Just thought I'd point out that in the Old Testament, terms that seem to at first clearly speak of the entire earth actually refer to only a localized region, such as the Babylonian Empire for example. Daniel, for example, plainly says that†Nebuchadnezzar was king of the entire earth, but we know now that it wasn't literal. In the New Testament, Paul says that the gospel had preached to the whole world (all nations) when in reality we now know that he only spoke of the Roman empire. So, when the flood is spoken of as engulfing all the earth, it only means a "local" region. Be careful about being so dogmatic on the flood. It's too easy to show from Scripture that it was not a global event. What I've presented here should raise a question in your mind about this and maybe keep you from developing subjective ideas with no solid proof that what you believe is really true. That's the way legalism develops and there's nothing more dangerous to truth than that. Islamics do this kind of thing all the time and look at how dangerous and unreasonable those people are.
Just a friendly suggestion.†
Now why would I entertain a suggestion from a person who has not read the biblical account in detail? Or who makes false parallels between Christians and Muslims? In fact, by your own statement you imply that you know that a literal reading of Genesis does state a world-wide flood, but you find that unacceptable. But to hint that believing God had destroyed the world with water will lead to violence is absolutely hilarious. What a typical liberal "defense."
The flood itself was a unique event in our world. The Hebrew word mabbul, translated as flood, is only used in Genesis 6-9 and in Psalms 29:10. When the New Testament writer referred to the flood, they used the Greek word kataklusmos, from which we get our word cataclysm. The implication is that this was not a typical local flood.
The Quantity of Water
The flood started seven days after entering the ark. God Himself shut and sealed the door to the ark. The start of the flood is measured from Noah's 600th year of life, in the second month and 17th day of that year. A world-wide rainstorm began that lasted 40 days. If you think about it, that is a lot of water. In our current climate the skies do not hold enough water to rain for 40 continuous days. However, if the world was covered by a water canopy (i.e. a large cloud layer), then there would have been enough water. In addition, God released the water from the great deep. In other words, the waters in various underground reservoirs were released.
"The water prevailed and increased greatly upon the earth, and the ark floated on the surface of the water. The water prevailed more and more upon the earth, so that all the high mountains everywhere under the heavens were covered. The water prevailed fifteen cubits higher, and the mountains were covered" (Genesis 7:18-20 NASB).
The water had to be at least 22 feet deep because the ark floated on the water during the flood and calculations indicate the draw of the ark would be 22 feet. The description of those waters is that they "prevailed" on the earth. The meaning of the word "prevailed" is "overwhelmingly mighty." This is not the description of a small amount of water. Later we read that the waters covered the high hills and the mountains. Not just some of the mountains, but all the mountains under the heavens. This would have to include Mt. Ararat where the ark eventually came to rest upon. Mt. Ararat is 17,000 feet high! This could not have been a regional flood. The account clearly states that the waters covered all the high mountains and then rose 22.5 feet higher.
The Extent of Destruction
The record obviously discusses a world-wide flood. If this does not describe a world-wide flood, what more could the writer add to indicate such? In the flood all human and animal life, except what was on the ark, was destroyed (II Peter 3:6).
Consider this, if it was just a local flood, why would there be a need to save all the various kinds of animals? Could they not simply move to an area that the flood would not reach? The reason for carrying the animals on the ark is that there were no safe areas in the world.
The Duration of the Flood
The waters continued to cover the earth for 150 days. Once again, this could not happen in a local flood. The waters would have receded much sooner in a regional flood.
Once the ark came to rest on Mt. Ararat, it took an additional two and half months before the other mountain peaks could be seen. Noah waited another 40 days (day 264 of the flood) and then sent out a raven through the window of the ark. The raven did not return as a raven does not mind standing on wet ground. A week later, day 271 of the flood, Noah sent out a dove. The dove returned to the ark. A dove will only roost in trees and on dry ground. Another week later, day 278 of the flood, the dove returned with olive leaves in its beak. This indicated plants had started to grow once again in the world. Notice that even after the flood had ended for four months, there still wasn't any dry ground (it still doesn't sound like a local flood). One week later, day 285 of the flood, Noah sent out a dove for the third time. This time the dove did not return.
On day 314 of the flood, 29 days after the last dove was sent out, Noah removed the roof from the ark. Fifty-seven days later, day 361 of the flood, Noah, his family, and the animals left the ark. It was over a year (53 weeks) from the time they entered the ark before the world was dry enough to permit human and animal life to live in the world again.
The Change in Topography
In Genesis 8:1, the winds began to blow. This is the first mention of winds in the Bible. It could be that it wasn't necessary to mention up to this time, but it could also mean that climate of the earth has now changed, causing non-uniform temperatures over the world, thereby producing winds. Other changes occurred as well. In Psalms 104:6-9, God mentions that the mountains rose and the valleys sank. This means the mountains are higher today than they were before the flood. The valleys probably refer to the deep ocean valleys being formed to hold all the water that covered the world. It is interesting to note that the mountains of Ararat are formed of pillow lava. Pillow lava is only formed by volcanic lava flows under great depths of water.
Global or Local?
The description of the flood isn't just that it covered the whole world. There is a wealth of description of the destruction that includes numbers for depths and duration. Having exact values means that this isn't some vague figurative speech. The description in every way does not match a regional flood. It can only describe a world-wide flood.
And I haven't even gone into the physical evidence of the Flood that exists throughout the world, such as fossils of sea creatures on the tops of mountains, the coal beds, the buried oil, or the fossils showing rapid burial.
Between you and I, I only see one person who isn't reasonable.