河道整治工程对游荡型河道断面形态的影响

Influence of river regulation works on the section shape of wandering reach

基于1960—2014年黄河下游游荡型河道整治工程修建情况和实测流量及断面地形资料,分析各时期工程密度和在同流量条件下断面形态(河宽、水深、河相系数)的变化情况,结果表明:黄河下游游荡型河道整治工程的修建有效改善了河道断面形态,在河道整治工程密度较小时不能有效控制河势,整治工程对河道断面形态影响较小;随着河道整治工程密度的增大,在同流量条件下河宽减小,水深增大,河相系数减小,河道断面形态向窄深方向发展,可见河道整治工程在达到一定密度时对河道断面形态有明显的改善作用,在一定程度上限制河段的游荡特性,起到了稳定主流、控制河势的作用。

The river channel of wandering type is wide and shallow;the water flow is scattered,the mainstream migrates uncertainly,the river regime changes violently,which is extremely unfavorable to flood control.In order to ensure the flood control safety on both banks of the lower Yellow River,the control and guide project was built in the curved section of the lower Yellow River as early as in 1950s,and gradually extended to the transition section,and finally successfully renovated in the wandering section.In recent years,with the continuous construction of the wandering channel regulation project in the lower Yellow River and the change of water and sand situation,the cross-section shape of the river has changed greatly.It is momentous to study the influence of river regulation projects on the shape of wandering channels,especially the relationship between engineering density and shape parameters of the river sections.Based on the construction process,measured discharge,and section topographic data of the river regulation project of the wandering river in the lower Yellow River from 1960 to 2014,the length and density of the river regulation project in different periods are calculated,and the relationship between the engineering density and the morphological indexes(width,depth and river phase coefficient)of each section in each period is established under the condition of the same discharge.The influence of river regulation projects in different periods on the evolution of river section morphology is analyzed.The results show that the density of the regulation project of the wandering reach of the lower Yellow River increases year by year,and now the density of the regulation project has reached over 70%.When the density of the regulation works is small,the wandering characteristics of the river reach are not completely controlled,and the width of the river varies greatly under the same discharge;after the river remediation,especially in the river section with complete engineering construction and high engineering density,the width of the river at the same flow is significantly narrowed.The regulation works have a certain impact on the section water depth.Under the same water and sediment conditions,the construction of the regulation project constrains the lateral expansion of the flow,and the flow begins to wash down the riverbed,which makes the water depth of the section increase gradually.Before river regulation,the river phase coefficient of the wandering river course and its variation range are all large.After river regulation,the river phase coefficient of cross-section decreases and tends to be stable as the density of regulation project increases under the condition of same discharge,which shows that the perfect river regulation project makes the cross-section form develop to narrow and deep direction,and the river regime is more stable.It is shown that the river regulation project can obviously improve the river section when the river regulation project reaches a certain density,and limit the wandering characteristics of the river section.With the increase of the density of the river regulation project,the width of the river decreases,the depth of water increases,and the coefficient of the river phase decreases.When the density of the river regulation project is low,the river regime can not be controlled effectively,and the wandering characteristics of the river section are prominent,the river width,water depth and river facies coefficient under the same flow change frequently and greatly.