Hb 

 Ho 



= 0.53 



■ Ho ■ 

 . Lo . 



-0.24 



392. Values of the empirical multiplicative coefficient and exponent in 

 the regression equation are very similar to those obtained by Battjes as 

 reported by Singamsetti and Wind (1980) and Sunamura (1981b) based on small- 

 scale laboratory data. In Figure 53, data from the CRIEPI experiments are 

 plotted together with Equation 24. The wave model uses Equation 24 to predict 

 the breaking condition, for which the bottom slope is evaluated over a 

 distance one third of the local wavelength seaward of the break point. 



393. The breaking wave height on the movable bed bottoms of the CE and 

 CRIEPI experiments normalized by the deepwater wave height was related to the 

 deepwater wave steepness. An average breaking wave height was used for each 

 case, making up a total of 32 cases for the analysis. Regression analysis 

 with the deepwater wave steepness explained 80 percent of the variation in the 

 data, leading to the equation 



(25) 



394. Inclusion of initial beach slope in the regression equation did 

 not improve predictability, probably due to the significant change in slope 

 that occurred seaward of the break point during the course of wave action. 

 Figure 54 illustrates the prediction from Equation 25 and the data points from 

 the studied cases. Data points associated with different initial slopes have 

 been plotted with different symbols. Note that the value of the empirically 

 determined exponent in Equation 25 is close to that which is obtained with 

 linear wave theory for shoaling of normally incident waves from deep water to 

 breaking (-0.20; see Komar and Gaughan 1973). 



Breaker decay model 



395. Several numerical models have been developed for describing wave 

 height decay in the surf zone (e.g., Battjes and Janssen 1979, Dally 1980, 

 Mizuguchi 1981, Svendsen 1984). All contain empirical parameters whose values 

 have to be established by calibration against measurements. The wave model 

 proposed by Dally (1980) and further discussed by Dally, Dean, and Dalrymple 

 (1985a, 1985b) was chosen for use here since it has been verified with both 

 laboratory data (Dally 1980) and field data (Ebersole 1987). Furthermore, the 



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