PART II: REVIEW OF RELATED STUDIES 



10. This chapter reviews previous studies on breaking waves to identify 

 principal variables and trends for comparison with results of the present 

 study. Main topics reviewed are breaker type, breaker index, plunge distance, 

 breaker vortex, wave decay, and runup. Previous studies concentrated on plane 

 sloping beaches; therefore, a background of these topics is necessary to 

 determine the effect, if any, of bars and artificial reefs on the various wave 

 breaking properties. The literature on breaking wave properties is vast, and 

 only the more pertinent studies are included. Original analysis of the 

 previous data is made at the end of the chapter. 



Breaker Type 



11. "Breaker type" refers to the form of a depth-limited wave at break- 

 ing and has an influence on other breaking wave properties. Although there 

 are several classifications of breaker type, it is generally accepted that 

 waves break by spilling (Figure 1), plunging (Figure 2), collapsing (Fig- 

 ure 3) , or surging. These photographs were taken during the present study, 

 and the case number is explained in Part IV. Galvin (1968) defined the fol- 

 lowing terminology; spilling breakers occur if the wave crest becomes unstable 

 and flows down the front face of the wave producing a foamy water surface; 

 plunging breakers occur if the crest curls over the front face and falls into 

 the base of the wave, resulting in a high splash; collapsing breakers occur if 

 the crest remains unbroken while the lower part of the front face steepens and 

 then falls, producing an irregular turbulent water surface; surging breakers 

 occur if the crest remains unbroken and the front face of the wave advances up 

 the beach with minor breaking. Breaker type is controlled by the bottom slope 

 and deepwater wave steepness. The deepwater steepness is defined as the ratio 

 of deepwater wave height H and deepwater wavelength L , which can be 

 calculated by linear wave theory as: 



£T 2 



L (1) 



2tt 



13 



