黄河口尾闾段河床形态调整及过流能力变化

Adjustments in reach-scale bankfull channel geometry and bankfull discharge in the Yellow River Estuary

为全面描述黄河口尾闾段的河床形态调整及过流能力变化,采用河段平均的计算方法,确定了尾闾段(利津—西河口)1990—2016年汛后断面及河段尺度的平滩特征参数,分析河段平滩河槽形态调整特点、河段平滩流量变化过程及其与累积河床冲淤量的关系。结果表明:近30年来黄河尾闾段的河床形态调整过程较为复杂,河相系数在1990—2003年呈振荡式升高,2003年以后持续减小,说明断面形态朝窄深方向发展;平滩流量变化与河段冲淤过程密切相关,淤积时平滩流量减小,反之则增大;建立这些河段平滩特征参数与利津站前4年汛期平均水流冲刷强度的幂函数关系,且相关系数均大于0.8,说明黄河口尾闾段河床形态调整及过流能力变化能较好地响应利津站水沙条件的改变。

Sediment load entering the Yellow River Estuary has been greatly reduced and the river bed has been eroded because of the operation of the Xiaolangdi Reservoir,with the occurrence of remarkable channel adjustments. In order to describe comprehensively the bankfull channel geometry and flood discharge capacity in the Yellow River Estuary,a reach-averaged method was used in this study to calculate the reach-scale bankfull channel dimensions and bankfull discharge in the Yellow River Estuary annually from 1990 to 2016. Effects of channel evolution on the reach-scale bankfull channel dimensions and bankfull discharge in the study reach were investigated. In addition,empirical relationships were established between the reach-scale bankfull characteristic parameters and the previous four-year average fluvial erosion intensity during flood seasons in the Yellow River Estuary. These results show that both channel widening and channel incision occurred in the reach after 2003,and the variation in cross-sectional profiles in the Yellow River Estuary was mainly characterized by channel narrowing. Furthermore,bankfull discharge decreased with channel aggradation,and increased with channel degradation. Additionally,the correlation between each bankfull characteristic parameter and fluvial erosion intensity in the Yellow River Estuary was greater than 0.8,indicating the remarkable response of bankfull parameters to the altered flow and sediment regime at Lijin.