Originally Posted by Asha'man

The Genesis flood myth is clearly based on the Babylonian myth of Gilgamesh. (It was even added to the Hebrew story collection during the Babylonian captivity.) The Babylonian myth is clearly based on an earlier Sumerian myth.

In the original story, the flood was indeed local, it was simply a larger version of the annual flooding of the Tigris river. (And archeology has confirmed that the Tigris has occasionally had some really big floods while the Sumerians were living along side it.) The hero of the story was probably a wealthy merchant who traded along the river, using a boat or barge to move livestock. According to the story, he was on his boat for a whole week(!) as the water carried him into the Persian Gulf.

However, this story grew in the telling until it became the pure fiction of the Genesis tale. The whole point of the Genesis story is that all of mankind was wicked, so God was going to commit genocide. He didn’t want to depopulate the world of animals in the process, so an ark was needed. Both of these points would be utterly lost if the flood was intended (by the authors of the story) to be read as local. If it was a local flood, animals and men from other areas would simply re-populate the flooded area from the outside. Clearly, the story demands a global flood interpretation, which is also exactly how it reads.

So, while the Noah flood story had it’s origins in a previous story of a local flood, I think the story is quite explicit that it refers to a global flood, and is therefore pure fiction.