A... "little known" fact about water is that it seeks its own level. By its nature, it is impossible for water to cover a mountain without covering it on every side. Thus, you cannot have a flood localised to a mountain or a valley. You can test this yourself. Get a cone shaped object, put it in a tub, and fill the tub with water. Try as you might, you will never be able to get the water above the object without having it completely cover the object.
This makes Genesis 7:19-20 one of many banes to Old Earth compromise. As the Genesis flood covered the mountains, it could not have been local. Water physics just does not work that way.
The only way compromisers can escape this is to suggest that maybe Genesis 7:19-20 isn't supposed to be taken literally. The first thing to note here is that this concedes the point. If they're saying it's not supposed to be taken literally, then they're saying the global flood is what the verses literally say. The question we have to ask is, what justification do we have for taking this as a metaphor?
As it turns out, beyond making scripture compatible with the atheistic creation myth, there is no justification for believing Genesis 7:19-20 is using a metaphor. In fact, it makes much more sense to take it literally, first of all because that's just the straightforward meaning of the text. The entirety of Genesis reads like historical narrative (and, of course, has always been taken as such). It makes no sense to randomly say that Genesis 1-11 are metaphorical, especially if you're wise enough to admit that 12-50 are not. Furthermore, if Genesis 1-11 is a metaphor, it is a metaphor that makes no sense. Those who compromise Genesis with old earth narratives never seem to use Genesis 1-11 in any other fashion than to shred it.
By contrast, Genesis 1-11 contains many theological lessons, and even serves as the foundation for several doctrines (doctrines which, coincidentally, tend to be rejected or altered by those who do not take Genesis 1-11 in its correct fashion) which are addressed elsewhere in scripture.
Referring specifically to the global nature of the flood, we first have the issue of God's reliability. See, local floods do happen, and have throughout history. If Noah's flood was also local, this would mean God either:
- Lied about His promise to never do this again (Genesis 9:11-15).
- Intended to keep that promise, but forgot.
- Intended to keep that promise, but failed.
In all three scenarios, God comes out as unreliable. You can't trust His promises. How, then, can you even call yourself a Christian, if that is the "god" you have? Personally, I feel uncomfortable even discussing the implications of the local flood doctrine. To me, even saying "if God hypothetically did this, then He has this hypothetical bad attribute", is too close to the sin of blasphemy. How so many Christians actually manage to preach that the hypothetical happened, I don't know.
Furthermore, if God is this unreliable with regard to something as simple as a flood, how can one trust Him to do something as complex as reconciling the sinner to Himself? If God failed in His promise to never again flood the Earth, how could we expect Him to keep His promise to make a new Heaven and a new Earth, and to give us an eternal home there? Or maybe these aren't literal promises either?
Furthermore, let us turn our attention to 2 Peter 3, which not only addresses the global nature of the flood, but the ignorance of those who deny it:
"Beloved, I now write to you this second epistle (in both of which I stir up your pure minds by way of reminder), that you may be mindful of the words which were spoken before by the holy prophets, and of the commandment of us, the apostles of the Lord and Savior, knowing this first: that scoffers will come in the last days, walking according to their own lusts, and saying, “Where is the promise of His coming? For since the fathers fell asleep, all things continue as they were from the beginning of creation.” For this they willfully forget: that by the word of God the heavens were of old, and the earth standing out of water and in the water, by which the world that then existed perished, being flooded with water. But the heavens and the earth which are now preserved by the same word, are reserved for fire until the day of judgment and perdition of ungodly men. But, beloved, do not forget this one thing, that with the Lord one day is as a thousand years, and a thousand years as one day. The Lord is not slack concerning His promise, as some count slackness, but is longsuffering toward us, not willing that any should perish but that all should come to repentance."
Now, already, this doesn't look good for Old Earth compromisers. But going back to the theology in Genesis, notice, the original global judgement is contrasted with the final global judgement. The only way to make the Genesis flood local is to also make the return of Christ local. But this doesn't bode well for us. It makes God a local god. I hope, and desperately pray, that I do not need to explain why that's problematic.
You see, then, how the local flood doctrine is impossible. It is nothing more than another modern heresy, held by those who are too spineless to stand firm in the faith, or too dishonest to desire the truth of God. May He have mercy on those who mishandle His word in such a way.