activities, such as numerical models for simulating beach profile change and 

 studies of breaker wave height decay. Measurements of breaking wave proper- 

 ties over bars and offshore berms and reefs on a microscale are also essen- 

 tial, but are left to future work. 



7. The experiment was conducted in a wave tank containing a 1 on 30 

 concrete slope. Bars and reefs of fixed geometry and constructed of wood were 

 placed on the slope to investigate wave breaking under natural conditions with 

 bars and engineered conditions with artificial reefs. Wave breaking was exam- 

 ined over a range of bar and reef geometries, wave periods, and wave heights 

 for a fixed water level. In nature, breaking waves change the geometry and 

 size of the bar, and these changes feed back to alter the breaking wave char- 

 acteristics. Bars subjected to steady, monochromatic waves and fixed water 

 levels develop an equilibrium profile (Kraus and Larson 1988; Larson, Kraus , 

 and Sunamura 1989; Larson and Kraus 1989). However, in reality bars are 

 subjected to irregular waves and fluctuating water levels, so an equilibrium 

 profile is only approached and never reached. Consequently, bars and waves 

 are continuously interacting with each other. The present study focuses on 

 the control that bars and artificial reefs exert on breaking waves. 



8. This study pertained only to macro -features of wave breaking; micro- 

 features of bottom velocity, turbulence, and bottom shear stresses were not 

 addressed. Also, the macro -features of wave celerity, return flow velocity, 

 and the important influence of wind on wave breaking, as discussed by Douglass 

 and Weggel (1989), were not obtained in this study. Although return flow was 

 not measured, qualitative observations and implications of the return flow are 

 discussed in Part IV. Data are available from the experiments to examine wave 

 celerity, but because of the considerable data analysis involved, it is left 

 for future work. 



Content 



9. Part II contains a review on essential properties of breaking waves, 

 including breaker type, breaker indices, reflection, plunge distance, wave 

 decay, and runup. Part III describes the design and execution of the experi- 

 ment, and Part IV presents major results. Conclusions and recommendations 

 for future study are given in Part V. Wave data from previous studies used in 

 the present study and data generated in the present study are listed in 



11 



