As a believer in the God of Abraham I would like to point out that it appears that you and others are failing to address the distinction that according to Hebrew tradition Moses got the flood story from the God who had caused it.
As a believer in the God of Abraham, one would have thought that you would have considered the possibility that there was a connection between Shem, the son of Noah, and Abraham via Melchizedek.
As Shem was still alive in the days of Abraham and Isaac, and Abraham's genealogy is traced directly back to Shem, it is entirely possible that Abraham was related the account of the Flood of Noah by a firsthand survivor.
The meeting of Abraham and Melchizedek adds weight to this proposition as, who else could the next High Priest of Salem be after Noah, if not his eldest son Shem - the last remaining survivor?
Of course, Isaac's son, Jacob (Israel), was taken to Egypt and could quite possibly have related the event to his progeny whilst there.
No need for any conversation by the God of Abraham with Moses.
In fact, no need to introduce the God of Abraham as the cause of the Flood at all. The whole story could just be a back engineered tale of a natural event with the purpose being to give rise to a priesthood who can control the followers by having them believe that without their intercession, then an all-powerful god can wreak death and destruction upon whomever he chooses at will.