Effect of wave height on cross-shore solute mixing*

The investigations reported relate to a series of hydrodynamic and fluorometric tracing experiments carried out in the U.K. Coastal Research Facility, located at H. R. Wallingford Ltd. Detailed measurements were made to examine the cross-shore spreading of a solute mostly outside the surf zone for shore-normal waves combined with a long-shore current. Data arc presented that characterize the solute transport processes and quantify the contribution of wave activity to the mixing processes in the coastal zone. Results suggest that the mixing increases with the square of the wave height, H, but that this variation incorporates the effects of several mixing mechanisms. The location of the breaker point is shown to be important for near-shore mixing studies. Using analytical procedures, it has been shown that by incorporating the theoretical wave-induced velocity with realistic estimates of the turbulence, an overall cross-shore depth-averaged theoretical mixing coefficient can be determined. When compared with the measured solute concentration data, the model results show qualitative agreement.