I would go for a sturdy John boat. Granted they are less efficient for paddling or poling and can't get into very tight spots like a canoe can but you do get something in return.

A john boat is much more stable. A consideration if you need to pull someone out of the water and working with or rescuing people who are unfamiliar with boats and how to get in and out of them. If the boat overturns your not going to be much use to yourself or others.

A john boat can more easily mount an outboard but this is a minor advantage. In a flood the water is likely to be choked with trash and materials that don't cooperate with outboards. I would plan on sculling, paddling or poling the boat. A john boat has a slight advantage in poling and they are hard to scull. You can pole a canoe but you risk falling in if you hit something or the current shifts.

The one real advantage a canoe has is that paddling it you have a better chance of fighting a current. Something to keep in mind if your location features raging torrents when it floods.

In selecting a john boat I would look for something light so it can be loaded or unloaded or portaged over obstacles by one person. One with at least enough capacity for four people or two people and a lot of gear. Also a design that resists abrasion and puncture if you go over a steel fence post and can take being beached on sharp rocks repeatedly. A design with a good amount of reserve flotation so it can still safely carry people if it is swamped.