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Laboratory investigation of bedform dynamics and resuspension of sandy sediments at field scale

Williams, J.J.; Bell, P.S.. 2006 Laboratory investigation of bedform dynamics and resuspension of sandy sediments at field scale. Journal of Coastal Research, SI39. 810-815.

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Abstract/Summary

Fundamental to the problem of predicting non-cohesive sediment transport is the incomplete understanding of the interactive feedback triad linking sediment resuspension with the hydrodynamics of natural waves and wave-generated bedforms. To address aspects of this problem measurements of sediment entrainment by random waves over rippled sand beds have been obtained using approximately co-located acoustic instruments in a large wave flume. Measured velocity, normal and Reynolds stress profiles conform to theory and to numerical model predictions. Wave-generated ripples classified as suborbital were present in most wave conditions examined. Improved empirical expressions to predict the height and wavelength of the suborbital ripples are presented. A time lag that increased with distance above the bed was observed within the suspended sediment concentration field. This was attributed to enhanced turbulence production at the bed by wave-related vortex shedding by bedforms. The magnitude of turbulence production by wave groups was related to the size and number of waves in a group and resulted in larger observed total suspended load values than those associated with single waves of similar height. Owing to the stochastic nature of the resuspension process, variability in suspended sediment concentration values for waves of comparable size was O (50%). A time delay was observed in the maximum suspended sediment concentration after the passage of the largest wave in a group. The shape of wave period-average suspended sediment concentration profiles, C-profiles, were found to change from approximately exponential to Rouse-like during passage of a wave group.

Item Type: Publication - Article
Programmes: POL Programmes
ISSN: 0749-0208
NORA Subject Terms: Marine Sciences
Date made live: 31 Aug 2012 13:17
URI: http://nora.nerc.ac.uk/id/eprint/19456

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