This makes me mad. Kid's gotta experiment, man. How's we supposed to learn the science stuff elsewise? >:p Feckin books? Screw books. I wanna build a thing, and watch it systemically alter itself over time based on fundamental laws!
@@Quotenwagnerianer I feel like that's a rather naieve view of science. To a certain degree it's true; you can accomplish a lot more by trusting the experts in the field to be generally correct and have a pretty good grasp on things, but science is ultimately about thinking critically and asking questions, and believing you can answer them. You build a much more intuitive understanding of a science when you're active in asking question in that field, and when you're just starting out with science, it is deeply informative and relatively straightforward to repeat experiments that have already been done, to come to your own conclusions based on those experiments, and so on. So I'm going to disagree with the sentiment you put forward. It's not a waste of time. Hell, replication studies are a huge part of scientific rigor that don't get nearly enough love; why should we discourage participation in the way you're suggesting? What does that really gain us? Fewer scientists, less question, less rigor, more biased assumptions made by a minority of people that happened to be the first to study a problem and therefore became the "experts". It is not a waste of time to study something that's already been thoroughly studied, because there is always more to learn. It is not a waste of time to tread ground that's already been tread, because until you tread that ground, you won't know what it feels like to do that, why people have made the decisions they've made. I cannot agree with the naieve assumption that science should be "left to scientists", because otherwise there will be no new scientists. That's my two cents anyway :p
@@Woodledude Half the joy in science is learning something, and later doing an experiment, any experiment, and going 'ohhh... so *thats* how that works out.'. used to spend entire days playing around in a local stream, come back muddy and sandy. but happy. would still do that if I wouldn't be looked at judgingly now I'm 20 years older XD
Rip rap may stabilize a portion of a river bank, but it creates further damage downstream. There are better and more natural ways to restore and protect a river bank, including when human infrastructure is at risk. Learn more here: www.ausableriver.org/programs/restoration
@@ausablecenter Wouldn't it be better if the riprap extended along the full length of the curve, ie from one straight to the next, rather than as placed? I understand this is for educational purposes, I'm just wondering.
This was in my recommended because I've watched one of these live, and then have watched a couple videos like this, and one of a guy just unclogging street drainage
I can imagine a bunch of people the ausable river association sitting around drinking tea and talking about rip-rafts and meanders and spring sappings.
I know you're here to help people know how to stop rivers from ruining places and stuff, but please do more videos like this. I think the entertainment value of it alone will catch people's attention which would help spread awareness much faster than most other methods. I've love to see a time lapse of how a river naturally forms from a water source. Also, making a big mountain and seeing how long it takes to erode away and collapse would be epic. uwu
@@foodforthesoul1326 Except that this is how rivers work. A sand model works the same except it speeds up the developments. Where this took a few hours a real life river will take decades/centuries
Wow, RU-vid algorithm finally recommended something good! 👍 That’s a really nice example of meandering channels and how they evolve thru time. Did my MS thesis on a very closely related subject back 20 some years ago - used ModFlow to see if drainage ditches along a road would affect cutbank erosion (inconclusive). I like how your run clearly shows the effects of riprap, and the meander cutoff was great to see, though I’m surprised you didn’t require more time.
Having already seen a similar video, I was pleasantly surprised how good this video is. I like the addition of the riprap and the detailed explanations of particular events.
Its amazing to see it happen at both scales. I saw that effect of the river eroding and getting one turn cut, making the stream go straight. I saw it using animations and images from google maps, and it was quite impressive, but seeing it happen in real time here is so much better.
I love how this exemplifies that the outside radius of a turn in most situations is where most of the energy tends to be applied to the media and where most of the wear and turbulence will occur.
Very interesting indeed. I live in a havy meander area (lower Paraná) and it could be important to talk how these kind of river usually meander inside a "flood valley". Urban development tend to ignore this area and catastrophe comes knocking at your door when the "thin" and curvy stream becomes a straight and thick river, swallowing up all the banks.
This video is very neat, I wasn't aware that the erosion of soil via groundwater was called spring sapping. Thank you for the entertainment and valuable information! :)
When using riprap it should be extended around the bends and keyed in at stable locations in the banks. I wish I had the equipment to make cool simulations like this. Excellent information. Thank you.
