Another dating methods that disproves a worldwide flood: dendrochronology. Matching patterns in tree rings have made it possible to construct a tree ring database up to 11.000 years back for some regions.
Guess those tree just kept growing while under water for a year.
Or varve dating...the layers deposited in lakes. Lake Suigetsu shows no signs of a global deluge in the last 52000 years, or we would have heard about it.