FOREST COYER IX PROTECTING RESERYOIRS 5 
ests have generalized too much from particular cases, those who rely 
upon mechanical means of stream control haYe likewise drawn their 
conclusions from inadequate data and from a too restricted field. 
At any rate it will be shown that forests, under certain conditions, 
have a most significant influence in determining the permanence of 
the development of a stream — development which enables storm 
water to be stored for power purposes, which to a limited extent 
equalizes stream flow for navigation, and which under some condi- 
tions may be of material benefit in the control of floods. 7 
Even if it were conceded, as is claimed by Mead. 9 that forests have 
little influence upon stream flow and the development of water re- 
sources in northern Wisconsin, and in regions of similar sandy or 
glaciated soils, the situation would not be the same in other regions 
with different soil and climatic conditions. The protective influence 
of the forest is of great importance in most regions subject to exces- 
sive erosion when the naked soil is exposed. In the sandy soils of 
the Coastal Plain region of the Southern States, where the condi- 
tions are very similar to those in the Great Lakes Region, forest in- 
fluences are prevailingly at a minimum and are often negligible, 9 but 
these influences increase in other regions, apparently reaching their 
maxima, as will be shown further on. in the Sierras of California, in 
the southern Appalachians, and in the southern Piedmont. 
The discussion in this bulletin will be restricted to erosion, the sec- 
tions of the United States where it is most prevalent, the conditions 
of rainfall, surface and soil which cause excessive erosion, and the 
means of reducing it for the protection of water-power resources. 
SOURCES OF SOLID BURDEN OF STREAMS 
The solid burden carried by streams is derived from several sources, 
summarized as follows : 
Farming lands, especially such as are situated on steep slopes. 
Woodland and brush land in which the soil cover of litter does not afford an 
adequate protection. 
Grasslands, especially thinly stocked prairies and the plains of the Western 
and Southwestern States where the sod, or sod and brush, is not sufficiently 
dense to protect the soil and prevent erosion. 
Earth roads subject to degradation, ditches along roads, and unprotected cuts 
and fills along railroads and highways. 
Washings of ore and clay, mine water, etc.. which in place of being retained 
in settling basins are disposed of in waterways. 
Corrasion of banks of streams. 
which he supports by figures of run-off. that forests may have a limited influence, at the 
headwaters of the Mississippi River, in obstructing the run-off, and that brush land 
efficaciously performs the same function. Potter, C. L. some suggested ways of con- 
trolling the Mississippi floods. Engin. News-Rec, 94 : 558. 1925. The repository of 
arguments for and against the benefits of forests to stream flow is a paper by H. M. 
Chittenden, with its accompanying discussoin. Chittenden, H. M. forests and reser- 
voirs IN THEIR RELATION TO STREAM FLOW. WITH PARTICULAR REFERENCE TO NAVIGABLE 
rivers. Amer. Soc. Civ. Engin. Trans., 62 : 245-318, illus. 1909. (Discussion, p. 319- 
546. ) Unfortunately generalizations control most of the discussions. It is seldom that 
all the essential facts are given or that proper weight is given to different factors, and 
this is particularly the case in those portions of the discussion which refer to erosion of 
soil and corrasion of stream banks. 
7 See Leighton. M. O. relation of water conservation to flood prevention and 
navigation in ohio river. In Preliminary- Report of the [U. S.] Inland Waterways Com- 
mission, pp. 451-490. 1908. (U. S. Congress, 60th, 1st sess., Senate Doc. 325.) See 
also [Pittsburgh. Flood Commission.] report of flood commission of Pittsburgh, 
penna. 252 pp.. illus. [Pittsburgh. 1012.1 
8 Mead, D. W. the flow of streams and the factors that modify it, with special 
reference to Wisconsin conditions. Wis. Univ. Bui. 425 : 62. 1911. (Engin. Ser., 
v. 6. no. 5.) 
'■' Ashe. W. W. forests and the cost of textile production. 11 pp. [n. p.] 
[1908.] 
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