By J, of course, I'm talking about the Yahwist strand within the Torah. (And, yes, while I believe the original version of the documentary hypothesis doesn't hold water, I do believe a modern, updated version is the best explanation of the Torah's development and I reject any full-on fragmentary hypothesis.)

Now that that's out of the way?

Idan Dershowitz, who continues to show himself a name to watch in Torah exegesis, argues well in a brief paper that the earliest version of J's primeval Narrative, ie, creation to Flood, did NOT end in a flood but rather a great famine.

Dershowitz starts with the descriptors of Lamech's descendants in Gen. 4. He next notes that Yahweh's promise, after Noah's post-Flood sacrifice, to never curse the ground again has language that elsewhere ties to famines. 

From there, he connects dots from Lamech to Noah. He then goes to look at the Noah references in Ezekiel and Deutero-Isaiah.

How did this become a flood narrative, then? Dershowitz says the popularity of the Babylonian eventually "flooded" the original J narrative.

Sidebar: Exegesis like this shows that van Seters' semi-strawmanning claim that editors didn't exist in antiquity is not true. Maybe how they worked was different from, and harder than, today. But, they were there.