If the answer to all the contradictions and physical impossibilities in the Flood account is "miracle! miracle! miracle!", that's fine -- a believer is entitled to their beliefs, irrespective of the factual evidence.
For all I know, any believer with whom I engage in a debate might
need the idea of God, however unsupportable such a belief is, to help them lead a satisfying and compassionate life. Who am I to disabuse them of their irrational viewpoint? I can offer some information or some links if they're interested in the science of any matter at hand, but I hold no vehemence or disregard for those who choose to reject supportable facts, and hold instead to their faith.
With that said, what indeed is the purpose of trying to back up the patently absurd pronouncements in the Bible with physical "evidence" and attempts at logic? There is no logic in the miraculous; no evidence of the impossible. There is no need to point to an ancient hunk of wood, or a sunken city, or a fossil, and say: "Look! The Flood happened!" -- because objectively none of those things support any such assertion. The science of the matter is utterly damning. The only recourse for faith is to leave science out of it altogether.
From the 65-mya iridium layer, to the taxonomic and genetic problems of "kinds", to the total impossibilities of 8 people caring for the needs of thousands or millions of plants and animals, etc. etc. etc., the Flood simply cannot have happened in the world as we understand it according to empirical science. One can exclaim "Miracle!" to hand-wave any objection raised on scientific (geological, biological, engineering, etc.) grounds, but that is an appeal to the supernatural, a logical fallacy which could be made to support any proposition, no matter how implausible.
For example:
It's a miracle that I, Noah David Henson, am in fact a reincarnation of the Prophet Noah, sent back to 21st century America to challenge true believers to find the faithful among you all! Repent now and send me a jillion dollars! My evidence is that my first name is Noah, my second is another biblical king (from whose line I am of course descended), and my last name means "Son of God" in Anglicized Welsh. Ergo, I am a Prophet. Evidence leads to faith. It is written in the Book of Revelation etc. etc. argumenta ad authoritas, "miracle miracle miracle," send me a jillion dollars, miracle!
On the other hand, since there is no rational basis for accepting these wild statements as factual, you can safely reject them all as the steaming heap of poppycock that they are. It's the same thing with the Flood: There is no factual basis for accepting these wild statement, in Genesis or from the many creationist commentators who seek to "prove" it on putative evidential grounds. You can believe them all if you like, and hand-wave away all peer-reviewed, verified and corroborated science on the question that decimates creationist "proofs". But you cannot have both science and faith; in this case, especially, science and faith are mutually exclusive. No appeal to one will satisfy the demands of the other.
/soapbox
