Instead, the scientists with USDA's Agricultural Research Service (ARS) have confirmed that stream bank collapse and failure can be chief contributors to high sediment levels in the silty streams and rivers that flow into the Mississippi. ARS is USDA's chief intramural scientific research agency.
The U.S. Environmental Protection Agency lists sediment as the most common pollutant of rivers, streams, lakes and reservoirs in the United States. Trapped sediment can reduce the useful lifespan of dams and reservoirs, exacerbate flooding, harm aquatic plants and animals, and transport other pollutants downstream. Over the years, billions of dollars have been spent on stream bank protection and restoration efforts to stem erosion and reduce sedimentation loads.
The source of this sediment load is often attributed to erosion and runoff from farm fields. But ARS hydrologist Glenn Wilson, who works at the agency's National Sedimentation Laboratory in Oxford, Miss., spent several years looking more closely at the causes of stream bank erosion. His studies focused on how seepage—the lateral movement of water through the ground—could prompt conditions that led to stream bank failure.
Wilson and others confirmed for the first time that a stable stream bank can quickly become unstable when seepage erosion is added to the mix of factors that promote bank failure. They found that seepage from stream banks was eroding layers of soil that subsequently would wash down the face of the stream bank and into the stream itself. This added to the sediment load in the stream and also left the bank itself weakened and vulnerable to collapse.
The researchers concluded that stream bank failure may stem as much—or more—from the effect of seepage erosion undercutting the stream banks as from the added weight of the waterlogged stream banks.
Results from this work were published in the Journal of Hydrologic Engineering and Earth Surface Processes and Landforms.
Read more about this research in the February 2011 issue of Agricultural Research magazine.
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There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.
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Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...
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Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
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