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United States Department of Agriculture

Agricultural Research Service

Title: Sedimentation Patterns Within a Flood Control Reservoir: Grenada Lake, Ms

Authors
item Dunbar, J - BAYLOR UNIVERSITY
item Bennett, Sean
item Higley, P - SPECIALTY DEVICES,INC
item Rhoton, Fred

Submitted to: Laboratory Publication
Publication Type: Government Publication
Publication Acceptance Date: August 5, 2003
Publication Date: August 5, 2003
Citation: DUNBAR, J.A., BENNETT, S.J., HIGLEY, P.D., RHOTON, F.E. SEDIMENTATION PATTERNS WITHIN A FLOOD CONTROL RESERVOIR: GRENADA LAKE, MS. USDA-ARS National SEDIMENTATION LABORATORY RESEARCH REPORT. 2003. NO. 38. 44 PP.

Interpretive Summary: Grenada Lake flood control reservoir, built in 1954 by the U.S. Army Corps of Engineers, is located directly downstream of the Skuna and Yalobusha Rivers in north-central Mississippi. Along the Yalobusha River, 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 deposited within Grenada Lake must be determined to assess if any impact will occur as a result of the upstream channel works. A multi-frequency acoustic profiling system was used to image the amount of sediment that has accumulated in the lake since construction. There is very good agreement between the amount of sediment deposited since dam construction using the profiling system as compared to an analysis using sediment dating techniques. Although there are small pockets of very thick sediment, >2 m, the impounded sediment in the arms of the Yalobusha and Skuna Rivers is about 0.5 to 1.0 m thick and about 1.5 m thick in the main pool of the lake. Using values for the reservoir storage capacity and the volume of deposited sediment, the loss of storage since dam construction is approximately 3.3%. Thus, the reservoir has an annual storage loss of about 0.1%. These data will serve as baseline information by the U.S. Corps of Engineers to determine if upstream channel works will impact future rates of sedimentation in Grenada Lake.

Technical Abstract: Grenada Lake flood control reservoir, built in 1954 by the U.S. Army Corps of Engineers, is located directly downstream of the Skuna and Yalobusha Rivers in north-central Mississippi. Along the Yalobusha River, severe channel erosion has caused the formation of a nearly 2-mi long woody debris plug. This plug has significantly increased flooding frequency and magnitude in nearby Calhoun City. Before the Corps of Engineers initiates plug removal and channel improvements, an assessment of sedimentation within Grenada Lake is required. A multi-frequency acoustic profiling system was used to image the post-impoundment sediment below the bottom of the lake. Using the results from stratigraphic analysis, there is very good agreement between the acoustically-determined impoundment horizons and the stratigraphically-determined sediment thicknesses. Although there are small pockets of very thick sediment, >2 m, the impounded sediment in the arms of the Yalobusha and Skuna Rivers is about 0.5 to 1.0 m thick and about 1.5 m thick in the main pool of the lake. Using values for the reservoir storage capacity and the volume of deposited sediment, the loss of storage since dam construction is approximately 3.3%. Thus, the reservoir has an annual storage loss of about 0.1%.

Last Modified: 10/24/2014
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