nonexistent the year following site closure but, over 3 years surface flow 

 v^jas re-established. Although the site was not studied when surface flow was 

 absent, the effect on fish would have been to prohibit passage. Epibenthic 

 communities would have been reduced due to the lack of surface water. Fol- 

 lowing re-establishment of surface flow, benthic communities characteristic 

 of riffle zones would be most common due to channel spread and reduced water 

 depth. 



The change from a single channel to a braided channel can significantly 

 affect the local distribution of aquatic organisms. The altered community 

 would be similar to that typically found in a naturally braided system. 

 Reduced water velocity enhances sediment deposition and can alter water 

 temperatures. During the study, changes in water temperature were noted 

 between the upstream and disturbed sample areas, but a difference in sus- 

 pended solids was not found. 



The impact on the terrestrial environment frequently entails removal of 

 vegetation and other habitats along the bank. Little change to the ter- 

 restrial environment would be expected when gravel is mined only on unvege- 

 tated gravel bars, unless the hydraulic characteristics of the channel are 

 changed significantly following site closure. Also, little change would be 

 expected in the scenic quality of an area as a result of gravel removal, 

 unless vegetation is removed. At Aufeis Creek, changes in both the ter- 

 restrial environment and scenic quality resulted from the gravel removal 

 operation because of the area disturbed, the site location, and operating 

 procedures that were used, none of which complemented the floodplain char- 

 acter i st i cs. 



At Skeetercake Creek the hydraulic changes were somewhat different. 

 The exposed gravel deposits were limited because this was a small river. 

 Thus, gravel was mined from vegetated areas in the floodplain, with concom- 

 itant effects on the terrestrial fauna. The gravel removal activity affected 

 channel stability by facilitating a channel cutoff, however, the channel did 

 not braid due, at least in part, to the restricted floodplain. The cutoff 

 formed an oxbow lake in the abandoned site. The floodplain in this reach of 



342 



