Figure 58. Large area of aufei s at the upper gravel removal 

 area at Washington Creek as it appeared in early June. 



In evaluating the potential for aufeis development at each of the 

 study sites, it was assumed that wide, shallow channels were more likely to 

 develop aufeis than narrow, deep channels. This assumption is probably valid 

 because shallow channels are more likely to freeze to their bed and to have 

 a shallow talik (unfrozen zone) than deep channels carrying equivalent flow. 

 The results of this evaluation of aufeis potential are listed in Table 9, 

 along with the identification of those rivers with aufe is activity or po- 

 tential aufeis activity prior to the gravel removal operation. 



Most of the observations of increases or potential increases in aufe i s 

 activity were associated with mining activities in straight and sinuous 

 rivers, although some activities in braided, split, and meandering rivers 

 also caused potential increases. Increases in aufeis activity were associ- 

 ated with scraping operations. Increased aufeis activity or potential aufeis 

 activity often occurred at those sites where the gravel removal operation 

 was located in active or high-water channels and in locations immediately 



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