braided stream sediment flume experiment

This video is a fast motion record of a sediment flume experiment illustrating braided channel processes similar to what may be found operating on an aluvial fan surface. The dimensions of the sediment flume are 6 meters long by 3 meters wide. Throughout the experiment, water and sediment were fed continuosly through the flume, while the floor of the flume was made to subside continuously effecting a continuous drop in base level similar to what might occur in a basin that is subsiding tectonically. The total amount of time elapsed for the experiment is 45 minutes.

Channel processes on display include channel avulsion (a change in flow direction brought on by a buildup or deposition of sediment), channel expansion (an increase of channel width brought on by a decrease in sediment supply or increase in water flow [aka a flood]), sweeping avulsion (a change in flow direction that occurs in a radial pattern), and bar growth (arcuate deposits of sediment that divide [mid-channel bars] or enclose [lateral bars] channel flow).

Number of occurences for each type of event:

avulsions, 5
channel expansions, 4
sweeping avulsions, 1
instances of bar growth, 2

Video and experiment by Chris Paola of the St. Anthony Falls Laboratory, University of Minnesota. Date of experiment unknown. Video downloaded from the webpage of Dr. Paul Heller (http://faculty.gg.uwyo.edu/heller/), Department of Geology and Geophysics, University of Wyoming, USA. Video uploaded to YouTube with the permission of Dr. Heller.

Category:

Science & Technology

Tags:

• braide
• stream
• sediment
• flume
• experiment
• channel
• processes
• geomorphology
• alluvial
• fan
• geology
• hydrology
• water
• flow

[jaritos675]

hey bapyou, i was wondering what kind of sediment this person used on their experiment? how large was it? how did he get it?

[bapyou]

You'll find information about the person who conducted this experiment in the video description at right. But it looks as though sand only (?) was used for the experiment.

I did not conduct this experiment. I was given permission to upload it to my channel by Dr. Paul Heller from the Univ/Wyoming. You can download the video yourself from his website. Link at right --->

Good thinking on your part, though: Sediment size is always an important scaling consideration in any flume experiment.

[raymondlawust]

The flow process is good. A frequent occurrence of avulsions. If the inclination is higher I guess entrainment may take place more frequently than avulsions.

[bapyou]

Hey, thank you for hypothesizing. This isn't my video. It's from a researcher in Minnesota. On what do you base your hypothesis concerning slope and entrainment?

[raymondlawust]

Avulsion may be considered as a type of deposition. This is enhanced by gentle slope inclination. Entrainment is just the reverse. Higher inclination promote that. Correct me if I am wrong. Thanks.

[bapyou]

Your explanation sounds like a plausible scenario. I have several texts on fluvial geomorphology and sedimentation, but I've never digested them to the depth that I would like to have done. Thank you for the discussion. Are you a researcher?

[happinesson]

beautiful braided result! Amazing!

[verifunction]

I liked this, thank you for posting it

[raymondlawust]

Yes I am. An interesting area of research. Yet, too much observation but too much precise measurement to support existing postulations...

[bapyou]

Hello atman.

Stream channel avulsions are, quite simply, a change in channel direction. Frequently this occurs when a channel overtops its banks, which may be due to a slug of sediment becoming wedged in the site of the channel avulsion.

Channel expansion means exactly what it says: The expansion of channel dimensions due to increased flow.