One of the evidences for the flood of Noah comes by way of cultural tales around the Black sea area. Although it is possible that some of these stories have been embellished a bit by missionaries, there is actually much support for some type of catastrophic flood from various cultures of the past. Some of the cultures that relate a flood story include: Sumerians, Babylonians, and Hurrians.
One interesting part of the stories involves the commonality they share with the Genesis story. For example, the name of Noah is similar within the Hurrian culture. The birds being released in the Sumerian story closely matches the Genesis account. The Summarian account even has a story of how long the people lived before the flood took place, which is again consistent with the Genesis account.
There is outside support for some type of cataclismic flood. Although cultural stories are somewhat similar to the Genesis account, a solid case cannot be made solely on these past stories. However, it is interesting that past cultures have recorded a story like Noah's account and with other scientific evidence, a strong cumulative case can be made for the flood story as recorded in Genesis 6 and following.
* Bowman, Robert, Scripture: Outline Studies in Authority, Canon, and Criticism, p. 62