Was Noah’s flood local or universal? As this question is highly divisive between scientists and theologians, the answer to be defended will be presented up front. Universal. From a theological point of view, this must be the case. The questions then become, “Why must this be the case?” and “Why do scientists always disagree with this idea?” After answering these two questions, an attempt will be made to explain a moderately satisfactory answer to scientists as to why the theological point of view does not disagree with the most recent scientific investigation.
Why Must this Be the Case?
For Theologians who interpret the Bible with a literal grammatical historical hermeneutic, who try to determine what the original author meant when he wrote the book, it is undeniable that the Noahic flood was universal, meaning that it covered the entire earth, not merely a portion of it. Genesis is clear on this when it describes the flood’s extent. Genesis 7:19-22 says:
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. All flesh that moved on the earth perished, birds and cattle and beasts and every swarming thing that swarms upon the earth, and all mankind; of all that was on the dry land, all in whose nostrils was the breath of the spirit of life, died.
It is unavoidable hermeneutically to say that this account means only “the area around Mesopotamia.” For every mountain under the heavens to be covered with fifteen cubits of water you have to cover every mountain with fifteen cubits of water. That means that Mt. Everest, the tallest mountain in the world, had twenty-two and a half feet of water covering it. Explaining how this happened scientifically is another story, but the Bible is very clear on the point that Noah’s flood, rather God’s flood that Noah survived, was universal, not local. Period and full stop.
Why Do Scientists Always Disagree With this Idea?
Christian scientists always disagree with the idea of a universal flood for a few main reasons. One, their worldview does not allow for the idea that the earth has ever operated in a different manner than it currently operates. Put another way, they can’t accept the idea that men used to live to eight and nine hundred, or that God, a supernatural being, once audibly spoke and physically walked on the earth, or that a flood of water was once so massive that it covered the entire earth because they haven’t observed anything like that happen to them.
One author on the flood put it this way when considering the amount of water described in the Bible. “As we contemplate these facts with all their implications, the problems involved grow to such proportions as to make it well-nigh impossible to believe that the literal meaning of the words were intended, and hence that some other interpretation must be sought.” The question that then comes to mind is, “Why now?” His worldview was so constrained by what science has deemed is possible in this day and age that it could not conceive a world when these constraints did not exist.
The nature and definition of science is necessary to understand both why they can’t accept a universal flood, and why they should. Webster’s definition of science, in the context of scientists, is, “knowledge covering general truths or the operation of general laws as obtained and tested through the scientific method.” The scientific method is defined as, “[the pursuit of knowledge through] the collection of data through observation and experiment, and the formulation and testing of hypotheses.” Put more simply, science is done through guessing, then testing, then repeating that test over and over again to see if the result is always the same.
This basic fact about science is why scientists shouldn’t hypothesize about things like creation, or the noahic flood, because it is impossible to test, or more importantly repeat, their hypothesis to come to an answer. Because they can’t test or repeat the actual process, they test and repeat things about our natural world, assuming that things have always been that way as far back as the world goes. This is where science as defined above stops being science as defined above and starts being guesswork, or faith. What they refuse to see is that science of this kind, historical science, requires as much faith as belief in any other history, namely, the Universal Noahic flood.
The reason scientists can’t accept a universal flood is because the things they have been testing and repeating in their laboratories suggest that a universal flood could not naturally happen in our own time, so they assume that it could not have happened thousands of years ago in Noah’s time. What they ignore are the facts that (1) they don’t know what conditions existed in Noah’s time or how similar they are to today’s conditions, (2) God was directly involved in superseding natural conditions making this a supernatural event, something that science can never test or repeat, so even if they could prove that the flood could not have naturally happened, (which we’ve already established can’t be done) it would matter very little in terms of disproving the Bible’s account of the flood. It is precisely because of these two facts that they should embrace a universal Noahic flood, because the only resource left for us to determine what “actually happened” is eye-witness accounts, and the only eye-witness account that we have is the Bible: God’s eye witness account.
A Moderately Satisfactory Answer to Scientists as to Why the Theological Point of View Does Not Disagree With the Most Recent Scientific Investigation
The above arguments aside, a moderately satisfactory answer to a universal flood will now be presented in an attempt to harmonize both modern day science and a belief in a universal flood. It is of course unnecessary if one understands the reasoning above, but if this theory helps to nudge some Christian scientists closer to the biblical perspective it will be counted as useful nonetheless.
There is a theory, commonly referred to as Canopy Theory, which has presented some middle ground on the subject. It was originally put forth in the book The Genesis Flood by John Whitcomb and Henry Morris. Put loosely, the idea is that a layer of vaporized water existed around the earth in the pre-flood world. This is what the Bible means in Genesis 1:6-8 when it says that God separated, “the waters above” from “the waters below.” The theory also states that this layer of dense water vapor would explain why men lived longer in antiquity, because a more sophisticated filtration system of the sun’s rays would have existed, as well as explain where the water came from that was plentiful enough to actually cover the earth. 
While there are still questions to be answered, this theory is scientifically plausible. There is a certain distance away from the earth’s surface that a layer of water vapor could have existed just as our gaseous atmosphere currently exists. It would also explain a few of the problems that Christian scientists have with a Universal flood. It does not explain all of the problems, but it explains some, thus it was worth mention.
All in all, a universal Noahic Flood is the most theologically accurate view to hold on the flood. While a local flood is defended by well meaning Christians, their attempts to change the Bible based on science is unnecessary and dangerous. If these Christians understood the fallacy that they commit by extrapolating data to the extreme and thus leave true science behind, they would, and should, adhere to the view of a Universal Noahic flood.
Enns, Paul. The Moody Handbook of Theology: Revised and Expanded. Chicago, IL: Moody Publishers, 2008.
Mish, Frederick C. Webster’s Ninth New Collegiate Dictionary. United States: Merriam-Webster Inc., 1986.
Rehwinkle, Alfred M. The Flood: In light of The Bible, Geology, and Archaeology. Saint Louis, MO: Concordia Publishing House, 1951.
Whitcomb, John C., Henry M. Morris. The Genesis Flood. Philadelphia, PA: Presbyterian and Reformed Publishing Co, 1961.
Walvoord, John F ed., Zuck, Roy B ed. The Bible Knowledge Commentary: Old Testament. Colorado Springs, CO: Cook Communications Ministries, 2000.
 Alfred M. Rehwinkle, The Flood: In light of The Bible, Geology, and Archaeology, (Saint Louis, MO: Concordia Publishing House, 1951), 96.
 Frederick C. Mish, Webster’s Ninth New Collegiate Dictionary (United States: Merriam-Webster Inc., 1986), 1053.
 Mish, 1053.
 John C. Whitcomb, Henry M. Morris, The Genesis Flood (Philadelphia, PA: Presbyterian and Reformed Publishing Co, 1961).