“st BULLETIN 832, U. S. DEPARTMENT OF AGRICULTURE. 
channel for the two sets of measurements. In Table 4 are given the 
values of n obtained for the years 1916 and 1917, respectively. From 
this table it is seen that the values of n obtained for the low stages — 
during 1916 are lower than those obtained for the higher stages during 
1917. This is due to the fact that the upper portion of the channel is 
irregular and covered with growth, as may be seen from the view of 
of the channel. During the gaugings and slopemeasurements the water 
was not as fully laden with silt as in the case of the ditches in the vicin- 
ity of the Missouri Valley, nor were the sides of the channel so well 
coated with mud. The bed and the flatter portions of the sides of 
the channel were covered with silt, varying in depth from 4 to 14 feet. 
(See fig. 7 # for average cross section of channel.) 
LITTLE SIOUX RIVER CUT-OFF. 
Gaugings of the Little Sioux River were made from the highway 
bridge on the Onawa-Turin road, about one-half mile from Turin. 
Values of n for the channel were obtained during 1916 and 1917. Views 
of the slope course taken during June, 1916, and June, 1917, areshown 
in Plates XV, figures 1 and 2. The length of the slope course for the 
measurements made in 1916 was 1, 212 feet, and for those made in 
1917 was 1,654 feet. The slope course was located on the straight 
stretch of channel above the gauging station at the highway bridge. 
The soil in the upper part of the channel is a dark silty loam, while in 
the lower part it is a heavy firm clay. There was practically no silt 
in the bed of the channel during the time that the experiments were 
made. The channel during 1916 was fairly uniform in section, and 
the left bank, which is shown on the right-hand side of the view (PI. 
XV, fig. 1), was quite regular. The right bank was somewhat irregu- 
lar, due to caving. (See fig. 7 F, for average cross sections of the 
channel.) There was some vegetation on both side slopes of the chan- 
nel, as may beseen from the view. The values of n obtained for this 
channel, shown in Table 4, are about what would be expected for a 
channel in its condition. 
- Plate XV, figure 2, shows the condition of the same channel in June, 
1917. The right bank, which in 1916 was covered with trees, has 
caved into the channel, and the left bank is considerably rougher 
than it was in June, 1916. The two values of n obtained, 0.075 and 
0.076, are considerably higher than those obtained in 1916. This may 
readily be ascribed to the caving of the right bank, which carried into 
the channel large trees and other obstructions. The water during the 
experiments was not laden with silt, as in the case of the ditches near 
Missouri Valley, and the channel was not coated with mud after the 
subsidence of the water. 
