NASA: USA - New Land on the Louisiana Coast - 02.12.15
Posted by Ricardo Marcenaro | Posted in NASA: USA - New Land on the Louisiana Coast - 02.12.15 | Posted on 13:19
acquired November 7, 1984
download large image (4 MB, JPEG, 2400x2400)
acquired November 7, 1984
download GeoTIFF file (10 MB, TIFF, 2400x2400)
acquired October 25, 2014
download large image (3 MB, JPEG, 2400x2400)
acquired October 25, 2014
download GeoTIFF file (9 MB, TIFF, 2400x2400)
acquired 1984 - 2014
download Google Earth file (KML)
While most of the delta plain of the Mississippi River Delta is losing ground, new land is forming in Atchafalaya Bay at the mouths of the Wax Lake Outlet and the Atchafalaya River.
Geologists first noticed mud deposits building up in Atchafalaya Bay
in the 1950s, but new land first rose above the water line in 1973 after
a severe flood. Since then, both deltas have grown considerably.
According to one estimate
by scientists from Louisiana State University (LSU), the Atchafalaya
and Wax Lake Outlet deltas have combined to grow by 2.8 square
kilometers (1 square mile) per year.
This pair of false-color
satellite images illustrates the growth of the two deltas between 1984
(top) and 2014 (bottom). Both images were acquired by sensors aboard Landsat
satellites. A combination of shortwave infrared, near infrared, and
green light was used to accentuate differences between land and water.
Water appears dark blue; vegetation is green; bare ground is pink. All
of the images were acquired in autumn, when river discharge tends to be
low. Vegetation appears slightly brown in 1984 because the image was
acquired later in the year. Use the image comparison tool to slide
between the two images.
The Atchafalaya is a distributary
of the Mississippi River that connects to the “Big Muddy” in south
central Louisiana near Simmesport. Wax Lake Outlet, an artificial
channel designed to reduce the severity of floods in Morgan City,
delivers about 40 percent of the Atchafalaya’s water into the bay about
16 kilometers (10 miles) west of where the main river empties.
The deltas’ rate of growth has varied considerably, mainly due to the
timing of major floods and hurricanes. Floods transport large volumes
of extra sediment to Atchafalaya Bay, while hurricanes redistribute
sediment within the bay and transport it offshore into deeper waters.
Hurricanes also destroy coastal vegetation that would otherwise protect
land from erosion.
The Atchafalaya delta has grown at a faster rate than its
neighbor—about 1.6 (0.6 square miles) square kilometers per year, versus
1.2 square kilometers (0.46 square miles) per year for the Wax Lake
delta. The difference is due to regular dredging and channel widening on
the lower Atchafalaya, which delivers extra sediment to its delta. Due
to the lack of dredging, Wax Lake delta is more natural in character,
with a more symmetric, lobate shape.
“We are looking carefully at the Wax Lake and Atchafalaya deltas as
models for building new land and preserving some of our coastal
marshlands,” said Harry Roberts,
director of the Coastal Studies Institute at LSU. “If we start
diverting significant portions of the water and sediment from the main
channel of the Mississippi River into adjacent wetlands, lakes, and
bays—as happens now in Atchafalaya Bay—we’ll be taking an important
first step toward saving a significant part of Louisiana’s coastal
plain.”
Learn more and see more imagery by reading “Growing Deltas in Atchafalaya Bay.”
NASA Earth Observatory images by Jesse Allen, using Landsat data from the U.S. Geological Survey. Caption by Adam Voiland.
- Instrument(s):
- Landsat 5 - TM
- Landsat 8 - OLI
NASA: USA - New Land on the Louisiana Coast - 02.12.15
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