These dams accumulate carbon, humus, reduce erosive forces, can slow water speed and lessen turbidity. This course particulate allows better water flow/infiltration compared to small, finer particulate. It allows better water infiltration into the soil, meaning less directly evaporates off to the air. "Check dams" are made so people can harvest clean water even when the surface is "dry." So the course particulate also allows ease of water to move laterally underground within the channel. If you make small, frequent rainwater-harvesting catchments like this you can rebuild/repair deep cuts/gullies etc. The land has a better chance of keeping more even hydrological cycles. This also supports plant life better, reduces downstream flooding, and so on...

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What is not shown off screen is the downstream gate at the end of the flume being closed. This is from the video's description box: "This clips shows basic hydraulics over a weir in the absence of bed material (though there is a small amount of material present in the flume). At the clip beginning dye is injected into flow upstream of the weir to show the transition from relatively deep, low velocity flow to critical and supercritical flow over the weir. Below the dam, supercritical flow is much faster and shallower. As the downstream gate is closed, stage rises and hydraulic jump appears downstream. Here we can also see the loss of energy due to the jump by comparing the elevation of the water surface below the dam with that above the dam. This energy loss is one of the things that make grade control structures work-they act to dissipate the energy of flow at a point of our choosing. Note the turbulence and reverse roller (the sort that is very dangerous to be caught in) below the weir."

Hello & sorry if this reply comes too late. Yes, the "vegetation" we demo is little plastic trees (actually deconstructed craft store decorative swag). Hope your maiden Emriver voyage went well!

@@emriver that's ok. It went well. I learned a lot over the course of the day.

Yes, that is correct.

We gotchu! Click here and take your pick 🙂 www.youtube.com/@emriver/streams

It's water, multiple grains of sand, a box, and a pump.

@@ForkEnthusiast-tw8fg I don't want to make it myself, I want it made for me and deliverered directly to my house then installed so that not one moment of my time is spent on this ordeal.

@@beep_the_foolish That's precisely what this company offers. They make and sell these models. They are mostly sold to museums, Universities, and such. The cost is in the same range as for a nice swimming pool.

Very cool indeed, but this is just an example and there are lot of different factors in "real cases"... A dam itself can bring not only benefits but also damages to the environment, not just as simple as stated in the question and depends on how wrong the urbanization of the stream banks has been occupied, if the purpose was to protect against flooding (remember that floods are natural and it's the use of the water/river banks that must define if a Dam is beneficial or not... In this example one simply doesn't have soil cohesion that is different with other types of soil, existing vegetation and man made bank protecting infrastructures. What it helps me prove to other consultants/clients is that the protective river structures design must be made taking in account the higher flow and less frequent storms for the general solution and, for the lower inside channel, a different design for the estimated two year flood return...

@@MS_APA Thank you for the detailed response. It's always more complicated and interconnected than we think isn't it? Lots of angles and variables that are in play.