Physical and stratigraphic characteristics of sediments impounded within a flood control reservoir in Oklahoma

Since 1948, the USDA-NRCS has constructed almost 11,000 upstream flood control dams across the U.S., and many of the reservoirs are filling with sediment as they near the end of their 50-year economic life. Removing the sediment remains a viable option for dam rehabilitation, yet little information exists on the physical and spatial characteristics of sediments impounded by these small reservoirs. To this end, the characteristics of sediment impounded in a flood control reservoir in Oklahoma were defined. Ten continuous, undisturbed sediment cores were obtained using vibracoring equipment, and the subsurface sediment distributions were imaged using an acoustic profiling system. Stratigraphic analyses showed that silt- and clay-sized sediments dominate the deposits within the reservoir pool, relatively high silt and clay contents were associated with relatively high total organic contents (about 2% by mass), and sand deposition was restricted to tributary and surface erosion sources. Stratigraphic correlation of sediment units across the reservoir was possible using the acoustic profiling results, pre-impoundment sediment was discriminated from post-construction deposition, and a map showing total thickness of deposited sediment was constructed. These results provide detailed information on sedimentation characteristics within a typical USDA-NRCS flood control reservoir. Moreover, the methods used herein were shown to effectively quantify reservoir sedimentation, which is critically important in reservoir management and rehabilitation programs nationwide.