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USGS CMG InfoBank: Dikes

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Comment: 21:13 - 22:32 (01:19)
Source: Annenberg/CPB Resources - Earth Revealed - 19. Running Water I: Rivers, Erosion and Deposition
Keywords: "Tom J. Pokrefke", river, "U.S. Army Corps of Engineers", "Red Eye Crossing", "river channel", WES, "Waterways Experiment Station", modeling, dike, "point bar", sediment, transportation, bank, scouring, "flow velocity"

Our transcription: Potential solutions to the problem at Red Eye Crossing are tested on the computer.
The construction of walls or dikes within the channel is factored into the program.
According to the computer, dikes help to eliminate the point bars.
Eventually, dikes will be built and tested on the physical model to test their effects on sediment transport.
The way dikes function as far as opening the channel and making it wide enough and deep enough, is they actually take the channel, that has a relatively wide width from top bank to top bank, and it contracts it nominally on one side and makes it a little bit narrow.
What that does is Mother Nature and the River itself says "I need to have so much area available to me," so when you pinch the size, the only thing that can happen is the bed scour.
The thing is that you want to make sure that the bed scour is enough, that the channel is wide enough and deep enough year-round, be it high water or low water.
The other thing is you don't want to pinch it down too much that all of a sudden the velocities start getting high going through that dike field, and then it becomes a problem of navigation also.

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