Vertical structure of cross-shore currents from wind-induced setup



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Most of the storm surge models presented in the literature are vertically averaged and calculate only the sea-surface elevation and mean flow. Whereas these models may be adequate for predicting storm surge heights for flooding purposes, they neglect the vertical structure of the flow and the boundary shear stress, which are both critical for predicting cross-shore sediment transport. The steady and horizontally uniform equations of motion are used here to compute the sea-surface slope, the vertical structure of the cross-shore currents, and the boundary shear stress in a shallow wind dominated environment. The steady state model developed here balances the pressure gradient and the stress divergence, resulting in sea-surface slope and associated pressure gradient in the opposite direction of the wind, thus inducing a reversal in the currents near the bed. The Reynolds stress is modeled with a depth-dependent turbulent diffusion coefficient so that both the boundary shear stress and the velocity field are calculated, avoiding the need to set a bottom drag coefficient. Input parameters for this model are simply the wind stress, the water depth, and z0, the bed roughness parameter. A sensitivity test of the model results to various values of z0 indicates that large changes in z0 cause only minor differences in the surface slope, and moderate differences in the velocity field and boundary shear stress. Given the sediment size distribution and the small scale morphology of the bed, a reasonable estimate of z0 may be obtained and the above uncertainty will be nearly eliminated.

Additional Publication Details

Publication type:
Conference Paper
Publication Subtype:
Conference Paper
Vertical structure of cross-shore currents from wind-induced setup
Year Published:
Publ by ASCE
Publisher location:
New York, NY, United States
First page:
Last page:
Number of Pages:
Conference Title:
Proceedings of a Specialty Conference on Quantitative Approaches to Coastal Sediment Processes
Conference Location:
Seattle, WA, USA
Conference Date:
25 June 1991 through 27 June 1991