黄河下游纵剖面自调整特性

本文根据丰富观测资料，对黄河下游纵剖面平行抬高趋向性、塑造均衡剖面趋向性、河口流路改道及其长期延伸地均衡剖面塑造的影响作了较深入的讨论。

Characteristics of Self-adjusting in Longitudinal Stream Profile of the Lower Yellow River

There are two taxises for self-adjusting in longitudinal profile of the Lower Yellow River, the tendency toward quasi-parallel rise and the tendency toward moulding a graded profile, in order to regulate the sediment carrying capacity of flow to be suitable to the oncoming bed material load. 2. The two taxises are the two aspects of the unity of opposites in bed-forming processes in the Lower Yellow River. Deposition causes the profile of river bed an increase in steepness approaching a graded profile. Extension of river mouth caused by deposition makes the profile a decrease in steepness. The two processes are feedback with each other and result in the two taxises, parallel rise of the profile in height and moulding a graded profile, in the Lower Yellow River. 3. During the past half century, the self-adjusting of channel, on the whole, underwent following six stages;1) the aggradation in the 1950s;2) the degradation from 1960 to 1964 due to pulling the Sanmenxia Reservoir into operation;3) the heavy aggradation from 1965 to 1973 as low level operation of the reservoir;4) the normal aggradation from 1974 to 1980;5) the degradation from 1981 to 1985 and 6) the aggradation since 1986. The profile in elevation approached parallel rise and its concavity slightly decreased during aggradation. Conversely, the profile cut down and sloped more gently during degradation. 4. The adjustment as retrogressive scour caused by change in the course on delta manifests two modes, i.e., eliminating knick point on river bed and then cutting down, the channel to be transformed the channel from braided mouth channels into a single. 5. The impact range of retrogressive scour or silting can reach to Liujiayuan, 176km above the course change point, but the impact of backward scour on upstream channel can generally be neutralized by retrogressive deposition as mouth extending.