G30 JOURNAL 01^ FORESTRY 



Another fact confirnied in the Emmental investigation was that 

 streams fed from a forested watershed have a more uniform discharge 

 and carry less debris into the larger rivers to wdiich they flow than 

 streams coming from an unforested watershed. The more numerous 

 and greater high water stages in streams in an unforested region dur- 

 ing heavy rains or rapid thaw, increase erosion and carry the debris 

 downward, where it is deposited on the alluvial cones or in the river 

 channels and raises the river bed. That the raising of- the river bed 

 causes floods and damage to property is a well-established fact. 



The Swiss experiments have conclusively shown that extensive 

 damage from floods occurs less frequently in streams coming from 

 forested watersheds than from the streams rising in poorly forested or 

 treeless watersheds. There is, of course, no absolute guarantee against 

 the power of the elements. We must be content with limiting and 

 weakening their effects as much as possible. 



The great importance of forests in hilly and mountainous regions 

 in feeding springs has been proved beyond a doubt in the Swiss ex- 

 periments. 



While the total average annual discharge of the two streams meas- 

 ured remained about 60 per cent of the precipitation over both water- 

 sheds for the entire period of observation, their behavior after heavy 

 rainfall of short duration, such as thunderstorms and cloudbursts, or 

 after uniform heavy general rainfall or general rainfall of variable in- 

 tensity or at the time when snow melted rapidly in spring or winter, was 

 very different. Thus in the spring and winter with a sudden thawing of 

 snow the highest water stage and the total amount of rainfall and run-off 

 w^ere considerably lower in the stream flowing from the forested water- 

 shed than in the stream from the lightly forested w^atershed. When the 

 ground in the forested watershed was not frozen and was not sat- 

 , urated with water from previous rains, all the snow water was ab- 

 sorbed and the greater part of it was stored in the interstices of the 

 soil on the forested watershed. No conditions occurred which enabled 

 the Zurich Forest Experiment Station to determine how the stream in 

 the forested watershed would behave were the rain to fall on solidly 

 frozen ground as the ground in the forested watershed froze less than 

 in the lightly forested, and when it did freeze the frost did not pene- 

 trate deep. 



In heavy rainfall of short duration the retaining capacity of the 

 soil in the forested watershed was remarkably great. The maximum 

 amount of run-off per second in the forested watershed was only one- 



