2.8 



2.4 - 



2.0 - 



«l.6 



E 

 I 



^1.2 

 0.8 

 0.4 







4 1 4 



4 pr~T 







4 1 



7I7 BWl 







4 7^1.4 ds/h=I.O 

 11 26 W 14 7 





4 



14 18 2^ 21 26 





7 



\ 

 7 4 22 14 264 





7 



4 26 11 : 4 18 4 4 





4 7 



1 32 32 17 26 4 114 





7 7 



23 180 J 25 28 11114 4 





4 32 



/ 26 18 7 4 4 





4 18 4 ZJ 



■^'' 7 18 4 INCIDENT 



7803270952 





21>4^4 4 



7 

 1 1 1 1 



2.8 



2.4 



2.0 - 



1.6 - 



1.2 - 



0.8 





10/ 6 









10/ 8 



"^ 



T 





6 U 10 

 6 6 jlO 10 









Z< 16 

 8 6 10 6 20 









10 6 16/16 16 10 









10 16 16/16 18 8 





6 





10 29 34 111 10 18 6 16 





E 





34 34 39(24 20 8 24 



6 







10 24 6 39) 20 10 20 

 10 6 10 \yiQ 20 16 



8 







29 3^4 16 6 





TRdNSniTTED 

 7803270952 



6 b, 



1 1 1 





1 1 



0.4 



0.8 1.2 

 T/Tp 



1.6 



2.0 



0.4 0.8 1.2 

 T/Tp 



1.6 



2.0 



Figure 26. Sample incident and transmitted joint distributions of wave 

 height and period. 



heights and periods (Goda, 1978) was observed to be 0.13 < r(H,T) < 0.26 for 

 the incident wave conditions tested with approximately the same values for 

 transmitted waves. The major difference between observed and transmitted 

 joint distributions of height and periods is that the mean period of smaller 

 waves is lower for the transmitted waves (Fig. 26) than for the incident waves, 



2. Wave Transmission and Reflection for Permeable Breakwaters . 



a. Observed Trends in Transmission and Reflection Coefficients . As a 

 wave approaches and interacts with a rough permeable breakwater the sequence 

 of action is similar to that for an impermeable breakwater, but with important 

 differences. First, some of the wave energy moves through the permeable break- 

 water and this flow through the porous medium may dissipate a significant 

 amount of wave energy. Second, because the breakwater absorbs some of the 

 wave energy and water, the runup and reflection coefficients on a rough 

 permeable breakwater are less than for the same wave condition on a similar 

 smooth impermeable structure. If the runup level exceeds the height of the 

 structure, wave transmission by both overtopping and transmission through the 

 structure will contribute to the overall transmission coefficient, Ky (Fig. 

 27). 



39 