Something that blows my mind is the scale. I kayak rivers in my free time and the one by my house has bends that exceed a 1/4 mile. The amount of erosion that happens on that scale is insane
Funny how channel meander models have to start with the meanders. What will happen eventually is the formation of a braided network with multiple meander channels of varying sizes, discharges and sinuosity.
Hi Andy, Thanks for the comment. It can take a while for the meanders to develop naturally, so I think a lot of videos dig out the channel to speed up the process. In this case, I had a few hours to work with, so I formed a channel to start the model and let it run. Many factors affect the development of braided channels versus a meandering, single thread channel, including slope, sediment load, seasonal variability in discharge, etc. It can be hard to translate exactly what's happening in this model to real-life. For instance, this is an alluvial channel model with no vegetation and hard, structural controls provided by the stainless steel basin where the sediment is contained. That's not exactly a scenario found in nature. The meanders can only migrate so far before they reach the edge of the table. However, I think there is some value in seeing how a meander changes through time. Cut banks will migrate outward, chute cutoffs will occur, oxbow lakes will form, etc. It's also interesting to observe the fluid dynamics at play within the channel, and the multi-colored sediment allows for that visualization. You can see the erosion due to higher velocities on the outer edge of the channel causing cantilever failures on the cut bank, and the deposition of sediment by slower currents at the inside edge. Thanks again for engaging with us on this.
@@ausablecenter we're always making models, but sometimes, a simple one (even if oversimplified for truly practical applications to be feaseable) can give greater understanding of a subject down the line. thank you for sharing this! Would've been nice to see a reference to oxbow lakes at the very end, but given the angle you seem to have been working on (as well as the really permeable substrate) it wouldn't realy have been anything. for a teaching aid, this would be quite usefull I think. sometimes you have to learn things that are somewhat wrong, so you can later go 'ah, it's not quite right. here's how we improve it' while learning and understanding more then you did before at every step of the way.
This is a bit off topic but I believe that remnants of meander cutoffs have been observed on Mars which is another big reason to believe that water once flowed throughout the planet.
I do have a few questions: I know it would mostly depend on the local area but how long would this particular outcome take on average? Would adding more ripraps increase erosion speed downstream?
Hmm, interesting. So, a question or so.... The wave formation of the river channel when you start is high amplitude, and short wave cycle. I remember flying into Winnipeg and seeing the river that runs through it, and it was similar to your model, except that the shape was more like that folded ribbon candy where the long sides of the wave almost touched, and the arc of the curve was very wide. I am thinking that this is a more common shape in rivers that flow through very flat land, and the more hilly the area is, the shorter the wave length is and the shorter the amplitude of the wave is. Correct, or is some thing else going on. Oh, in flat land, water flow rates would be much slower than in steeper areas, and I don't know if that would just slow the erosion process down in the flat lands but end up with a similar shape and process...
You're correct that when a river's slope is low, meanders tend to form and erode the landscape laterally. This creates wide, flat valley bottoms with the "folded ribbon candy" shape that you're describing. Over time, those long sides of the wave will narrow the meander neck, and a cutoff will form, like the one in the video. Steeper channels have very low sinuosity and erode their landscapes vertically, creating deep, narrow V-shaped valleys.
I have a river near my house and I have seen a lot of these formations in it. It's not nearly as bendy but now I know how in some parts there are just these ledges and in others, "beaches" were created.
I can remember being told 40 to 50 years ago that the more the river meanders the less the fall in the land. Greater fall leads to straighter river and more current. Is this still correct? I think this info came from The US Army of engineers and the attempts to straighten the Mississippi River. The straight river was trying to meander again
I’m not fully versed on this stuff but I assume riprap is rocks or other material used on the banks of streams to try and keep it in place and meander is the soil/sediment. Am I Right?
Natural stream restoration methods is the better solution. This is a complicated process outside the scope of a RU-vid comment. You can learn more about natural stream restoration on our website: www.ausableriver.org/programs/restoration/natural-stream-restoration
So thought experiment question; if given enough time and assuming all factors controlled (human activity, plate tectonics long term, etc) would all rivers eventually strive to be as straight as possible? It reminds me of the coffee creamer and entropy comparison.
Not quite. Check out our blog to learn more: www.ausableriver.org/blog/why-do-streams-meander#:~:text=Meanders%20are%20produced%20when%20water,pool%20structure%20of%20a%20stream.
