EQUALIZING INFLUENCE OF FORESTS 



559 



floods zi'ould have been increased. If a 

 given amount of snow has to be car- 

 ried off into the streams, it is obvious 

 that the flow of the streams will be more 

 regular if the period of melting is ex- 

 tended, and this is the effect of the 

 forests. 



A further instance of illogical rea- 

 soning is found in Colonel Chittenden's 

 reference to the great floods which oc- 

 curred in the state of Washington. He 

 says : "The great flood of 1906 in this 

 section was a perfect demonstration not 

 only of the vast intensifying effects of 

 forests upon floods due to snow melt- 

 ing, but of the utter helplessness of the 

 forest bed, when saturated with long 

 rains, to restrain floods. It will be 

 clear, however, upon reflection, that this 

 flood is no demonstration of any "in- 

 tensifying effect." It simply demon- 

 strates that there may be heavy floods 

 from forested areas. If those forests 

 were cut down, that same flood might, 

 and probably would, have been much 

 more violent. Colonel Chittenden here 

 apparently forgets the difficulties in 

 studying this problem which arise from 

 the fact that the effect of the forests 

 cannot be separated from the other ele- 

 ments entering into the problem. 



Similarly inconclusive is the state- 

 ment about the flood of the American 

 River compared with Puta Creek in 

 California. Watersheds differ not alone 

 as regards forests, but in other respects. 

 The facts stated simply seem to show 

 that in this case the forests did not reg- 

 ulate its flow to an extent sufficient to 

 counterbalance other factors. For in- 

 stance, if the writer is correctly in- 

 formed, the slopes of the Sierras are 

 steeper than those of the coast range. 

 Again, the shape of the drainage area 

 is a matter of considerable importance 

 with reference to the maximum rise of 

 water at a given point. 



The writer has not had the opportu- 

 nity to study to any extent the condi- 

 tions in the Rocky Mountains, but he 

 observes that Prof. L. G. Carpenter, of 

 the Colorado State Ao-ricultural College, 

 than whom there is no more competent 

 authority, in his paper on "Forests and 

 Snow." comes to the conclusion that: 



(a) * * * the greater the amount of 

 forest cover the less violent the daily fluc- 

 tuation, the more uniform the flow through- 

 out the day and throughout the season, and 

 the later the stream maintains its flow. 



(b) The loss of the forest cover means 

 more violent fluctuation during the day, 

 greater difficulty in regulating the head- 

 gates and keeping a uniform flow in ditches, 

 and hence an additional difficulty in the eco- 

 nomic distribution of water. Also the water 

 runs ofif sooner, hence the streams drop 

 earlier in the summer ; and, on account of 

 the lessening of the springs, the smaller is 

 the winter flow. 



(c) The preservation of the forest is an 

 absolute necessity for the interest of irri- 

 gated agriculture. 



Colonel Chittenden, however, after 

 devoting so much space to considering 

 the effects of forests upon extremes of 

 flow, does not on the whole take his own 

 arguments seriously, for, later on, he 

 says : "In the records of precipitation, 

 wherever they exist, will be found a 

 full and complete explanation of every 

 one of the floods that have seemed un- 

 usually freqtient and severe in recent 

 years." After citing the conditions, he 

 goes on to say : "Similar conditions 

 prevail in every great flood and the tnie 

 explanation is found in them, and not 

 at all in the presence or absence of for- 

 ests on the zvatersheds." 



Reference has already been made to 

 the fact that the amount and distribu- 

 tion of rainfall are the most important 

 factors affecting the flow of streatns. 

 yet it is quite unreasonable to conclude 

 that on that account the forests have 

 no effect at all. 



These quotations are cited, however, 

 to show the apparent contradictions in 

 Colonel Chittenden's arguments. 



It would take too long to analyze in 

 detail the remainder of Colonel Chitten- 

 den's paper and to criticize his many 

 statements. If his views, however. 

 have weight, attention should be called 

 to one statement which he makes with 

 reference to erosion. He states (page 

 055 et seq.) that the sediment carried 

 into the Gulf of Mexico by the Missis- 

 sippi "all comes from the uplands far 

 and near, but particularly from the 

 more remote and hilly regions. This 

 load is in the nature of through traffic. 

 The local freight picked up from a cav- 



