Just playing devil’s advocate here folks…
Here are my thoughts as to how this could all be explained that the flood was needed. I thought of all of this as a young man after reading “Angels and Women” (which I wrote about in my first book I found in the Bethel library.)
This was my thinking on why the flood had to happen:
First, the Nephilim blood line needed to be taken out of the human gene pool.
Satan did his level best to completely “ruin” God’s creation by introducing an abomination of Angel/Women hybrids. This “ruined” the Earth, not just with violence itself, but with violent beings who were part of the gene pool. Getting rid of this gene pool could not be done in one fell swoop however. At least one of Noah’s son’s wives could have had some of that nasty blood-line in her, so it persisted even after the flood. It persisted to a lesser degree however, but showed up later in the “sons of Anakin” you know, Goliath like people. But God wiped them all out as because He insisted that the Isrealites never intermarry with these folks. This drastic measure wasn’t just for religious purity, it was for the genetic elimination of the Nephilim once and for all. Thus, the genocide of many peoples written about in the books of Moses were spelled out specifically. With the last of those people gone, the last of the Nephilim bloodline was gone too. Gene pool ruination score: God 1, Satan 0.
Second, the Earth itself needed to be changed.
I never could figure out exactly why God didn’t make the Earth the way it is now right from the start, but it seems that the old Earth, one with a water canopy above and a fountain of water below had to change. What God would have done to cause this change should Adam NOT have sinned, I haven’t the foggiest idea. Maybe he would have had them build a TON of arks to save themselves. Or maybe God just knew ahead of time Adam would sin and the Earth would have to change in this way anyway… unknown answer… It is a very philosophical question actually, did God KNOW Adam would sin? Of course! He’s omniscient. But knowing something would happen and being responsible for it are two different things. He gave men free will to screw up in lieu of creating robots who did as they were programmed. But He knew which route they would take too.
Anyway, the Earth changed, continents moved, polar ice caps formed, mountains formed, deserts formed, the Grand Canyon formed, Wooly Mammoths are trapped in ice with buttercups in their mouths, etc. Without the flood, the Earth wouldn’t look like it does now. Which is freaking beautiful. Anyway, that was my theory as a child.
Third, to show God’s power
The flood is used in the Bible as a cautionary tale and an indicator of how God can and will step in on a worldwide scale when He decides to. Yes wickedness returned after the flood, but that was because it was still baked into us. Yes, He could use Angels to do his work again (and has, example 185,000 Assyrian soldiers killed by one Angel in one night), but he also can use nature itself. The Red Sea, the giant hailstones, serpents, earthquakes opening up and swallowing, etc. All of this is to be a precursor of even an even greater display of God’s wrath on the entire Earth during judgement day. I had always imagined that God would use every kind of destructive force when he decided to… floods, earthquakes, angels, animals, pestilence, fire, brimstone, hailstones, Donald Trump tweets…
Again, Devil’s advocate…
Now, go ahead and tear this apart… :)