How does one prove that a flood did not occur in, say, Omaha Nebraska in c, 2200 bce? Must a flood always leave evidence, even a very deep flood? Could not subsequent events, a wind or sand storm perhaps or other anomaly, remove all evidence of such a flood?
But that is the beauty of falsification. So you cannot do it at one site such as Omaha Neb. As Coyote and Grayseal have pointed out, all you need is proof of continuity of some feature at ANY site (and we have many) which would have been destroyed or altered by a world wide flood. In my opinion the geological column is the biggest impediment to the flooders - particularly in places like the Grand Canyon. You just cannot explain the Grand Canyon with a world wide flood within the past several hundred million years.