摘要
自从 1986年开始 ,黄河下游进入了一个新的历史时期 ,即以低流量为主并发生间歇性断流的时期 ,河床发生强烈淤积。我们以这一时期黄河下游河道的实测资料 ,分析了这一时期中的河床沉积过程与形态调整。河床淤积过程可以概括为滩唇 (天然堤 )垂向加积、河底垂向加积和河岸侧向加积 3种类型。河床横断面形态的调整与上述 3种加积过程的速率有密切的关系。文中建立了表达河床形态调整指标与这 3种加积速率之间关系的回归方程 ,可以用于估算黄河下游不同河段的河床形态调整趋势。受河床边界条件和水沙过程沿程调整的影响 ,3种加积速率都表现出明显的沿程变化规律。受其影响 ,河床调整的方式也表现出明显的沿程差异。在低流量条件下 ,黄河下游平滩比降和河底比降的变化趋势是相反的 ,平滩比降趋于增大 ,河底比降趋于减小。在漫滩机率较小、低流量占优势的情形下 ,后者居于主导地位 ,故黄河下游输沙能力趋于减小 ,淤积趋势加强。
Since 1986, the lower Yellow River enters a new period that is characterized by small discharges with seasonal desiccations. As a result, strong sedimentation occurs. The sedimentation can be classified as three types in terms of different morphological units, i.e., the vertical deposition of natural levee, the vertical deposition of riverbed and the lateral deposition of riverbank. The rates of the three types of deposition have been measured and reported in this study.\;The adjustment of channel shape of the lower Yellow River at small discharges is closely related to the rates of the three types of deposition. A multi\|regression equation has been established to express the relationship between the three rates of deposition and the channel shape adjustment index Φ that is defined as the ratio of the bankfull width to depth before the adjustment, to that after the adjustment. The equation can be used to estimate the channel adjustment tendency for different reaches of the lower Yellow River. Influenced by the difference in channel boundary material and by the downstream variation in water discharge and sediment load, the three indices of channel deposition rate show clear tendency of downstream variation. Controlled by this, the manner of channel adjustment also shows clear difference downstream.\;Under the hydrological regime dominated by small discharges, the tendencies of adjustment of channel slope and bankfull slope are inverse, i.e., the channel slope tends to decrease but the bankull discharge increases. At the present, the former tendency is dominant; thus the sediment carrying capacity of the lower Yellow River tends to decrease, which intensifies channel sedimentation.
出处
《泥沙研究》
CSCD
北大核心
2002年第1期10-17,共8页
Journal of Sediment Research
基金
国家重点基础研究发展规划项目 (编号 :G19990 436 0 4)
中国科学院地理科学与资源研究所知识创新工程领域前沿项目(CXIOG A0 0 0 5 0 1)
关键词
间歇性断流
河床演变
河流沉积
河床调整
黄河下游
river sedimentation
channel adjustment
river shrinkage
human influences
the Yellow River
