黄河下游游荡性河道水位涨率偏大的主要影响因素分析

认为影响黄河下游游荡性河道水位涨率的因素是多方面的 ,河宽只是其中的原因之一。利用黄河下游花园口、夹河滩等水文站历次实测大洪水测流断面资料 ,计算了各水文断面不同槽宽的水位流量关系。在洪水涨水阶段 ,同样的流量涨幅 ,等河宽的平均河底高程变化 ,河南河道和山东河道没有明显差别 ,但河南河道的比降是山东河道的 2倍 ,同河宽的水位涨率必然小于山东河道。对游荡性河道已发生的几场水位涨率偏大的原因作了分析 ,认为游荡性河道十分宽浅 ,河势摆动频繁 ,大洪水时形成顶冲、局部壅水 ,它对水位涨率的影响远大于河宽缩窄的影响 ;复式河槽在洪水漫滩后 ,由于滩槽水流的动量交换 ,引起主槽的阻力增大 ,也是导致水位涨率增大的重要原因。

Analysis on main affecting factors of relatively larger rising rate of water level in the meandering Lower Yellow River

There are a lot of factors to affect the rising rate of water level in the meandering Lower Yellow River and river width is only one of them. Using measuring sections data of observed large floods in hydrological stations of Huayuankou, Jiahetan and etc. in the lower Yellow River, water level-discharge relations of these hydrological cross sections with different river channel width are calculated. During rising period of one flood, with same rising range and same river width, there is no obvious difference in average change of riverbed elevation between Henan reach and Shandong reach. However, the slope of river channel in Henan reach is two times of that in Shandong reach. Therefore, the rising rate of water level is surely less than that of Shandong reach at the same river width. Causes of relatively larger rising rate of several past floods in the meandering channel are analyzed and it is thought that meandering river channel is shallow and wide with frequent swinging and main flow directly rushing at bank or engineering works and dammed water appears in large floods, which has a much larger effect on rising rate of water level than the contraction of river width. After a floodplain in multiple channel, momentum exchange of flow in floodplain results in the resistance of main channel increasing, which is also an important factor resulting in a higher rising rate of water level.