Saving Cajun Country
Saving Cajun Country Archeologists and engineers will soon be using NASA
satellite data to restore endangered wetlands without accidentally
destroying Native American cultural sites.
November 1, 2002: A 56-year-old
blue-crab fisher, Michael Comardelle has lived in the Louisiana
bayou almost all his life. His father, too, was born in the bayou,
atop a low mound of earth that Native Americans once built as
the foundation for a temple.
Now the temple mound is gone, washed away along with much of the wetlands of the Louisiana coast. An epidemic of erosion, rising sea-levels, and slowly sinking land has been eating away at these wetlands at the rapid pace of 25 to 35 square miles each year (65 to 91 square km). With the wetlands goes the homeland of Comardelle's Cajun culture, as well as the buried relics of the Native American cultures that came before it.
"That was our playground," Comardelle laughs. "The
swamp and the bayou were right at our doorstep. That's just the
way we lived. All that's eroding away so quick, so fast, it disappears
in front of your eyes just about."
"In my lifetime, I've seen [about] 50 percent of the area I used to go [crab fishing] in washed away," he says.
Human alteration of the flow of the Mississippi is the primary culprit. Flood-control levees along its banks prevent the river from spilling out into the surrounding wetlands. Sediment from the river would normally build up the wetlands and help counter erosional processes. Levees, however, block the influx of sediment and erosion goes unchecked.
Below: Canals and levees criss-cross much of coastal Louisiana. In many cases these artificial waterways disrupt natural patterns of circulation and accelerate erosion. [more]
The loss is particularly worrisome because southern Louisiana is home to 40 percent of the coastal wetlands in the 48 contiguous states. Beyond the natural functions that they serve as water purifiers and bastions of biodiversity, these marshes and estuaries are vital to the local fishing and tourism industries, and they provide a buffer against flooding by storm surges during hurricanes. For example, during the recent one-two punch of Tropical Storm Isidore followed a week later by Hurricane Lili, Comardelle says that, "people who've been living there 20 or 30 years have never seen storm surges come up that high."
To counter this loss of wetlands, the Army Corps of Engineers
and the Louisiana Department of Natural Resources are spearheading
an ambitious restoration project called Coast 2050. It will be
a project of mammoth proportions: a budget of US$14 billion and
a time frame extending 50 years into the future to try
to restore 20,000 square miles of wetlands.
Right: Nearly 1,000 sq. miles of Louisiana's wetlands--an area nearly the size of Rhode Island (inset)--will become open water by 2050 unless something changes. [more]
Earthworks projects like these require detailed measurements of the landscape with which to plan, but surveying such a large area is not easy. That's why the Army Corps of Engineers is recruiting data from NASA satellites to help out.
"These swamps and marshes are often very dense and hard
to get around in," says Marco Giardino, a scientist at NASA's
Stennis Space Center in Mississippi who's helping coordinate
NASA's involvement in Coast 2050. "By using satellite imagery
from NASA's fleet of Earth science sensors, we can supplement
traditional surveying techniques and improve decision making,"
The first target will be the hundreds of ancient Native American sites scattered throughout the bayou. Most of these are visible only as wide mounds rising just a few feet in elevation, such as the temple mound on which Comardelle's father was born. The National Historic Preservation Act requires projects like Coast 2050 to identify such archeological sites and to evaluate them as candidates for the National Register of Historic Places.
Left: Louisiana is dotted with ancient Native American mounds like this one at Marksville State Park. [more]
How can a satellite in orbit spot a subtle mound in the midst
of a vast swamp? Actually, in much the same way that Comardelle
Besides being a commercial blue-crab fisher, Comardelle is a knowledgeable amateur archeologist. In fact, Comardelle has been acting as a local guide for the scientists on the project, taking them out in the swamp and showing them around.
From the bow of his boat, he can point out Native American
sites just by noticing variations in the swamp's vegetation.
Oak trees, swamp maples, palmettos, hackberry, and wax myrtle
signal a slight rise in elevation that may be a remnant of the
area's ancient inhabitants.
"Sometimes it's [a] natural [feature like a levee], but most of the time it's an Indian feature," Comardelle says.
Satellites can notice these changes in vegetation as well.
The sunlight reflecting off a patch of swamp carries the "fingerprints"
of the area's plant life embedded in its spectrum of colors.
A patch of oaks will have a different spectral fingerprint than
a patch of reeds or grasses.
So by looking at the reflected light's spectrum, satellites like NASA's Terra, EO-1, and Landsat 7 can map out the raised areas in a large bayou or swamp, and thus identify archeological sites. If this method proves effective in the Barataria Basin test area, it will be used in future Coast 2050 efforts as well, says Joan Exnicios, an archeologist with the Army Corps of Engineers.
Right: This false-color satellite image of the Mississippi
delta was captured by the Multi-angle Imaging SpectroRadiometer
onboard NASA's Terra satellite. [more]
"It will make it possible for archeologists to pinpoint areas to look at on the ground without having to first undertake extensive terrestrial surveys," says Dave Davis, an archeologist at Tulane University and a consultant for Coast 2050.
NASA will also collaborate with the Army Corps of Engineers
on other aspects of the project, such as freshwater diversions,
marsh rejuvenation, and saltwater intrusion, but details are
yet to be worked out.
Taken together, these efforts will preserve habitat for thousands of species and restore the buffer between Gulf storm surges and inland cities. They will also help save the bayou that Cajuns like Comardelle call home, and preserve the heritage of Native Americans who called it home ages ago.
Earth Science Applications Directorate -- (Stennis Space Center) supports NASA involvement in Coast 2050.
Coast 2050 -- project home page.
Right: Much of coastal Louisiana is literally being washed away. This photo was taken at Constance Beach, Louisiana. Image courtesy The Coalition to Restore Coastal Louisiana.
Coastal Louisiana -- (USGS)
LACoast -- (USGS National Wetlands Research Center) Approximately 40 percent of the coastal wetlands of the lower 48 US states is located in Louisiana. The animations area of this web site illustrates how these wetlands are fast-disappearing.
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