Indeed, let us answer this: why think the Noah version is the original?

Let us state the bad news first: there is no knock-down argument that the Noah version is the original, apart from the argument that begins that the Bible is the word of God. It is all speculative. (Some claim that Gilgamesh greatly antedated the Bible, but that too is greatly speculative.) But now the good news: there are several plausible points to insist upon in defense of the Noah story. (1) It is the longest and most detailed of all the Flood stories. (2) It is embedded in a relatively “naturalistic” and otherwise theologically coherent (and sane) set of background beliefs. (3) By contrast, other details in the other versions of the story feature things like a mother goddess giving birth to the first seven couples, the gods requiring the food and drink of sacrifices, and generally gods acting much like primitive and corrupt human beings.