10. And a river went out of Eden to water the garden; and from thence it was parted, and became into four heads.So I've been pushing on with my reading of Gerhard von Rad, who summarises the scholarly opinion here.
11: The name of the first is Pison: that is it which compasseth the whole land of Havilah, where there is gold;
12: And the gold of that land is good: there is bdellium and the onyx stone.
13: And the name of the second river is Gihon: the same is it that compasseth the whole land of Ethiopia.
14: And the name of the third river is Hiddekel: that is it which goeth toward the east of Assyria. And the fourth river is Euphrates.
One river waters Paradise and then divides into four branches. Now suddenly we find ourselves in our historical and geographical world! The author projects a picture of the great river system that surrounded the world he knew, for the number “four” circumscribes the entire world (cf. the four horns as the kingdoms of the world, Zech. 2/1ff) The first river … does it refer to the ocean surrounding the Arabian peninsula or even to the distant Indus? The second river cannot be the Nile, more probably the Nubian Nile, south of the first cataract … Or does Cush not refer to Ethiopia, but to kussu, the land of the Cossaeans in the West Iranian hill country? … The third river is the Tigris, the fourth the Euphrates. [von Rad, 79]The urge topographically to pin down this Eden narrative, whilst of course understandable, human even, is daft: might as well try to pin down the exact relationship between our world and Middle Earth. The game, as von Rad sees, is not in the topographic specifics, but the fact of connection in the first place. The simplicity of this is obvious: nobody thinking twice about the narrative could believe (for instance) that a boat-trip up the Euphrates, or the Tigris, would lead to Eden. The point is a spiritual, not a geographical, one; that paradise is connected to reality in a direct and a sequential manner. To quote von Rad again: ‘what an inexpressible amount of water was in Paradise, if the river, after having watered the garden, could still enclose the entire world with four arms and fructify it! All the water outside Paradise, which supplies all civilisations, is, so to speak, only a remainder of residue from the water of Paradise!’ 
This has the smack of a poetic truth. But there’s another aspect to it, which the excellently-named von Rad does not touch upon. It is not just that according to this story the real world, our world, is connected to Paradise in a direct and (chronologically) sequential manner; but that the nature of that connection is fluid. Water, of course, is essential to life; a fructifying power (if I were called in to construct a religion…). But it is also formless, a fluid continuation of the oceanic formlessness out of which Genesis’s God creates the cosmos at the beginning of the book (viz., 'And the earth was without form, and void; and darkness was upon the sea of chaos. And the Typhoon of God vexed the waters.')
Where does this water come from? Not out of the sky, as rain; but not, either, out of the ground—as, for instance, a spring or source. The J-author is puzzlingly specific about this. Where does all the water in the world come from? ‘There went up a mist from the earth, and watered the whole face of the ground’ [Genesis, 1:6]. This ‘mist’ is a famous crux: the Hebrew is ’ēd.
What is it? Karl Barth thinks ‘surely we can see a reference here to something already well known to primitive man—the origin of rain from the clouds and of the clouds from the moisture which rises from the earth.’ [Church Dogmatics, 3:1 241]. But this is daft. The point here is to locate the origin of the waters of the world as specifically not chthonic, nor as falling out of the sky. And this is fundamentally not because those realms are incompatible with YAHWEH’s power, but for a simpler reason: Eden, as a place, has neither a subterra, nor a sky. It is not material after the manner of our material world.
It is, though, evidently saturated with water; enough to wash the whole world. It is also the crucible out of which mankind emerges. But man is not water; man is the dessicated, adam-(a)dāma, man-earth/dirt/dust. For dust thou art, to dust though shalt—I forget how the rest of that goes.
Life flows fourfold, or manifold, from a single source not once but many times in the Bible. Here’s the first:
17: And Cain knew his wife; and she conceived, and bare Enoch: and he builded a city, and called the name of the city, after the name of his son, Enoch.Lamech begets Jabal, Jubal, Tubal-cain, Naamah; and these individuals stand at the head of the major divisions of human culture: shepherds; poets; metalworkers. But this is also a famous, major crux. Because immediately following this aetiological myth of origin we are given a narrative that absolutely contradicts it, or—since the story in question is The Flood, perhaps I should say dissolves it.
18: And unto Enoch was born Irad: and Irad begat Mehujael: and Mehujael begat Methusael: and Methusael begat Lamech.
19: And Lamech took unto him two wives: the name of the one was Adah, and the name of the other Zillah.
20: And Adah bare Jabal: he was the father of such as dwell in tents, and of such as have cattle.
21: And his brother's name was Jubal: he was the father of all such as handle the harp and organ.
22: And Zillah, she also bare Tubal-cain, an instructer of every artificer in brass and iron: and the sister of Tubal-cain was Naamah.
10: And it came to pass after seven days, that the waters of the flood were upon the earth.But if humanity must pass through this pinchpoint, Noah and his family, then the offspring of Cain cannot stand at the head of generations of shepherds, poets and metalworkers. How to reconcile this contradiction?
11: In the six hundredth year of Noah's life, in the second month, the seventeenth day of the month, the same day were all the fountains of the great deep broken up, and the windows of heaven were opened.
12: And the rain was upon the earth forty days and forty nights.
13: In the selfsame day entered Noah, and Shem, and Ham, and Japheth, the sons of Noah, and Noah's wife, and the three wives of his sons with them, into the ark;
14: They, and every beast after his kind, and all the cattle after their kind, and every creeping thing that creepeth upon the earth after his kind, and every fowl after his kind, every bird of every sort.
15: And they went in unto Noah into the ark, two and two of all flesh, wherein is the breath of life.
16: And they that went in, went in male and female of all flesh, as God had commanded him: and the LORD shut him in.
17: And the flood was forty days upon the earth; and the waters increased, and bare up the ark, and it was lift up above the earth.
18: And the waters prevailed, and were increased greatly upon the earth; and the ark went upon the face of the waters.
19: And the waters prevailed exceedingly upon the earth; and all the high hills, that were under the whole heaven, were covered.
20: Fifteen cubits upward did the waters prevail; and the mountains were covered.
21: And all flesh died that moved upon the earth, both of fowl, and of cattle, and of beast, and of every creeping thing that creepeth upon the earth, and every man:
22: All in whose nostrils was the breath of life, of all that was in the dry land, died.
23: And every living substance was destroyed which was upon the face of the ground, both man, and cattle, and the creeping things, and the fowl of the heaven; and they were destroyed from the earth: and Noah only remained alive, and they that were with him in the ark.
24: And the waters prevailed upon the earth an hundred and fifty days.
This, rather obviously, is what these rivers are: the flow of genealogy. And this is what the narrative is saying: from what seems like the most tenuous of origins (a ‘mist’; a single stream; a spurt of sperm; a helpless baby) oceans can flow. And this is why the writer is unconcerned that Noah’s flood contradicts the preceding narrative. What the Flood narrative does is dramatise the way the surging mass of everybody else in the wide-world threatens to overwhelm the individual coherency of the family-unit. Water in this text is fertility, and the flood is the fable of excess fertility. In symbolic terms, this ocean of people is Cainite humanity—is us, in other words; we shepherds, we poets, we metalworkers. And the ark is the much smaller group of chosen folk, Israel, beset on all sides.