of birds allows them to redistribute in the floodplain just as large mammals 

 do that are dependent on floodplain habitat. 



Material sites on islands will affect the scenic quality of the flood- 

 plain, but the type of vegetation characteristic of the area would determine 

 the long-term visibility of the site. Where stands of timber block view of 

 the site except from the air, as with the Tanana River-Downstream site, 

 little change would occur. Where such timber is not present the material 

 site could be quite conspicuous and affect the appearance of the floodplain 

 environment more than if the site was located along the edge of the flood- 

 plain. In either case, maintenance of an undisturbed buffer zone between the 

 material site and the active channel reduces the induced disturbances that 

 could further detract from the natural appearance of the floodplain. 



Summary. The problems associated with material sites located separate 

 from the active channel are essential ly dependent upon maintenance of the 

 integrity of intervening buffer zones. Where this is maintained, and the 

 hydraulic geometry of the river is not affected, very little or no change 

 would be expected relative to hydrology-hydraulics, water quality, and 

 aquatic biota. The terrestrial system and scenic quality of the floodplain 

 will be affected because usual ly vegetation must be removed to expose under- 

 lying gravel deposits. Generally, sites located back from the channel are 

 favored from a practical standpoint because they can be operated in a dry 

 condition making for a more efficient and easier operation. Excavating a pit 

 would be an exception because the depths of excavation would normally be 

 below the water table. 



DIKES AND STOCKPILES 



The location of certain material sites and the gravel removal opera- 

 tions require the construction of a protective structure and/or the stock- 

 piling of overburden and gravel in or near the material site. Protective 

 structures prevent water from entering the material site and include channel 

 plugs and diversion dikes. Overburden piles consisting of brush, slash, 

 groundcover, and organic soil are located either permanently or temporarily. 



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