I think there was a global event on a scale not seen in a long time.. Many civilizations speak of a major event similar to the flood.
You might enjoy The Cycle of Cosmic Catastrophes--anybody interested in these discussions might. Despite its sensationalist title, it's actually a serious scientific investigation of evidence for what the authors believe to have been some combination of impacts of debris from a "nearby" supernova and a comet strike about 12-15,000 years ago. The scenarios they describe would certainly have had effects all over the world, if not caused a single global flood, and would have been recent enough to possibly result in legends that survive today. The book has flaws, and I ended up skimming much of it, but it's an intriguing idea.