Hi Donald,
I reckon the vertical banding mentioned is generated by the 'diamond' open section of the lattice steelworks of the bridge. If you count the 'stripes', they correspond to the open diamonds and this, along with the long exposure and ripples on the river are, IMHO the most probable culprits ?
Nice picture by the way.
P.S. I have been on this forum since around 2009 but unfortunately forgot my log in details !!!!
Cheers.