The phrase "global flood" refers to a cataclysmic event where a large amount of water covers the entire Earth, submerging all landmasses. It implies that the flood was so enormous that it affected every corner of the world. Full definition
Climate models suggest that global flood risk will change as the world warms. (livescience.com)
I wasn't sure from your post if you took the local or global flood position. (redeeminggod.com)
As even the most optimistic warming scenario of 1.5 °C would lead to a doubling of global flood risk, effective adaptation plans must be implemented to keep the flood risk rates at or below current levels, according to the authors. (helixclimate.eu)