5 Conclusions 



Results from a laboratory study of wave breaking on an ebb current at an 

 idealized inlet are presented. The measurements show increased wave shoaling 

 and breaking in the presence of the ebb current, as is expected from the conserva- 

 tion of waves and linear wave theory. The measurements also show a down- 

 shifting of the peak frequency (peak period became longer as much as 16 per- 

 cent). Energy was dissipated at the peak and higher frequencies of the spectra. 

 Dissipation rates calculated from the measurements were proportional to wave 

 height. 



Dissipation algorithms were examined with the data. Whitecapping formula- 

 tions (Komen, Hasselmann, and Hasselmann 1984; Komen et al. 1994; Resio 

 1987), which are strongly dependent on wave steepness, generally underpredicted 

 dissipation. Application of Resio's whitecapping formulation gave a correlation 

 coefficient of 0.46 for predicting dissipation through the idealized inlet. The 

 Battjes and Janssen breaking algorithm worked well for predicting wave height 

 through the idealized inlet, despite considerable scatter in the dissipation predic- 

 tion {/ = 0.25). A relationship for dissipation as a function of wave height 

 squared gave improved agreement between calculated and predicted dissipations 

 (/^ = 0.78), but no substantial improvement over the Battjes and Janssen formula- 

 tion for modeling the wave height. 



A dissipation function or breaking criterion applied at a coastal inlet must 

 include relative depth and wave steepness, as well as wave-current interaction. 

 Depth-limited breaking is more important for longer period waves and steepness 

 for shorter period waves. 



The next phase of experiments in the idealized inlet includes construction of an 

 ebb shoal and extension of the measurement array farther offshore. Breaking 

 over the ebb shoal, wave blocking, scaling relationships, and oblique wave 

 incidence will be studied. 



28 Chapters Conclusions 



