Who is playing in our sandbox?
Year after year, storm driven and natural erosion contour and change the Louisiana landscape. Much of the region was initially shaped by sand and silt deposits left behind by the southward flowing Mississippi River. As washouts erode and compact more land while upstream dams block the flow of additional sand, residents and officials worry what will come of sensitive Louisiana wetlands.
Science Daily reports that a new study indicates the supply of the natural material used to rebuild vanishing property won't diminish for hundreds of years to come. One expert says that while the total amount of sediment has indeed lessened, upstream dam construction has not reduced the amount of sand in the lower Mississippi and won't for at least 300-600 years.
In the attached satellite images, note record low water levels in 2012 showing off a large amount of sand (top) typically covered by water (bottom).
Fear of diminishing sand supply originally stemmed from another man-made revision to the natural landscape also brought on by human dread. Levees and dams designed to control flooding, and protect the millions of residents who live downstream, have lessened the supply of sand and silt from the north-- material that is used by officials to sure up compacting deltas and wetlands. The study reveals that the key element used to reinvigorate Bayou State marshlands is still plentiful.
But how can the sand supply not be dwindling if upstream dams are cutting off the continuing supply? In the Science Daily report, researchers explain that the clearer water flowing out of the dams churns up sand that has been lying dormant for centuries and deposits it downstream.
The lead author of the new research, Jeffrey Nittrouer, is an assistant professor of Earth science at Rice University. Nittrouer also did research that contributed to maintenance of the Bonnet Carre Spillway.
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