You can't prove that miracles never happened, because miracles, by definition, don't follow physical laws.
However, such events as the Flood are physically impossible, and if they happened they left no trace in the soils of the past 10,000 years, and the current genetic diversity was poofed into existence following the flood.
What I was taught, growing up, was that miracles were physically possible. What makes the events miracles weren't that they happened, but that they happened at the right time to be useful.
OTOH, the cantor who taught me that, was talking about the Ten Plagues and Flight out of Egypt. I'm not sure how he handled the Flood.