236 



AMERICAN FORESTRY 



EROSION 



The most important question con- 

 nected with this whole matter is the 

 effect of the forests on erosion, which 

 has been already incidentally referred to. 

 This matter Professor Moore passes over 

 with astonishing silence, and if it was 

 his intention to offer a scientific contri- 

 bution to the subject of the effect of 

 forests, it is difficult to understand his 

 reticence on this point. The fundamental 

 principle is self-evident. The surface 

 water running off from forest ground 

 takes less earthy matter with it than the 

 surface water from bare ground, from 

 partially wooded ground, from grass 

 land, or from cultivated land, especially 

 on steep slopes. Land partially grown 

 up in forest or bushes, or grass land, is 

 of course better than cultivated land in 

 this respect, but neither is anything like 

 as effective as forest land. Forests, 

 therefore, are the most efficient protec- 

 tion of the ground against erosion, and 

 this is the strongest argument in favor 

 of their preservation on steep slopes. 



In his argument before the Commit- 

 tee on Agriculture, March ist, Profes- 

 sor Moore stated that erosion was "a 

 beneficent action." In his published 

 paper, however, only about half a page 

 has been devoted to this important sub- 

 ject as against fourteen pages to the en- 

 tirely unimportant subject of the effect 

 of forests on rainfall! In his paper he 

 again befogs the issue on this point by 

 bringing forward the argument that 

 "every acre that will grow food for the 

 people and thereby reduce its cost and 

 furnish sustenance to the population 

 and the teeming millions that are on 

 their way to these shores, should be so 

 employed." In other words, again "the 

 pleading of the poor man's children for 

 bread and meat" is allowed to stand in 

 the way of the fair discussion of a great 

 public policy. 



Everybody knows that streams that 

 flow from forested mountain areas are 

 comparatively clear, while streams 

 which flow from bare ground are com- 

 paratively muddy, and the efficiency of 

 forests in preventing erosion of the 



ground is admitted by all competent 

 authorities. 



First in importance, then, is the effect 

 of forests in preventing erosion ; second 

 is their effect in moderating, in general, 

 the violence of floods and in maintain- 

 ing a high low-water stage, and least or 

 insignificant in importance is their effecr 

 upon climate. 



RATIO OF MOUNTAIN WATERSHEDS TO 

 THE TOTAL WATERSHED 



Another claim put forward by Pro- 

 fessor Moore is that the ratio of the 

 mountain watershed in a large basin 

 like that of the Ohio River, is so small 

 that the reforesting of the mountain 

 area will be of little benefit. A brief 

 examination will show the fallacy of 

 this and the unfairness of Professor 

 Moore's reasoning, and to make this 

 clear it will be necessary here to explain, 

 briefly, the cause and action of a flood. 



The fundamental cause of the flood, 

 of course, as every one admits, is ex- 

 cessive and long continued precipitation 

 over a large area. The rain which falls 

 on the mountain sides is gathered rapidly 

 into the brooks and larger streams, but 

 much more rapidly from bare areas than 

 from forested areas, and carrying much 

 more sediment. The transporting power 

 of water varies about as the sixth power 

 of the velocity ; that is to say, if we dou- 

 ble the velocity of flowing water it can 

 move a cubical particle of rock or earthv 

 matter sixty-four times as large as be- 

 fore. The waters come down from 

 bare hill-sides, therefore carrying large 

 masses of sediment, and as the waters 

 reach the upper navigable portions of 

 the streams where the slope is flattened, 

 they gradually deposit their sediment. 

 Succeeding floods carry portions of this 

 sediment further down, and so it grad- 

 ually reaches — perhaps only after a con- 

 siderable length of time — the lower 

 reaches of the river. The immediate 

 effect of deforestation on floods and on 

 the deposition of sediment will clearly 

 be felt first in the upper reaches of the 

 streams : on the Ohio River, for in- 

 stance, at Pittsburg and points above, 

 rather than at Cincinnati, Cairo, Mem- 



