The great flood myths across the world are quite possibly ancestral memories of this kind of flood on a continental scale. Retreating ice age glaciers would make lakes the size of states held at bay by an impromptu dam of various kinds of debris (or more glacier) which then would break dumping great lake amounts of water hundreds of miles into the ocean within days. This kind of thing probably happened in lots of places.
It is supposed that such an event happened, when the land between continental Europe and England got flooded. This was as well during a warmer period when glacier melted. And there was human population on that land.
Oh there's geological evidence of these things happening in the pacific northwest, the waves and water scouring the landscape in an unimaginable fashion left evidence to be seen today. Like 1000 Niagra falls for a month straight. Outflows measured in billions of gallons per second or 10+ cubic kilometers per hour.
Yes this is exactly the kind of thing i'm talking about and in the time frame which is at least plausible to make its way through mythology to modern day (not so much for the flooding of a dry mediterranean sea five million years ago)
