HR: 17:45h
AN: H14B-07 INVITED    [Abstracts]
TI: The links between flow structure and suspended sediment over sand dunes revealed using phase coherence wavelet analysis
AU: * Parsons, D R
EM: d.parsons@see.leeds.ac.uk
AF: Univerity of Leeds, Woodhouse Lane, LEEDS, LS29JT, United Kingdom
AU: Shugar, D
EM: dshugar@sfu.ca
AF: Simon Fraser University, University Drive, Burnaby, BC V5A1S6, Canada
AU: Best, J L
EM: jimbest@uiuc.edu
AF: University of Illinois, Green St., Urbana, IL 61801, United States
AU: Hardy, R J
EM: r.j.hardy@durham.ac.uk
AF: University of Durham, University Road, Durham, DH1 3HP, United Kingdom
AU: Kostaschuk, R
EM: rkostasc@uoguelph.ca
AF: University of Guelph, Stone Road East, Guelph, ON N1G2W1, Canada
AU: Lane, S N
EM: s.n.lane@durham.ac.uk
AF: University of Illinois, Green St., Urbana, IL 61801, United States
AU: Lane, S N
EM: s.n.lane@durham.ac.uk
AF: University of Durham, University Road, Durham, DH1 3HP, United Kingdom
AU: Orfeo, O
EM: orfeo@arnet.com.ar
AF: CECOAL-CONICET, Ruta 5, 2.5KM, Corrientes, 3400, Argentina
AB: Alluvial sand dunes are characterized by their association with large-scale turbulence that may advect through the entire boundary layer thickness. Such turbulence has been held responsible for both controlling the flow-depth scaling of dunes and also the suspension of sediment above these bedforms. Here, we present field data from the Rio Paraná, Argentina, which reveals the nature of large-scale turbulence and associated sediment suspension over large alluvial sand dunes. The study uses three-dimensional velocity data obtained using a 600 kHz Teledyne RDI acoustic Doppler current profiler. Additionally, we calibrate the backscatter acoustic intensity from the instrument to allow simultaneous analysis of the temporal patterns of velocity and suspended sediment. Wavelet analysis is used to examine the nature and origin of the dune-related macroturbulence, which appears principally associated with eddy shedding and wake flapping in the dune leeside. Furthermore, phase coherence wavelet analysis shows that streamwise and vertical velocities are strongly and inversely correlated over both dune crest and trough, where flow decelerations are linked to fluid upwellings and vice versa. The inverse correlation between streamwise velocity and suspended sediment concentration (SSC), and the positive correlation between vertical velocity and SSC, indicates that fluid ejections sourced near the bed, and associated with the lee side flow, are suspending sand into the overlying flow field and are thus important mechanisms of sediment transport.
UR: http://homepages.see.leeds.ac.uk/~eardpa/index.shtml
DE: 1815 Erosion
DE: 1825 Geomorphology: fluvial (1625)
DE: 1856 River channels (0483, 0744)
DE: 1895 Instruments and techniques: monitoring
SC: Hydrology [H]
MN: 2007 Fall Meeting