There are people who believe in the Bible based on strong archeological evidence, strong historical accuracy of the events recorded, and all the Biblical prophecies written hundreds and thousands of years ago which many have clearly come to pass.
All this, on top of testimonials of miracles, as well as personal experience of God's presence.
These people, based on these strong evidences for the divinity of the Bible, also assume, as you do for evolution, that the Bible is true.
So you while you criticize Creationists for already assuming the flood is true, you say your the assumptions you make for evolution are are well founded, based on strong evidence.
The Bible, also has strong evidence.
So don't criticize Creationists for already assuming it's true when evolutionists do the same thing with thier beliefs.