That's because there's zero evidence to support a worldwide flood at any point in the last 3 billion years. Also, my Bible reading may be off, but I only recall one Flood. The Holocene extinction, which saw the end of the saber tooth cat and the woolly mammoth, was fully 65 million years after the extinction of the dinosaurs. How many floods were there?
But since there is no faith, and people need to see before they believe
http://www.creationscience.com/onlinebook/index.html