黄河下游河槽横断面调整规律及治理方式探讨

通过对影响河槽挟沙能力诸因素的分析,作者认为目前黄河下游只有河槽形态是一个人为可调节的控制河道淤积的要素。分析黄河下游河道横剖面形态的特征及其调整规律,考虑来沙组成变化、河槽综合阻力变化,计算得到黄河下游典型断面的实际挟沙能力及平均水沙条件下河槽平衡输沙横剖面,经与实际断面形态对比,得出必须以多级河槽方式缩窄7000m³/s流量以下即中、小水期的河槽,方能显着减少黄河下游河槽中的淤积的结论。这样才能真正实现潘季驯的“束水攻沙”的治黄方略。

A STUDY ON THE REGULARITY OF ADJUSTMENT OF CHANNEL CROSS-SECTIONS AND DIRECTION OF CHANNEL TRAINING OF THE LOWER YELLOW RIVER

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.