France is a country that is built upon rivers and streams. And now and then some of them flood. In the last 15 or so years I've been living here, most of the serious flooding has been in the south - not in the area you're considering.

But, like you say, global warming and all, and who knows. In France you are rarely very far from some river or another. And if not a river, then one of the zillions (or so it seems) of canals that connect the various rivers.

You might ask at the local mairie about flooding - when was the last time they had floods in the area, or if there are any particular problem areas in town. In some areas, there is a whole administration set up to deal with the river - traffic on the river, services for those who live along the riverside (boat moorings or whatever). If there is something like that in the area in which you're looking, they might also be able to give you some information about flood risks in the area.
Cheers,
Bev