EQUALIZING INFLUENCE OF FORESTS 



49 i 



be washed away and the water will not 

 be gathered into torrents flowing 

 clown through eroded channels. More- 

 over, it seems a strange argument to 

 maintain that because the retentive 

 power of the forest is not unlimited it 

 is not therefore useful. Even if it be 

 admitted, however, that under a torren- 

 tial rainfall the water flows away from 

 the forest without hindrance, it is under 

 just such a condition that the forest is 

 most valuable in prcrcn'ing erosion, for 

 the water is distributed over the forest 

 floor and does not carry with it the 

 earth beneath. With reference to this 

 point, however. Colonel Chittenden 

 maintains that there is no more erosion 

 from cut-over lands than from for- 

 ested lands. There are certain reasons 

 for believing that he is not correct. In 

 the first place, the forest cover is al- 

 ways more or less disturbed or injured 

 by the cutting, and after cutting is 

 done it is more exposed to the sun and 

 becomes dryer in summer and more 

 liable to take fire. It is believed to be 

 a fact that fire very frequently follows 

 the lumberman and originates on cut- 

 over land. This still further destroys 

 the forest cover, and heavy rain falling 



m/ O 



on deforested ground is not broken in 

 its fall by the leaves and branches of 

 the trees. In many places, of course, a 

 new growth springs up after the forest 

 is cut. if it is not prevented by fire, 

 and this new growth will in the course 

 of time become a new forest, and the 

 old conditions will be restored, but in 

 the meantime there is a deterioration 

 of the soil covering, and a greater lia- 

 bility to erosion, as well as a smaller 

 power of retention, and consequently 

 more rapid discharge of the rain waters. 

 In some parts of the White Mountains, 

 tracts once cut clean and burned over 

 do not grow up again. 



Colonel Chittenden suggests that un- 

 der extreme flood conditions such as 

 have been referred to, the presence of 

 a forest may actually produce a worse 

 condition than if the country were 

 cleared, and asserts positively, but with- 

 out proof, "that the forest does promote 

 tributary combinations * * * and that 

 it may therefore aggravate flood condi- 



tions." He continues "that forests never 

 diminish great floods, and they prob- 

 ably do increase them somewhat." As 

 this statement is not proved, it can only 

 be regarded as Colonel Chittenden's 

 personal opinion. There is certainly no 

 more reason for believing that forests 

 promote the combination of floods from 

 different tributaries than that they have 

 the opposite effect. It may be ad- 

 mitted, however, that it is possible to 

 conceive of circumstances in which, un- 

 der extreme conditions, the presence of 

 a particular forest may increase a par- 

 ticular 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 

 seepage, it must in the vast majority of 

 cases reduce the frequency and violence 

 of floods. 



It is true, as stated by Colonel Chit- 

 tenden, that the records of high water 

 in most streams do not show that the 

 waters now rise under extreme condi- 

 tions higher than extreme floods which 

 have occurred in the past. The highest 

 recorded flood on the Connecticut River 

 occurred in 1854, long before the pres- 

 ent 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 in this question. To represent 

 them as doing so is like arguing against 

 the benefit of food for the reason that 

 a man's food may choke him, or against 

 the benefits of the <un's heat, for the 

 reason that people occasionally get sun- 

 struck. 



Colonel Chittenden illustrates the ac- 

 tion of a forest by considering an in- 

 clined plane surface "practically imper- 

 vious to water" with a layer of sand 

 covering some small portion of it, and 

 to which a spray of water is applied. 

 This comparison, ho\vever, is not a 

 correct one, for the forest cover does 



