Keep in mind the belief held at that time, since God is creator, was that every action was an act of God. You didn't move your little finger, it was an act of God because God created you. The intent was not to create the image of God as puppet master, but a reminder of our own humbleness before God.
Therefore at the time, "God sent the flood" is very much on par with "God just moved my little finger." All actions are acts of God. Cultural perspective and true that the Creator is the ultimate cause/reason for everything.
Rephrasing the question: What was the immediate cause of the flood? Would you agree the immediate cause to be a natural disaster on the same order as volcanoes and blizzards? Or do you believe that on one earthly morning, God chose to snap His fingers, bring about the flood, and if there had been no God the flood never would have happened?