« » >■ 



0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 



Time (fraction of tidal cycle), t/T 



Figure 20. Time variation of incident and transmitted 

 wave heights. 



*************** EXAMPLE PROBLEM 4*************** 



GIVEN : The same conditions given for the preceding example; however, a 

 rubble weir is used with a crest width of 15 feet and a side slope of 1 

 on 2. 



FIND : The wave height variation in the deposition basin over a tidal cycle 

 assuming the waves approach perpendicular to the weir. 



SOLUTION : For a rubble weir, equations (12) and (13) can be used with 

 a = 0.692 and b = 0.504. The transmission coefficient is given by 



-£■-(0.51- 0.11- J(l -| 



»i V h / V R J 



with R given by equation (13a) 



\1 + b? / i 



with (eq. 13b) 



5 = 



tan 

 •V L o 



Results of the calculations are given in Table 6; the solution is pre- 

 sented graphically in Figure 21. Maximum wave transmission occurs at 

 high tide with H t = 2.55 feet. Note that transmitted wave heights for 

 the rubble weir are significantly lower than transmitted wave heights for 

 the sheet-pile weir of the preceding example. 



39 



