Dirt: The Erosion of Civilizations - Kootenay Local Agricultural Society

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by the color of dirt eroded from the river’s deforested headwaters. Before
the first levees and dikes were constructed in 340 bc, the river meandered
across a broad floodplain. In the second century bc the river’s Chinese name
changed from Great River to Yellow River when the sediment load
increased tenfold as farmers began plowing up the highly erodible silty
(loess) soils into the river’s headwaters.
The earliest communities along the Yellow River were situated on elevated
terraces along tributaries. Only later, after the area became densely
populated, did people crowd onto the floodplain. Extensive levees to protect
farmlands and towns along the river kept floodwaters, and the sediment
they carried, confined between the levees. Where the river hit the
plains, the weakening current began dropping sediment out between the
levees instead of across the floodplain. Rebuilding levees ever higher to
contain the floodwaters ensured that the riverbed climbed above the alluvial
plain about a foot every century.
By the 1920s the surface of the river towered thirty feet above the floodplain
during the high-water season. This guaranteed that any flood that
breached the levees was devastating. Floodwaters released from the confines
of the levees roared down onto the floodplain, submerging farms,
towns, and sometimes even whole cities beneath a temporary lake. In 1852
the river jumped its dikes and flowed north, flooding cities and villages and
killing millions of people before draining out hundreds of miles to the
north. More than two million people drowned or died in the resulting
famine when the river breached its southern dike and submerged the
province of Henan during the flood of 1887–89. With the river flowing
high above its floodplain, levee breaches are always catastrophic.
Soil erosion in northern China grabbed international attention when a
withering drought killed half a million people in 1920–21. Some twenty
million people were reduced to eating literally anything that grew from the
soil. In some areas starving people stripped the landscape down to bare
dirt. The ensuing erosion triggered mass migrations when fields blew away.
But this was not unusual. A 1920s famine-relief study documented that
famine had occurred in some part of China during each of the previous
two thousand years.
In 1922 forester and Rhodes scholar Walter Lowdermilk took a job at the
University of Nanking to work on famine prevention in China. Touring
the country, he deduced how soil abuse had influenced Chinese society.
The experience impressed upon him the fact that soil erosion could crip-
rivers of life