Watery tornadoes where two rivers collide

Researchers have found sideways, tornado-like vortices whirling where two rivers collide. The features had been predicted in computer simulations, but not confirmed until now. To observe the vortices, the researchers studied an aerial view of the flowing together of a very turbid river with a relatively clearwater river. The key to forming the ribbon-like vortices, according to the simulations, is that the two rivers' waters have slightly different densities. Such differences can be created by different water temperatures and different amounts of sediment suspended in the waters.

Source:
Aerial Observations and Numerical Simulations Confirm Density-Driven Streamwise Vortices at a River Confluence;
J. Duguay, P. M. Biron, J. Lacey [2022] Water Resources Research

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2021WR031527