Figure 8. — Surface erosion 

 on road fills con- 

 structed from granitic 

 materials 1 year after 

 construction . 



the entire 6-year study period. Fredriksen (1970) reported similar slides on roads in 

 steep, unstable terrain in western Oregon. Major failures of this type are not related 

 to surface erosion rates, but rather tend to occur during large climatic events on 

 those areas where the potential exists. 



As with surface erosion, much mass erosion of road fills can be avoided by careful 

 location, design, construction, and maintenance measures. Gonsior and Gardner (1971) 

 listed guidelines for this purpose based on studies of slope failures in the vicinity 

 of the Zena Creek logging study. 



Table 5 .--Erosion control on road fills in the Idaho Batholith 



Percent 



Stabilization measures 1 



: Road location 



: change in 



: References 









: erosion 2 







None (except seed + fertilizer) 



Bogus Basin 



+ 15 



Bethlahmy and Kidd 



1966 3 



Planted ponderosa pine 



Deadwood River 



-47 



Unpublished data 4 





Wood-chip mulch 



Bogus Basin 



-61 



Bethlahmy $ Kidd 1966 



Straw mulch 



Zena Creek 



-72 



Ohlander 1964 





Jute netting 



Zena Creek 



-93 



Ohlander 1964 





Asphalt - straw mulch 



Zena Creek 



-97 



Ohlander 1964 





Straw mulch + netting + 



Deadwood River 



-98 



Unpublished data 4 





planted ponderosa pine 











Straw mulch + netting 



Bogus Basin 



-99 



Bethlahmy and Kidd 



1966 



Al 1 measures except trees 



include items shown + grass 



seed and fertilizers. 





As compared to untreated 



control plots. 









3 Erosion was increased by 



15 percent, possibly by the method of applying seed 



and 



fertilizer. 











4 0n file at the Station's 



Forestry Sciences 



Laboratory 



in Boise, Idaho. 





12 



