HOW HAS THE LOWER YELLOW RIVER DEVELOPED INTO A TWO-STEP-SUSPENDED RIVER?

摘要

The Yellow River, in term of cross sections, is characterized by the fact that the crests of the banks of its main channel, are higher than the floodplains while the latter are higher than the land beyond the river dikes. This feature is termed by Chinese hydraulic engineers as a two-step-suspended river. The development of the two-step-suspended river has caused so many problems to the local people and the management in the recent years that it has to be solved. This paper is intended to analyze the history of how the Lower Yellow River has developed into such a two-step-suspended river, and find the factors influencing the developing process. With the analysis, the authors have arrived at conclusions that the strikingly special incoming river flow and sediment to the Lower Yellow River, especially, the high-concentrated floods, are the dominant factors in the formation of such a two-step-suspended river while presence of the local summer dikes (also called farming dikes by locals) and river training structures, as secondary factors, accelerates the developing process.