Module 5

January 31, 2022

Field Observations: Hydraulics

Step 1: Location Map

Stop 1: Logan River Access near Second Dam, Logan Utah

Stop 2: Logan River Access near Spring Hollow Campground, Logan, Utah

Step 2: Field Sketch: Location Stop 2

Note: the numbers in this photo correspond to the recorded observations displayed Figure 3. Numbers 1-4 were thought to be examples of flow separation point (1), flow reattachment zone (2), flow seam (3), and the shear zone (4) as shown in Figure 1, but looking at the field photo again of this area, it seemed to be a more complicated riverscape to read. The shorter arrows denote slower flows while the longer arrows denote faster flows.

Figure 1. Location: Stop 2: First attempt at identifying features

This image displays my first attempt at identifying the flow separation point, the flow reattachment zone, the flow seam, and the shear zone. This image corresponds with the field sketch above. After discussing this image with Joe, this is a more complicated riverscape as there is interference happening with this being a confluence of two streams.

Step 3: Field Photos

Figure 2: Location: Stop 1

Examples of flow separation point, flow reattachment zone, flow seam, the shear zone type (in this case an eddy). The flow is separating at the rock and is reattaching just upstream of the tree in the top left of the image. This image also explains where the flow is faster and where it is slower. The longer blue arrows represent faster flows while the shorter blue arrows represent slower flows.

Figure 3: Location: Stop 2

Examples of convergent flow (green arrows) (5), divergent flow (yellow arrows) (6), uniform flow (blue arrows) (7), and non-uniform flow (blue arrows) (8). The yellow and green arrows do not show flow magnitude, however the blue arrows do. The non-uniform flow is moving faster than the uniform flow.

Figure 4: Location: Stop 2

Another example of divergent flow, but this time it is coming off an alluvial fan as displayed by the green arrow.

Examples of Flow Types displayed at Stop 1, Second Dam

The dominant flow type at Stop 1 was riffle as displayed in the image above.

Another flow type present at stop 1 was a waterfall. However, this image displays an example of a frozen waterfall. Once the ice melts, this feature will form a waterfall. Although, not a natural waterfall, a waterfall none of the less.

Step 4: Discharge Estimate of the Channel at Stop 1

Discharge was estimated using the "orange peel" method at Second Dam (Stop 1). We first took some rough measurements of the width and average depth of the channel. To obtain some rough velocity measurements, we dropped a stick off the bridge and into the middle of the channel and timed how long it took the stick to go under the width of the bridge since we had a rough estimate of how wide the bridge was.

Estimated width of channel: 60 ft = 18.29 m

Estimated depth of channel: 1 ft = 0.30 m

It took the stick to 4.98 seconds to travel 6 ft/1.83 m (the width of the bridge) = Velocity = 1.20 ft/second = 0.37 m/second

Q = VA

Q = 0.37 m/second * 18.29 m * 0.30 m = 2.03 cms

Q = 1.20 ft/second * 60 ft * 1 ft = 72 cfs

Step 5: Cross-Section Field Sketch

Location: Spot 1

The yellow line on this picture represents the area of where I drew my cross section.

Location: Stop 1

Cross section drawn in the field.

Step 6: Hydraulic Jump

Demonstration of Hydraulic Jump at Stop 2, Spring Hollow Campground

Although not the best demonstration, in this video, Joe is demonstrating where a hydraulic jump can be found in this stretch of the river. The flow upstream is subcritical, then it transitions to supercritical to the hydraulic jump itself, and then transitions back to subcritical flow downstream.

Picture of Hydraulic Jump at Stop 2, Spring Hollow Campground

The picture displays the flow upstream is subcritical, then it transitions to supercritical to the hydraulic jump itself, and then transitions back to subcritical flow downstream.

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