42 



BULLETIN" 832, U. S. DEPAETMEK" T OF AGRICULTURE. 



is very similar to that of Allen Creek, and the values of n obtained, 

 as given in Table 4, are practically the same as those obtained for 

 Allen Creek. 



BOTER SIVEK. 



Gaugings of the Boyer River were made at the Lincoln Highway 

 bridge about 1 mile from Missouri Valley. The downstream end of 

 the slope course was 197 feet above the bridge. The length of the 

 slope course was 868 feet. A view of the slope course looking 

 upstream is shown in Plate XIII, figure 2. The downstream slope 

 posts are barely visible on the left-hand side of the view, just above 



Distance slong S/op& Course in feet 

 500 



20 1 ! 1 









1 



— \ 













-4 



















20| 









1 









— i- 



ALLEN CREEK 



Average Maximum Depth 



7.S — — - 



LLOW CREI 



7.0 

 Ml 



-20 



-20 



i r 



~ i - 



— I — ' 

 i 





i i 



p^iJ^ 













1 



I i 



— i — 1 — - 





1 



r 



Fig. 3. — Graphs for experiments in western Iowa, showing per cent variation from average cross sectional 

 area for all cross sections along slope course. 



the break in the bank. It can be seen that above this break in the 

 bank the course of the channel is straight and fairly uniform in cross 

 section (fig. 8 G). The sides of the upper part of the channel stand 

 at a slope of about 1 to 1 (see fig. 7 C). The soil in the upper part 

 of the sides of the channel consists of a dark loam and in the lower 

 part it is a hard yellow clay. The channel is practically free from 

 any form of vegetation, which condition is largely due to its rapid 

 enlargement caused by erosion. Since the channel was constructed, 

 in 1910, it has enlarged to almost double its original size. 



During flood stages the condition of the channel was very similar 

 to that described for the Allen and Willow Creek channels. After the 





