2 acres close to a river

Hei, we are considering buying a little property (not our final home) close to a river which possibly can rise up to about 7 meters (23 feet).

We have not being on site yet and I’d like some info on how to calculate where the water line would be in case of worst case flom scenario. We have a map made from the a state Department and it seems that all of the property would get flooded. I want to learn how to calculate up to which level of the house and the barn the water could get.

Thanks 🌱