Interesting idea, but with a rise in water of such a level there is going to be a lot of debris headed downstream that may destroy the boat or take it on its way.

Perhaps a boat could be tied on the downstream side of the house. Maybe it's safer to keep an inflatable on the second floor of the house, but I think the best plan is to get out before there's a need for a boat.

I'm afraid that I've never lived in a flood plane, and don't know what to do about a boat for such emergencies. I'll be interested in what more experienced people have to say about the idea.