APPENDIX. 



FORESTS AND RESERVOIRS IN THEIR RELATION TO STREAM FLOW WITH PARTICULAR 

 REFERENCE TO NAVIGABLE RIVERS. 



[By H. M. CMttenden, M. Am. Soc. C. E.] 



The following paper is presented at this time with the purpose of eliciting 

 from the society membership the results of observation and experience touch- 

 ing the important matters of which it treats. They are vital features of one 

 of the chief living questions before the public to-day, and an expression of views 

 by men accustomed to look at things from a practical standpoint can not fail to 

 be of great value to our legislators upon whom the ultimate responsibility for 

 action must rest. 



While the author's views traverse to some extent currently accepted theories, 

 they are based upon long observation and study and are what seem to be 

 unavoidable conclusions therefrom ; but he is committed to no theory as such 

 and his mind is entirely open to conviction upon any point in which his opinions 

 may be shown to be erroneous. His sympathies are wholly on the side of the 

 present movenfent for the conservation of our natural resources, and, so far as 

 this paper takes issue with certain tendencies of that movement, it is only for 

 the purpose of inquiring whether such tendencies are not really inimical to the 

 cause to which they pertain. 



With this preliminary statement, the author will take up the first part of his 

 paper, viz, the influence of forests upon stream flow. 



FORESTS AND STREAM FLOW. 



The commonly accepted opinion is that forests have a beneficial influence on 

 stream flow : 



(1) By storing the waters from rain and melting snow in the bed of humus 

 that develops under forest cover, preventing their rapid rush to the streams 

 and paying them out gradually afterwards, thus acting as true reservoirs in 

 equalizing the run-off. 



(2) By retarding the snow melting in the spring and prolonging the run-off 

 from that source. 



(3) By increasing precipitation. 



(4) By preventing erosion of the soil on steep slopes and thereby protecting 

 water courses, canals, reservoirs, and similar work from accumulations of silt. 



There are many subsidiary influences, but, broadly stated, the above proposi- 

 tions cover the ground. They were first given general currency nearly forty 

 years ago through the writings of Sir Gustav Wex, chief engineer on the im- 

 provement of the Danube, whose treatise was translated into English by the 

 late General Weitzel, of the Corps of Engineers. Wex's theories were stoutly 

 resisted at the time by many European engineers, and still find only a limited 

 acceptance in the profession, though in the popular mind they have gained 

 ground, and in the United States are now accepted practically without question. 



To establish by definite proof the truth or falsity of these propositions is an ex- 

 tremely difficult task. One would not think so, indeed, to judge from the cheerful 

 confidence with which the popular thought accepts them ; but it is nevertheless 

 so. The elements of the problem are so many and conflicting, the necessary 

 evidence is so hard to get, and comparative records are of such recent date, that 

 precise demonstration is scarcely possible. The popular belief is based upon a 

 fact and an assumption, forming together a basis for a conclusion. The fact is 



"Almost simultaneously with the publication of Wex's treatise, a similar work 

 was published in France by M. F. Valle, taking exactly the opposite view of the 

 question. 



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