Natural Disasters of the Lower Reaches of Yellow River during the Longshan Period——The Natural Background of Dayu's Flood Control

It is very important to study the archaeological culture and origin of civilization in ancient China.The changes of the channels in the lower reaches of the Yellow River in the prehistoric period are part of the natural environmental background of the development of the ancient civilization in that area to be explored.This paper presents a series of legends,indications,scientific evidence,and macroscopic geographical background information of the evolution in the lower reaches of the Yellow River during the Longshan period.At first the river flowed from Northern Henan and Hebei to southwestern Shandong Province and Northern Anhui–Jiangsu provinces,and the mainstream of the Yellow River changed from the southeast to return to the north and flowed into the Bohai Sea in the late Longshan Period.During this period,floods were frequent.Various ethnic groups in the northern China plains suffered natural disasters and made great migrations which also contributed to the ethnic exchanges and integration.The people of the Central Plains made more dynamic adjustments in the relationship between mankind and the land by primitively escaping from the water and self–defensively controlling the rivers then to maintaining the local ecological environment by large–scale flood control measures,which promoted the settlement of Shandong,Henan,Jiangsu and Anhui provinces,the urban cultural development,and social evolution.Based on these events,the culture symbol of Dayu's Flood Control could be formed.

Simulating cross-sectional geometry of the main channel in response to changes in water and sediment in Lower Yellow River

To understand the non-equilibrium morphological adjustment of a river in response to environmental changes,it is essential to(i)accurately identify how past conditions of water and sediment have impacted current morphological adjustment of the river,and(ii)establish a corresponding simulation for non-equilibrium conditions.Based on discharge and suspended sediment concentration(SSC)as well as 82 cross-sectional data items for the Huayuankou-Lijin reach of the Lower Yellow River in the period 1965-2015,the process of adjustment of the geometry of the main channel(area,width,depth,and geomorphic coefficient),and its responses to changes in discharge and SSC for different reaches are statistically analyzed.Following this,a delayed response model(DRM)of the geometry of the main channel subjected to variations in discharge and SSC is established using a multi-step analytical model,with the discharge and SSC as the main controlling factors.The results show that the area,width,and depth of the main channel decreased initially,then increased,decreased again,and finally increased again.These features of the geometry of the channel were positively correlated with the 4-year moving average discharge and negatively with the 4-year moving average SSC.The geomorphic coefficient for the Huayuankou-Sunkou reach exhibited a trend of decrease,whereas that of the Sunkou-Lijin reach decreased initially,then increased,decreased again,and finally increased again.Except for the Huayuankou-Gaocun reach in 1965-1999,the coefficient was negatively correlated with the 4-year moving average discharge and positively with SSC.The simulated values of the morphological parameters of the main channel for all sub-reaches obtained using the DRM agreed well with the measured values.This indicates that the DRM can be used to simulate the process of response of the cross-sectional geometry of the main channel to variations in the water and sediment.The results of the model show that the adjustment of the geometry of the main channel was affected by the discharge and the SSC at present(30%)as well as for the previous 7 years(70%).The proposed model offers insights into the mechanism whereby past water and sediment influence the current morphological adjustment of the river,and provides an effective method for predicting the magnitude and trend of the geometry of the main channel under different flow conditions.

Adjustment in the main-channel geometry of the lower Yellow River before and after the operation of the Xiaolangdi Reservoir from 1986 to 2015

