Submitted to: International Conference on Water Resources Engineering Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/1/1999
Publication Date: N/A
Interpretive Summary: Determining the amount of sediment a river carries has much practical importance. High rates of sediment movement can be used to identify unstable streams and loss of productive agricultural lands, and these high rates can have deleterious effects on both water quality and aquatic ecology. The success of measures designed by land managers to reduce erosion and conserve agricultural lands is often gauged by a reduction in the rate of sediment movement in streams and rivers. Hence, much depends on the accuracy of measuring sediment movement and on the interpretation of these data. Experiments were conducted to examine the distribution of sediment in a model river channel. A new method of predicting the mixing of sediments and pollutants in a stream was developed and tested using the information collected in this study. This new method and the new information will allow federal and other agencies to improve guidelines for river sampling programs that currently are labor intensive and very costly.
Technical Abstract: The distribution of suspended sediment is important in several areas of river and water resources engineering. The vertical distribution has been well characterized by many previous studies, while the transverse distribution has received less attention and is less well understood. Among other things, the transverse distribution affects the accuracy of total load calculations and the side-by-side testing of suspended sediment measurement techniques. An experimental program was initiated to investigate the transverse distribution of suspended sediment concentration and flow parameters over an upper stage plane bed in a recirculating laboratory flume. An isokinetic pump sampling system, acoustic Doppler velocimeter, optical backscatter probe, and an acoustic bed height probe were used to collect concomitant data on turbulent flow, suspended sediment flux, and bed topography. Sampling density was such that contour maps of suspended sediment concentration and other flow parameters were produced. Suspended sediment concentration at a given depth was found to be uniform across the tested half of the flume. A possible new method for calculating the transverse eddy diffusivity is presented, and turbulence modulation due to suspended sediment was investigated.