黄河上游内蒙古段河床演变及其与水沙变化的关系

doi:10.13249/j.cnki.sgs.2016.06.012

摘要/Abstract

摘要：

对黄河内蒙古段河道大断面进行了连续4 a的测量,分析了断面泥沙冲淤与形态调整的变化过程;通过对河床形态指标变化与水沙条件的相关分析,揭示了河床调整主要的影响因素。结果显示：近4 a内不存在河槽萎缩的现象,整个河段河道存在总的冲刷降低的趋势,继承了自2004年以来该段河道以深度加大为主,河槽逐渐缓慢扩大的变化方向。整个河段平均从2011年汛后至2014年汛后,全断面冲刷了64 m²,河槽河底降低了0.16 m,河槽断面面积增加了4.4%,平均深度增加了4.9%,河槽宽度只增加了0.88%,河槽宽深比减小了4.8%。河槽冲刷和形态调整主要发生在2011年汛后至2012年汛后期间,与2012年较大的洪峰有关。分析河槽冲淤和断面形态变化与水沙条件的关系,结果显示滩唇高度、河槽过水面积、平均深度及宽深比变率与流量大小关系密切。滩唇高度、河槽过水面积、平均深度随着流量的增大而增加,宽深比随着流量的增大而减小。相反,河床断面面积和主槽宽度的变化与水沙条件的关系不显著。除了滩唇高度与平均含沙量有关外,平均含沙量和来沙系数与河床冲淤以及河槽形态变化之间关系都不显著。揭示出近年来内蒙河道主槽以垂向冲淤为主,并且流量变化控制着河槽冲淤与形态调整过程。

关键词: 黄河上游, 河槽形态, 河床演变

Abstract:

The Inner Mongolia reach of the upper Huanghe River has an alluvial channel, and its flood carrying capacity reduced considerably owing to aggravating siltation in the last decades. This study investigated the processes of sedimentation and channel geometric changes of the river reach based on the data of geometric survey of 28 channel cross sections of the river reach made in 2011-2014. Through correlation analysis of the changes in channel geometric indices with water and sediment conditions, the principal factors inducing the channel changes were determined. The results show that the incessant channel aggradation and shrinkage of channel capacity in the river reach in the last about 20 years of the 20th century did not occur in the past four years but the general trend of channel degradation starting from 2004 was continued with a gradual and slow increase of channel capacity principally through channel deepening. From the end of flood season in 2011 to that in 2014, each of the cross sections was scoured by a mean area of 64 m² with a decline of 0.16 m in the bed elevation, an increase of 4.4% in the capacity, an increase of 4.9% in the depth, a reduction of 4.8% in the width/depth ratio, and a decrease of only 0.88% in the width of the main channel in the whole reach from the uppermost cross section Sns3 to the downmost cross section at Toudaoguai. Scouring and filling in channel and the adjustments of channel geometry occurred mainly during the period from the end of flood season in 2011 to that in 2012, as a result of the high floods in 2012. The results of correlation between the change rates of channel geometric indices and water and sediment indices show that there were significant relations between the water discharge and the bankfull level, capacity, mean depth, and with/depth ratio of the main channel. The bankfull level, capacity, and mean depth of the main channel increased and the with/depth ratio decreased with the water discharge. In contrast, the area of the whole cross-sections and the width of the main channel did not respond to changes in either water or sediment significantly. Except for the relation between bankfull level and mean sediment concentration, the relations were insignificant between the incoming sediment coefficient (the ratio of sediment concentration to water discharge) or sediment concentration and channel erosion/deposition and channel geometric indices. The relations of changes in channel geometry with water and sediment indexes suggest that scouring and silting in the main channel in the reach studied mainly occurred on the channel bed, and the variation of water discharge was the dominant driver for scouring and filling in the main channel and the adjustment of channel geometry in recent years.

Key words: the upper Huanghe River, channel geometry, channel change

中图分类号:

P931.1

师长兴. 黄河上游内蒙古段河床演变及其与水沙变化的关系[J]. 地理科学, 2016, 36(6): 895-901.

Changxing Shi. Channel Adjustments of the Inner Mongolia Reach of the Upper Huanghe River to Changes in Water Discharge and Sediment Load[J]. SCIENTIA GEOGRAPHICA SINICA, 2016, 36(6): 895-901.

图/表 5

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	流量	含沙量	来沙系数	全断面面积	水位	平均河底高	过水面积	平均深度	平均河宽	宽深比
流量	1.00	0.73^**	-0.40	-0.28	0.67^**	-0.42	0.64^*	0.57^*	0.12	-0.53^*
含沙量		1.00	0.31	-0.04	0.61^*	-0.13	0.31	0.28	0.14	-0.1
来沙系数			1.00	0.34	0.03	0.4	-0.38	-0.35	0.01	0.42