The Great Flood of China that was believed to have launched the Xia dynasty was one of the biggest freshwater floods of the last 10,000 years, scientists have discovered. Geological evidence from the Yellow River has shown an earthquake led to water flows of up to 500,000 cubic metres per second. The event, scientists say, shows how natural disasters can shape and change the course of human history.
China's Great Flood has been subject to debate for many years. The original story showed how Emperor Yu took control of the country (heralding the start of the Xia dynasty) by taking control of the flood through dredging and guiding the waters back into their channels.
This story was told for 1,000 years before being recorded in historical records. Because geological evidence for the flood had been lacking, some scholars had argued the size of the flood had been amplified over time. Or, indeed, that it was propaganda created so Yu could centralise power and rule.
Wu Qinglong, from Peking University in Beijing, and an international team of researchers have now reconstructed the events that took place on the Yellow River to find there was a huge flood just a few hundred years after ancient historical texts indicated it was.
By analysing sediment at the Yellow River Basin, the team found evidence of a natural landslide that gave way around 4,100 years ago. They then reconstructed the events surrounding the flood, along with the discharge in order to understand when it happened and how catastrophic it was.
Their findings, published in Science, showed an earthquake triggered a landslide which caused a dam in the Yellow River. The water built up over six to nine months. When the dam eventually burst, it caused one of the biggest floods of the Holocene.
Darryl Granger, a geologist at Purdue University who worked on the study, said: "[It was] roughly equivalent to the largest flood ever measured on the Amazon River, the world's largest river. It's among the largest known floods to have happened on earth during the past 10,000 years, and it's more than 500 times larger than a flood we might expect on the Yellow River from a massive rainfall event. So this cataclysmic flood would've been a truly devastating event for anyone living on the Yellow River downstream."
To work out when the flood happened, researchers used radiocarbon dating techniques on the skeletons of children killed in the earthquake. Analysis showed they died around 1920 BC – "several centuries later than traditionally thought".
This finding, the researchers say, means we now have an accurate date for the origins of the Xia dynasty. David Cohen, an archaeologist at National Taiwan University, said: "Because this flood happens at a critical turning point in the development of Chinese civilisation, this geological event takes on even greater significance. This is because the flood dates to the likely period where China's legendary great flood. This is the first time a flood of scale large enough to account for it has been found. The outburst flood could've caused social disruptions downstream lasting for years, and if this is the case, we think it could've been the source of the great flood legend.
"[In historical records], the culture hero (Yu) was able to control the great flood through dredging and guiding the waters back into their channels. In doing this, he brings order out of chaos and he defines the land, separating what could become a civilised Chinese centre."