Noah pleases God

From the wickedness, corruption, violence on Earth that made God willing to destroy "all flesh" on Earth, there was a single man that found favor with God. He was Noah. Noah was perfect in God's eyes. He was also only a handful of men who was described as "walked with God".

We all know the story from there. Noah obeyed God and build the Ark, then he gathered the animals in pairs to go into the Ark. On a deeper note, in v18, God specifically renewed His Covenant with Noah. The Covenant which is to be an everlasting Covenant shows God's faithfulness to His Promise.

Another thing to note is that, God being the Almighty that He is, does have the power to recreate the animals and man again if he totally destroyed all living things in the Flood. But the only humans He created directly were Adam and Eve and also the animals at Creation. After the Flood, God's plan was to let Noah and his family and the animals in the Ark to re-populate the Earth. It was not in His will to create more humans and animals after the Flood. Perhaps this indicates God's Creation was complete in the beginning, and that His Creation Work was Good. Even though man became corrupt, and God had to cause the Flood, God already  knew this before Creation - and His Creation was perfect, there was no need for another creation or plan B.

Genesis 6
⁹ This is the genealogy of Noah. Noah was a just man, perfect in his generations. Noah walked with God. ¹⁰ And Noah begot three sons: Shem, Ham, and Japheth. 
¹¹ The earth also was corrupt before God, and the earth was filled with violence. ¹² So God looked upon the earth, and indeed it was corrupt; for all flesh had corrupted their way on the earth.

¹³ And God said to Noah, “The end of all flesh has come before Me, for the earth is filled with violence through them; and behold, I will destroy them with the earth. ¹⁴ Make yourself an ark of gopherwood; make rooms in the ark, and cover it inside and outside with pitch. ¹⁵ And this is how you shall make it: The length of the ark shall be three hundred cubits, its width fifty cubits, and its height thirty cubits. ¹⁶ You shall make a window for the ark, and you shall finish it to a cubit from above; and set the door of the ark in its side. You shall make it with lower, second, and thirddecks. ¹⁷ And behold, I Myself am bringing floodwaters on the earth, to destroy from under heaven all flesh in which is the breath of life; everything that is on the earth shall die. ¹⁸ But I will establish My covenant with you; and you shall go into the ark—you, your sons, your wife, and your sons’ wives with you. ¹⁹ And of every living thing of all flesh you shall bring two of every sort into the ark, to keep them alive with you; they shall be male and female. ²⁰ Of the birds after their kind, of animals after their kind, and of every creeping thing of the earth after its kind, two of every kind will come to you to keep them alive. ²¹ And you shall take for yourself of all food that is eaten, and you shall gather it to yourself; and it shall be food for you and for them.” 

²² Thus Noah did; according to all that God commanded him, so he did.