Four years later and the pattern is still there

There was a pattern in this gill on the slopes of Rest Dodd when I last went past four years ago http://wigtonphysics.blogspot.com/2015/08/interesting-wave-like-pattern-in-gill.html It was in a slightly different part of the pool but was still there. This time I could see progressive waves moving through the pattern. There is a vertical stone at the back which would reflect them so this should be a good site for a stationary wave to appear so perhaps the pattern shows nodes and antinodes. It has occurred to me that I could test this hypothesis in the lab by setting up a ripple tank with a reflective barrier and adding detergent.