a 0.6 



I 



I 0.4 



I 0.4 - 

 0.2 - 



1.0 



0.8 - 



jaO.6 - 



X 



X 0.4 - 

 0.2 - 



Period, T-sec 

 o 1.65 

 • 2.37 

 D 3.43 

 » 4.80 



S°. * 



S=.022 





0.2 0.4 0.6 0.8 1.0 0.2 0.4 0.6 aS 1.0 



(ij + 0)/(^b*Ob) X/Xb 



Figure 74. Wave height versus total water depth and surf zone width from 

 laboratory experiments (after van Dorn, 1976) . 



The model developed by Goda (1975) is similar to that by Battjes 

 (1975) and Battjes and Jansen (1978) except that wave breaking is assumed 

 to occur over a range of wave heights with varying probability. The choice 

 of the range was arbitrary but found to agree with both laboratory and 

 field data. This is said to ". . . represent the inherent variability 

 of breaker heights and partly compensate [for] the inaccuracy of using 

 a single wave period in the estimation of breaker height" (Goda, 1975). 

 A semiempirical nonlinear theory of wave shoaling (Shuto, 1974)"" is also 

 used in Goda's theory. His theoretical results for various beach slopes 

 and wave steepnesses versus laboratory data from an irregular wave flume 

 are presented in Figure 75. Agreement could be classed as better for low 

 steepness waves which again shoal up considerably on steep beaches before 

 breaking. In fatt, Battjes and Jansen (1978) indicated that their simpler 

 model was a first effort to be later refined by incorporation of Goda's 

 smoother cutoff criteria. 



The most recent experimental versus theoretical attempt at surf zone 

 modeling has been reported by Mizuguchi (1980). It also employed the wave 



^^SHUTO, N. , "Nonlinear Long Waves in a Channel of Variable Section," Coasta' 

 Engineering in Japan, Vol. 17, 1974, pp. 1-12 (not in bibliography). 



196 



