The wave transmission coefficients, C t , versus the ratio of wavelength, 

 L, to breakwater width, W, are presented in Figure 201. In wavelengths 

 ranging from 30 to 55 feet, the steep waves (steepness of 0.055 to 0.075) 

 had a higher transmission coefficient than did the waves of relatively small 

 steepness (steepness of 0.022 to 0.030). The two curves coincided at a wave- 

 length of about 60 feet; in wavelengths ranging from 65 to 90 feet, the rela- 

 tionship was opposite of that for the smaller wavelengths. This phenomenon is 

 explained by the steep waves breaking partially on the beach and partially 

 spilling over the top of the beach, causing dynamic pressure fluctuations and 

 considerable mixing of the water to a depth of about 15 feet. This action, 

 consequently, interfered with the orbital motion of the incident waves. 

 Conversely, relatively small-amplitude waves broke completely on the beach. 

 For a large-amplitude wave, part of the energy dissipation occurred in break- 

 ing and part occurred in the mixing process; for a relatively flat wave, all 

 the energy dissipation was accomplished in the breaking process. In addition, 

 the longer waves transmitted wave energy under the structure. The longer 

 waves also caused a horizontal motion of the floating breakwater, and the 

 vertical wall acted as a wave generator on the lee side. 



Ratio of Wavelength-to-Breakwater Width, L/W 

 I 2 



0L9 





© 



Hi/L «/* 

 STEEP WAVES 0.055 - 0.075 / 



0.8 



- 



o 



FLAT WAVES 0.022 - 0.031 Vo 

 STEEP SLOPE) MODIFIED / 

 FLAT SLOPE J MODEL c±r~ c *-g' 



0.7 







1 v / 



0.6 



- 





?T\ / 



0.5 



- 





// 



0.4 



- 





jk if 



0.3 

 0.2 



- 





p • \ A 



/o° €> \ J/ 



0.1 







PROTOTYPE LENGTH = 43.5 Ft 











I 1 1 1 1 1 1 



20 30 



40 50 60 



Wavelength, L 



70 



(ft) 



80 



90 100 



Figure 201. Effect of incident wave steepness, H^/L, and 

 relative breakwater width, L/W, on transmis- 

 sion coefficient, C t , for slope-floating beach 

 with pontoons (after Chen and Wiegel, 1969). 



259 



