117 
high water (16 feet), tests made about half a mile below the 
mouth of Spoon River with a steam launch indicate a current 
at that point of about 3 miles per hour. The figures quoted from 
the report of the Engineers give the mean velocity for the whole 
stream at the place of observation, while our tests were made 
in mid-channel and refer to that point alone. The results of 
our own tests and those of the Engineers both indicate that the 
current at low water is but one fourth as rapid as at times of 
overflow. The current in the bottom-lands at time of overflow 
is much slower than it is in the channel, being retarded by the 
vegetation and by the natural and artificial irregularities of the 
surface, such as the deposits of tributary streams, the embank- 
ments of railroads, and the levees about cultivated lands. The 
bottom-lands thus serve as impounding areas from which the 
water, except at times of maximum flood, is slowly drawn off 
through the main channel. 
The rate at which the current moves down the stream is 
not, however, an index of the rate at which the crest of a 
flood traverses the same distance. For example, the crest of 
the flood of May, 1892, as shown in the appended table, passed 
from Morris to the mouth of the river in fifteen days, while the 
current in the main channel, under these flood conditions, 
would traverse this distance in four or five days—less than a 
third of this time. 
FLOOD MOVEMENT IN THE ILLINOIS RIVER. 
Distance Rate 
Place | Date Miles below Morris | Miles per hour 
INMIGITIS meters rast faloesiaets, can May 6 race aoe 
CopperasiCreek. 52.3. <5:<<0 May Io 124.3 1.29 
AGGKane Gr ei escleicciacse te May 16 183.7 0.41 
Ream psvillecnetmeksomer ace May 19 230.0 0.63 
IMOuEn SS sarcsieasne Setcieicieiat esc May 21* 259.2 0.61 
*Estimated. 
As stated on a previous page, the current at high water ranges 
from two to three miles per hour, at which rate, as above shown, 
water in the main channel would pass from Morris to the 
mouth of the river in four or five days, This flood was sudden 
