Why was the river tillingbourne artificially straightened at abinger hammer?

Question

Why was the river tillingbourne artificially straightened at abinger hammer?

Answer 1

It was to provide a supply of water to a waterwheel which operated a trip-hammer (which gave the village it's name).

That part of Surrey was once one of England's most important iron-producing and metal-working areas.

Answer 2

I bet it was because someone wanted to use that part of the river for a building project

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What man wants man destroys if he can not take it

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Answer 3

If this is where I think it is, this is actually an improvement project for the spawning of fish in this area.  A new channel was built to bypass a derelict mill that had made the river impassable at that point.