The model also does a good job of predicting the coefficient of 

 transmission through a permeable breakwater armored with tribars 

 tested by Davidson (1969) (Fig. 36). However, the effective trans- 

 mission by overtopping coefficient, C, is larger than would be 

 expected from Figure 15 for B/h = 0.30. Fortunately, the observed 

 transmission coefficient appears to be approaching a value of approxi- 

 mately 0.48, the limiting value of the overtopping wave transmission 

 coefficient for this breakwater predicted from equations (14) and (15). 

 The relatively high porosity of artificial armor units apparently 

 increases the size of the wave transmission by overtopping coefficient 

 over a limited range of wave heights for this case where the Stillwater 

 level is above the core and close to the breakwater crest (D. Davidson, 

 Chief, Wave Research Branch, U.S. Army Waterways Experiment Station, 

 personal communication, 1979). 



1 on 1.5 Slope 





-A-3 



= 0.692 



■r— B-l 



b = 0.504 



0.6 



0.5 



04 



■0.3 



02 - 



0.1 - 



1 > 1 1 



B/h = 0.30 

 ds/h^0 84 



1 1 



063 



1 1 



1 



Predict 

 Kt 

 Observed - 



• / 



/ ^ 

 L / 



/ ^ 

 / / 



1 



1 1 1 



ed using C=0 86 



>4 / Limiting Predicted 



1 

 t 



1 1 1 



d/gT^ = 0.0 



1 III 



0.0004 0.0006 



0.001 



0.002 



0.004 



H/gT= 



Figure 36. Wave transmission past a heavily overtopped breakwater 



with tribar armor units (laboratory data from Davidson, 1969) 



48 



