FOREST LANDS FOR THE PROTECTION OF WATERSHEDS. 105 



the opposite effect. It may be admitted, however, that it is possible to con- 

 ceive of circumstances in which, under extreme conditions, the presence of a 

 particular forest may increase a particular flood at a particular point. It is 

 equally possible to imagine many more conditions under which the reverse 

 would be true, and it is clear that if the forest has a restraining influence on 

 the discharge of water from the surface, increasing the amount of percolation 

 into the ground, to reach the surface later at lower levels by springs and seep- 

 age, it must, in the vast majority of cases, reduce the frequency and violence of 

 floods. 



It is true, as stated by Colonel Chittenden, that the records of high water 

 in most streams do not show that the waters now rise, under extreme conditions, 

 higher than extreme floods which have occurred in the past. The highest re- 

 corded flood on the Connecticut River occurred in 1S54, long before the present 

 rapid rate of cutting on its upper headwaters had begun. Similar facts are no 

 doubt true of other streams. Exceptional conditions are always likely to occur, 

 but, as mentioned above, it is not exceptional conditions which should govern hi 

 this question. To do so is like arguing against the benefit of food for the rea- 

 son that a man's food may choke him, or against the benefits of the sun's heat 

 for the reason that people occasionally get sunstruck. 



Colonel Chitteuden illustrates the action of a forest by considering an inclined- 

 plane surface " practically impervious to water," with a layer of sand covering 

 some small portion of it, and to which a spray of water is applied. This com- 

 parison, however, is not a correct one, for the forest cover does not rest upon 

 an impervious surface. The forest and its cover prevent the earth beneath from 

 being baked by the sun and compacted by the rain. It is kept in a porous con- 

 dition, ready to absorb water which filters down to it through the forest cover. 

 Any conclusions, therefore, drawn from Colonel Chittenden's simile must be 

 inaccurate. 



The author's summary of this part of the discussion is perhaps contained in 

 the following sentence: "That the forest does promote tributary combinations 

 there would seem to be no question, and that it may therefore aggravate flood 

 conditions necessarily follows. It is not contended that this increase is ever 

 very great, but it is contended that forests never diminish great floods and that 

 they probably do increase them somewhat." 



It would seem to be much nearer the truth to say that forests generally 

 diminish floods, although it is conceivable that a forest may slightly increase a 

 given flood at some points. 



The author further states that " the forests are virtually automatic reservoirs, 

 not subject to intelligent control, and act just as the system of reservoirs once 

 proposed by the French Government for the control of the floods of the River 

 Rhone would have acted if built. These reservoirs were to have open outlets, 

 not capable of .being closed, which were intended to restrain only a portion of 

 the flow. A careful study of their operation in certain recorded floods showed 

 that they would actually have produced conditions more dangerous than would 

 have occurred without them." 



The last sentence of this quotation is rather conjectural and its meaning 

 not quite clear, but it will be surprising to most people to be told that a reser- 

 voir not subject to intelligent control does not regulate, and they will hardly 

 accept the statement. Of course a lake is a more efficient regulator than a 

 forest, because if its level is rising the discharge from its lower end is always 

 less than the flow into its upper end, while in the case of the forest, when its 

 storage is exceeded, its level can not rise, and it can simply hinder the discharge 

 of later rainwater by physically obstructing its flow. 



The general aspect of this part of the subject seems, after all, quite simple. 

 The forest floor absorbs a large amount of water, prevents it from flowing off 

 rapidly, and allows it to gradually percolate into the porous ground beneath. 

 If the land were clear of vegetation, or if it were cultivated, and especially if 

 the slopes were steep, the erosion would be greater and might sooner or later 

 leave no soil upon the rocks to servo as n reservoir in future storms. The 

 author's argument, therefore, leaves unassailed the beneficial effects of forests 

 in regulating flow. 



The fact must be emphasized that those who believe in the beneficial effect 

 of forests upon flow do not urge the preservation of the forests on lands needed 

 for agriculture. The beneficial effects of the forests on flat lands in modifying 

 the violence of freshets and increasing the low-water flow is much less clear 



