【作者】 赵连军；

【导师】 谈广鸣；

【作者基本信息】 武汉大学 ， 港口、海岸及近海工程， 2005， 博士

【摘要】 目前在黄河口淤积延伸和流路变迁对黄河下游河道反馈影响的问题上,许多学者意见不一。本文作者对现有的研究成果进行了认真的总结分析后认为,黄河下游河道演变与河口演变影响因素繁多,各因素之间的相互作用极为复杂。过去各家由于受研究手段的限制,不能理清各个因素的作用与全面地分析各种关系,切入点不同,结论也就各不相同。黄河口为弱潮陆相河口,从长时段看,因进入河口沙量很大,河口演变主要表现为流路的淤积延伸与改道,两者交替发展形成了目前的三角洲。黄河下游河道演变与河口演变的一个重要特点是,其受上游来水来沙条件变化的影响非常大,河床(包括河口)冲淤变形调整非常剧烈,这一点是其它任何河流也不可比拟的。例如,有的改道初期上游来沙量很大,其作用掩盖了改道溯源冲刷的发展,造成改道影响不大甚至没有影响的假象。因而,单纯的不全面的实测资料分析往往不能获得正确的认识。本文的主要特点之一,就是运用较全面反映各因素之间相互关系的水动力学泥沙数学模型,对黄河下游河道与河口冲淤演变之间的关系以及来水来沙对它们的影响作系统的、定量的研究。 针对黄河下游河道与河口水沙演进传播及演变特点,本文通过理论探讨与实测资料分析,建立了黄河下游河道糙率公式、含沙量及悬沙组成沿河宽分布公式及悬移质泥沙与床沙交换基本方程,对悬移质泥沙与床沙交换基本方程中的有关参数、黄河下游水流挟沙力计算、河槽在冲淤过程中河宽变化调整模拟方法、床沙粒径调整计算方法、河口淤积延伸计算模式等进行了深入研究,在此基础上,研制开发了统一计算黄河下游河道演变与河口演变耦合作用的水沙数学模型,并采用1976年7月～1996年6月水沙系列对模型进行了系统检验。 本文采用天然实测资料分析与多种组合方案下数学模型计算相结合的方法,把来水来沙、下游河道冲淤演变、河口淤积延伸以及流路改道作为一个整体来研究,探讨黄河下游河道演变与河口演变相互作用规律,得出如下几点认识与创新: (1) 黄河下游来水来沙年际变化很大,以致于河道演变出现了总体上为累积淤积,但在某些时期冲淤交替发展的过程。利津以下河口段河道的冲淤演变既受上游来水来沙条件的影响,又受河口改道变迁与延伸的影响。黄河口延伸长度与进入河口沙量成正比,但不同河口流路、或同一流路的不同发展阶段,其比例系数并不相同。 (2) 来水来沙条件是影响黄河下游河道演变与河口演变的主要因素,花园口～利津河段的年冲淤量与花园口来水量的平方成反比,与来沙量成正比,淤积量及淤积比随来沙组成的变粗而增大,根据实测资料回归建立了体现上述规律的长系列多年平均情况下该河段河道冲淤量计算公式。当花园口来沙量增加或减少时,各河段淤积量均随之增大或减少;河道冲淤幅度是自上而下逐渐变小的,河道纵比降也将作出新的调整;通过几百公里河道的冲淤调节,进入河口沙量仍不更多还原