Based on the measured discharge,sediment load,and cross-sectional data from 1986 to 2015 for the lower Yellow River,changes in the morphological parameters(width,depth,and cross-sectional geomorphic coefficient)of the main channel are analyzed in this paper.The results show that before the operation of the Xiaolangdi Reservoir(XLDR)from 1986 to 1999,the main channel shrunk continually,with decreasing width and depth.The rate of reduction in its width decreased along the river whereas that of depth increased in the downstream direction.Because the rate of decrease in the width of the main channel was greater than that in channel depth,the cross-sectional geomorphic coefficient decreased in the sub-reach above Gaocun.By contrast,for the sub-reach below Gaocun,the rate of decrease in channel width was smaller than that in channel depth,and the cross-sectional geomorphic coefficient increased.Once the XLDR had begun operation,the main channel eroded continually,and both its width and depth increased from 2000 to 2015.The rate of increase in channel width decreased in the longitudinal direction,and the depth of the main channel in all sub-reaches increased by more than 2 m.Because the rate of increase in the depth of the main channel was clearly larger than that of its width,the cross-sectional geomorphic coefficient decreased in all sub-reaches.The cross-sectional geometry of the main-channel of the lower Yellow River exhibited different adjustment patterns before and after the XLDR began operation.Before its operation,the main channel mainly narrowed in the transverse direction and silted in the vertical direction in the sub-reach above Aishan;in the sub-reach below Aishan,it primarily silted in the vertical direction.After the XLDR began operation,the main channel adjusted by widening in the transverse direction and deepening in the vertical direction in the sub-reach above Aishan;in the sub-reach below it,the main channel adjusted mainly by deepening in the vertical direction.Compared with the rates of decrease in the width and depth of the main channel during the siltation period,the rate of increase in channel width during the scouring period was clearly smaller while the rate of increase in channel depth was larger.After continual siltation and scouring from 1986 to 2015,the cross-sectional geometry of the main-channel changed from wide and shallow to relatively narrow and deep.The pattern of adjustment in the main channel was closely related to the water and sediment conditions.For the braided reach,the cross-sectional geomorphic coefficient was negatively correlated with discharge and positively correlated with suspended sediment concentration(SSC)during the siltation period.By contrast,the cross-sectional geomorphic coefficient was positively correlated with discharge and negatively correlated with SSC during the scouring period.For the transitional and meandering reaches,the cross-sectional geomorphic coefficient was negatively correlated with discharge and positively correlated with SSC.

Characteristics of the Lower Yellow River channel shrinkage and its discriminant parameters

This paper analyzes the changing trends of the Lower Yellow River(LYR) transverse profile parameters and their aberrance points by the time series analysis method.Research results show that there has been a trend of changes in the LYR channel transverse profile parameters since the 1950s.The main river channel has a tendency of shrinkage year by year and the trend will be continued in the future.The main features of the LYR channel shrinkage are remarkable reductions of bankfull dis-charges and bankfull areas,corresponding decreases of bankfull widths,average bankfull water depths and maximal bankfull water depths,as well as increases of bankfull water levels and width-depth ratios accompanied.The discriminant parameters for threshold of the LYR main channel shrinkage were put forward.It indicates that the LYR main channel began to shrink in the 1970s and has entered into a serious phase of channel shrinkage since the 1990s.The incompatible index of discharged water-sediment processes of the Sanmenxia Reservoir was introduced,which revealed that there was a trend of increasing in the incompatibility between water flow and sediment load.Response relations between the LYR main channel shrinkage parameters and discharged water-sediment processes of the Sanmenxia Reservoir were founded,which indicate that the LYR main channel shrinkage can be mitigated and improved through the regulation of discharged water-sediment processes of the reservoir,especially through the regulation of water-sediment incompatible index.The LYR channel for water and sediment transportation can be restored and maintained.

Comparison of channel geometry changes in Inner Mongolian reach of the Yellow River before and after joint operation of large upstream reservoirs

