D.
The USGS serves the Nation by providing reliable scientific information to
describe and understand the Earth; minimize loss of life and property from
natural disasters; manage water, biological, energy, and mineral resources;
and enhance and protect our quality of life.
For more information contact Gaye S. Farris at 337-266-8550 or
gaye_farris@usgs.gov
***********************************************************************