For comparison the example calculation presented in Section II. 4 

 corresponds to an equivalent incident wave amplitude between Run 

 Numbers 470 and 469 and the transmission and reflection coefficients, 

 (eq. 78), correspondingly fall between the results of Run Numbers 470 

 and 469 listed in Table 7. 



The results obtained in Table 7 correspond, as previously stated, 

 to the simplifying assumption that the magnitude of AHg/AH-j- is unity. 

 This simplifying assumption enabled a direct determination of the width 

 of the equivalent breakwater, £g. With the ratios of runup on the 

 equivalent rectangular breakwater to runup on the trapezoidal breakwater 

 given by equation [161) the equivalent rectangular breakwater width may 

 be obtained from equation (163) , 



(1 + RJRtt 



i =2.52 ^^ ^ ^^ feet . (172) 



e ZR 



u 



Adopting as a preliminary value of Rj the value obtained in Table 7 

 and the value of Rjj given in Table 6 for a given experimental run, a 

 better estimate of the equivalent breakwater width may be obtained 

 from equation (172) provided a reasonable estimate of the runup to 

 incident wave height ratio, R^, is available. As previously mentioned 

 the runup prediction afforded by the semiempirical procedure developed 

 in Section III of this report and carried out in Section IV. 3 may be 

 expected to yield a conservative, i.e., too large, value of R^. However, 

 if this value of R^ (Table 6) is adopted the procedure developed here 

 is entirely self-contained and although slightly conservative this 

 choice of R^ is made here. Thus, with Rjj and R^ obtained from 

 Table 6 and Rj obtained from Table 7 the equivalent breakwater width 

 may now be obtained from equation (172) for each experimental run 

 performed by Sollitt and Cross (1972). 



For each experimental run listed in Tables 6 and 7 the equivalent 

 rectangular breakwater width, £g, is obtained from equation (172) and 

 the corresponding value of the linearized friction factor, f, is obtained 

 from equation (57) with I = Iq. This procedure is identical to the 

 procedure illustrated in the numerical example. Section 1 1. 4, and with 

 f obtained the values of Tj and Rj are obtained from Figures 2 and 3 

 using the appropriate value of nk £ and S^ given by equation (171). 



The computations are summarized in Table 8. By comparison with 

 the results listed in Table 7, the reflection coefficients are practically 

 identical, thus justifying the use of Rj as obtained in Table 7 in 

 equation (172) for the purpose of determining the width of the equivalent 

 breakwater. Had the values of Rj obtained in Table 8 been drastically 

 different from those given in Table 7 the computations should have been 

 repeated using the updated values of R in equation (172) . 



94 



