During the end of the last "ice age" we had thousands of floods all over the planet.
Because that is what happens if a mountain of ice melts, and then a dam of rubble breaks.
There are huge areas in north America that are formed by: the flood
Then there are hundreds of floods that had similar reasons, like the break from the mediterranen sea into the black sea.
That was a slow flood .... it only flooded the area over the course of 30 years by roughly 100m (100 yards).
That is 3yards per year, roughly 1cm/half an inch - PER DAY.
Why do we know that? Oh, because we found sunken towns, with bronce age tools in the lake, and all the surrounding towns are stone age - they lost the knowledge how to make metal tools.
That the black sea was flooded, we now because the fossils of clams below 100m are all fresh water clams, and those above are sea water clams ...
And then again, by coincidence, we had 3 meteor or comet impacts in a row at the end of the last ice age, two hit Greenland and one west of Africa in the ocean.
That explains the "rain" floods. And yes, Gilgamesh and the Tora refer to the impact west of Africa.