HYDRAUL ICS 



Hydraulic characteristics exhibiting changes as a result of gravel 

 removal operations included the hydraulic geometry (including width, depth, 

 velocity, and conveyance), overall channel slope, local slope redistri- 

 bution, flow obstructions, and area of ponded water. Increases in channel 

 width, conveyance, overall slope, flow obstructions, and ponded water 

 were typical responses to gravel removal, as were decreases in channel 

 depth and velocity. One or more of these effects from gravel removal were 

 observed at al I of the sites except those pit excavated sites that were 

 separated from the active channels by a buffer. Sma I I river systems typ- 

 ical ly had sma I ler f loodplains which forced the gravel removal operation 

 closer to active or high-water channels, causing hydraulic changes. 



SEDIMENTATION 



Sedimentation characteristics which appeared to have changed as a 

 result of gravel removal operations included armor layer and subsurface 

 material site distributions, channel degradation, and suspended and bed 

 loads. The most common significant change in sediment size distribution 

 resulting from gravel removal was a decrease in the size caused by fine 

 material deposition in the material site. This change was reflected in 

 the surface material at six sites and the subsurface material at six sites, 

 three of which were different from those with surface material changes. 

 Channel degradation was observed at four sites and may have been develop- 

 ing at three other sites. Changes in sediment transport due to gravel 

 removal apparently took the form of increases as we I I as decreases, with 

 apparent changes occurring at II sites. Most changes in the sediment char- 

 acteristics resulting from gravel removal operations occurred at scraped 

 sites in or immediately adjacent to active and high-water channels and 

 at those sites where fine sediment sources were left in the floodplain 

 near the channe I . 



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