These verese describe the spliting of a single river that was going through Edenin into four rivers parting . The first two of these rivers are called the Pison and Gihon and despite the decryptions of their locations they have no match to any post Flood rivers. The third is called the Hiddekel, which is another name for the Tigris. The forth is called Euphrates, but no location is given.
Interesting note the Precambrian rock that the modern Euphrates flows over has a significant depression in it. It is possible given that the Noah's Food laid down everything above the Precambrian that this depression is the remains of the preflood Euphrates river valley.