limit activities to the inside of a meander and maintain undisturbed buffers 

 the site must be located on at least a medium sized river. 



Any activity inside a meander, that would reduce the integrity of the 

 banks or weaken the cross-sectional area, could lead to premature cut off of 

 the meander. In many Alaskan rivers during breakup, water often flows over 

 the ice in the channel and, if sufficiently high, over the banks and down 

 the floodplain. A depression resulting from a material site located near the 

 channel on the inside of the meander would aid in channeling the water 

 through the site. Depending on the erodability of the soil separating the 

 material site from the channel, a channel could erode at both the upstream 

 and downstream portion of the meander and thus eventually establish a cut- 

 off. The erodability of the soil would govern the length of time required 

 for this natural event to occur. When a pit material site is connected to 

 the active channel, the probability of a cutoff occurring could be enhanced 

 greatly, even in a very short time. Such an event occurred at Skeetercake 

 Creek on the North Slope. The inside of a meander of this sma I I river was 

 mined for gravel and when the site was studied II years after site closure, 

 a cutoff had occurred. The time required for this event to occur is unknown. 



A pit visited during site selection, but not studied in this project, 

 that showed a potential for channel diversion, was located at Hess Creek in 

 the Southern Interior region. The buffer strip was breached during the 

 first spring breakup following site opening while the site was being op- 

 erated. The initial breach was temporary and the water remained in the 

 active channel when the flow receded. 



The key point of concern when mining in the inside of a meander is 

 maintenance of a sufficiently wide undisturbed buffer zone between the 

 active channel and the perimeter of the material site. The size will depend 

 greatly on factors such as the discharge of the river, flood frequency, and 

 soil erodability and must, therefore, be determined on a site-specific 

 basis. In order to maintain the integrity of the channel over the long-term 

 it may be necessary to dig deeper to obtain needed gravel volumes, rather 

 than decrease the buffer width. 



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