No mythology is “true.” Not the story of Zeus as creator of humans and splitting them in half, and not the story of the Nephillim and the global flood that killed them. Each story, however, can be useful if read in the right context.
Like I said in my previous post, flooding is a pretty common disaster and there are many myths that incorporate it, not just the Christian one, so it’s not really anything special. There are also mythologies that end the world in fire, and ice, so pretty much whatever a culture’s climate, their mythology will incorporate it.
By the way, deserts, like those where Christianity has its origins, can have flash floods, which are caused by an enormous amount of water falling in a very short amount of time. They are very rare, but when they do happen they can seem like the end of the world when you live in a usually warm and dry climate.