Jens Ammon
Hydraulics - Field Observations
Right Fork Logan River
Steel Hollow Trail (#013)
February 10
2021
The accompanying observations are from a section of the Right Fork Logan River, next to the parking loop for Steel Hollow Trail in Logan Canyon, UT.
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This reach studied is a low sinuosity, single channel river in a partially confined valley. Sediment ranges from a coarse gravel to large boulders.
Site Field Map
Divergent Flow: The single channel splits into two around a mid channel bar.
Convergent Flow: Multiple small channels flowing around a vegetated mid channel bar rejoin the main channel.
Uniform Flow: All points in this section of stream generally have the same flow direction, velocity, and turbulence.
Structural Forcing: The boulder is forcing flow to separate and move around it. The water inside the flow seam is moving much slower than the main channel. Immediately behind the boulder are small eddies, and beyond is a mix of wake and eddy flow.
Surface Flow
Most of the river flow is turbulent, however small pockets of smooth and undulating flow can be found on inside bends and areas with dense vegetation.
Estimated Discharge
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In the straight section of river where the cross section was taken, a floating object traveled 29 ft. in 12.68 seconds. While this was only a measure of surface flow, it gives a rough estimation of flow velocity at 2.3 ft./second.
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From the cross section, a rough estimation of cross sectional area for the channel is 5.5 ft.
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A rough discharge (Q=VA) can then be calculated as 2.3 x 5.5 =
12.7 ft. /second
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Hydraulic Jump