This brings up an interesting question--do we know that it has to be a natural event? Do we know it ever actually occured? I mean, Aesop's Fables never occurred; neither did Jesus' parables. We know that the ancients had a concept of fiction, and that they frequently used it to demonstrate morality/ethics. This is pretty much what the Flood story did. It's entirely possible that this myth is based on NOTHING, just a story that someone told to illustrate a point and which grew with the telling. Floods aren't uncommon, after all, particularly in that region, and the idea of someone putting their goods on a boat to protect them isn't that unusual (Penn and Teller discuss one example of such an event).the GLOBAL flood never happened. But the MYTH most probably has origins in a real event (or series of events), obviously, a NATURAL event, with no intervention from any god/gods.
I'm not saying you're right or wrong here. I'm merely questioning the practice of accepting that there's something to explain here. It could just as easily be that it's a story taken out of context, and expanded well beyond what it started as.