When bad things happen in this world like the flood, God takes the responsibility for them because He created a world where such evil things are possible. When the flood came, it is not something that God sent, but is something that happened under His rule, or “on His watch.”
In seeking to understand what is going on in the account of the flood and why the waters that came upon the earth, we must understand the ANE cosmology. The waters of the flood cause the world to revert the the chaos of a pre-creation state. The flood reveals cosmic warfare between God and Yamm, the god of chaos and storms.