Embedded Files
Interactive Map of Site LOCATION
Interactive Map of Site LOCATION
Field Map Sketch
Field Map Sketch
This field map shows the site of my field observations. The reach is roughly 200 yds long. The locations and rough orientations for photo-based observations are noted in orange.
Flow types
Flow types
Convergent, Divergent, & UNIFORM flow
Convergent, Divergent, & UNIFORM flow
This picture (1) was taken from the bridge. As the channel passes under the bridge, it has uniform flow. It then diverges in response to the gravel bar and converges at the tail end of the bar.
FLOW SEAM
FLOW SEAM
This photo (2) shows a seam created at the interface of two flows moving at different speeds. The right channel is fast, but the left channel is slow. Where these two flows converge, a seam is created. The arrows within the yellow box indicate the seam flow. Small bubbles were present along the seam line.
Flow separation, Reattachment zone, & eddy
Flow separation, Reattachment zone, & eddy
This photo (3) shows the flow being separated by a gravel bar, forming an eddy at the tail end. The flow reattaches at the base of the eddy.
Cross-Section
Cross-Section
XS-1. Cross-section view of the channel. Location noted on Field Map Sketch. Discharge was calculated to be 43 cfs. The channel is at low flow during field observations, but it likely covers much more of the gravel bar on RB when flow conditions are higher. I noticed wooly mullein growing on a bench of the gravel bar. Because wooly mullein only grows in dry places, I interpreted this to mean that the flow had not exceeded that height during the growing season.
Wooly mullein growing on gravel bar bench.
View of cross-section location looking down-channel. Approximate cross-section is drawn in yellow.
Discharge Calculations
Discharge Calculations
To calculate discharge at the site of the cross-section, we measured a 12-foot length and tracked the time it took for 3 sticks of varying sizes to travel that distance in the channel. We took the average of those 3 runs for our average velocity. Depth and flow width were sight-estimated.
Average depth: 0.75 ft
Average velocity: 3.8 ft / second
Flow width: 15 ft
Discharge: (0.75 ft)(15 ft)(3.8 ft/s) = 43 cfs
Hydraulic Jump
Hydraulic Jump
This video (4) shows water pouring over woody structure in the channel. Above the structure, subcritical flow is present. As the water travels over the debris, it transitions to supercritical flow, and then back to subcritical flow. The pocket of whitewater is a visual indicator of the hydraulic jump, which causes turbulence in the flow as the change in flow characteristics result in an energy loss.
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