潼关高程下降对渭河下游河床演变的影响

潼关高程变化与渭河下游累计淤积关系密切。潼关高程下降后 ,渭河下游主槽会产生溯源冲刷 ,在大水少沙情况下 ,近槽滩地会受到冲刷 ,洪水漫滩后滩地会发生淤积 ;冲刷在靠近潼关的华阴和华县河段表现明显 ,向上游逐渐减弱 ;冲刷河段主槽过洪能力有所增大 ,常水位和一般洪水位都有所降低 ,但大洪水的威胁依然存在。此外 ,渭河下游各河段河相系数均减小 ,河道向着窄深方向发展 ;由于侵蚀基准降低 ,自然裁弯动力增强且易发生 ,河道弯曲系数变小 ,河道由摆动型向稳定型弯曲河道发展。水流移床力的分析表明 ,潼关高程下降期间 ,河道运动强度与脉动流量关系减弱 ,基本上维持在某一常数 ;由于流量的脉动客观存在 ,河道仍会摆动 ,平均每年移动量在 12 0～ 4 0 0m之间。

Impacts of descending Tongguan elevation on fluvial process in the Weihe River

The Weihe River, the largest tributary of the Yellow River, empties itself into the Yellow River at Tongguan. The lower Weihe River is in the backwater region of the Sanmenxia Reservoir. The Tongguan's elevation is defined as the stage of a flood discharge at 1000 m 3/s at Tongguan hydrologic station, which is essentially the datum plane of the bed profile of the Weihe River. Severe sedimentation has occurred in the lower Weihe River since the impoundment of the Sanmenxia Reservoir in Sept 1960 because the Tongguan's elevation has risen by 5 meters. If Tongguan's elevation falls by 2m, strong erosion in the Huayin and Huaxian reaches will occur. The discharge capacity of the channel will increase, thus small and mid-scale flood stage will fall. The channel regime coefficients in the lower Weihe River will decrease and the channel became deep and narrow. As a meandering-wandering river, the channel will still wandering and the sinuosity will reduce. More stabilization engineering projects are still needed to maintain the river channel stable.