Defending Genesis as literal truth is a pretty hard challenge for any Christian. I no longer do it.
I can no longer even argue that the Hebrews were ever enslaved in Egypt. There's not a shred of credible evidence to support it, and the Egyptians documented everything. And the timing is all wrong. Their Golden Age occurred during the time when they were reported to be brought to their knees by Moses and the ten plagues. It just never happened.
Once I realized that, it shook my faith. I mean, if that's not true, what else is not true?
But the bottom line is that Christianity is not based, nor either passes or fails, on the prehistoric accounts in the books contained in the bible. What does it matter whether there was a Noah's Flood or not? It doesn't.
There was no Noah's Ark. Not in the sense that it's being sought by the ark hunters. The story may have its origins in some local event, but the account was never recorded in the book of Genesis until a thousand years later. It's like King Arthur or Robin Hood. The account was not recorded until the story got retold enough times to get really good.
That's my opinion, and everyone else's mileage may vary.