This doesn't really happen in natural situations, because riverbeds generally aren't this smooth.
When I first noticed it, I was reminded of waterfalls, especially the way they were portrayed in 8 bit games. [1] It turns out not to be that easy to find a good real world example, at least not without watching hours of waterfall footage, but this one [2] does an acceptable job showing it. I have no idea if this could be caused by the same or at least a similar mechanism.
When I first noticed it, I was reminded of waterfalls, especially the way they were portrayed in 8 bit games. [1] It turns out not to be that easy to find a good real world example, at least not without watching hours of waterfall footage, but this one [2] does an acceptable job showing it. I have no idea if this could be caused by the same or at least a similar mechanism.
[1] https://www.youtube.com/watch?v=qfOKHuzn1Hs
[2] https://www.youtube.com/watch?v=7L3m_3aRiHE&t=190