d = 2 ~ 20.5 feet . 



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

 function of water depth (Fig. 15) . 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, i.e.. 



o 0.080 + 0.095 _ n 

 £^= 2 °' 



088 



For d = 20.5 feet, H^ = 3 feet, and U = 70 miles per hour from 

 Figures 1 or 6 



Sa__ 32.2 x205 ^^^ 

 U2 (102.7)2 



gHi 32.2 X 3 



0.00916 



and from Figure 1 



U2 (102.7)2 



4= 12.2 



For ff =0.01, 



for f^ = 0.088, 



U^ f 102. 7") 2 



Fg = 12.2 ^^ = 12.2 '^ 32 2 "" '*'°°° ^®®^ * 



^f "i ^x 0.01 X 3 X 5,000 



d2 ^ 20.52 = "-^^^ ' 



^/ % ^x ^ 0.088 X 3 X 5,000 _ 3 ^4 

 d^ 20.52 



For the period, t = 3.2 seconds, and d = 20.5 feet, 



2iTd ^ 2^ (20.5) Q_3g^ 



gT^ 32.2 (3.2)2 



For 2TTd/(gT2) = 0.391 (from Fig. 16) 



33 



