FLOW OF WATER IN. DREDGED DRAINAGE DITCHES. 43 
water subsided the sides of the channel were left coated with a thin 
layer of mud. The values of x obtained (Table 4) are higher than 
those obtained for Allen and Willow Creeks, which is attributed to the 
fact that the sides of the channei are considerably more irregular, 
as may be seen by comparing the views of the channels. Also, it is 
believed that the reduction of friction, due to the coating of mud on 
the sides of the channels, was much more effective on the rather flat 
side slopes of Willow and Allen Creeks than on the steeper side slopes 
of the Boyer River channel. It will be noted that, for the Boyer 
River channel, the value of n increases as the stage decreases. This 
is due, no doubt, to the fact that the lower part of the channel is more 
irregular than the upper part. 
PIGEON CREEK. 
Gaugings of Pigeon Creek were made atthe highway bridge about 
one-half mile above the Chicago & North Western Railroad, near the 
town of Crescent. A view of the course of slope measurements is 
shown in Plate XIV, figure 1. This view was taken locking down- 
stream from the gauging station. The upstream slope posts, which 
were about 65 feet below the bridge, can be seen on the right-hand side 
of the view. 
The upper portion of the sides of the channel stand at a slope of 
about 1 to 1 (see figs. 7 D, and 8 2). There was very little vegeta- 
tion in the channel when the gaugings and slope measurements were 
made. The soil in the channel is a heavy dark loam, and the bottom 
of the channel is generaily covered with 4 to 1 foot of mud. The chan- 
nel was dug in 1907,and has increased somewhat in depth since that 
time but not much in width. The right bank of the channel is 
rather smooth and regular, while the left bank is rough and irregular. 
During flood stages the channel was coated with mud, as described for 
the channels near Missouri Valley. 
In Table 4, measurements ii and 12, are shown two values a n 
obtained for en stages in the channel. ese values are much larger 
than those obtained for Willow and Alien Creeks, which is perhaps due 
to the rougher condition and greater fali of the channel, both ef which 
conditions probably rendered less effective the mud coating in reduc- 
ing friction. 
MONONA-HARRISGN DITCH. 
A view of the slope course on the Monona-Harrison ditch, near 
Onawa, is shown in Plate XIV, figure 2. This view was taken looking 
upstream from the gauging station, which was located at the highway 
bridge on the Turin-Onawa road. The length of the slope course 
was 948 feet. Experiments were made during the years 1916 and 1917, 
and not much difference was found in the size and condition of the 
