Has similarities in tactical use with Unstable Gas.
Flooding would add 9damage for 3

+1 card + duo and 9 more for +1

to a total of 18 for 4

+1 card + duo. However it would limit the number of Gravity creatures you could play. Steam Machines would only deal 2 damage.
Voodoo Dolls would deal 3 damage.
I would have to playtest the card to get a good estimate of the expected damage.
Unstable Gas costs 6

+1 turn +1

+duo +1card for 20 damage and a 2 edged Thunderstorm.
Chain of Atlas costs 7

+ prep on your side + 1card | 9

+ prep on either side + 1card + upgrade.
Expected balanced average damage over both turns to be ~20 (32 with Flooding due to restricted space for Gravity creatures.)