Site Response Groups B through E did not display any apparent similar 

 Physical Site Characteristics. Thus, it was judged that drainage basin size, 

 channel width, channel configuration, channel slope, or stream origin were 

 not significant factors in governing the responses of terrestrial biota. 



Gravel Removal Area Characteristics 



The most significant similarities in Gravel Removal Area Character- 

 istics were those that led to permanent or frequent hydraulic influence 

 within the disturbed area. This annual stress led to a significant and often 

 long-term impediment of site vegetative recovery. Two similar Gravel Removal 

 Area Characteristics were observed that produced this result. They were: 

 scraping within the active channel at any location along the river coarse; 

 and scraping adjacent to an active channel primarily on an inside bend, and 

 without an adequate buffer along the channel. 



Scraping Within the Active Channel. Wherever gravel was scraped from 

 within the active channel, the scraping also extended beyond the original 

 channel to adjacent gravel bars. In these areas gravel was scraped to depths 

 equal to or slightly below normal water levels. This characteristic produced 

 a long-term decrease in Biotic Group I (primarily shrub thickets and passer- 

 ines). The hydraulic changes that occurred in these areas were the prime 

 factor found to be influencing site vegetative recovery. These changes are 

 discussed in further detail in EFFECTS OF GRAVEL REMOVAL ON RIVER HYDROLOGY 

 AND HYDRAUL ICS. 



Scraping Adjoining the Active Channel on an Inside Bend . At seven sites 

 gravel removal occurred on a point bar or inside meander but did not extend 

 into the adjacent active channels. All sites were of sinuous or meandering 

 configuration and were scraped on sharp inside bends. At five of these sites 

 (Penny River, Ugnuravik River, Skeetercake Creek, Middle Fork Koyukuk R i ver- 

 Upstream, and Middle Fork Koyukuk River-Downstream) the scraping occurred to 

 within or below the water level. Except at Middle Fork Koyukuk River- 

 Upstream, no buffer was maintained between the scraped area and the main 

 river channel. At the Middle Fork Koyukuk R i ver-Upstream site a 30-m wide 

 vegetated buffer was maintained. However, within a few years the rivers had 

 formed cut-off channels through the scraped areas at all five sites. 



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