Imagine a sphere big enough to contain all the floodwaters. Determine the radius of that based on the height of the water indicated in the bible. Then calculate the volume of that sphere.
Hang onto that number. Call it "A". The radius of the earth is something like 3500 miles.
Use this to calculate the volume of the sphere of Earth itself. Subtract this number from "A" and you know how much water there is. However, there is a more important question: the moral question: was it right for God to horribly drown babies, children, kittens, puppies, birdies, piggies, horsies, and all sorts of cuddly creatures just because some of the grownups were misbehaving?
If the water "god" put there evaporated, it would have fallen back down as rain. That is where weather comes from. Also, the water recedes when the ice caps freeze, the water will rise as the ice caps melt.
It is a cycle. Earth always has the same amount of water. If you want to mathematically figure it out, don't look at the bible for answers.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.