I've never been asked that question before, therefore, I'll try to brainstorm some other possible better ways:
1. He could have made the Nephilim (evil hybrid offspring) and the wicked humans dissolve away into smoke or nothingness.
2. He could have sucked the Nephilim and the wicked humans into an active volcano to get rid of them... That is, if there were volcanoes that existed at that time.
3. He could have made the Nephilim and the wicked humans drop dead on the face of the earth.
That's all that I could think of without becoming repetitive, but by doing something other than a flood, then that would have prevented the horrible weather that we often have on this planet and the extreme cold at the poles and the extreme heat and the lack water in the deserts.
First of all, I find Revelation 11:18 B says God will bring to ruin those ruining the Earth.
So, Man, Not God, is the one polluting the Earth ( includes highway litter bugs ).
Not another Flood, but the 'words from Jesus' mouth' will rid the Earth of the wicked - Isaiah 11:3-4; Rev. 19:14-15
Jesus will regulate weather phenomenon as he did at Mark 6:51; Mark 4:39
The deserts will blossom as described in Isaiah 35th chapter.
So, what we see today is temporary just until calendar Day One of Jesus' coming 1,000 year reign over Earth.