From photographic evidence 26/01/2016, even with the stream below the weir partially blocked by fallen trees, I estimate that the drop from the Thames to the stream is currently about 1.5 meters. If the stream were to be cleared to allow free flow downstream then it is likely that the range will increase, possibly up to 2 meters which would then mean that King’s Weir/lock would be dry and so would Oxford (without Wytham Weir).
Please note, for the entire length of the ‘old’ Thames from Wytham in the North to Sandford in the South along the western edge of the flood plain, it is at a lower elevation to the Isis which runs along the eastern edge of the flood plain between the same two end points.
Obviously without some serious maintenance of the whole length ‘old’ Thames stream/river bed from Wytham to Sandford and necessary upgrades to return any ‘lost’ drainage channels, diversions of this nature would not be possible in the short term.
“1885: The Royal River –
The picture from here is exceptionally interesting. A rustic bridge spans a backwater trending towards Witham Mill, and in the direction of Oxford. The thickset woods stand out in prominent relief, and another farmhouse of the higher class, surrounded by ricks, appears to the left.
Hagley Pool, which is merely a lake-like widening of the water at the bend, is covered with yellow water-lilies.”
Weir Stream leaving on Right Bank.
The Seacourt Stream is probably an old course of the river which entirely by-passes Oxford, going through Hinksey and rejoining below Iffley Lock. I think this can be canoed.”