The Noah story has to be made up. Nothing about it works. If you have to resort to magic
to fill in all the places where the story breaks down scientifically, yes, the flood seems like overkill.
First of all, we know what floods do to landscapes. We know what floods leave behind in terms of evidence. And there was no global flood because there is no evidence. But even assuming that god magically hid all the evidence somehow, you end up with, at minimum, millions of dead, rotting people, plants and animals. This would pollute the water and soil massively, creating a disease vector like nothing ever seen on earth.
Then you need bang, right out of the ark, human, plant and animal evolution happening so fast that every few generations has to be completely different. No gradual descent with modification, no time for that. But nobody notices people giving birth to different races of babies--Middle Eastern/Turkish folks would have to instantly produce Swedish, Spanish, Inuit, Chinese, Peruvian, Khoisan, Fijian, Sudanese and Samoan looking children, who then would have to make their way thousands of miles to their new homes. Or else Turkish looking people would have to migrate all over the world and then
suddenly produce all those different races.
Reptiles would be giving birth to parakeets, whales giving birth to horses, and saber tooth tigers giving birth to hyenas. Kangaroos and platypuses show up all of a sudden, somehow. But nobody takes any notice.
Then, for some unknown reason, about the time people start doing science, all this rapid hyperevolution slows to almost a standstill until it is barely detectable. Then to make it even more absurd, nobody bothers to document the evidence for actual, slow, biological evolution until the 19th century, and Christians to this day deny it is real .....