The section cut off becomes a billabong, or oxbow lake. The billabong might dry out over time, or become filled when the river floods its banks and overflows back into it.
This was super helpful in helping me understand for a uni assignment! If the model was deeper with more sand under the rip rap, would it eventually undercut the rip rap & cause it to collapse?
Is there much difference if you vary the stream flow periodically over time ? IRL there would be annual spring runoffs followed by summer dries and then back again, would this lead to a significant difference in the outcome ?
This would lead to a variable outcome, however this simulation is designed to speed up the meander/erosion process, and the results you see would take place over a long period of time (see answers to similar questions below). The amount of time this process takes will take into account the variability of stream flow over time.
I don't know if it's considered rip rap, but I've seen rivers and creeks in Oklahoma where farmers had placed old cars, tires, and other junk into the banks to prevent erosion (mostly so they didn't lose land for farming etc.) Kind of interesting when you run across those things.
There are methods to help combat erosion induced structural collapse of housing and other buildings along river banks, but ultimately the water consumes all. It’s best to build a safe distance away from the water’s edge. That said, if you do build too close to the banks, and you _really_ want the building to last centuries down the line when the erosion eventually will be an issue to the foundations, place it on piles going into bedrock, and elevate the building well above the flood line.
That largely depends on the type of tree and geomorphological nature of the river. Trees are a critical component for bank stabilization, but major flood events can still have an adverse impact on erosion, and some trees (such as white pines) provide limited root structure to hold soil in place compared to other species (like silky dogwood, who's roots can extend 12 or more feet into the soil).
Great question! I have bachelor's and master's degrees in geology and have been a licensed professional geoscientist for 15 years. Unfortunately, even I don't get to play with the table all day, every day :-( If you'd like to make a career out of playing with these kinds of toys, I might suggest becoming a professor of geomorphology at a university. Good luck!
For the non-Earth Science peeps in the comments, basically the turning points of the water are cutbanks and are banks that are cut(no way lol). This is because erosion is higher here since water wants to continue to move straight(inertia) so most of the force is forward on these cutbanks.
In some cases if the cut off bend in the river doesn't dry up you get a little lake or pond with a bent shape. Translated from Swedish they're called sausage lakes. :D
This is a very interesting subject I didn't realize I wanted to watch, but even the time lapse portions of the video are out of focus, let alone the rest of it. The bitrate of youtube already makes it difficult to make out what's going on with all the moving sand
Super interesting, great video! Somehow I think it's noticeable that the starting state of the model is artificial, i.e artificially narrow river and so on. But we have to start somewhere.
We didn't make the houses. They came with the stream table. I agree that it would have been better to have something other than a clear plastic structure to use in the simulation. For an in-person demonstration, they are easy to see. They can be a bit difficult to make out on camera.
@@Kyle-xk2rb I just worked out an approach which I guess could work. Would you like to see the algorithm? If it eventually works, it's possible to finish developing the mod.
I fully get what's going on in this video, but I lost my shit at the moment when, after going the whole video speaking in terms which DO make sense but, when used in this context without any real base knowledge of the topic, sound like absolute gibberish, the guy said in a very calm yet serious voice: "The house has collapsed into the river."
What happens if you keep the simulation running? Of course you have to put the washed away sand back to the start, but aside from that, you can keep this running forever and it will eventually keep forming new meanders, right?
Rivers will naturally continue to meander. You can learn more about this process via our blog: www.ausableriver.org/blog/why-do-streams-meander#:~:text=Meanders%20are%20produced%20when%20water,pool%20structure%20of%20a%20stream.
Not a weird question at all. This is from the website of the company that makes these tables: "The media is made of recycled, ground melamine plastic and is about 60 percent the density of quartz sand (1.6 g/cc). This means the media can demonstrate river behavior and channel morphology with impressive accuracy at the space and time scales of our river models."
No comment on how the river was cutting into the bank before the riprap, and how you had to fix it at one point because it had cut *behind* the riprap?
I didn't interfere with the banks during the simulation. I believe that I did point out how the eddies were scouring the bank immediately upstream of the riprap. If the simulation had continued, the scouring would have likely flanked the riprap and caused the bank to fail. Thanks for engaging on this topic with us.
