The story of Noah and the flood was one of ethics and sanctions. God saw that what He had created was wicked. Mankind had become so evil that its heart and mind had been consumed with wickedness. In other words mankind had become ethically unsound. So God put a negative sanction on them (death). But God found one man ethically suitable, and gave the positive sanction of life to him and his family. God then destroyed everything that was evil in the world with a great flood. After the flood God made a covenant with Noah and all of mankind to never again destroy the world in such a way.