【Abstract】 At present, many researchers disagree with each other on the problem of feedback influence in the lower Yellow River due to the estuary extension and changes of the course. After analyzing the exist results, the author thinks that there are many factors that influence the riverway in the lower Yellow River and estuary evolution, and their interaction is extremely complicated. But by the limit of methods, previous research failed to recognize the interaction between different factors and to analyze the relation scientifically, and as the researches are based on different aspects of the problem, the results are diverse from each other. The estuary of Yellow River has weak tide like a inland estuary. For a long period, because the amount of incoming sediment is very big, estuary evolution mainly displays as the river course extension and changes of the course, and the alternate action of these two factors comes into being present delta. One obvious characteristic of riverway and estuary evolution in Yellow River is that the incoming flow and sediment change greatly and the erosion and deposition of riverbed in the lower reach including estuary, adjust strongly. This is the most obvious characteristic that any other river can’t compare with. For example, in initial stage of river changing its course, as the sediment inflow is very large, the effect of sediment deposition conceals the development of scouring which traces to the source. So a false appearance is that river changing its course takes little effect on the lower river scouring. Therefore, the results based on simple and the one-sided field data analysis are not correct. In this paper, by using hydrodynamic sediment mathematic model that can reflect relation among each factor, the relation between estuary and riverway scouring and deposition is studied, and influence of incoming flow and sediment also is considered in quantities.Aiming at the characteristics of the lower river evolution and estuary evolution, based on field data analysis and academic discussion, the formula of roughness, the distribution equations of sediment concentration and suspended across the river width, exchanging equations about suspended load and bed load are set up in this paper. And the relevant parameters in exchanging equations, the formula of sediment transport capacity, simulation method of river width changes in the process of erosion and deposition, and bed load diameter adjustment, estuary deposition and extension are studied. Finally, a flow and sediment mathematic model is proposed, which is used to simulate the interaction between the lower river and estuary in the process of erosion and deposition, and it is systematically verified by the data from July 1976 to June 1996.Several research methods are used in this paper, including field data analysis and mathematical model calculation of multiple combination schemes. The research takes the incoming flow and sediment, erosion and deposition, estuary extension and changes of the river course as a whole. And the interaction between the lower river evolution and estuary evolution is also discussed. The results and the innovation viewpoints are listed as followed:(1) The annual incoming flow and sediment of the lower river change greatly so that the riverbed evolution appears accumulative deposition, but in a certain period it also experiences a process of erosion and deposition alternatively. The riverbed evolution from the downstream of the LiJin station is both influenced by the incoming flow and sediment, river changing its course and estuary extension. There is a direct proportion between the incoming sediment and the distance of estuary extension. And the proportionality coefficients are different between courses and evolution stages of the same course.(2) The incoming flow and sediment, as the main reason, influences evolution of the lower river and estuary. The annual mean deposition amount between HuaYuanKou and LiJin is inversely proportional to square of the incoming flow amount from HuaYuanKou, and it is direct proportional to the incoming sediment amount. And with the increase of sediment grain size, the amount and rate of sediment deposition increases too. According to regression analysis of field data, an empirical formula is established, which is used to calculate the amount of erosion and deposition of this reach and this reflects the average amount for a long time. When the incoming sediment increases or decreases at HuaYuanKou, the corresponding sedimentation amount of each reach will increase or decrease. The degree of erosion or deposition reduces gradually from upstream to downstream, and the longitudinal gradient becomes steeper or slower. By the self-adjustment of riverbed about several hundreds kilometer, the amount of sediment into the estuary still can’t achieve to the level in equilibrium state. With the increasing or decreasing of incoming sediment at HuaYuanKou, the speed of estuary extension changes. But the rate of change of estuary extension is less than that of incoming sediment at HuaYuanKou, and they have the exponential relation with the coefficient of 0.58.(3) At present, compared with the historical situation, the boundary condition in the lower river has changed obviously. Under the present boundary condition, if there recurs a same flow and sediment process with an old one, the erosion amount of the lower river will reduce, the deposition amount of will increase, and the distribution of erosion and deposition along the river will adjust too. The influence of water and sediment diversion on lower river erosion and deposition is dual. On the hand, when the proportion of water diversion to total incoming flow is very high, as result of losing sediment with big proportion simultaneously, the river deposition will reduce. On the other hand, when the proportion is not very high, the river deposition will increase. For a long time, under the influence of water and sediment diversion along the river, the sediment deposition will increase in the river, and the distance of estuary extension will shorten. The water division along the river is the main reason that leads to the fact that the bankfull discharge is relatively higher in upstream of GaoCun station and downstream of AiShan station, and it is relatively lower between these two stations. This phenomenon is the concurrent result of water division, which led to the increase of river deposition, and river diversion to QingShuiGou course in 1976, which led to decrease of river deposition. For the reach between GaoCun and AiShan, the influenceof water division along the river, which leads to river deposition and the water level increase, is relatively great, and the influence of river diversion to QingShuiGou, which leads to decrease of deposition, is small.(4) As numerical simulating results show that, during the period of 20 years after Yellow Rvier changing its course to QingShuiGou in 1976, compared with running the course of DiaoKou, the deposition amount of its upstream reduced. From 1976 to 1995, the reduced deposition amount from HuanYuanKou station to YuWa station is about 15.3% of the total in the reach. And the reduced deposition amount is smaller in the upstream and larger in the downstream. Before the flood season in 1996, the reduced-deposition-reach has extended to the reach of HuangZhuang Station, and its distance is about 370km far from the diversion point. Compared with non-extension of estuary, its extension in the QingShuiGou’s course leads to increase of the deposition amount. And the increased deposition amount between HuanYuanKou and QingThree is about 16.2% of total amount from 1976 to 1995. The increase amplitude of deposition amount decreases gradually from downstream to upstream. Before the flood season in 1996, the increase-deposition-reach has extended to Zhangcun cross section upstream of LuoKou Station, and its distance is about 275km far from the diversion point.(5) From the point view of practicability for engineering application, the range of feedback influence due to the estuary extension is confirmed, and two dominate indexes, which are obvious influence and relatively serious influence, are proposed. And a new concept of increment rate of the feedback influence due to the estuary extension is brought forward. The course of influence distance increase can be partitioned into two periods. In the first period, the extension distance is about 28-30 km from division location, and the feedback influence distance is about 160~170km. In this period, dominant factor that influences the increment rate is the estuary landform at the beginning of division, and subordinate factor is the landform of influenced-reach. In the second period, the estuary extends farther, and dominant factor is the landform of influenced-reach. Base on this, a formula that is used to calculate the influence distance due to the estuary extension is established. When the extension distance from the XiHeKou is about 98km, the feedback influence will extend to GaoCun reach, and when the extension distance from the XiHeKou is about 125km, it will extend to HuaYuanKou reach. With the increase of longitudinal gradient, the increment rate of the feedback influence due to the estuary extension decreases from downstream to upstream. If the incoming flow and sediment change, the longitudinal gradient will adjust, and the relation between the estuary extension distance and feedback influence distance will change too, but the amplitude of change is small. And according to the comparison of river course evolution between ShenXianGou, DiaoKou and QingShuiGou, it is concluded that feedback influence due to estuary extension will not exceed to AiShan, but downstream of LuoKou will been influenced greatly.更多还原