The idea of mesopotamian floods being the base for the Biblical flood story is not new at all. It was an explanation that I first heard decades ago.
What is new (less than 5 years) is the idea that the stories orginated with the flood filling the black sea about 7 or so 1,000 years ago. Google something like "black sea flood" and you will get some discussion of it.
see
National Geographic - 404
However, I've seen a bit of mention here of other ideas that I know little about. The concept is that it is a metaphor. That the "waters" were the orgin out of which the world and all was formed originally. That the waters would "cleanse" the evil in a symbolic way and return it to start over again.
I suspect that some combination of the two ideas is as good as any.
Certainly, I don't think the idea of a great flood would be used in the stories of a culture that had not experienced flooding. There are many flood stories around the world. As far as I'm aware they all are in locations where catastrophic flooding occurs once in a life time or three.
All the details of Noah being a merchant and desert rains for months on end do not sound very credible to me -- but I know nothing about it ; it is just the way its sounds to me. I suspect these are very speculative things made up to fill a bit of TV time.