the active channel. The vegetated buffer was approximately 30 m wide and 

 roughly I m in height; vegetation was missing in and adjacent to a high- 

 water channel which crossed the buffer. Low (0.3 m) dikes were used to 

 block off this high-water channel. Flow began to divert through the material 

 site during the first breakup following the removal of gravel. The buffer 

 breached, apparently caused by overtopping and subsequent erosion of the top 

 and downstream face during the flood. At the time of the site visit in 1978, 

 32 years after the mining took place, 85 percent of the flow was going 

 through the material site. Scraped sites with a large amount, but not all, 

 of the flow diverted through the material site by the time the site was 

 visited included Sinuk River (in-channel site), upper Oregon Creek, 

 Ugnuravik River, Sagavan i rk tok River, and Kavik River. None of these sites 

 had a vegetated buffer. 



A major consequence of flow diversion through scraped sites was the 

 development of braiding characteristics, as was discussed in the previous 

 section. Another consequence was that flow in the former main channel (s) 

 was eliminated or significantly reduced, thus affecting their hydraulics 

 and their regime. Flow through scraped sites that had the potential to 

 aid the replenishment of gravel within the site occurred at Sinuk River 

 (in-channel site), Washington Creek, Oregon Creek, Ugnuravik River, Aufeis 

 Creek, Kavik River, and Phelan Creek. At other sites, such as Penny River 

 and Middle Fork Koyukuk R i ver-Upstream, flow through the site was probably 

 eroding more sediments than it was depositing. 



Most (6 of 7) pit excavated sites had vegetated buffers separating 

 the material site from the active channel (s). The exception is Ugnuravik 

 River (Figure 26), which had only a 5- to I 0-m wide gravel bar separating 

 the material site from the active channel. Therefore, the potential for 

 flow diversion through this pit is high; flow has diverted through the 

 site during floods, but the diversion has not yet been permanent. 



The two pit excavated sites on the Tanana River were judged to have 

 moderate to high potential for some of the flow diverted permanently through 

 the site within several decades following site closure. Both sites had 



97 



