Author
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Bennett, Sean |
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VENDITTI, JEREMY - UNIV. OF S. CALIFORNIA |
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Submitted to: Management of Landscapes Disturbed by Channel Incision Stabilization Rehabi
Publication Type: Proceedings Publication Acceptance Date: 5/1/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Eroded sediments and associated chemicals derived from agricultural areas due to farming practices are continually being introduced to streams and rivers. The movement of these contaminated solids and their sites of deposition can have detrimental effects on water quality, ecology, and river flow processes such as conveyance and the severity of floods. Transport of suspended solids is strongly affected by the presence of rive bed topography such as sand dunes and gravel bars. A laboratory study was conducted to determine how the characteristics of the flow can be related to the movement of sediment over dunes. This study used a laboratory channel, 0.1 mm diameter sand, rigid dune bedforms fixed in place to the bottom of the flume, and special instruments to measure the turbulence of the flow and the amount of sediment carried in suspension. Preliminary results show that the fluctuations in volumetric concentration of suspended sediment do not correlate well with the turbulent mixing within the flow. This may be due, in part, to the design of the experiment and the type of data analysis employed, and further work is on-going. The goal of this research is to provide better predictive technologies for total sediment load in streams and rivers, information which is important to other federal agencies which assess sedimentation problems such as loss of ecological habitat and increased flood potential. Technical Abstract: Measurements of fluid turbulence and suspended sediment concentration were obtained concomitantly over fixed dunes in a laboratory channel using acoustic Doppler and electromagnetic current meters and optical backscatter probes. Results show that: (1) the correlation of Reynolds stress with turbulent velocity and turbulent kinetic energy are similar to clear-water, flat-bed flows; (2) weak correlation is observed for turbulent fluctuations in the downstream velocity component over distances close to the mean flow depth; (3) suspended sediment fluxes do not correlate well with turbulence, and; (4) the balance between the upward sediment flux due to turbulence diffusion and downward flux due to gravitational settling is not applicable in flows over dunes |
