PART V: SUMMARY AND CONCLUSIONS 



174. The purpose of this study was to examine the macroscale features 

 of wave breaking over bars and artificial reefs in a wave tank. All major 

 experiments on wave breaking prior to this one were conducted on plane 

 beaches, and relationships for breaker indices and plunge distances developed 

 from these studies were expected to be invalid for complex profiles. The 

 present experiments demonstrated that waves break differently (their forms are 

 different) on a barred profile as compared with on a plane slope, and wave 

 breaking properties such as breaker index and plunge distance also differ. 

 Equations were developed incorporating seaward bar angle and deepwater wave 

 steepness for describing breaker indices, plunge distance, splash distance, 

 penetration distance, and vortex area. New relationships were also developed 

 for breaker index and plunge distance based on a large data set developed from 

 previous plane -slope experiments. 



Monochromatic Tests 



175. Breaker type transition values for spilling and plunging waves 

 over barred profiles were lower than the commonly accepted values given by 

 Battjes (1975) that apply to plane slopes. A strong return flow was observed 

 if seaward bar angles were steep or wave steepness was low. The return flow 

 influenced breaker type by causing the wave to "trip" over the bar, rather 

 than to break as a result of becoming unstable due to limiting depth. The 

 return flow was also strong if the shoreward bar angle was horizontal (ter- 

 raced bottom). Depth-limited or well-behaved breaking occurred for conditions 

 in which the seaward length of the bar was at least 75 percent as long as the 

 wavelength at breaking. Complex breaking occurred for conditions in which the 

 bar faces were steep, and the seaward bar length was shorter than the breaking 

 wavelength. 



176. Breaker depth index was greatly influenced by return flow, based 

 on visual observations. Breaker depth data were scattered for collapsing 

 waves and for plunging waves with large values of the surf similarity param- 

 eter. A relationship was developed for breaker depth index for plunging and 

 spilling waves having seaward bar angles less than 10 deg, which restricted 

 the analysis to depth-limited breaking (small return flow). The seaward bar 



144 



