Excavations at two ancient communities in the lower Yellow River floodplain in China’s Henan province revealed a 10,000-year history of sediment deposition. Analysis of the organisation of soil grains revealed whether earthen structures identified within the deposits were human-built or laid down as part of a natural sedimentation process, while radiocarbon dating of snail shells and other organic matter helped to identify the timeframes during which the structures were created. The results suggest that the Chinese began building levee systems along the lower reaches of the river about 2,900–2,700 years ago – the earliest known archaeological evidence for human construction of large-scale levees and other flood-control systems in China.

‘Our evidence suggests that the first levees were built to be about six to seven feet [1.8–2.1 metres] high, but within a decade, the one at Anshang was doubled in height and width,’ said the study’s lead author TR Kidder, of Washington University in St Louis. ‘It’s easy to see the trap they fell into: building levees causes sediments to accumulate in the river bed, raising the river higher, and making it more vulnerable to flooding, which requires you to build the levee higher, which causes the sediments to accumulate, and the process repeats itself.’

This story was published in the August 2014 edition of Geographical Magazine