The impact of reservoirs on downstream river channel change has been a scientific issue in fluvial geomorphology during the last few decades. However, it is still a difficult issue as to how to express quantitatively the channel adjustment in the Inner Mongolian reach of the Yellow River induced by the joint operation of upstream reservoirs. Based on the shape parameters of channel cross-sections at four gauging stations in this river reach over a flooding season in two periods, 1978–1982 and 2008–2012, the present work investigated the channel changes in terms of shape parameter change rate under the same controlling water level in each flooding season at the channel cross-sections. Results showed that most of the change rates of the parameters evidently increased over a flooding season in both periods. However, the change rate of each parameter at the cross-sections decreased evidently in the latter period, compared with the former period. At the same time, the distribution pattern of the change rate of the shape parameters along the cross-sections thus changed from a convex curve in the former period to an S-shaped curve in the latter period. The obvious decrease of the change rates is related to the joint operation of the Liujiaxia and Longyangxia reservoirs. The reservoirs stored a large volume of water and decreased the peak discharge and maximum velocity in the flooding season; as a result, the erosion ability of the flood decreased accordingly. With the joint operation of the large reservoirs, the Inner Mongolian channel shrunk markedly. Therefore, the channel will present the possibility of an extreme flood in the future. Consequently, it is reasonable to adjust the function of the reservoirs in future. The total water and sediment discharges and the peak discharge in flooding seasons should be effectively controlled. Continuous shrinkage of the channel can thus be avoided and it can be ready for a potential extreme flood.

Can the narrowing of the Lower Yellow River by regulation result in non-siltation and even channel scouring？

This study considered whether the narrowing of the upper （broad and wandering） reaches of the Lower Yellow River could result in a reduction in sedimentation and even an increase in channel erosion in both the upper and the lower （narrow and meandering） reaches. Analysis of field data and numerical modeling results both justify the proposal to narrow the channel. A positive correlation was found between channel eroded-area and the channel width. Therefore narrowing under conditions of low flow will reduce the amount of erosion in the reach, which, in turn, will reduce the amount of sediment transported into the lower channel. This will reduce the amount of siltation in the lower reaches of the river. However, narrowing under conditions of high flow with a low concentration of sediment will reduce both the extent of flood attenuation along the narrowed channel and the amount of lateral channel bank collapse, which results in increased flows and less sedimentation in the lower channel, leading to increased erosion. When flows with a high concentration of sediment are released from the Xiaolangdi Reservoir, both the lower narrow channel and the upper channel can transport a large amount of the sediment load. It is concluded that the narrowing of the upper broad channel will result in a reduction in sedimentation, or even in channel erosion, in both the upper and the lower channels if the reservoir is operated such that the volume of sediment added during low flows is balanced by the volume eroded during high flows with a low concentration of sediment.

Quantitative relationship of the sedimentation in the lower Yellow River with its mouth channel extension

THE effect of extension of the mouth channel on the sedimentation in the lower Yellow

Simulation on the stochastic evolution of hydraulic geometry relationships with the stochastic changing bankfull discharges in the Lower Yellow River

Extreme weather is an important noise factor in affecting dynamic access to river morphology information.The response characteristics of river channel on climate disturbances draw us to develop a method to investigate the dynamic evolution of bankfull channel geometries(including the hydraulic geometry variables and bankfull discharges)with stochastic differential equations in this study.Three different forms of random inputs,including single Gaussian white noise and compound Gaussian/Fractional white noise plus Poisson noise,are explored respectively on the basis of the classical deterministic models.The model parameters are consistently estimated by applying a composite nonparametric maximum likelihood estimation(MLE)method.Results of the model application in the Lower Yellow River reveal the potential responses of bankfull channel geometries to climate disturbances in a probabilistic way,and,the calculated average trends mainly run to synchronize with the measured values.Comparisons among the three models confirm the advantage of Fractional jump-diffusion model,and through further discussion,stream power based on such a model is concluded as a better systematic measure of river dynamics.The proposed method helps to offer an effective tool for analyzing fluvial relationships and improves the ability of crisis management of river system under varying environment conditions.

Adjustment of flood discharge capacity with varying boundary conditions in a braided reach of the Lower Yellow River

