Gravel Removal Area Characteristics 



All of the Gravel Removal Area Characteristics were found to signifi- 

 cantly influence the effects of gravel mining. The location of the material 

 site relative to the active channel is considered to be the most important 

 factor. Whether a material site is scraped or pit-excavated is important, 

 but often pits are located away from an active channel, avoiding the types 

 of changes that can be associated with scraping in active floodplains. 



The major effects of pit sites located in inactive floodplains and 

 terraces are the loss of vegetated habitat, the possibility for the occur- 

 rence of fish entrapment, a change in the appearance of the floodplain, and 

 long-term delay in the re-establishment of predi sturbance conditions. Where 

 pit sites are situated close to active channels, particularly on the inside 

 bends in meandering systems, the possibility exists for diversion of the 

 channel through the pit, eventually forming a channel cutoff in the meander. 

 This highlights the importance of providing a buffer between the material 

 site and the active channel. Where pit sites are of suitable size, of suffi- 

 cient depth, and have contoured perimeters, they can increase local habitat 

 diversity and provide conditions suitable for fish and various species of 

 terrestrial fauna. 



Scraped material sites in active floodplains have minimal effects 

 on the floodplain environment when only exposed gravel bars are excavated 

 above the water level, and when slope and contours are maintained (resem- 

 bling those of natural bars). Removal of vegetated areas or banks, which 

 resu I ts in decreased I atera I stab i I i ty of act i ve channel s or a I lows water to 

 spread over a large area, is not desirable. Decreased water depth and veloc- 

 ity increases sedimentation rates, alters water temperature, and alters 

 dissolved oxygen levels. These changes in aquatic habitat usually affect the 

 local distribution and community structure of benthos and fish. 



The effects of scraping in vegetated areas of inactive floodplains 

 and terraces can be similar to those described for pits. However, long-term 

 changes typically are minimal because the lack of standing water in the 



