Effects of breakwater on nearshore currents due to breaking waves.

This study provides a semiempirical theory of nearshore currents due to breaking waves in the presence of a shore-connected breakwater or an offshore breakwater. The effects of diffraction are studied in addition to refraction by shoaling water. The concept of radiation stresses applied to uniform longshore current and rip currents forms the starting point of the theory. Many empirical relations included in this study with regard to the surf zone are similar to, and extrapolations of, the ones used in related works. Ignoring convective inertia and lateral turbulent diffusion, the governing equations are solved numerically by the method of finite differnces. Sample results for stream functions and mean sea levels are plotted for various beach profiles or incidence angles. For the offshore breakwater, the predicted current pattern is consisten with available laboratory observations and the known tendency of tombolo formation; for the shore-connected breakwater, the computed flow pattern exhibits cells in both downwave and upwave regions. Directly relevant observations have not been found but part of the predicted features has some indirect experimetnal support. More experimental and theoretical work is suggested. (A) (Microfiche)