heights. The model of Goda (1975) gives a range of breaking wave heights that 

 has compared well with measurements in the field (Thornton, Wu, and Guza 

 1985) . Although there is no distinct breaker location, the "mean breaker 

 line" gives an indication of where waves break. 



Plunge Distance 



48. The crest of a wave at breaking travels some distance shoreward and 

 strikes the water surface (Figure 7) , displacing a volume of water which also 

 travels shoreward. Galvin (1969) defined plunge distance as distance from the 

 break point to the crest touchdown point, and splash distance as distance 

 from the crest touchdown point to the splash touchdown point. Sunamura (1987) 

 adds that the plunge point is the "point where breaking waves completely 



PLUNGE POINT 



BREAK POINT 



SCALE 



SCALE 



INCHES CENTIMETERS 



Figure 7. Definition sketch of plunge distance and vortex area 



disintegrate as their crest enters the underlying water." Plunge distance is 

 usually associated with plunging waves, but the crests of spilling and col- 

 lapsing waves also plunge shoreward into the water column and, therefore, have 

 a plunge distance associated with them. 

 Review 



49. Galvin (1969) conducted laboratory experiments on three planar 

 slopes (1/5, 1/10, 1/20) and found that plunge distance Xp normalized by 

 breaking wave height was given by 



33 



