After finding your site, I read an article about Cush, Ethiopia and the rivers that ran through Eden. To be clear, I am not writing to dispute your perspective or opinion, but I am writing to question some of what you said more for the sake of biblical study than anything else.
You said, "Because the great flood of Noah's day wiped out the geography of that time, we have no idea where any of the regions mention in the early chapters of Genesis existed. ... Ethiopia is called the land of Cush, not because it matches the location near Eden, but because its founding ancestor was named Cush."
With respect to the first statement, I'm curious to know what data you are relying on to support your claim. There is clear evidence that the terrain remained the same after the flood because mountains were still in place after the flood. This is confirmed in and out of the Bible. The ark landed on something (a mountain) and that mountain and the ark, or remnants of it, still exist. God wiped out a lot of things. Much of it came in the form of human and animal life. There is no evidence that the world, was made flat.
With respect to the second statement, you had me going, initially. There are some (several) translations that specifically lists or says Ethiopia vs. Cush.
- כּוּשׁ= Kuwsh is "black" by word definition.
- Kush, as a person, is the son of Ham and grandson of Noah, who is the founder of Ethiopia, the land that the river went through
I believe it is here that you are missing the mark in your statement. The land is given the name because of the people who occupied it. It was already there and the Scripture makes that clear. I am using the NKJV but other translations (WEB) say the same or very similar thing: "The name of the second river is Gihon; it is the one which goes around the whole land of Cush." But Genesis 2:13 (WEB) says, "The name of the second river is Gihon: the same river that flows through the whole land of Cush."
The name of the land could have had any other name, but it would have been the same land because the river flowed through it.
I am more than convinced that God masked a great many things that took place in the Old and New Testaments such that we would not be able to rely on stuff to prove His existence, especially the seemingly impossible events and places. Some speak of earthquakes dividing the land such that Saudia Arabia was pulled from Africa and the rivers were lost. That may be, but it's still speculation and unfounded. We need not strive to root our faith in facts of man but only in what God said.
When we trust fully in Him and what He said, the facts or dispute of them are like the wrapper on a piece of candy. We discard the wrapper and enjoy the sweetness of the candy, no matter what.
That the earth's geography was altered is confirmed by "You covered it with the deep as with a garment; the waters were standing above the mountains. At Your rebuke they fled, at the sound of Your thunder they hurried away. The mountains rose; the valleys sank down to the place which You established for them. You set a boundary that they may not pass over, so that they will not return to cover the earth" (Psalm 104:6-9). I don't know why you concluded that the alterations would flatten the earth.
A change in geography would also alter the courses of rivers. Eden was described as having a spring from which four major rivers originated. "Now a river flowed out of Eden to water the garden; and from there it divided and became four rivers. The name of the first is Pishon; it flows around the whole land of Havilah, where there is gold. The gold of that land is good; the bdellium and the onyx stone are there. The name of the second river is Gihon; it flows around the whole land of Cush. The name of the third river is Tigris; it flows east of Assyria. And the fourth river is the Euphrates" (Genesis 2:10-14). We have two rivers named the Tigris and Euphrates in today's world, but they do not originate from a single source. Nor can you find on the map a single source that produces four major rivers. This further supports the idea that the geography has changed at the time of the flood.
The Hebrew word for "black" is shachor. We don't know what kush means beyond that it was a proper name. There are a few books that assign the meaning of "black" to it, but they do so without evidence.