RANGE PRESERVATION AND EROSION CONTROL. 
15 
A significant feature to be noted from the 1916 precipitation and 
run-off records is the fact that run-off occurred on area A as a result 
of storms that produced no flow from area B, in spite of the fact that 
area B received just as much or generally more rain than area A. 
Surface conditions again account for this fact. 
Table 4 summarizes the rainfall for the two years 1915 and 1916 
and the resulting erosion and run-off. It shows the comparative 
effects of gentle storms and storms of unusual violence, such as not 
infrequently occur in the higher mountain region of the Manti 
Forest. From Table 4 it is apparent that of the summer rains of 
1910, totaling 7.T0 inches on area A and 8.13 inches on area B, 14 
storms on area A and 8 on area B were effective in producing run-off. 
In 1915 there was but one such storm, yet the erosion from this sin- 
gle storm was very much greater than from the several storms of 
1916. The most significant fact shown is that the per cent of sedi- 
ment carried in the run-off is proportionately higher as the velocity 
of the flow increases. Thus if we apply the established formula, 
namely, that the transporting power varies directly as the sixth 
power of its velocity, it is evident that if the velocity of a flow is 
increased two times its transporting power is increased 64 times. It 
is understood too, of course, that the larger the flow the greater is 
the velocity of that flow. 
To sum up, the extent of erosion and run-off depends upon (1) 
the rate at which the rain falls, (2) the steepness of the slope, (3) 
the presence of well-established gullies, (4) the character of the soil, 
and (5) the density and character of the vegetation. 
Table 4. — Run-off and erosion from rainstorms. 
Year. 
Area. 
Total 
number 
of storm 
days. 
Total 
rainfall. 
Effec- 
tive i 
storm 
days. 
Effec- 
tive i 
rainfall. 
Run-off. 
Sedi- 
ment. 
Sedi- 
ment. 
1915 
A 
26 
26 
36 
36 
5.79 
6.48 
7.70 
8.13 
1 
1 
14 
8 
Inches. 
0.70 
1.43 
4.05 
3.23 
Cubic feet. 
3,018.96 
335. 15 
2, 266. 68 
835. 55 
Cubic feet. 
716. 92 
94.29 
197. 49 
59.81 
Per cent. 
23.70 
1915 
B 
A 
B 
28.13 
1916 
8.70 
1916 
7.20 
1 Effective here refers to storms that produced run-off. 
WIND. 
In addition to the conspicuous action of the gully or shoe-string 
type of erosion described above, erosion caused by the action of the 
wind more or less uniformly over the soil surface is a factor of high 
importance in determining the fertility of the soil under certain 
conditions. 
Following the destruction of the vegetative cover, either entirely 
or in part, the wind movement becomes particularly active in the 
