Influence of infiltration into the bed on suspended sediment under waves

Obhrai, C., Nielsen, P. and Vincent, C. E. (2002) Influence of infiltration into the bed on suspended sediment under waves. Coastal Engineering (45). pp. 111-123.

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Abstract

The effect of percolation through a permeable bed on sediment suspension under regular waves was examined in a laboratory wave tank (28 m×1 m×1 m), using acoustic backscatter sensors to make rapid (3 Hz) suspended sand profile measurements (0.005 m vertical resolution). Waves of 1.7 s period and heights ranging from 0.14 to 0.185 m were used over sand with a D50 of 255 μm. Infiltration velocities of 0–5.0×10−4 m s−1 were used. With percolation through an initially flat bed, ripple development was suppressed, particularly at lower wave heights; ripples took longer to form and were more three-dimensional. Suspension was also suppressed. The total suspended load was correlated with Shields number (at the 1% significance level) when the Shields number was modified to take account of both the infiltration [Nielsen, P., 1997. Coastal groundwater dynamics. Proceedings of Coastal Dynamics, American Society of Civil Engineers, pp. 546–555] and ripple steepness [Coastal Eng. (1986) 23]. The ripple steepness was found to be the most important factor relating to the reduction in the total suspended loads. The influence of infiltration on time-averaged concentration profiles over equilibrium ripples was investigated by switching the percolation on and off for 5-min periods. The total suspended loads were reduced by up to 50% with percolation on. These results suggest that fluctuation of the water table and drainage within a beach will affect sediment transport and ripple dynamics, and that for sand of 0.25 mm, percolation will tend to reduce suspension and transport.

Item Type:	Article
Faculty \ School:	Faculty of Science > School of Environmental Sciences
UEA Research Groups:	Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences Faculty of Science > Research Groups > Geosciences Faculty of Science > Research Groups > Marine and Atmospheric Sciences (former - to 2017)
Depositing User:	Rachel Snow
Date Deposited:	06 Apr 2011 14:09
Last Modified:	23 Jul 2024 12:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/28263
DOI:	10.1016/S0378-3839(02)00041-8

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