B/h = 0.61 



SYMBOL d/gT2 



1.0 - 



0.8 



0.6 



0.4 



0.2 



0.0001 



0.001 

 H/gT2 



ftJ" 



0.01 



Figure 7-50. Wave transmission through a rubble-mound breakwater (d /H 

 0.69) . ® ^ 



e. Estimating Wave Transmission Coefficients for Permeable Breakwaters . 

 There are several approaches to estimating transmission coefficients for 

 permeable breakwaters . 



(a) One approach is to use results from previous model studies. 

 Figure 7-52, for example, gives transmission and reflection coefficients 

 for a breakwater with a flat seaward slope that might be built in 

 moderate-depth water. Another example, for a structure composed primarily 

 of armor that would be built in relatively shallow water, is illustrated 

 in Figure 7-53. Several examples showing the effects of structure height 

 and width are given in Figures 7-54 and 7-55. 



(b) Another approach is to use the computer program available in 

 Seelig (1979). This program uses the model of Madsen and White (1976), 

 together with the overtopping model in Section II, 3, c. Wave Transmission 

 by Overtopping, above, to estimate local transmission coefficients. The 

 advantages of the program are that it can be used to make a preliminary 

 evaluation of a large number of alternative structure designs, water 

 levels, and wave conditions quickly and at low cost. Example program 

 predictions are shown in Figure 7-56. 



7-82 



