黄河下游堤距对河道沉积速率的影响

以黄河下游堤距和1934～1985年间河道淤积速率的实测资料为基础，研究了堤距与沉积速率的关系。沿流程向下，黄河下游堤距在总体上表现出先增大，然后再迅速减小的趋势。水位变幅与堤距之间有较强的负相关，堤距越小，水位变幅越大。水位变幅较大，反映洪水中水深的增加幅度较大，在其他条件相同时，流速会因此而增大，使得水流挟沙能力也增强。沉积速率随堤距的变化是非线性的。当堤距由15km缩窄到10km时，堤距的缩小对沉积速率不发生影响；当堤距由10km减到6km时，河槽中的水流动力并不会因堤距束窄而显著加强，由于堤距束窄使泥沙的堆积空间减小，故沉积速率反而增大，并达到峰值；当堤距从6km继续减小时，大堤对水流的约束作用使水动力得到显著强化，挟沙能力加强，这一作用抵消了堤距减小使堆积空间减小的影响而有余，因而沉积速率减小。

Influence of Width between Aritificial Levees on Channel Sedimentation of the Lower Yellow River, China

Based on the data from the lower Yellow River, a study on channel sedimentation rate as influenced by the width between artificial levees (WRT) has been made. The WRT increases to a peak and then decreases sharply along the river. There is a negative correlation between the mean annual water stage range and the WRT. This means that, when the WRT is narrow, water depth during a flood is large, then the flow velocity is high and therefore sediment carrying capacity is high. A nonlinear relationship between channel sedimentation rate and WRT has been found. When WRT is reduced from 15km to 10km, the reduction of WRT has no influence on channel sedimentation rate. When WRT is reduced from 10km to 6km, the streamflow strength may not be enhanced by the reduction of WRT, but the reduction of WRT reduces the space for sediment deposition, thus channel sedimentation rate increases and reaches peak values. When the WRT becomes smaller than 6km, the confinement of levees on streamflow enhances flow strength significantly. This effect that reduces sedimentation may prevail on the effect of reduced space that might increase sedimentation, and then sedimentation rate declines.