With the flooding of what is now the Black sea and Persian Gulf on people's recent memory due to Glacier melt after the Ice Age.
That's the Ryan and Pitman theory from 1997. They said there was a 270 ft sea level rise in 300 days about 5600 BCE. That's 2000 years before ANE
myth making. By 2007 it had been disputed by other geologists that it was 100 ft and happened more like 7400 BCE.http://en.wikipedia.org/wiki/Black_Sea_deluge_theory
There are precedents for a legend lasting that long. The myths of the Germanic people start with the entire Earth covered with ice and after some creation stuff with a giant cow and a giant named Ymir (which looks like immer
= German for forever
) then a flood of water breaks out of the ice and floods across the world and leaves 2 people standing. That describes a jöjkullhlaup aka an ice dam which is an event that people living near a glacier sometimes suffer. So the Germanic people remember the end of the Ice Age when they moved north and lived at the edge of the retreating glacier. That would be about 7000 BCE to 6000 BCE. Despite the fact that that doesn't describe a heavy rainfall nor the ocean rising up to take over the land creationists tout that as yet another flood legend constating Genesis.
(In parochial school I was told that the miles deep Noachide Flood froze all the way to the bottom in the winter months of the year that is was on the Earth and left the Ice Age glacier as an aftermath.)
So another Babylonian/Sumerian version is that the Flood was the Demoness of Chaos. Tiamat, and her servant/ally, the Sea Demon, L'th'n (vowels unknown), trying to take over the land but the God of Rain, Bel Marduk, beat them back.
HP Lovecraft combined L'th'n, aka Leviathan, with another monster sea god, Kaitos (usually known by the Latin spelling Cetus), to make his Cthulhu.
So consider the Burckle Crater discovered in 2006:
It is 18 miles wide where the ocean is over 2 miles deep. It was discovered because chevrons of tsunami debris in Madagascar and Australia point to it. The debris dates around 3000 BCE which is the time of the ANE myth making. It would produce a tsunami followed by a rain storm of the ocean water blasted into space falling back as rain.
Here's the Wikipedia summary:http://en.wikipedia.org/wiki/Burckle_crater
Here is a formal paper on it:http://www.earth2class.org/k12/w8_s2007/CRBurckleAbyssalImpactCra%5B1%5D.htm
That is coauthored by Dr. W. Bruce Masse of Los Alamos National Laboratory. He assembled 175 myths from around the Indian Ocean and said 14 of them agree that there was an solar eclipse as an omen shortly before. So he dates the Flood to May 10, 2807 BCE exactly. However, I'd like to point out that Dr Masse is not an ethnologist and, as in the case of the Elder Eddas, an enthusiastic advocate may distort a legend to get what he wants from it.
Of course, old legends do not need a single source. Similar events even centuries apart become combined in people's minds. I see that even today where people get modern events wrong by 10 years.
On the other hand, consider that there was once in northern Europe a species -- a people as it were -- of talking bears who made and used tools. They had culture and cultural relations with human societies. They, according to legends, founded Berlin and Berne, Switzerland. They lived in houses and according to one legend, liked to eat porridge for breakfast and go for walks if the porridge was too hot. I mean considering all these German-Slavic legends of talking bears there must be a scientific origin for it. It couldn't just be stories.