Southeastern Section - 54th Annual Meeting (March 17–18, 2005)

Paper No. 1
Presentation Time: 8:00 AM-12:00 PM

CHANNEL-BED CHARACTERISTICS IN THE MISSISSIPPI RIVER AT THE RED EYE CROSSING


MILLER, J. Zachary1, BOWLER, Adrienne P.1 and LECLAIR, Suzanne F.2, (1)Department of Earth and Environmental Sciences, Tulane University, 6823 St Charles ave, Dinwiddie Hall, New Orleans, LA 70118, (2)Department of Earth and Environmental Sciences, Tulane Univ, 6823 St Charles ave, Dinwiddie Hall, New Orleans, LA 70118, jmiller1@tulane.edu

Recent developments in sediment continuity models have demonstrated the relationships between dune morphology, especially trough-scour depth, and the composition and rate of sediment transport. The probability distribution of bed elevation over a train of dunes is a key element of these new depth-continuous models. In the Mississippi, trains of multi-scale dunes are observed superimposed on, or adjacent to, each other as they migrate over channel-scale bedwaves. The analysis of the probability distribution of bed elevation of selected stretches of the river is a powerful tool for estimating (quantitatively) the height of different groups of dune and assessing (qualitatively - -for now) the relative sediment-transport conditions. We surveyed a major sailing line of the Mississippi River several times, recording bed elevations with a 1MHz transducer and high-precision echo sounder, and flow-velocity fields with an ADCP. Results show that the ratio of dune height/flow depth is low (about 0.1) for the largest dunes in the thalweg and even lower (<0.06) for the small superimposed dunes. This may be due to the complexity of the flow field and/or grain size (fine sand). Future research will include relating the probability distribution to vertical sorting, velocity profiles and estimates of sediment transport from acoustic measurements, as well as associated stratigraphy.