PHYSICAL AND STRATIGRAPHIC CHARACTERISTICS OF SEDIMENTS IMPOUNDED WITHIN A FLOOD CONTROL RESERVOIR IN OKLAHOMA

Abstract

Since 1948, the USDANRCS has constructed almost 11,000 upstream flood control dams across the U.S., andmany of the reservoirs are filling with sediment as they near the end of their 50year economic life. Removing the sedimentremains a viable option for dam rehabilitation, yet little information exists on the physical and spatial characteristics ofsediments impounded by these small reservoirs. To this end, the characteristics of sediment impounded in a flood controlreservoir 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 thatsilt and claysized sediments dominate the deposits within the reservoir pool, relatively high silt and clay contents wereassociated with relatively high total organic contents (about 2% by mass), and sand deposition was restricted to tributaryand surface erosion sources. Stratigraphic correlation of sediment units across the reservoir was possible using the acousticprofiling results, preimpoundment sediment was discriminated from postconstruction deposition, and a map showing totalthickness of deposited sediment was constructed. These results provide detailed information on sedimentation characteristicswithin a typical USDANRCS flood control reservoir. Moreover, the methods used herein were shown to effectively quantifyreservoir sedimentation, which is critically important in reservoir management and rehabilitation programs nationwide.