It is of necessity to investigate the adjustment of flood discharge capacity in the Lower Yellow River(LYR)because of its profound importance in sediment transport and flood control decision-making,and additionally its magnitude is influenced by the channel and upstream boundary conditions,which have significantly varied with the ongoing implementation of soil and water conservation measures in the Loess Plateau and the operation of the Xiaolangdi Reservoir.The braided reach between two hydrometric stations of Huayuankou and Gaocun in the LYR was selected as the study area.Different parameters in the study reach during the period 1986-2015 were calculated,covering bankfull discharge(the indicator of flood discharge capacity),the pre-flood geomorphic coefficient(the indicator of channel boundary condition),and the previous five-year average fluvial erosion intensity during flood seasons(the indicator of incoming flow and sediment regime).Functional linkages at scales of section and reach were then developed respectively to quantitatively demonstrate the integrated effects of channel and upstream boundary conditions on the flood discharge capacity.Results show that:(1)the reach-scale bankfull discharge in the pre-dam stage(1986-1999)decreased rapidly by 50%,accompanied with severe channel aggradation and main-channel shrinkage.It recovered gradually as the geometry of main channel became narrower and deeper in the post-dam stage,with the geomorphic coefficient continuously reducing to less than 15 m-12.(2)The response of bankfull discharge to the channel and upstream boundary conditions varied at scales of section and reach,and consequently the determination coefficients differed for the comprehensive equations,with a smallest value at the Jiahetan station and a highest value(0.91)at reach scale.Generally,the verified results calculated using the comprehensive equations agreed well with the corresponding measured values in 2014-2015.(3)The effect of channel boundary condition was more prominent than that of upstream boundary condition on the adjustment of bankfull discharge at the Jiahetan station and the braided reach,which was proved by a larger improvement in determination coefficients for the comprehensive equations and a better performance of geomorphic coefficient on the increase of bankfull discharge.

初论黄河下游河道的河槽线

黄河白鹤镇至陶城铺河段两岸堤距宽,历史上河道冲淤变化迅速、河势游荡多变,经多年河道整治,总体上河势得到基本控制,滩槽逐步稳定。在此条件下,为促进黄河的生态保护和滩区发展,提高河道管理水平,将河道粗分为河槽与滩地,首次提出河槽线的概念,明确了河槽线的含义及绘制河槽线的原则,强调绘制河槽线要以防洪安全为前提,给出了河槽线的绘制方法及其现场标示办法,分析了河槽线的作用等。

黄河下游花园口以上河段滞沙能力分析

黄河下游河床调整主要取决于来水来沙和河床边界条件,河床调整沿程不均衡特征明显,花园口以上河段床演变对水沙条件的变化响应尤为突出,泥沙冲淤调整幅度最大。基于河道冲淤及水沙演进特性、滞沙可行性、河槽几何特性等分析,提出了花园口以上河段可作为泥沙天然反调节“库”概念,结合黄河下游实测洪水资料,采用水力计算方法,计算了花园口以上河段的河槽排洪能力及不同河槽规模条件下河槽允许滞沙量,提出了反调“库”滞沙能力,可为小浪底水库排沙指标的确定提供依据,对维持小浪底水库有效库容、弥补后续清水河床沙源不足、改善黄河下游河槽冲淤不均衡现象具有重要意义。

黄河下游灌区引黄涵闸引水能力变化原因分析

黄河下游引黄涵闸受河床下切、河势变化等因素共同影响,引水条件与设计情况相比发生了变化,造成部分河段涵闸引水困难,影响农业适时灌溉和生产。为给应对引黄涵闸引水能力下降问题提供参考,基于黄河下游2000—2016年引黄涵闸引水水位和河道断面实测数据,分析引黄涵闸引水水位变化、河槽冲刷、引黄渠道淤积变化等因素对引黄涵闸引水能力产生的影响。结果表明:1)2016年黄河来水300~900 m^(3)/s时,黄河下游引黄涵闸实际引水能力仅为设计引水能力的13.63%~39.43%,引黄涵闸引水能力明显下降;2)相较2000年,2016年的引黄涵闸设计值对应黄河流量的水位,高村以上河段下降了2.95~3.35 m,高村以下河段下降了1.55~2.95 m;3)从河段河床平均冲刷厚度看,花园口—夹河滩、夹河滩—高村、高村—孙口、孙口—艾山、艾山—泺口、泺口—利津河段的冲刷厚度分别为3.88、3.06、1.84、1.88、1.88、2.02 m,河槽连续冲刷导致同流量水位明显降低,严重影响河南和山东段引黄涵闸正常引水;4)涵闸前后引、输水渠道淤积会导致引黄涵闸引水能力降低。

