Dragons aside, we have a clear case for a one time monster flood. Such a flood would overwhelm thousands of years of natural hydraulics producing new swamps and river beds. That all would demand a generation of hydraulic engineering as the tradition reports.
We really need to carefully investigate many of the great river basins for similar events as well. This is no easy task and scant financial reward. Yet the knowledge would outline general risks and allow them to be identified elsewhere.
Do note just how large the yellow river basin happens to be.