On July 25, 2017, after we had a lot of rainfall, I did a trip to take photos and videos of dams with a high river flow. This is from the east bank of the Fox River in Montgomery, IL.
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(new window) As the comments in my video indicates, I was surprised to see multiple hydraulic jumps.
Because I was in the area, I checked out what the dam looked like when there was less water in the river. I'm learning that the flow in the river is evidently always rather brisk. The river must be on a rather significant gradient. Also, the multiple hydraulic jumps may be caused by the dam's design since I still saw them with less water going over the dam. If so, I wonder what the design looks like.
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A standard ogee crest dam has a curved top and a rather vertical drop to the river bed. But that design causes dangerous undertows at the face of the dam that have drowned people. It appears that this dam has a short vertical drop that then has a shallow incline down to the river bed. So instead of one huge hydraulic jump that causes a backflow towards the dam face, this design seems to have multiple, smaller jumps that acts more like a rapids instead of an undertow. Even though it is not a rolling dam, I used the "wwDamRolling" because it seems to be an alternative (safer) design to the rolling dam.
I got a closeup of the high water mark on the dam's abutment. I can't figure out what caused the "jagged" watermark that is way above the regular watermarks.
I took this photo to record that the water level was rather low. During my July 2017 visit, the water had been up on the flat grass that we see on the far bank. And the trunks of some of those trees were in the water.
At the end of the second video, I was surprised by how clear the water was. I wonder what the white stripe signifies.
Several photos of the flooded river bank in the South Broadway Park are available in my photo log. And move photos of the dam are available in my Nov 2020 photo log.
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