refraction coefficient, K^, is given by equation (7-12) of Wiegel (1964) 



cos a \i/2 



'^y 



K^Mttt-^I (C-15) 



The depth, d, the period, T, and the angle a are measured in the 

 laboratory studies. The deepwater approximation for the wavelength, L^ = 

 5.12 T^, obtains d/L, and hence L, from d/L^ and Wiegel's tables. Then, 

 a^ can be calculated from 



sin clq = - — sin a (C-16) 



and aj can be calculated from 



Lj - 

 sm % = — sm a^ (C-17) 



so that equation (C-15) can be evaluated to give the refraction coefficient, 

 K^, at the breaker position. 



To summarize, 23 field data points were used to derive equation (C-1), the 

 relation between Q and P^g . The values for P£g for the nine data points 

 taken from Watts (1953) and Caldwell (1956) were computed from equation (C-2), 

 using values of significant wave height, period, and direction, as estimated 

 by Watts (1953) and Caldwell (1956). The values of Pis for the 14 data 

 points taken from Komar (1969) were computed from equation (C-10) whose input 

 comes from the mean square water elevation, <ti^>> obtained from the wave 

 sensor records, the use of linear theory, and equations (C-11) and (C-9) to 

 get the a^j. It is again emphasized that only field data were used to compute 

 equation (C-1) , and the equations for P|^g require the use of the observed 

 significant height. 



34 



