Lita Cosner and Robert Carter have just said, finding the four floods of paradise after the Flood is impossible, due to the devastation of all land by floodwaters also from below.
Here is where they say it:
Option 1: Pre-Flood and post-Flood designations are identical
The first option is that the Havilah, Cush, Assyria, Tigris, and Euphrates in Genesis 2 are the same as their post-Flood designations.
As we noted, this option fails to appreciate the devastation the Flood would have had on the continents, literally reshaping the surface of the planet as miles of sediment were eroded and laid down. Furthermore, as we have shown, it is impossible to match the Bible’s geographical description with the names in Genesis 2. So while biblical creationists such as Luther, Calvin, and many others held this view historically, it is no longer a viable biblical creationist option in light of current geological knowledge.
Now, what is post-Flood Shinar in modern geographic terms? It is Iraq, Syria and Turkey, or rather parts of all these.*
Now, how many geological layers are there in these countries? I checked the palaeocritti** site, "by location", and saw Iraq and Syria missing, and as for Turkey I only saw one "Miocene" whale - from Kurtchuk-Tchekmedje which seems to be part of the Northern shore of Bosphorus - so, wrong part of Turkey.
 The name of the one is Phison: that is it which compasseth all the land of Hevilath, where gold groweth.  And the gold of that land is very good: there is found bdellium, and the onyx stone.  And the name of the second river is Gehon: the same is it that compasseth all the land of Ethiopia.  And the name of the third river is Tigris: the same passeth along by the Assyrians. And the fourth river is Euphrates.
Kush and its translation Ethiopia only make sense in a post-Flood context. In other words, Phison has to involve Black Africa, and if not literally all of it (though all of what in Moses' time would have been Cush or Ethiopia) at least fairly much of it. The Nile is clearly at least part of it.
And where Douay Rheims has "the same", LXX has οὗτος. It means "this".
11 ὄνομα τῷ ἑνὶ Φισῶν· οὗτος ὁ κυκλῶν πᾶσαν τὴν γῆν Εὐιλάτ, ἐκεῖ οὗ ἐστι τὸ χρυσίον· 12 τὸ δὲ χρυσίον τῆς γῆς ἐκείνης καλόν· καὶ ἐκεῖ ἐστιν ὁ ἄνθραξ καὶ ὁ λίθος ὁ πράσινος. 13 καὶ ὄνομα τῷ ποταμῷ τῷ δευτέρῳ Γεῶν· οὗτος ὁ κυκλῶν πᾶσαν τὴν γῆν Αἰθιοπίας. 14 καὶ ὁ ποταμὸς ὁ τρίτος Τίγρις· οὗτος ὁ προπορευόμενος κατέναντι ᾿Ασσυρίων. ὁ δὲ ποταμὸς ὁ τέταρτος Εὐφράτης.
Assur or Assyria also clearly is only meaningful after Table of Nations.
Moses was clearly giving rivers and lands contemporary names and predicating identity with pre-Flood topography - if not total, at least partial.
One can debate how probable it is that Cush is instead of "Ethiopia" sth like Kish, near Lagash (also named after patriarch Kush, probably). But one cannot go to a totally "generic" solution, unless I misunderstand the term.
If people’s names could be reused on such a scale, then surely it is not a stretch to imagine that generic names could also be reapplied to places. So post-Flood Havilah (the place) was named after post-Flood Havilah (a person), who happens to share the name with pre-Flood Havilah (the place, but possibly also an unnamed pre-Flood person).
Well, no. Greek has "houtos" = "this" and speaks of it in the present tense. While Hebrew grammar permits, the universality of translations does not permit the meaning shade "that is it which was compassing" or "that which passed along".
Note, as a once (or when redacting Genesis still?) "apprentice Pharao", it stands to reason that Moses would have known where to get good gold or bdellium. By trade (or in certain Egyptian pragmatic solutions : conquest and taxation, if need be, also known as pillage, though Moses probably didn't do that even before hitting the overseer to death).
Havilah could well be in Arabian Peninsula, and as to bdellium, while at present Arabia seems poor in Commiphora wightii, Commiphora africana you do find the Hyphaene thebaica (Doum palm) there : it is referred to by Arabs as Jewish bdellium and it was sacred in Ancient Egypt, meaning there is a chance this is what was meant. Moses would have known and cared about it. Unless one wants to place Cush (Ethiopia) further inland than is now usual, and consider our "Ethiopia" (Abyssinia and Erythrea) as Havilah, in which case Phison could be the Blue Nile. Gihon being then the White Nile.
The problem with any identification with any four modern rivers, like Euphrates and Tigris as obvious ones for third and fourth and Blue and White Niles at least somewhat probable ones for first and second, is obviously, in the post-Flood world they do not show as coming from a single river.
 And a river went out of the place of pleasure to water paradise, which from thence is divided into four heads.
Past tense, as in Latin :
Et fluvius egrediebatur de loco voluptatis ad irrigandum paradisum, qui inde dividitur in quatuor capita.
However, the LXX:
10 ποταμὸς δὲ ἐκπορεύεται ἐξ ᾿Εδὲμ ποτίζειν τὸν παράδεισον· ἐκεῖθεν ἀφορίζεται εἰς τέσσαρας ἀρχάς.
Here we have present, though the sense would post-Flood be past tense ... so, I could be overdoing the reasoning from present tense in following verses.
My solution has been, so far, that the common source was post-Flood blocked from flowing into the four rivers and they even started to flow towards each other, probably because tectonic movements reverses the slant of the land. While much land would have been devastated, and slopes could have been reversed, a general dimple like a great riverbed could arguably survive even getting several layers of sediment on it. So, suppose a river went South and then divided into Blue and White Niles, and the White Nile continued into Congo River and the Blue Nile into Ganges ... suppose a river went North and then divided into Tigris and Euphrates, and Tigris continued into the Syr Daria and Amu Daria and perhaps to the rivers of China, and Euphrates continued into Danube and Danube into Rhine and Rhone and Garonne, and Euphrates (or even Tigris) continued into Volga and Don ...
Next question : would Noah have known the geography well enough to know where the rivers flowed pre-Flood? And would he have recognised them post-Flood?
I'd have to answer both in the affirmative. If Noah knew when the highest mountains were covered with 15 cubits of water, it could theoretically have been a pure revelation, but it is more probable he knew the waterline of the Ark (at least when the weather calmed, by experimenting with how long ropes are needed to touch the water, if not by calculation beforehand) and he would also have known he had built the Ark on one of the highest mountains, either the sole highest one or one of two or more of equal height. In that case, Noah would have known when the Ark started moving that "now the highest mountains are covered by water to the waterline of the Ark" and either before or after checked the waterline as being 15 cubits.
But knowing the highest mountains of the pre-Flood world means having a very good sense of pre-Flood geography. This means, he would have known where the four rivers went. And hence he would also have at least a good headway at checking in the post-Flood world where similar great river beds went - and finding some had reversed the direction of the water.
Hans Georg Lundahl
* Main divisions of Shinar : Babylonia and Assyria. Babylonia is in Mid-Iraq, Assyria is straddling NW Iraq, N Syria and E Turkey.
** A Google site which used to have a customised URL and now has the longer and more cumbruous URL:
Back when I thought that not only customised URL but also all content was going down in 2016, I made a back up blog for it, with the agreement of one contributor. http://palaeocritti.blogspot.com/