[CT-Freeper]

Honestly, I think HairOfTheDog is probably correct - the story of the flood is most likely a legend used to describe the Wrath of God, and what happens when people turn their backs on Him.

Concerning why so many different ancient cultures have flood stories, well that's easy: floods happen! Every region certainly has a "Great Flood" once every few centuries or so.

[HairOfTheDog]

Furthermore, if other worldwide flood stories were indeed related to ~the~ flood, there'd be no legend from those regions at all... there would have been no survivors to tell the tale.