Dams Will Not Reduce Flow of Sand to Mississippi River Delta, Study Finds
Researchers have found that the Mississippi River Delta’s supply of sand—a critical material engineers need to rebuild the ecosystem—will stay constant for centuries despite upstream dams and the rapid sinking and erosion of wetlands.
The study, published this week in Nature Geoscience, provides positive evidence for scientists and government officials who are working to shore up southeastern Louisiana’s disappearing wetlands.
Water management such as flood-control measures have cut about half of the annual supply of sediment that flows downriver, a naturally occurring material that once counteracted the subsidence, according to the conducted by researchers from Rice University and the University of South Carolina.
The conversion of wetlands to open water was thought to be inevitable due to the decline in the load of total suspended sediment—both sand and and mud—carried by the Mississippi River.
The researchers found that sand, which is in abundant supply, could be more important than mud for delta growth. The sand could help replenish diminished wetlands and mitigate land loss by scouring river bed upstream, the researcher say.
Upstream dam construction has not reduced the amount of sand in the lower Mississippi River and won’t for at least 300 to 600 years, according to the study’s lead author Jeffrey Nittrouer, assistant professor of Earth science at Rice University.
Last year, low water levels threatened to shut down commerce on the Mississippi River, despite attempts by the US Army Corps of Engineers to release water from a southern Illinois lake. Water on the river was near record lows because of the worst US drought in 50 years.
A shutdown of the river would put more than $2 billion in agricultural commodities such as corn and wheat at risk, the American Wetlands Foundation said at the time.
Some 86 percent of water used to produce the nation’s corn and soybeans comes from the Mississippi River Basin, which produces 92 percent of US agricultural exports. The bulk of products and goods from America’s heartland — worth about $10 billion a year — are shipped out of Louisiana ports, and the Mississippi is also the storm drain for 41 percent of America, according to AWF.
Photo: Satellite image of Mississippi River from NASA Earth Observatory
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