The similarities of the two floods are, that the extent of the floods were global, Utnapishtim and Noah were both ordered to build a boat. The boats were very similar, one door, at least one window, many compartments, and had all species of animals on there. Also, they both sent out birds to test and find land, and were both blessed after the flood. These similarities are what make people wonder if the writer of Genesis plagiarized the story of the flood, but there are also some differences.
In Genesis, Noah was directed from God and in the Epic of Gilgamesh, Utnapishtim's means of announcement was in a dream. Even though they both sent out birds to test to find land they sent out different birds and amounts. Noah sent out a raven and three doves, and Utnapishtim sent out a dove, a swallow, and a raven. Also, the durations were different. Genesis was a long forty days and forty nights, and in Gilgamesh it was a short six days and six