H . 0.02 U^, 0.02 (31.3)^ ^^^^ 

 sm g 9.8 ' 



Therefore, the initial wave will increase in height; the first step is to 

 adjust the fetch (segment) for conformance with equations (3-42), (3-43), 

 and (3-44). 



0.25 d^ = 0.25 (7) = 1.75 m (5.74 ft) 



Ad=7-4=3m (9.84 ft) 



(A d > 0.25 d^) 



Since this does not meet the condition of equation (3-42), the area 

 should be divided into fetch segments. Assuming a uniform variation in 

 depth, take the first segment as a distance Ax = 1525 meters with a 

 depth variation from 7 to 5.5 meters. Then 



Ad = 7 - 5.5 = 1.5 m (4.92 ft) 



Thus, 



Ad < 0.25 d^ (3-42) 



From Figure 3-37, curve B 



and 



therefore. 



f^ = 0.080 (depth = 7 meters) 



f^ = 0.095 (depth = 5.5 meters) 



and 



Af „ = 0.095 - 0.080 = 0.015 

 0.25 fjy^ = 0.25 (0.080) = 0.020 



Af „< 0.25 f„. (3-43) 



Equations (3-42) and (3-43) are satisfied, so the 1525-meter fetch 

 segment is used. For a uniformly varying depth, the average depth can be 

 taken as the average of the depths at the beginning and the end of the 

 segment : 



d = ^ ^^^'^ = 6.25 m (20.5 ft) 



For a uniform type of vegetation, the friction factor will vary as a 

 function of water depth as shown in Figure 3-37. As an approximation, 

 the average friction factor can be taken as the average of the friction 

 factors at the beginning and the end of the segment; 



3-72 



