Assessing sedimentation issues within aging flood control reservoirs in Oklahoma

Since 1948, the USDA-NRCS has constructed nearly 11,000 flood control dams across the United States, and many of the reservoirs are rapidly filling with sediment. To rehabilitate these structures, the impounded sediment must be assessed to determine the volume of accumulated sediment and the potential hazard this sediment may pose if reintroduced to the environment. An assessment of sedimentation issues within two reservoirs, Sugar Creek No. 12, Hinton, Oklahoma, and Sergeant Major No. 4, Cheyenne, Oklahoma, is presented. Sediment cores obtained using a vibracoring system were composed of alternating layers of gravel, sand, silt, and clay. Stratigraphic analysis coupled with ¹³⁷Cs dating techniques enabled the discrimination of pre-construction sediment from post-construction deposition. An acoustic profiling system was unencumbered by the relatively shallow water depth at Sugar Creek No. 12 and the seismic horizons agreed well with the sediment core data. Total sediment volume determined from the acoustic survey and the sediment core data for comparable areas differed by only 1.4 percent. The seismic profiling system worked well in the relatively deeper lake of Sergeant Major No. 4 and showed good correspondence to the collected core data. Detailed chemical analyses showed that overall sediment quality was good at both locations and that chemical composition was spatially invariant. Implementation of these techniques will aid action agencies such as the USDA-NRCS in their assessment and effective management of aging flood control reservoirs.