I have had the principles of Noahs flood used by JW's to encourage me to attend meetings recently and this has got me musing about the flood....again.
Depending on what outcome you are after, you could through Noah back at the person and say that any religion that teaches Noah's flood as literal is not the truth and hence you won't be going back. Then go over the endless reasons why it is impossible.
Genesis states that a river flowed from Eden and branched out into four rivers, two of which being the Tigris and the Euphrates.
Good point that there could be no mighty rivers without rain, something I had never thought of before. Further is that the Tigris and Euphrates existed according to Genesis before the flood, and afterward. A global flood, particularly the Watchtower one that completely changed the landscape and pushed Mount Everest 9km high, would have erased these rivers. The fact they remained after the flood shows the flood was just local, or figurative.