Velocity Moments in Nearshore
Publication: Journal of Waterway, Port, Coastal, and Ocean Engineering
Volume 111, Issue 2
Abstract
Recent models for nearshore sediment transport suggest the importance of various moments of the fluid velocity field in determining transport rates. Using two days of field data from a low slope beach with moderate wave heights some low order, normalized moments are compared to results from simple monochromatic and linear random wave models. Not surprisingly, the random wave model is substantially more accurate than the monochromatic model. However, wave breaking and other nonlinearities introduce effects not explained by either formalism. The observed cross‐shore velocity variance is decomposed into wind wave and surf beat components. The surf beat contribution is maximum at the shoreline, while the wind wave component is maximum offshore. The total variance is nearly constant across the surf zone. This observation contradicts assumptions that are fundamental to many models of surf zone dynamics and sediment transport. Analysis of a wider range of wave conditions is needed to assess the generality of these preliminary results. Using field data in the sediment transport model of Bailard (1981) suggests that both bed and suspended load are significant cross‐shore transporting mechanisms on this low slope beach with moderate wave energy. Asymmetries in the oscillatory wave field tend to transport sediment shoreward, while the interaction of the offshore mean flow with waves produces an offshore sediment flux.
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References
1.
Bagnold, R. A., “Mechanics of Marine Sedimentation,” The Sea: Ideas and Observations, Vol. 3, Interscience Publishers, New York, N.Y., 1963, pp. 507–528.
2.
Bagnold, R. A., “An Approach to the Sediment Transport Problem from General Physics,” U.S. Geological Survey Professional Paper, No. 422‐I, U.S. Government Printing Office, Washington, D.C., 1967, 37 pp.
3.
Bailard, J. A., and Inman, D. L., “An Energetics Bed Load Model for a Plane Sloping Beach, Part 1: Local Transport,” Journal of Geophysical Research, Vol. 86, No. C3, 1981, pp. 2035–2043.
4.
Bailard, J. A., “An Energetics Total Load Sediment Transport Model for a Plane Sloping Beach,” Journal of Geophysical Research, Vol. 86, 1981, pp. 10938–10954.
5.
Battjes, J. A., “Computations of Set‐Up Longshore Currents, Run‐Up Overtopping Due to Wind‐Generated Waves,” Report 74‐2, Delft University of Technology, Delft, The Netherlands, 1974.
6.
Bitner, E. M., “Non‐Linear Effects of the Statistical Model of Shallow‐Water Wind Waves,” Journal of Applied Ocean Research, Vol. 2, 1980, pp. 63–73.
7.
Bowen, A. J., “Simple Models of Nearshore Sedimentation; Beach Profiles and Longshore Bars; in the Coastline of Canada,” Geological Survey of Canada, 1980, pp. 21–30.
8.
Bowen, A. J., “Nearshore Velocity Measurements and Beach Equilibrium,” Canadian Coastal Conference, 1980, pp. 1–10.
9.
Cunningham, P. M., Guza, R. T., and Lowe, R. L., “Dynamics Calibration of Electromagnetic Flow Meters,” IEEE Oceans, Vol. 79, 1979, pp. 298–301.
10.
Flick, R. E., Guza, R., and Inman, D. L., “Elevation and Velocity Measurements of Laboratory Shoaling Waves,” Journal of Geophysical Research, Vol. 86, No. C5, 1981, pp. 4149–4160.
11.
Guza, R. T., and Thornton, E. B., “Longshore Current Variability,” Proceedings of the International Coastal Engineering Conference, ASCE, 1979, pp. 756–775.
12.
Guza, R. T., and Thornton, E. B., “Local and Shoaled Comparisons of Sea Surface Elevations, Pressures and Velocities,” Journal of Geophysical Research, Vol. 85, 1980, pp. 1524–1530.
13.
Guza, R. T., and Thornton, E. B., “Swash Oscillations on a Natural Beach,” Journal of Geophysical Research, Vol. 87, 1982, pp. 483–491.
14.
Higgins, A. L., Seymour, R. J., and Pawka, S. S., “A Compact Representation of Ocean Wave Directionality,” Journal of Applied Ocean Research, Vol. 3, 1981, pp. 105–112.
15.
Huntley, D. A., and Bowen, A. J., “Comparison of the Hydrodynamics of Steep and Shallow Beaches,” Proceedings, Symposium on Nearshore Sediment Dynamics and Sedimentation. Southampton 1973, J. R. Hails and A. Carr, eds., Wiley, London, England, 1975, pp. 69–109.
16.
Inman, D. L., and Bagnold, R. A., “Littoral Processes,” The Sea: Ideas and Observations, Vol. 3, Interscience Publishers, New York, N.Y., 1963, pp. 529–533.
17.
Komar, P. D., and Inman, D. L., “Longshore Sand Transport on Beaches,” Journal of Geophysical Research, Vol. 75, No. 30, 1970, pp. 5914–5927.
18.
Longuet‐Higgins, M. S., “Mass Transport in Water Waves,” Phil. Transactions of the Royal Society (London), Series A, Vol. 245, 1953, pp. 535–581.
19.
Thompson, E. F., “Shallow Water Surface Wave Elevation Distributions,” Journal of the Waterway, Port, Coastal, and Ocean Division, ASCE, Vol. 106, 1980, pp. 285–289.
20.
Thornton, E. B., and Guza, R. T., “Phase Speeds and Energy Saturation Measured on a Natural Beach,” Journal of Geophysical Research, Vol. 87, 1982, pp. 9499–9508.
21.
Thornton, E. B., and Guza, R. T., “Longshore Currents and Bed Shear Stress,” Directional Wave Spectra Applications, ASCE, 1982, pp. 147–164.
22.
Wright, L. D., Guza, R. T., and Short, A. D., “Dynamics of a High‐Energy Dissipative Surf Zone,” Marine Geology, Vol. 45, 1982, pp. 41–62.
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Published In
Journal of Waterway, Port, Coastal, and Ocean Engineering
Volume 111 • Issue 2 • March 1985
Pages: 235 - 256
Copyright
Copyright © 1985 ASCE.
History
Published online: Mar 1, 1985
Published in print: Mar 1985
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