usual ly at the edges of sites. Gravel stockpi les are considered to be tem- 

 porary and are located within the material site. Dikes and stockpiles of 

 unused gravel were sometimes left intact when the site was abandoned, thus, 

 contributing to the long-term effect of the gravel removal operation. 



Any dikes or stockpiles deflecting or otherwise modifying flow patterns 

 could aggravate the long-term hydraulic effects of the material site. Flow 

 alterations could significantly modify the hydraulic forces in the local 

 reach of the affected floodplain and cause other damage. Alterations to 

 natural flow patterns in the winter could induce or aggravate auf e i s forma- 

 tion. 



The water quality of an area could be affected by the location of these 

 structures in the floodplain. Any erosion of overburden piles by active flow 

 could introduce large quantities of organic materials for suspension and 

 eventual downstream deposition. Also, any structures that would impound 

 waters, after high flows have receded, would result in differences in the 

 water quality between the active channel and impounded waters. 



Aquatic biota could be affected by the presence of obstructions. Fish 

 could become entrapped behind any structures that impound water. The suspen- 

 sion of fines in the water column as a result of erosion could cause redis- 

 tribution of fish and reduction of riffle invertebrates. 



Overburden piles provided a nucleus for revegetation of abandoned 

 material sites. The organics, and particularly the root stocks and slash, 

 facilitated re-establishment of vegetation in localized areas of the site. 

 Overburden piles were used for denning by ground squirrels and, because they 

 were vegetated, provided habitat for small mammals and nesting passerine 

 birds. Abandoned stockpiles of gravel were less prone to provide these 

 cond i t i ons. 



In the long-term, any alterations of flow patterns that resulted from 

 abandoned structures probably would be detrimental to vegetative recovery 



377 



