After the fall into sin, the world plunged farther and farther from God; ultimately bringing God to the brink of destroying it all. However, because of God’s great love for us and His promise to send a Savior, He saved humanity through Noah and the ark that God had him build. The flood would remake the face of the earth, but God’s people were saved.
As an interesting side note, the flood foreshadows the salvation we receive in our Baptism, where God washes us clean from our sins by water and His Word. (1st Peter 3:18-22)