and at the 18-foot depth (curve B) , 







£ r 



0, 



.095 













Af / = 



0, 



,095 



- 



0.080 



= 0.015 



0, 



.25 



ffi = 



0. 



,25 



(0. 



080) = 



0.020 







Af / < 







.25 



*ft • 





Equations (4) and (5) are satisfied, so the fetch segment chosen 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 seg- 

 ment; i.e., 



23 + 18 _ n c c «. 

 d = s = 20.5 feet . 



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

 function of water depth (see Fig. 13). 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., 



0.080 ♦ 0.095 , 



J 2 



For d = 20.5 feet, H = 3 feet, and U = 70 miles per hour (102.7 feet 

 per second) , 



4 - I 2 ' 2 * 2Q ' 5 - 0.0626 

 U 2 (102.7) 2 



£L= 52 ' 2 X 5 = 0.00916 



u z cio.2.7) 2 



and from Figure 1 



£- = 12.2 



F« = 12.2 — = 12.2 (1 " 2 -P = 4,000 feet . 

 • e 32.2 



For f f = 0.01, 



for ff= 0.0? 



f f *k Ax _ 0.01 x 3 x 5,000 _ 357 . 

 d 2 20. 5 2 



29 



