Could the ancient flood myths simply be humanity’s diary during, say, the Younger Dryas Impact? Or some other cataclysmic event that we know of?
While you're waiting for a response, you might look through some answers to a similar questions
"Why does so many cultures have a Great Flood myth? Did a flood really occur or is it a mythological archetype?"
"Why is it that nearly every ancient culture around the world has a flood myth but a worldwide flood theory is not accepted by historians."