A NATIONAL PLAN FOR AMERICAN FORESTRY 459 



tically all the smaller towns and cities obtain their water from forested 

 watersheds. Most of these municipal watersheds are within national 

 forests and have been set aside as special reserves on which other uses 

 are restricted or entirely eliminated. The larger cities have developed 

 water storage for dry periods. The pure, clear water from the heavily 

 forested slopes is ideal for municipal use and for long life of storage 

 reservoirs. 



Within the upper Willamette, the Rogue, and other river drainages 

 of southwestern Oregon, irrigation has made it possible to produce 

 high- value crops such as fruits and vegetables in the rather dry interior 

 valleys. Approximately 80,000 acres of otherwise low-value land has 

 been placed under irrigation, and as a result a considerable number of 

 prosperous communities and cities have been developed. 



Without forest cover or other protective vegetative growth the soil 

 over the greater portion of these drainages would erode easily; where 

 there is a heavy forest cover, however, indications of erosion are prac- 

 tically lacking. Logging operations cover some 200,000 acres in these 

 drainages each year, but because of the heaviness of the timber growth 

 the individual logging areas are relatively small. The destructive 

 logging methods used in the Douglas fir type, including the burning 

 of slash following cutting^ expose the soil to sheet and gully erosion. 

 Rank herbaceous vegetation and a brush cover of sprouts quickly 

 reclothe the soil surface and check whatever erosion has started. It 

 is but a few years until the rapidly growing timber reproduction which 

 comes in thickly on the exposed mineral soil following the slash burn 

 overtops the low-growing vegetation and true forest conditions are 

 restored. If repeated fires take place, however, the timber cover is 

 destroyed and forested areas are transformed into brush fields, which 

 according to Forest Service observers are less capable of retarding 

 snow melt and of regulating stream flow from the heavy precipitation. 



On the upper slopes of the Cascade Range, particularly in the north- 

 ern part of the range, avalanches occur commonly. Occasionally they 

 have been exceedingly destructive of life and property. Many of 

 them start above timber line, on steep slopes at the heads of canyons, 

 and follow a definite course down the canyons. Such avalanches, 

 known as "canyon slides", occurring almost yearly, keep a "slideway " 

 thoroughly stripped of sizeable tree growth. This type of slide must 

 be considered the inevitable consequence of very heavy snowfall on 

 steep, nonforested slopes. 



Another type of avalanche known as " slope slide" is characteristic 

 of hillsides that were once forested but have been devastated by fires 

 or logging. On such hillsides great areas of wet snow some tunes start 

 to slide, as snow does on a steep roof, carrying with them all in their 

 path. Slides of this type do not occur until the forest has been burned 

 or cut, because the trees pin the snow blanket to the ground, so to 

 speak, as nails hold the shingles to a roof. Keeping the steep slopes 

 well forested will forestall the damage which such avalanches do to all 

 in their path and to the valleys below. 



The main slopes of the Cascades are within the boundaries of na- 

 tional forests. The national forests of the Pacific Cascade drainages 

 include 8,588,000 acres of forested land in Federal ownership and large 

 acreages of private forest holdings. Of the Federal lands within the 

 national forests, the watershed-protective influence of approximately 

 5,188,000 acres is classified as major and that of about 3,400,000 acres 



