This shows the general flood pattern of the Yellow River in the recent time.
In particular, this picture outlines the flooded area during the most recent
flood in 1937, which reached the Yangtze River. In general, when the dykes
on the southern bank are breached at sites downstream from the illustrated
case, the flood water would inundate the Huai River valley. While the northern
dykes were breached, the flood water would rush northward to submerge the
Hai River valley. In the ancient time, before the dykes were constructed,
the river would flood randomly, both north and south of the Shandong pennisular,
in its delta building process. Both valleys would be unsafe for human habitation.
The linking of separate dykes into a complete dyking system for the Yellow
River's lower reaches was accomplished in the Eastern Han dynasty (c. 100),
and the river was kept under control for the next 800 years until the end
of the Tang dynasty. It was a marvel in civil engineering indeed. Its achievement
should rank in honor to the construction of the Great Wall, which protected
the central China from invasion by the northern nomadic tribes for at least
a thousand years. The following is a map of the present dyking system (outlined
in red).
Picture source: YRCC, Picture Albums of the Yellow River, China environmental Science Press, 1991.