Floods have no feet.
Venice floods quite often. The city hasn't been destroyed yet!
Port Royal has been underwater for many years. It's still there. It's a popular diving spot now. There are several such underwater cities. They are all not only recognizable cities, they are in remarkably good shape.
The Great Flood, according to the Bible lasted only 40 days.
Floods leave a layer of sediment.
Noah's flood lasted one year and 11 days.