Ten sites had more than twice as many channels in the material site 

 as were upstream. At four of these sites, Washington Creek, Nome River, 

 Sagavanirktok River, and Middle Fork Koyukuk R i ver-Upstream, the numbers of 

 channels increased more than three times due to gravel removal operations. 

 Most sites (7 of 10) with large increases in numbers of channels also had a 

 very substantial apparent decrease in the lateral stability of those chan- 

 nels. Lateral stability evaluations were based on subjective judgements of 

 stability indicators. Lateral stability indicators included the height and 

 erodibility of the gravel bars at the edge of the active channels, the bed 

 load transport characteristics evident at the time of the site visit, and 

 the channel configuration. 



The Nome River is an example of a material site with increased braided 

 characteristics (Figure 25). In this sinuous river, single channel flow 

 was prevalent prior to the gravel removal operation; exceptions to this 

 are the split in the channel immediately downstream from the material site 

 location and two high-water or sma I I active side channels adjacent to the 

 material site location. Approximately 20 years after the gravel was removed, 

 the river was flowing in numerous, poorly-defined channels through the 

 material site. The river apparently diverted into the scraped area soon 

 after the operation was completed and has attempted to develop a well- 

 defined channel since it diverted. The state of equilibrium between erosion 

 and deposition in the Nome River was disturbed by the gravel removal opera- 

 tion. To restore equilibrium it will probably take several decades from 

 the time of the initial disturbance. 



Flow Diversion Through Site. Gravel removal operations caused flow 

 diversion or a high potential for flow diversion at 12 of the 25 study 

 sites. Sites with a high potential for the diversion of all of the flow 

 permanently through the site included upper Washington Creek, Penny River, 

 Nome River, upper Aufeis Creek, Skeetercake Creek, lower Middle Fork Koyukuk 

 Ri ver-Upstream, and Phelan Creek. At most of these sites, all of the flow 

 had already diverted when the site was visited. All of these sites were 

 scraped and the lower Middle Fork Koyukuk R i ver-Upstream site was the only 

 site where a buffer was known to have been used to separate the site from 



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