The basic design of a canal means that they cannot flood.
If however they are not managed properly that is a different story.
In normal use a canal will not flood because the flow through the locks will prevent that.
There is however a dead or slack season for canals when traffic is restricted mainly because major maintenance work is carried out.
During that period, usually the winter, British Waterways have a duty to keep the water levels to as near as possible to normal.
