able to predict the decay over the island. In trial 9, the wave height decay over the bar was predicted correctly but under predicted over the island. The confused results for these two trials suggest that it is inappropriate to use the model for predicting wave height decay when co-flowing current exists by simply reducing the dissipation. If the model is to predict this condition correctly, the governing equations must be modified to incorporate terms reflecting the impact of the coexsiting current.
Return Flow Modeling
The results from the mass transport and return flow calculations confirm several conclusions in terms of bar formation and "significant" overwash. It is evident from the bed profiles and velocity distributions that the return flow is directly related to bar formation. In terms of the overwash process, it was apparent from the net flow rates that the mass transport in the upper part of the water column is able to sustain and transport suspended sediment shoreward. However, the simplistic approach taken in calculating these two flows does not correctly predict their strength. There are several probable contributing factors to this disagreement. In many cases, mass transport calculations from linear wave theory are over estimations since surf zone waves are not completely sinusoidal. This is somewhat accommodated by Svendsen (1984b) theory. He bases his mass transport equation in terms of a "surface roller" which is a simple empirical representation of a complex wave motion. The return flows computed are compared with velocity measurements that are approximately taken at mid-depth. Since the return flow in reality varies with depth, the calculated values may not necessarily correspond exactly with the measurements. A more thorough series of tests measuring wave height, set-up, and velocity profiles would permit the use of a return flow model for predicting the exact nature of the mean currents in the surf zone.