As to the Biblical Flood.
Neither Darwin nor Evolution say anything about the Flood. That's found in different fields of science, eg geology, archaeology, anthropology, etc.
Evolution only deal with biology, like natural selection, mutation, genetics, etc, and how the environments can change biological life, over successive generations or numbers of years. Life learn to adapt, because if they don't adapt, they don't survive (hence natural selection).
I have written it before in other threads, about Galápagos Islands. One of the places that Darwin had visited during his voyage on the HMS Beagle in 1830s.
He noticed that many creature from one island is different. One of my favorite examples are the tortoises living on those islands.
In some islands, the tortoises have dome shell, and have short neck and legs. They lived in the humid highland with low-lying vegetation, which they can easily feed on.
But on other islands with drier conditions and sparser vegetation, their food sources are higher up so it would be impossible for most dome shape tortoises to survive in this condition. And it is on these island, where the giant tortoise have different shell, known as saddleback shells. The shape allow longer neck which they crane up. Also the saddleback-type tortoises have longer legs than their dome-type cousins.
And those islands are not really far apart, so it is amazing how you would find diversity of species or subspecies, separated by different climatic and territorial differences.
The Galápagos tortoises are just one of the animals (but not the only one) that allowed Darwin to formulate his theory on Natural Selection.
And Natural Selection only just one mechanic of evolution. Other mechanics also exist (like Biased Mutation, Genetic Drift, Genetic Hitchhiking and Gene Flow), but none of them actually discredit or refute Darwin's Natural Selection. But the theory on Natural Selection has been updated in the 20th century, because more evidences have been discovered.