It's theological!

We believe the story goes way back to a period well before the invention of writing and, therefore, the advent of literature. In the far distant past (though we are unable to date it now) a devastating flood killed many people (see proposition fourteen). For reasons described in other parts of this book, we do not believe the flood was worldwide, but we do believe it was particularly devastating. We don’t think it is possible to date the event, locate the event, or reconstruct the event in our own terms. That is not a problem because the event itself, with which everyone in the Near East is familiar, is not what is inspired. What is inspired and thus the vehicle of God’s revelation is the literary-theological explanation that is given by the biblical author. We are interested in how the compiler of Genesis used the flood and how he described what God was doing in and with the flood.—Lost World of the Flood, 85