If there's one thing we know it's not, it's those kinds of floods, because those you talk about come from Ice Age and giant glaciers sliding or breaking down giant lakes. There was none of those in the Middle East when humans existed, not in Mesopotamia which is a giant flat plain, and that's where those stories came. We know the biblical account is a copy of the Sumerian account, and we know what event the Sumerian account comes from. It's not an Ice Age story, and it doesn't come from an earlier, older memory from WAY further North. The closest event to that is indeed the Black Sea expansion that happened at the end of that period, and we know that one took a few thousand years.