> 



wave height, H^; the wavelength, L, and transmission coefficient, 

 K+, can be determined. The wavelength, L, can be determined for a 

 given wave period, T, and water depth, d, by use of Figure 2 or the 

 equation - 



■■-£*«*(¥)• (1) 



The transmission coefficient, K^, can be determined using the following 

 relationship: 



Knowing the wavelength, L, and the transmission coefficient, K^, 

 the required breakwater width can be determined from Figure 3. Since the 

 overall efficiency of the breakwater decreases as the breakwater width 

 increases, the width determined from Figure 3 may be too small if the 

 indicated breakwater width is much greater than the maximum tested length 

 of 42 feet (12.8 meters). 



III. DETERMINATION OF MOORING LOADS 



Giles and Sorensen (1978) found that the mooring-line load for the 

 FTB system is essentially a function of the incident wave height. Figure 

 4 provides a procedure for determining the mooring-line load for a given 

 incident wave height. 



Since the design curve is based on limited data, care and engineer- 

 ing judgment should be used in extrapolating the curve for wave heights 

 greater than 4.5 feet. Also, if the breakwater width to wavelength ratio 

 is greater than 1.4 the actual load on the anchor may be slightly higher 

 due to additional modules being added. 



Figure 4 is applicable to mooring lines placed on a slope of 1 on 7. 

 If steeper mooring-line slopes are used, then the loads would be slightly 

 higher and proportional to the change in the tangent of the slope. 



The rear mooring system should be designed for the largest force 

 determined by either the force of the largest wave coming from the shore- 

 ward direction or 20 percent of the seaward force, whichever is greater. 



IV. SELECTION OF A MOORING SYSTEM 



1. Selection of the Mooring Line and Hardware . 



To minimize the vertical load on the anchor, < the mooring line should 

 have a minimum length of approximately eight times the maximum expected 

 water depth and the anchor should be positioned seven times the maximum 

 water depth from the breakwater. The anchor holding capacity must exceed 



