4.0 - 9.25m (36) 



Galvin noted that Xp/H b values reached as high as 4.5 and the average was 

 3.0. Splash distance X s was approximately the same as the plunge distance. 



50. Weisher and Byrne (1979) filmed breaking waves from a pier at 

 Virginia Beach, Virginia, and measured the plunge distance. Average Xp/H b 

 values were 5.9, and values ranged from 1 to 10 . 



51. Singamsetti and Wind (1980) collected plunge distance data in the 

 laboratory and found Xp/H b ~ 3 on a 1/5 slope with a range from 4 to 8 on a 

 1/40 slope. Singamsetti and Wind found that Equation 36 underestimated their 

 data by approximately 50 percent. 



52. Visser (1982) conducted laboratory experiments in a basin to mea- 

 sure longshore current. His measurements include plunge distance. Waves were 

 generated at an angle to a 1/20 slope, and Visser found Xp/H b ~ 6 . 



53. Larson and Kraus (1989) tested Equation 36 to predict plunge dis- 

 tance, which was a quantity required as input to a numerical model of beach 

 profile change. Equation 36 was found to underestimate Xp for steep bar 

 face slopes. Based on results of Singamsetti and Wind (1980), Larson and 

 Kraus used a constant value of X p /H b = 3 in their numerical model. 

 Summary 



54. Plunge distance data are limited, and only one relationship has 

 been given to estimate Xp . However, Equation 36 (Galvin 1969) gives values 

 of Xp/H b of 4 or less, and observations have shown Xp/H b as high as 10 in 

 the field and 8 in the laboratory. These large differences indicate a need 

 for a more reliable relationship to predict plunge distance. 



Breaker Vortex 



55. The cavity of entrapped air created by the overturning crest of the 

 wave at the plunge point is called the breaker vortex. The cross -sectional 

 area of the vortex A<, is shown in Figure 7 . Air and water mix as the vortex 

 penetrates the water column. On a movable bed bottom, sediment is suspended, 

 which either is transported by currents or settles to the bottom as the vortex 

 loses angular momentum, decelerates, and vanishes. 



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