The effect of ripple types on cross-shore suspended sediment flux
S. R. Kularatne1,†, J. Doucette2,*, and C. B. Pattiaratchi11School of Civil, Environmental and Mining Engineering and UWA Oceans Institute, CRAWLEY WA 6009, Australia 2School of Earth and Geographical Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia *now at: GHD Ltd, 6705 Millcreek Drive Unit 1 Mississauga ON L5N 5M4, Canada †deceased
Received: 08 Jan 2014 – Accepted for review: 23 Jan 2014 – Discussion started: 07 Apr 2014
Abstract. Field measurements, collected at several low energy, microtidal beaches in south-western Australia were used to study the cross-shore transport and sediment resuspension over different sand ripple types. The measurements included simultaneous records of the water surface elevation, cross-shore current velocity, and suspended sediment concentration, as well as free diver measurements of the ripple dimensions. The observed ripples were classified according to their geometry and sediment suspension patterns into six categories: flat bed, post-vortex ripples, two-dimensional (2-D) ripples, two/three-dimensional (2-D/3-D) ripples, three-dimensional (3-D) ripples, and cross ripples. Flat bed conditions were observed under the highest flow mobility numbers. Post-vortex ripples were observed under slightly lower mobility numbers. The other ripple types occurred under low mobility numbers, with no significant difference in the mobility number among them. Two-dimensional ripples were observed more than the other ripple types in the presence of coarse grains. The suspended sediment concentration at ∼0.05 m above the bed was greater over steep ripples. The net cross-shore suspended sediment flux close to the seabed (at ∼0.05 m) in the swell frequency band varied over the different ripples types: onshore over a flat bed, offshore over post-vortex ripples, onshore over 2-D and 2-D/3-D ripples, and offshore over 3-D ripples. The suspended sediment flux direction over the cross ripples varied between onshore and offshore.
Kularatne, S. R., Doucette, J., and Pattiaratchi, C. B.: The effect of ripple types on cross-shore suspended sediment flux, Earth Surf. Dynam. Discuss., 2, 215-254, doi:10.5194/esurfd-2-215-2014, 2014.