No doubt there have been major catastrophes in the past but the Epic of Gilgamesh is in no way an historical account of any flood. I've never read it previously but the Epic really is fantatstic. It's quite possible that Homer, the prophets and those whose work was added into the Bible may have sourced their intel from it. And that's just what has been written into clay.
The Flood of Noah is not a literal account either. None of the Genesis writings are. They all contain hidden meaning.
"Then Gilgamesh said to Utnapishtim the Faraway, ‘I look at you now, Utnapishtim, and your appearance is no different from mine; there is nothing strange in your features. Tell me truly, how was it that you came to enter the company of the gods and to possess everlasting life?'
Utnapishtim said to Gilgamesh, ‘I will reveal to you a mystery, I will tell you a secret of the gods.'"
"You know the city Shurrupak, it stands on the banks of Euphrates?
That city grew old and the gods that were in it were old.
In those days the world teemed, the people multiplied, the world bellowed like a wild bull, and the great god was aroused by the clamour. Enlil heard the clamour and he said to the gods in council, "The uproar of mankind is intolerable and sleep is no longer possible by reason of the babel."
So the gods agreed to exterminate mankind."