If the water is flowing it'll be fine and not stagnant. If you look at the environmental agency website you'll get an idea of the flooding potential, but I'd recommend a walk around the area to see what sluices etc are in place for water level control. I live next a canal and if I were flooded, the whole of the neighboring city would be under water.
Feeding the ducks, swans and other wild life is great fun. The only issue I have can see is if you have young children (for safety issues, unless they are competent swimmers) or a dog (as getting one out a canal can be a problem).