If you turn on the “terrain” function on google maps, you can see that the property is on a raised area which looks fairly flat and then it looks like the land north of the property drops down to the marshy area by the creek. That’s good. However, the higher ground isn’t very high. The house and grounds are not even twenty feet above the river and the house is not built up on a berm. You know it’s in a hundred-year flood plain; if a 500-year flood happens you could be looking at more than just a wet floor. Yikes. People and animals could die.
I think you are wise to pass on this property. Such a shame because it is beautiful.