Yellow River floods
The second and third deadliest floods in human history occurred along China's Yellow River (Huang He), in 1887 and 1938 respectively. Loss of life for the 1887 flood was estimated at around 900,000. The flood happened after heavy rainfall put overwhelming stress on the dikes built to contain the river's flow.
The Yellow River flood of 1938 had a far more sinister and tragic cause: it was purposeful. In an attempt to halt invading Japanese forces, the Nationalist government in central China opened the dikes along the river. The ensuing flood destroyed thousands of small villages and drowned an estimated 800,000 people. It has been called the "largest act of environmental warfare in history."