Of course God could've just started over. He didn't "need" Noah to do anything.
It's a story about preservation, holiness, grace, and salvation in the midst of universal sin. It prefigures and promises the coming of Christ. Taking two of every animal is symbolic of retaining the goodness/sinlessness of the natural world which God declared at its making. That sin will come and swallow everything and kill many but those who cling to God and His promises will find refuge and safety in the world redeemed. Arguing about the historicity of the flood or its narrative mechanics is missing the point.
This quote explains it pretty well:
The Sacred Authors are appropriating ancient source material, which also was a source for the Epic of Gilgamesh. They weave this source material into a larger theological narrative.
For example, the flood waters are the same chaotic waters that the Holy Spirit hovered over during creation of the world [Tohu wa-bohu]. Water is a mythopoetic symbol of chaos in this way. In fact, there is linguistic evidence that the chaotic waters are an echo of Tiamat in the Enūma Eliš. This is also why God is portrayed in the psalms as breaking up Leviathan, a sea monster. In the Enūma Eliš, Marduk slays Tiamat and forms the world out of her corpse. The idea is that order comes from the breaking up of chaos. Leviathan shows up in Job as well.
Discussion about a local flood instead of a universal flood is a dead end. It is what is called “concordism” and fails to understand how the text functions as a whole. Instead, it reads contemporary questions and concerns into the text.
The flood portrayed by Genesis is universal; it is an undoing of creation by sin. The disorder of sin undoes the order of the world, that world which was ordered out of the cosmic waters.
The covenant with all of creation, which must have some historical antecedent, signifies that God is going to work with creation and redeem it rather than allowing it to fall into chaos.
Noah’s Ark is a type of the Church and the flood waters are a type of baptism. It’s the same chaotic waters that poured down in the flood that Jesus is plunged into at his baptism. That chaotic realm is his passion and decent into hell, and the resurrection of Christ fulfills and elevates the covenant with creation through the New Covenant.
So, in short, the flood of Noah is historical in the way the cosmic waters are historical when the Spirit hovered over them.
