stream Flow in I^elation to Poresfc.* 



Bv GEOR.GE W. RAFTER, C. E. 



THE general subject announced in the title to this paper was discussed by 

 Mr. Thomas P. Roberts, at the Boston meeting, in September, 1885, and 

 also by Mr. C. C. Vermeule, at the annual meeting for 1895, and by others. 

 I wish to address myself particularly for a moment to the views announced by 

 Messrs. Roberts and Vermeule. The position taken by these two gentlemen is in 

 eflfect that forests influence stream flow only in a very slight degree or not at all. 

 My proposition, on the contrary, is that forests not only do influence stream flow, but 

 the influence is so exceedingly marked, that of the two contiguous New York State 

 drainage areas, one in forest and the other deforested, the deforested area may show 

 as much as five or si.\; inches less annual run-off because of change in water 

 yielding capacity due purely to deforestation. If it is true that there is such a 

 difference as this, not only should tiie fact be well understood by everybody, but 

 the gentlemen taking the contrary view may as well cease to advocate the error, if 

 on no other ground than that error once announced is persistent and will require 

 labor to eradicate. 



In attempting to show the' contrary of the proposition championed by Messrs. 

 Roberts and Vermeule I shall refer extensively to data gathered during the past four 

 years in the State of New York. 



Let us first briefly consider the views of Mr. Roberts. This author begins by 

 stating that he "will not undertake to deny that the conservation of the rainfall in 

 local districts is aided by forests," but he attempts to distinguish between local rains 

 and general storms, and between summer, fall, winter and spring floods. On such a 

 basis he arrives at the final conclusion that "the popular opinion no doubt will long 

 be that the destruction of forests increases the height of floods, but I am persuaded it is 

 not a belief founded on established fact." Mr. Roberts' position as defined through- 

 out his paper is that rainfall is conserved by local districts, but that for large areas 

 several thousand miles in extent there is such a balance of conditions as to lead to 

 essentially the same result whether the area is forested or deforested. I shall myself 



* This paper, which was read at a meeting of the American Forestry Association, is particularly 

 interesting because it embodies the result of several years of investigation by Mr. Rafter, who has 

 been employed by the State Engineer and Surveyor as expert in charge of the e.xtensive hydrologic 

 and hydraulic surveys made necessary by the canal enlargement, and the development of several 

 large storage projects in this State. 

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