Table 2. Comparison of refraction coefficients for selected 

 S* and a Q values at d/(gT|) = 0.01. 



s* 



2 



4 



10 



25 



75 



Infinity 









a Q 















0° 



0.85 



0.92 



0.97 



0.98 



0.99 



1.00 



45° 



0.77 



0.82 



0.85 



0.87 



0.88 



0.88 



90° 



0.56 



0.52 



0.44 



0.36 



0.29 



0.00 





a 





a o 















0° 



























45° 



11 



16 



22 



25 



25 



25 



90° 



22 



30 



34 



39 



40 



- 



The equivalent deepwater wave height, H^, is determined from 



*K n o (3) 



where H is defined as the deepwater significant wave height. H^ should 

 also include diffraction or any other loss coefficients if they are significant. 



4. Example Problem in Wave Refraction. 



GIVEN: The wave period, T g = 10 seconds, a dominant deepwater wave angle, 

 a = 40°, and a significant wave height, H Q = 2.0 meters. 



FIND : The equivalent deepwater significant wave height, H^, and the near- 

 shore angle, a, for wind waves at a water depth of 1.0 meter. 



SOLUTION : From Table 1 the value of S* = 4 is selected for wind waves. The 

 term d/ (gT 2 .) has the value 



1^0 



C9.8 x 10 2 ) 0.001 



From Appendix A, Kp = 0.80 and a = 4.5°, so from equation (3) the deepwater 

 equivalent wave height is 



H o = K i? Ho = 0.80(2.0) = 1.60 meters 



III. NEARSHORE WAVE BREAKING MODEL 



Goda (1975a, 1975b) developed a nearshore wave height prediction model for 

 irregular waves that accounts for wave breaking, nonlinear wave shoaling, ir- 

 regular wave setup, and surf beat. A brief description of Goda's model is 

 given below. 



1. Characteristics of Goda's Model. 



Goda assumed that the deepwater significant wave height, H , and the average 

 period of the significant waves, T s , are known or can be estimated. The wave 



13 



