the river tees has it ever been diverted?

Answer 1

I going to say yes.
Most rivers make their own path over time. Floods and erosion can affect the path it take. Today River Management uses levies and jetties to control the path of many rivers to keep them constant in where they go. Also, periodic dredging keeps the channels deep enough for shipping traffic. So, in a way, we divert the river to keep it where we want it to flow. I give a Copy and Paste;
The course of the valley until here has been generally east-southeast, but it now turns northeast and, nearing the sea, becomes an important commercial waterway, having on its banks the ports of Stockton-on-Tees and Middlesbrough. It passes through the Tees Barrage between Stockton-on-Tees and Middlesbrough, turning tidal downstream from the barrage.
Teesport is built on reclaimed land on the south side of the Tees estuary below Middlesbrough. Is the busiest port in the country, shipping over a million tonnes of cargo per year.
http://en.wikipedia.org/wiki/River_Tees