Frictional Resistance in Artificial 
Waterways 
The use of empirical formulas plays an important part in the 
design of channels for carrying water. Practically all such form¬ 
ulas contain a factor which represents the resistance to the flow of 
water offered by the material forming the channel, and conse¬ 
quently there are almost as many different values for this factor as 
there are kinds of material. The engineer designing an irrigation 
channel must exercise good judgment in choosing the value of this 
coefficient or the resulting section will be too large or too small to 
carry the volume of water desired. If the channel is too 1 large, 
the construction as well as the maintenance cost will be excessive, 
while if too small, there may be heavy crop losses because of in¬ 
sufficient water for irrigation. 
In order to add to the available information on proper values 
of the coefficient of roughness in various types of artificial water¬ 
ways, a series of field experiments was conducted in Colorado dur¬ 
ing the irrigation seasons of 1912 and 1913. The principal types 
of channels experimented upon were metallic, reinforced concrete 
and timber flumes, concrete-lined canals, earth canals, concrete and 
timber chutes, and inverted siphons of wood stave pipe, located on 
irrigation systems in the Cache la Poudre, Arkansas, Grande, Gun¬ 
nison, Uncompahgre and San Luis Valleys. 
PURPOSE OF INVESTIGATION. 1. To determine the 
coefficient of roughness in empirical formulas for several types of 
open channels; and also to determine whether such coefficient 
changes with variations of discharge of the channel. 
2. To determine the loss of head in water flowing through 
siphons, and to compare Kutter’s formula with the ordinary fric¬ 
tion formula as adapted to pressure pipes. 
3. To make current meter measurements throughout cross- 
sections of several channels to permit the vertical velocity curves 
to be plotted, and, from a standpoint of accuracy, to compare the 
integration and single point methods with the multiple point 
method. 
EQUIPMENT AND METHODS USED. The same cur¬ 
rent meter was used in all the experiments, being a light type of 
