Interesting article about Noah's Ark here:
This is, of course, a big problem for those who believe the Bible is literally true as here we have an earlier, different version of the same story. My view is that here we have an old folk memory from the Babylonian area that probably has some element of truth in it.
One theory is that the cradle of Western civilization was actually in a large low-lying fertile area that is now occupied by the Black Sea which was flooded when the Mediterranean broke through at the Bosphorus. The people living there would have had to flee from the only place they knew (the whole earth?) as the salt water arrived and it is possible that some fled to the Babylonian area taking the story of a mighty flood with them.
We may never know the truth but it does appear that the flood story predates the Bible.