The Biblical flood was very real, but it wasn't global, it didn't begin 4500 years ago, and it lasted far more than a year, right up to the current day. Around 10,000 years ago the Mediterranean breached the barrier separating it from the Black Sea, which was then half its current size. Water poured into the Black Sea over an immense waterfall for a century, eventually filling the Black Sea to current levels. The displaced civilizations scattered, some to the Levant where memories of the ancient flood became legends and myths that were one day recorded in the Bible.
--Percy