channel slope, and local flow characteristics at flow obstructions. Hy- 

 draulic geometry is defined as the geometric and hydraulic variables at a 

 cross section that vary with changes in discharge. The hydraulic geometry 

 variables discussed are top width, hydraulic depth, and mean velocity. Chan- 

 nel slope (gradient) is the reduction of the water surface elevation in the 

 downstream direction. A general discussion of these hydraulic parameters is 

 presented in the following subsection, followed by a description of the 

 effects on these parameters due to gravel removal. 



Undisturbed Condition 



The hydraulic geometry parameters considered herein are top width, 

 hydraulic depth, and mean velocity. The top width is the width of the water 

 surface at a given cross section and a given discharge (Figure 29). The 



Water Discharge ( Q ) 



Mean Velocity (V= x) 

 Hydraulic Depth (d=:^) 



Cross- Sectional Area (A) 



Figure 29. Schematic diagram illustrating definitions of channel geometric 

 and hydraulic variables. 



hydraulic depth is defined as the cross-sectional area of flow divided by 

 the top width. The mean velocity is defined as the ratio of discharge to 

 cross-sectional area of flow. An estimate of the carrying capacity of the 

 channel is the conveyance, which is defined by: 



102 



