I have over 500 river level measurements recorded from the gauges as the flood water rose and fell during the 2014 floods.
You can find my partial graphical analysis here River levels 2014
The datum levels vary along the Thames but this is not a problem. The interesting feature here is that the top line (Windsor Park) gauge shows a significant rise over time that is matched only by the Old Windsor gauge.
This chart clearly demonstrates that the river levels of a rising wave approaching from upstream over time are magnified downstream. This is due to water being funnelled into a single channel with reduced capacity as calculated by cross-section, gradient and rugosity. Could it be that the incoherence of the current version of the River Thames Scheme is now exposed?