黄河下游近期持续冲刷过程中床沙粗化特性分析

床沙组成的变化影响悬沙沿程恢复及河床阻力变化。本文基于黄河下游7个水文站1999—2020年的实测床沙资料,计算了各水文断面不同粒径组床沙占比的年际变化,分析了近二十年持续冲刷过程中不同河型河段床沙的时空粗化特性,讨论了河床冲淤过程对床沙粗化的影响。从时间来看,小浪底水库运用后,不同时期床沙的粗化特点不同,拦沙初期(2000—2006年)急剧粗化,拦沙后期(2007—2020年)粗化放缓,高村站及上游各站床沙呈波动粗化,高村站以下则变化不大,且粗化程度最强处由游荡段向下游过渡段转移;从空间来看,床沙沿程细化,游荡段以极粗沙为主,过渡段以粗沙和极粗沙为主,弯曲段的中细沙不可忽视。拦沙初期各河段床沙组成的调整表现为中细均冲;拦沙后期则表现为中粗均冲,极粗沙占比增大,利津以上各站细沙占比不足5%,对悬沙的补给受限,中沙和粗沙仍经受冲刷,极粗沙对相应悬沙有较好补给作用。河段汛后床沙中值粒径与河床累计冲刷量呈良好的幂函数正相关关系,但拦沙后期床面已粗化到相当程度,河床冲淤对床沙粗化的影响受限。研究结果有助于掌握近期整个黄河下游床沙的粗化现状及预测下游河道冲淤变形规律。

持续冲刷期内黄河下游河床演变特点分析

基于2006年10月至2018年11月黄河下游12个典型断面观测数据,通过分析断面主槽平滩形态特征参数变化率及深泓线和主槽中心线的摆动强度,探讨了持续冲刷期内下游河床的调整变化过程及特点。结果表明:黄河下游断面形态调整表现出既有横向展宽又有冲深下切或淤高态势;河床平面摆动促进了断面主槽形态调整,河相系数变化率与深泓线和主槽中心线摆动强度均成正相关关系;来水来沙条件是主槽形态改变的主要驱动力,且可引起局部河段深泓线摆动强度增大。通过调整小浪底水库的运行模式及布设控导工程可进一步塑造并维持稳定的黄河下游中水河槽。

黄河下游高村-孙口段冲淤变化及影响因素定量分析

为探究黄河过渡段河道滩槽演变规律,采用实测水沙和大断面数据,分析近年来高孙段河床冲淤、水沙条件和河床形态的演变,以年和汛期为时间尺度,用灰色关联度分析河槽冲淤量与水沙条件及河床形态的关联程度。结果表明,近年来高孙段以冲刷为主,汛期是年内输沙的主要时期;高村断面来沙系数可以分为波动减小(2002~2017年)和快速增加(2018~2019年)两大阶段,而河床形态中水力半径和宽深比变化趋势完全相反,糙率存在增大趋势;高村断面的水沙条件及河床形态与高孙段河道冲淤具有较高的关联程度,河床形态比水沙条件具有更高的相关性。

黄河下游漫滩洪水滩槽分流比变化及其影响因素分析

采用实测资料分析的方法,研究了黄河下游漫滩洪水滩槽分流比变化及其影响因素。研究结果表明:花园口4次漫滩洪水滩槽分流比均值为0.18,说明主槽是黄河下游泄洪排沙的主体;黄河下游上宽下窄,滩槽分流比沿程变大。1986年后,下游河道萎缩,平滩流量下降,滩槽分流比增大;2000年后,下游河道冲刷,平滩流量增大,滩槽分流比减小。滩槽分流比随滩槽糙率比的增大而减小,随滩槽水面宽度比、滩槽水深比的增大而增大。提高主槽过流能力,必须采用综合治理措施维护下游主槽适宜规模的平滩流量;提高滩地过流能力,必须降低人类活动对滩地的影响,给滩地留有足够的行洪空间,确保全断面行洪安全。

