关键词: 黄河下游, 横断面调整, 河道整治

Abstract: This paper deals with one way of controlling sedimentation in the channel of the lower Yellow River. Generally, for adapting to imposed water and sediment load, a river channel has three main factors to adjust, that is, bed material composition, slope and channel geometry. However, revealed by gauged hydrological and channel geometry surveying data over 20 years, the three factors of the lower Yellow River did not display detectable long-term changing tendencies in the process of channel silting up. Limited by concrete conditions in the lower Yellow River, the slope and bed material composition are not easy to change for alleviating markedly sedimentation, while channel geometry can be adjusted by channel training for this purpose. By analyzing 45 cross-sections of the river, it was found that the overall geometry, in the relation of width with relative height, of the cross-sections in the braided reaches took the shape of convex curve, and most of the cross-sections in the transitional and confined meandering reaches in the shape of concave curve. Based on analyzing the characteristic of the oncoming water and sediment of the river in the period from 1965 to 1985, and considering the effects of variations in the synthetic channel's hydraulic roughness and of grain size composition changes of different sediment concentration, the sediment transport capacity of some typical cross-sections is calculated, and the shape of the cross-sections with the slope and bed material composition of the typical ones demanded by sediment transport in equilibrium for all the discharge classes below 7 000 m³/s is figured out also. The results reveal that the present channel is too shallow and wide. The equilibrium shape of the channel follows a convex curve; therefore, the concave shape of cross-sections in the transitional and confined meandering reaches is not suitable for sediment transport keeping in equilibrium. Based on the results of analysis in the paper, we suggest that one of the best ways of harnessing the lower Yellow River is to reform its channel containing the discharges lower than 7 000 m³/s to compound one with over two steps of berm, to narrow the channel downward and downstream according to the future imposed water and sediment load. By this way, the strategy, ‘gathering water to erode sediment', advanced by a famous expert, Pan Jixun, in the Yellow River management over 400 years ago, may be realized fully.

Key words: the lower Yellow River, channel cross section adjustment, river channel training