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ARS Home » Southeast Area » Oxford, Mississippi » National Sedimentation Laboratory » Watershed Physical Processes Research » Research » Publications at this Location » Publication #140570
Title: ACOUSTIC IMAGING OF SEDIMENT IMPOUNDED WITHIN USDA-NRCS FLOOD CONTROL DAMS, WISCONSIN

Author
item DUNBAR, J - BAYLOR UNIVERSITY
item HIGLEY, P - SPECIALTY DEVICES, INC.
item Bennett, Sean

Submitted to: Laboratory Publication
Publication Type: Government Publication
Publication Acceptance Date: 11/4/2002
Publication Date: 11/4/2002
Citation: Dunbar, J.A., Higley, P.D., Bennett, S.J. 2002. Acoustic imaging of sediment impounded within USDA-NRCS flood control dams, Wisconsin. USDA-ARS Nationial Sedimentation Laboratory Research Report. No. 30. 34 pp.

Interpretive Summary: Since 1948, the USDA-NRCS has constructed nearly 11,000 upstream flood control dams in 2000 watersheds in 47 states, most with a design life of 50 years. But many of these reservoirs are filling with sediment. At the direct request of the USDA-NRCS in Wisconsin, two reservoirs, White Mound Lake located in Sauk County and Twin Valley Lake located in Iowa County, were chosen for sedimentation surveys using an acoustic profiling system. The acoustic profiling system consists of a control module, three acoustic transducers, and a navigation system all deployed from a single Johnboat. The surveys showed three distinct acoustic layers. The upper-most layer corresponded to fine-grain, water-rich sediments. The middle layer preferentially filled the reservoir lows, becoming thinning toward the upstream end of the lake. The bottom-most layer deposited on the dam face was relatively thin, but reached considerable thickness in the center of the reservoir. At Twin Valley Lake, a map of sediment thickness indicates a total volume of 458,659 cubic meters (371.8 acre-ft). At White Mound Lake, a map of sediment thickness indicates a total volume of 203,205 cubic meters (164.7 acre-ft). These values represent conservative estimates of sediment accumulation. The USDA-NRCS of Wisconsin now will use these sedimentation estimates in designing their rehabilitation programs for the two reservoirs.

Technical Abstract: Since 1948, the USDA-NRCS has constructed nearly 11,000 upstream flood control dams in 2000 watersheds in 47 states, most with a design life of 50 years. But many of these reservoirs are filling with sediment. At the direct request of the USDA-NRCS in Wisconsin, two reservoirs, White Mound Lake and Twin Valley Lake, were chosen for sedimentation surveys using an acoustic profiling system. The acoustic profiling system consists of a control module, three acoustic transducers, and a navigation system all deployed from a single Johnboat. The surveys showed three distinct acoustic layers. The upper-most layer corresponded to fine-grain, water-rich sediments. The middle layer preferentially filled the lows and channel axes, becoming thinning toward the upstream end of the lake. The bottom-most layer deposited on the dam face was relatively thin, but reaches considerable thickness in the center of the reservoir. At Twin Valley Lake, a map of sediment thickness indicates a total volume of 458,659 cubic meters (371.8 acre-ft). At White Mound Lake, a map of sediment thickness indicates a total volume of 203,205 cubic meters (164.7 acre-ft). The USDA-NRCS of Wisconsin now will use these sedimentation estimates in designing their rehabilitation programs for the two reservoirs.