4.0 



3.0 



2.0 



1.0 



(Hmo)t (ft) 



0.0 







D 





D 





□ 



i 



i 



12 



14 



16 18 



(Hmo)i (ft) 



20 



22 



Figure 19. Wave transmission, Plan 3, +0.9 ft mllw 



Transmission Test 



37. It was uncertain whether the excessive wave heights on the harbor 

 side were mostly by transmission through the structure or by wave overtopping. 

 In order to separate transmitted and overtopped energy, a sheet of metal, bent 

 at an upward angle, was mounted on the crown of the Plan 3 structure, and 

 three wave conditions were run. The sheet metal rested flat on the breakwater 

 crown to allow waves to overtop the crown, but the angled section prevented 

 overtopped waves from entering the harbor side. This configuration allowed 

 waves to overtop the structure as they would under normal conditions, but 

 prevented additional hydrostatic pressure to build on the seaward side, which 

 could force energy through the structure. Therefore, only waves transmitted 

 through the breakwater were measured on the harbor side. 



38. It is generally felt that the longer wave periods transmit more 

 wave energy; thus, wave heights using the longest wave periods within each of 

 the designated design groups (Table 1) were tested. They were 16-ft, 18-sec; 

 18-ft, 18-sec; and 20 ft, 16 -sec waves at a swl of +7 ft mllw. The results 

 are listed in Table 6, and transmitted wave height is plotted versus incident 

 wave height in Figure 20. The tests indicated that K t ~ 0.20 for waves 



28 