黄河下游游荡河段高含沙洪水期输沙规律研究

黄河下游河床长期处于淤积抬升状态,其冲淤演变规律对于下游河道治理有着重要影响。因此,快速预测不同量级高含沙洪水各河段的冲淤量以及判断高含沙洪水期黄河下游游荡河段冲淤影响很有必要。根据1960—2021年54场高含沙洪水的实测水沙资料,分析高含沙洪水期黄河下游游荡河段下站输沙率与上站流量、含沙量、输沙率之间的相关关系并建立关系式,系统地研究高含沙洪水的输沙规律。结果表明,下站输沙率与上站输沙率存在极强的相关性,进一步按来沙系数分级得到高含沙洪水期的输沙率公式,能够很好地模拟冲淤过程,极大地提高了与实测水沙资料的贴合度。以小浪底水文站为黄河下游游荡河段的进口控制水文站,采用按来沙系数分级所求的输沙率关系式能够较准确推求花园口站、夹河滩站、高村站的输沙率,从而计算小浪底—花园口、花园口—夹河滩和夹河滩—高村河段的累计冲淤量。

黄河下游河道平滩流量变化及其与汛期水沙条件的关系

采用实测资料分析的方法,研究了黄河下游河道平滩流量变化与汛期水沙条件的关系。黄河下游河道平滩流量的变化是先减小后增大,由20世纪中期的7 000~9 000 m^(3)/s减小到20世纪末期的2 000~4 000 m^(3)/s;21世纪后,平滩流量恢复至4 000~7 000 m^(3)/s。2000年前孙口平滩流量与汛期水沙条件关系点群与2000年后两者关系点群存在明显分区,表明小浪底水库蓄水拦沙运用后,下游河道冲刷演变机理与前期河道淤积演变机理存在较大差异。建立的孙口平滩流量与汛期水沙条件的定量关系表明,黄河下游河道平滩流量随着汛期平均水量的增大而增大,随着汛期平均来沙系数的增大而减小。

黄河下游典型概化心滩绕流近壁面流场水力特性

为了揭示黄河下游典型概化心滩绕流近壁面流场的水力特性,以下游马峪沟断面附近典型心滩作为研究对象,利用模型试验与数值模拟探究不同流量与水深条件下概化心滩绕流近壁面流场的水流流态、河床高程、水流挟沙力及床面阻力等特性,并验证平面二维水沙模型计算得到的流速分布与河床高程的正确性.结果表明:分流区断面受到滩头影响,流速变小,并且流速最大值出现在汊道.汇流区断面在滩尾影响下发生边界层分离,水槽中央流速达到最小,此后流速达到最大并趋于平均化;采用平面二维水沙模型计算得到的流速分布与河床高程的模拟值与试验值基本吻合,表明采用数值模拟探究心滩绕流近壁面流场水力特性是可行的.本研究将为揭示黄河下游典型冲积河段心滩形态特征调整过程的动力学机理提供理论基础.

黄河下游河道悬沙与床沙粒径智能预测研究

探究河道悬沙和床沙粒径分布有助于分析河道泥沙整体淤积情况,并反馈指导优化水库运用方式。为系统掌握黄河下游河道悬沙与床沙粒径的分布规律,收集整理黄河下游河道花园口等6个断面的水沙系列数据,采用递归特征消除算法进行变量筛选,并基于不同机器学习算法构建黄河下游河道泥沙粒径的预测模型。结果表明:变量筛选算法能够有效提取模型中的主要影响因子,而利用机器学习算法进行不同断面泥沙粒径预测时,在测试集上整体表现较好,各断面优选模型预测悬沙粒径的决定系数R2均在0.64~0.89之间,床沙的均在0.37~0.72之间。同时,采用2020年数据对模型预测效果进一步验证时,悬沙和床沙粒径预测值与实测值R2分别达0.6097和0.4456,表明所建模型能够有效实现黄河下游河道泥沙粒径预测。