In large rivers, a given amount of gravel can be removed from exposed 

 deposits with relatively less effect on the floodplain than at a small 

 river. If gravel requirements are very large, the alternatives are to use 

 multiple gravel deposits along the channel, or to expand the areal extent of 

 one site to include adjacent vegetated areas. In a small river system, there 

 are no real options. Gravel has to be removed from adjacent vegetated areas, 

 or from the active channel, or both. This solution was the case for seven of 

 the small rivers studied. The Gold Run Creek site exhibited less change than 

 the other small river systems (except for the site at Phelan Creek where 

 vegetation was not removed). At Gold Run Creek the gravel removal operation 

 was restricted principal ly to gravel bars and an island in the channel. A 

 bank was removed but the degree of floodplain disturbance was less than for 

 the sites on Washington, Oregon, and McManus Creeks, and Penny River. At 

 these latter sites, extensive adjacent floodplain disturbances tended to 

 either greatly expand the channel width or divert the channel. 



Phelan Creek is a braided system and has a small drainage basin above 

 the material site. Although the site is situated near the headwaters, the 

 channel is of medium width because of flow carried in the summer during 

 glacial melt. In this case the large exposed gravel deposits were scraped 

 and the material site included neither vegetated areas nor channels carrying 

 flow. Even though this is a small river system, the long-term effects are 

 minimal because of other overriding factors. Minimal effects are usually not 

 the case, however, on small rivers. 



Location of the material site is most critical on small river systems 

 because of the limited availability of exposed gravel deposits and the rela- 

 tively narrow floodplain. Extensive damage can occur to the entire flood- 

 plain reach being mined in these systems, while on large rivers the effects 

 are not as great because the material sites cover a sma I ler proportion of 

 the floodplain. Location of sites and potential effects are discussed in a 

 subsequent section. 



349 



