|Shields Jr, Fletcher|
Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/26/2007
Publication Date: 3/1/2008
Citation: Shields Jr, F.D. 2008. Effects of a Regional Channel Stabilization Project on Suspended Sediment Yield. Journal of Soil and Water Conservation. 63(2):59-69. Interpretive Summary: More than $300 million in federal funds have been spent for erosion control in 16 watersheds in northern Mississippi between 1985 and 2003, but effects on sediment yield have not been fully quantified. All available records of stream flow and suspended sediment concentration for seven of the larger watersheds were analyzed using statistical procedures designed to detect increasing or decreasing trends with time. A trend was found for only one of the seven gages, showing declining sediment concentration over the period 1986-1997. This analysis indicates that real reductions in sediment concentrations may be hard to achieve with the orthodox types of channel erosion controls applied in these watersheds.
Technical 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 site. 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 where 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 significant reductions in sediment yields require changes in watershed hydrology that reduce runoff and peak flows or changes in channel bed slope.