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United States Department of Agriculture

Agricultural Research Service

Title: Assessing Sedimentation Issues Within the Large Woody Debris Plug Along the Yalobusha River, Calhoun County, Ms

Authors
item Bennett, Sean
item Rhoton, Fred

Submitted to: Laboratory Publication
Publication Type: Government Publication
Publication Acceptance Date: September 17, 2003
Publication Date: September 17, 2003
Citation: Bennett, S.J., Rhoton, F.E. 2003. Assessing sedimentation issues within the large woody debris plug along the Yalobusha River, Calhoun County, MS. USDA-ARS, National Sedimentation Laboratory Research Report. No. 34. 111 pp.

Interpretive Summary: Along the Yalobusha River in north-central Mississippi, severe channel erosion has caused the formation of a nearly 2-mi long woody debris plug. This plug has significantly increased the frequency and magnitude of flooding in nearby Calhoun City. Before the Corps of Engineers can initiate the removal of the plug and improve the conveyance of water, the amount of sediment already impounded within the plug and its physical and chemical characteristics need to be determined. Ten continuous sediment cores were collected along the entire length of the debris plug. These cores are composed of a thin near-surface horizon (silty-clay sediment) and a thicker lower horizon (nearly all sand). Bulk chemical analysis of the sediment samples shows that the concentrations of major elements and select environmentally important elements are higher in the upper horizon as compared to the lower horizon. Historically-used pesticides were found in measurable concentrations and are nearly ubiquitous in the debris plug. The concentrations of elements and agrichemicals observed here are typical for agricultural watersheds in Mississippi. These data will assist the Corps of Engineers in designing their debris plug removal procedure.

Technical Abstract: Along the Yalobusha River in north-central Mississippi, severe channel erosion has caused the formation of a nearly 2-mi long woody debris plug. This plug has significantly increased the frequency and magnitude of flooding in nearby Calhoun City. Before the Corps of Engineers can initiate the removal of the plug and improve the conveyance of water, the amount of sediment already impounded within the plug and its physical and chemical characteristics need to be determined. Ten continuous sediment cores were collected along the entire length of the debris plug. These cores are composed of a near-surface sediment horizon composed of slit and clay and a lower sediment horizon composed of sand. Bulk chemical analysis of the sediment samples shows that environmentally important elements (As, Cr, Cu, Hg, Pb, and Zn) are 5 to 10 times higher in the silt and clay sediments as compared to the lower sand horizon. Within the sediment, BHC-alpha, BHC-beta, BHC-gamma, BHC-delta, aldrin, dieldrin, DDD, DDE, DDT, endosulfan sulfate, heptachlor, and heptachlor epoxide are found in measurable concentrations. The concentrations of elements and agrichemicals observed here are typical for agricultural watersheds in Mississippi.

Last Modified: 10/22/2014
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