Highest death toll from a flood

The highest death toll from a flood is a difficult record to determine with any certainty. We can be fairly sure, however, that the deadliest floods in history have occurred in China, where there are two major river basins – the Yellow River and the Yangtze River – that are both notoriously prone to flooding, and that have many densely populated regions along their banks. The Yellow River, in the north of the country, has changed course several times in the last thousand years, shifting the mouth of the river hundreds of kilometres up and down the east coast, or simply creating vast inland seas. Its most severe flood likely came in 1938, when the Chinese Nationalist Army deliberately breached dykes on the Yellow River near Huayuankou to slow the advancing Japanese Army. This caused a flood that is estimated to have killed as many as 900,000 people. Further to the south, the population of the Yangtze Valley has also experienced devastating flooding throughout its history. The Yangtze River was the epicentre of the 1931 Central China Floods, which killed an estimated two million people, making it the most likely candidate for the deadliest flood disaster in history.

A report published by the National Flood Relief Commission in 1933 put the number who died just from drowning in the initial inundation at 140,000 people. Flooding has continued to be a problem in the Yangtze River Valley, despite massive flood-defence engineering projects and mitigation policies. An inundation in 1954 killed around 149,000 people. Another mega-flood occurred in 1998, though fortunately the death toll was by this stage far lower.