The Environment Agency (and its predecessors) used a variety of hydraulic models to predict the performance and justify the construction of flood alleviation schemes and in particular, to support their assertion that operation of the Jubilee River does not exacerbate flooding in Datchet and further on downstream.
My hypothesis is that when operated, the Jubilee River bypass channel conveys flood water along a smoother, steeper and shorter route. This flood water travels faster, arrives downstream earlier and is superimposed onto still rising (because it is slower) Thames water. Consequently flooding in Datchet and downstream is exacerbated due to use of the Jubilee River, lack of local flood defences, deficient (i.e. unmaintained) land drainage infrastructure (main rivers and ordinary watercourses) and climate change.
UNDER CONSTRUCTION