The first major flood hit the Hebei region, in the lower reaches of the Yellow River in 1048, followed by an average of one flood every two years for the following eighty years. The floods caused major depopulation in the region, with the millions of people being killed or forced to flee. Rich agricultural lands were destroyed as the Yellow River broke over its northern bank Throughout this period the river actually changed its course, moving northwards and merging with other rivers.
One Chinese writer, Ren Boyu (1047-1119) expressed how disastrous the situation was in Hebei: "In Yongling Commandery and to it north, 30 to 40 percent of the resident survived. In northern Cangzhou, 10 to 20 percent survived. The situation in other prefectures is generally the same. So desolate are these districts that for the span of a thousand li there was little sign of human activity."
Meanwhile, the waters brought heavy silting, which destroyed other rivers and stopped shipping traffic. The Chinese government attempted to keep dredging the rivers, but this proved ineffective and was criticized by contemporaries. One minister, Wen Yanbo, complained, "Even very stupid men living along the riverside all know that the river-dredging harrow does no good."
Another government measure to deal with the flooding was to rebuild embankments by using timber, wooden sticks, bamboo reeds, earth and stone, most of which was collected in Hebei. This soon led to the land being stripped of its trees and vegetation, leading to the soil becoming sandy and unproductive. Although officials knew of the environmental damage being caused by this practice, they had little choice but to continue. The process of sandization in northern China continued, and even in the present day sandstorms are not uncommon.
Ling Zhang's article, "Changing with the Yellow River: An Environmental History of Hebei, 1048-1128" appears in the Harvard Journal of Asiatic Studies (Volume 69:1 - June 2009)