Is the Gilgamesh flood story similar to the Noah's Flood story?

You might want to check OAHSPE for a correlation between Arc of Noa and the sinking of Atlantis (Pan).

It might be shorter to find the differences - there aren't many!

In both stories you find that

- a deity confides in a man that there is going to be a flood which will destroy all living things.

- nobody else is given this message

- the deity tells the man to save himself, his family, and animals by building a boat

- the dimensions and materials of the boat are specified in detail, as are some of the ritual observations, such as sacrifices, that the man must make

- the man does so. Other people are scornful or surprised by what he's doing

- the building and waterproofing of the boat is described in some detail, as is the gathering of different types of animals

- the boat is finished, all the chosen get on board, and down comes the rain.

- the rain lasts for a long time, killing everyone except those on the boat.

- the boat comes to rest on a mountain top

- the man releases first one bird, then another (2 in Noah, 3 in Gilgamesh). One bird is a dove, one is a raven. One comes back, one never does.

- The non-return of the last bird is taken as a sign that the world is coming back to life, because the bird has been able to find food

- the passengers and animals come out of the boat and spread out across the land

- the man makes an animal sacrifice, and the sacrifice is found acceptable

- there is a general resolution that the god or gods will not send another flood again

There are a number of other deluge myths in different cultures including Greek with Deucalion's flood, and even in Central America. But few have as many details in common as these two.