Abstract
Under legislation passed in 1984, three federal agencies constructed more than $300 million worth of channel erosion control measures in 16 watersheds in northern Mississippi between 1985 and 2003. Most work was completed between 1985 and 1995 and was confined to six larger watersheds. Flows of water and suspended sediment emanating from these watersheds were measured from 1986 until 1997 and for longer periods for two of these gages and one additional gage. Statistical analyses of flow-adjusted instantaneous measured concentration data failed to detect significant trends at six of the seven gages. A downward trend was noted for a watershed in which eight reservoirs were constructed. These results indicate that watershed-level effects of even large-scale erosion control measures are difficult to detect over 5 to 15 years. Evidently substantial reductions in sediment yields require changes in watershed hydrology that reduce runoff and peak flows or changes in channel bed slope.
Footnotes
F. Douglas Shields Jr. is a research hydraulic engineer at the National Sediment Laboratory, USDA Agricultural Research Service, Oxford, Mississippi.
- © 2008 by the Soil and Water Conservation Society
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