Why Are There So Many Flood Myths?

Why are there so many flood myths about floods, which sometimes end in rainbows? There's more flood myths than there are songs about rainbows. You would think that this would be the largest. But what really greets you as you come up to the third deck is a life size Ken Ham. I stand up of Ken Ham clutching his Bible and smiling at you. Is that wood cardboard with his spectacles? Slash. A hologram or maybe like foam core poster board or something.