Random fluid dynamics thoughts (and videos)

I was riding my bike this morning along one of the man-made drainage channels in my extended neighborhood.  Couldn't help to watch the water flow patterns and make connections between fluid dynamics and fluid/sediment flow patterns in modern environments.  The short video below shows the fluid dispersal patterns not dissimilar with what one would see in a river reaching a shoreline and changing flow from confined to unconfined on a gently dipping slope.  Note how the fluid dispersal pattern is fan-like, not different from a fan shape in a distributary channel system.  There is a sharp change in slope, about half way through the image.  Note how the dispersal pattern changes from fan-shape to almost parallel stream lines.

There was something else that caught my attention.  To the right of the location in this first video, there was a change in slope, where two concrete slabs came together at an angle.  At the same location, water was flowing from two directions, the stream lines joining at almost 90deg angle.

This caused the flow to have its top surface split in two.  Are these standing waves?  What else are they called and what causes their formation?  The change in slope? Flow directions joining at 90deg angle? A combination of both?  Watch the video and let me know.