I hardly think Jesus would have alluded to an event people were familiar with if it wasn't true.
He could have done this. If the people themselves considered it metaphor. (not saying this is true... it seems to me that the people did not consider this story a myth, but you never know) Or... if it is the point of the story that mattered more than the literal nature of the story. OR... there could be truth to it, but the story could be told in a simple terms that the people could understand. He also could have alluded to a story that the people understood so that they would more easily understand the lesson or point He was teaching.
It could have been a localized flood that they thought was world-wide. It could have been a much, much, older event than the Israelites thought. It could be translated wrong. It could even be 100% literal, even down to the timeline the bible points it as being, and scientific findings as we currently know and accept them could be wrong.
But it is the truth derived from the story that matters.
To deny the Flood, I might as well deny Christ.
I hope the above can make you reconsider this. The truth of Christ is not dependent on a biblical, inerrant, literal flood story.
Peace to you, truthseeker,
Tammy