so that the maximum significant wave height is 



0.0075 U^ „ ^„,. ,,„.2 



„ _ A _ 0.0075 (40) _ 1 00 ^ // m f^\ 



H = = ^r—x = 1.22 m (4.02 ft) 



sm g 9.8 



Since H> is greater than H (2 meters > 1.22 meters) then wave decay 

 will occur. Therefore, the fractional reduction R- must be determined 

 using equation (3-51). 



From equation (3-50), 



H^ = 0.78d = 0.78 (3) = 2.34 m (7.68 ft) 



9 "^L — 9 



h " H - H " 2.34 - 1.22 " °'^°^ 



m sm 



From equation (3-52), the equivalent initial wave height 



Hv^ = K- H„m = 0-304 X 1.22 = 0.371 m (1.22 ft) 



from Figure 3-21, for 



and 



it is found that 



from which F is found to be 



gH^l.SJO^^ 0.00227 

 U^ (40)^ 



^ = 0.0184 

 U 



-f = 2.25 



"a 



Fg = 367 m (1205 ft) 



Since the vegetation does not match any of the curves in Figure 3-37, it 

 is assumed that a moderate amount of brush will give a friction effect 

 about halfway between curves B and C. From curve B, for d = 3 meters, 

 f^ is 0.20 and from curve C, for d = 3 meters , f^ is 0.485 . The 

 bottom friction is then taken, in this case, as the average of the two 

 values 



For tf = 0.01, 



^ 0.20 + 0.485 „ „,„ 

 f^ = X = 0.343 



f U Av 



T ^ _ 0.01 X 2 X 1000 _ oo 

 d^ (3)^ 



and for f^ = 0.343, 



^f 



V \ ^^ 0.343 X 2 X 1000 ^, „» 



_ = _ = IK). II 



^ or 



3-75 



