THE INFLUENCE OF FORESTS ON CLIMATE AND FLOODS 2.^7 



phis or New Orleans. It is hardly fair, 

 therefore, as Professor Moore does, to 

 compare the mountain watershed of the 

 Ohio River with the entire drainage 

 area of that stream. The mountain 

 watershed is more fairly to be compared 

 with the drainage area above Pittsburg, 

 of which it would form a considerable 

 proportion. 



The sediment brought down by the 

 mountain stream is, in the course of 

 years, washed farther and farther 

 down the river, and that carried in sus- 

 pension is gradually deposited, as the 

 slope becomes less and the velocity of 

 the flowing water correspondingly less, 

 in the bed of the stream. Subsequent 

 floods find therefore a smaller chan- 

 nel in which to flow, the bed of the 

 river having been raised by sediment 

 brought down by previous floods. The 

 floods, therefore, in the lower reaches, 

 finding the channel contracted, are, 

 obliged to rise higher and to overflow 

 bottom lands, and in doing so they wash 

 away the banks where these are al- 

 luvial, causing still more material to 

 be swept into the channel of the river. 

 At the same time, some of the sedi- 

 ment from above is deposited over the 

 bottom lands. 



Now, the point is — and it may as 

 well be once more emphasized — that 

 even if the banks in these lower por- 

 tions were protected against washing 

 away, the gradual filling up of the chan- 

 nel of the stream by sediment brought 

 down from above would in itself cause 

 the floods to rise higher and higher as 

 the years go by, and to overflow larger 

 and larger areas. Once more to quote 

 Major Suter and Colonel Chittenden, 

 "the influx of sand from above must 

 first be stopped." 



To estimate, therefore, the value of 

 the forests in preventing erosion, it is 

 grossly incorrect to compare the moun- 

 tainous area with the total area of a 

 large drainage basin. If we could pro- 

 tect the mountain sides, and limit the 

 erosion to what would naturally come 

 from flat, cultivated land, and from 

 .caving banks, the problem would be 



comparatively easy ; and it should fur- 

 ther be noted that the erosion from flat, 

 cultivated lands can be largely pre- 

 vented by proper methods of cultivation 

 and plowing, which will not allow the 

 water to flow with great velocity 

 through the furrows. Plowing should 

 be done not up and down the slopes, 

 but along the contours. Land suitable 

 for cultivation should be used for culti- 

 vation if necessary, but there is noth- 

 ing in all this discussion of Professor 

 Moore's which casts a shadow of doubt 

 on the efficacy of the mountain forests 

 as conservators of the navigability of 

 streams. 



Before leaving this subject, it may be 

 as well to say that probably the best 

 authorities upon it are neither meteorol- 

 ogists nor engineers in general practice, 

 but foresters and forest engineers, and 

 that these are practically, if not quite, 

 unanimous as to the value of forests. 

 An engineer whose duty it is to main- 

 tain harbors and the navigable por- 

 tions of streams, like the officers of our 

 Corps of Engineers, does not, in the 

 course of his daily experience, have 

 much opportunity to observe or study 

 forest questions. He sees banks cave 

 and the material form a bar below ; he 

 does not see the constantly-moving mass 

 of sediment in the bottom of the 

 stream ; he does not see the erosion on 

 the mountain slopes ; out of sight is out 

 of mind, and he may easily fai-l to rec- 

 ognize the importance of what he does 

 not observe. Professor Moore ad- 

 mitted that he had never studied ero- 

 sion in the mountains, and yet he pre- 

 sents a paper which dismisses this most 

 important element in less than one page 

 and which is offered as a presumably 

 weighty contribution to a great sub- 

 ject! 



A volume could be filled with quota- 

 tions from the writings of those who 

 have observed this matter, but as an 

 illustration only one will be given from 

 a review of a work published in 1901 

 on "Forestry in British India." by 

 Berthold Ribbentrop, who has spent 

 thirty-four years in the forest service. 



