What was the worst flood in history?

Answer 1

The worst flood in history was when God flooded the whole earth and killed every living thing on the face of the earth with the exception of Noah and his family.

Evidence for this global flood has been objectively documented on every continent.

Genesis Chapters 6,7, & 8 explain why our Creator rightly passed judgment through this unique event in history. It is, after all, the only consistent record of the account that has been passed down through the generations.

http://www.answersingenesis.org/articles/nab/really-a-flood-and-ark

Of course considering that you are speaking of modern history , the answer given may be the best answer ..

However, if you get your information from more than one book, you could know that many civilization did indeed have great flood stories in their history because the majority of ancient civilizations lived in close proximity to major river (Tigris, Euphrates,Ganges, Nile, Yangtzee, ect) and these river all have seasons where they will flood and some floods are much larger than others due to number of variables.

For info of great floods in modern history: during Chang Kai Chek's retreat from Japanese troops he destroyed dams on the yellow river killing between 500,000 and 900,000 in 1938 however a flood in 1931 killed between 1 - 3.7 million while a flood in 1898 killed between 1 and 2 million.