What great flood? are you talking about the flood for which there is no evidence?
HI stamp,
The believer is not so concerned with physical evidence. You see, for us, if all we're going to entertain as truth is only what we can find physical evidence for, then we'd never make it to Jesus. There is no physical evidence that he was the Son of God, even though God himself said that he was, according to the Scriptures. There is no physical evidence that his death really paid any suitable sacrifice to God for sin, although the Scriptures tell us that he did. There is no physical evidence that he was raised from the dead three days after his death, although again, the Scriptures tell us that he did. There is no physical evidence that he ascended to heaven as his disciples looked on, although the Scriptures tell us that he did.
So, hopefully you'll understand that the believer's faith never rests on the evidence of the natural properties of things. For many of us, and I purposefully use the word 'many' rather than 'all' because you will find those among us who are not a part of us just as the first apostles describe in their day, our faith rests on the foundation that God's word is true. He said the whole earth was flooded and describes for us some of the evidences of that, such as all the mountains were covered and that all creatures that move about the earth died.
The waters rose and covered the mountains to a depth of more than fifteen cubits. Every living thing that moved on land perished—birds, livestock, wild animals, all the creatures that swarm over the earth, and all mankind. Everything on dry land that had the breath of life in its nostrils died. Every living thing on the face of the earth was wiped out; people and animals and the creatures that move along the ground and the birds were wiped from the earth. Only Noah was left, and those with him in the ark. The waters flooded the earth for a hundred and fifty days.
The waters covered the mountains more than fifteen cubits. 'Every' living thing that moved on land perished and it lists birds, livestock, wild animals. 'all' creatures that swarm over the earth and mankind. 'Everything' on dry land that had the breath of life in its nostrilss died. 'Every' living thing on the face of the earth was wiped out. People and animals and creatures that move along the ground and the birds were wiped from the earth. The Scriptures seem to take an inordinate amount of effort to impress upon the reader that everything on the whole earth died.
Then we are told that the water flooded the earth for 150 days. Now, we've had a lot of pretty awesome floods recorded on the earth, but there's honestly no way that a local flood will flood the earth for 150 days. The standing water is going to be absorbed by the earth and run out where there are valleys between the mountains. When we accept all the descriptions of the flood, it's really very hard to understand that it could be a local flood.
But, I do understand that there are a lot of people, even among those who call themselves believers, who don't actually believe all that the Scriptures describe.
God bless you,
In Christ, ted