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Roads are the primary cause of accelerated erosion and sediment increases 

 from forestry practices (2,4,13,25,27,34,48,50,53,57,69,71). Sediment 

 problems may result from construction activities, poor road design and 

 location, and road use and maintenance practices. 



Vegetation removal can also lead to increased sediment loads in forest 

 streams (13,27,46,52,61,62). The associated methods of vegetation removal 

 (skidding, yarding, etc.) may also contribute to accelerated erosion, 

 depending upon the degree of soil disturbance (43,53). 



Sediment increases may also result from the effects of fire upon the soil 

 mantle. These effects vary depending upon the severity of the fire; 

 natural forest fires may affect the soil mantle differently than certain 

 prescribed burning methods (1,3,4,18,27,28,35,52,60,66). 



Research specific to Montana is outlined below: 



Weisel and Newman (67) studied the Blackfoot River drainage in Montana 

 and concluded that irrigation practices have a greater sediment effect 

 than forestry practices on the area's streams. 



A study done in northwestern Montana by Packer and Williams (52) found 

 that clearcuttinq and slash burning result in erosion and stream sedimen- 

 tation. They noted that erosion stopped after three years on north 

 facing slopes, but south facing slopes were not healed for seven years. 



B. Channel Morphology 



Some silvicultural activities may affect stream channel morphology, including: 

 harvesting practices, road construction, and burning. Changing channel 

 morphology may accelerate erosion, creating sedimentation problems (as 

 outlined previously). 



