The characteristics of dike-break flood in different scenarios of the lower Yellow River based on numerical simulations

The lower Yellow River still faces the threat of flood due to the unusual precipitation caused by global environmental change, river channel sedimentation, hidden danger in the dike and unfavorable river regime of ＂hanging river＂. According to the characteristics of the dike-break flood of the Yellow River, this paper has simulated, in six different scenarios, the dike-break flood routing by inputting the terrain data, typical historical flood data and land use data of study area to two-dimensional unsteady flow model. The results show that： firstly, the routing process of flood will occupy other rivers on the way and return to the rivers after reaching the lower reaches; secondly, in the same river reach, flood inundating area of north band is bigger than that at corresponding location of south bank under the same historical flood; thirdly, it is different in the degree of flood inundation in different regions due to different geographical locations in flood plain; fourthly, the area of mainstream where flood is deep and flow velocity is quick is relatively smaller, but the area of non-mainstream, where flood is shallow and flow velocity is slow, is relatively big; and finally, the possible influenced area of the dike-break flood is 141,948 km^2.

A PRELIMINARY STUDY OF THE YELLOW RIVER'S PALEOCHANNELS IN NORTH SHANDONG PLAIN

According to buried depth, the Yellow Rver's Paleochannels can be divided into ground Paleochannels (buried depth 0-8m) and shallowburied Paleochannels theried depth 8-50m). Each of them can be roughly divided into three major Paleochannel belts, stretching Parallel with each other from SW to NE. Sedimentary layers of the paleochannels were mainly made up by sand levee of meanders or natural leavee deposits, and the flooding sedments were found bebeen the layers. The paleochannels in North Shadong Plain were formed in three stags; stage I (buried depth 50-15m) in later period of late Pleistocene-early period of Holocene, stag II (20-8m) in earlymiddle period of HOlocene; and stag III (8-0m) in midddle-late period of Holocene.

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.

Flood Risk Forecasting and Early Warning Technology for Medium and Small Rivers in the Yellow River Basin Induced by Heavy Rain

The Yellow River Basin is one of the important sand-producing and sediment-transporting areas in China,and one of the three most important sand-producing areas in the world.The amount of sand and dust days in the“Three Norths”(Dongbei,Xibei,and Huabei)area has increased,and regional sand and dust storms have occurred frequently.There are generally more serious hidden danger points of debris flow geological disasters in small and medium-sized river basins.The technical achievements of flood risk forecasting and early warning for medium and small rivers in the Yellow River Basin based on rainstorm-induced floods are important technical supports for flood forecasting and early warning for medium and small rivers.Based on this,a case study was carried out on the problems such as the weak forecasting and early warning ability of flood disasters induced by heavy rain and the low accuracy of flood disaster loss assessment in the flood disasters of medium and small rivers,for the reference of relevant personnel.

Evaluation of dynamic characteristics of silt in Yellow River Flood Field after freeze-thaw cycles

Frothing is a main disease of highways in Yellow River Flood Field, due to the loss of dynamic strength of roadbed soils under the couple effects of temperature, salt, and vehicle traffic load. This is strongly linked to the dynamic characteristics of silt in this region. To analyze these couple effects on the dynamic characteristics of silt, a series of tests(i.e., freeze-thaw cycling tests, vibration triaxial tests and ultrasonic wave velocity tests) were conducted and two kinds of silt(i.e., salt-free and 3%-salt silt) were designed. The results indicate that the dynamic shear strength and dynamic modulus decrease with increasing freeze-thaw cycles, while the damping ratio simultaneously increases. Furthermore, compared to salt-free silt, the decrement of dynamic shear strength and dynamic modulus of silt with 3% salt is more significant, but the damping ratio of 3%-salt silt is larger. In ultrasonic wave velocity tests, ultrasonic wave velocity of frozen soil specimens decreases as the number of freeze-thaw cycles increases. Based on the results of ultrasonic wave velocity tests, a preliminary model is proposed to evaluate damage of silt through field measurement ultrasonic data. The study could provide a theoretical basis for the treatment of silty soil highway.

Yellow River Valley flood and drought disaster：spatial－temporal distribution prediction and early－warning

By means of analysing the historical data of flood-drought grade series in the past 2000 years(A.D.0-1900),especially in the last 5000 years (1470-1900) , this paper revealed the spatial-temporaldistribution features of severe flood and drought in Yellow River Valley. Statistical methods of varianceanalysis, probability transition and the principles of scale correspondence were employed tocomprehensively predicate 90's tendency of severe flood and drought in the Yellow River Valley. In addi-tion, this paper pointed out the possible breaching dikes, sectors and the flooding ranges by future's se-vere flood, meanwhile estimating the associated economic losses and impact to environment.

An Experiment on Releasing Water from Water Tanks by Xu Youzhen during the Ming Dynasty

In 1453,Xu Youzhen,a scholar-bureaucrat and hydrologist in Ming China,was dispatched to Shandong to find a way to harness the Yellow River.He proposed the opening up of multiple channels to diverge the flood waters.An experiment was conducted to compare the efficiency of releasing water using one large opening with the use of a number of small openings.This experiment proved that opening up multiple channels outperformed the construction of only one,thereby convincing the emperor and officials of the efficacy of this method.Xu’s method for water control proved to be successful in averting a flood that occurred in 1456.

How is geotextile playing a role in the sponge city?

On July 11th,Beijing-Tianjin-Hebei region suffered the maximum rainfall intensity since the flood season.The National Meteorological Center has been continuously issuing severe convective weather and yellow warning on rainstorm.In late July,Zhengzhou in Henan province experienced heavy rainfall,and the water level even reached at most as high as a three-storied building,seriously endangering people's property and safety.

隧道施工引发粉土地面沉降模拟与分析

为研究黄泛区粉土地层内开挖双线地铁隧道对地上及其周边地面沉降的影响,以某双线地铁隧道开挖工程为例,考虑地下水、隧道间距对地面沉降的影响,采用流固耦合数值方法和理论分析方法对隧道施工引起的地面沉降规律进行分析。将数值模拟数据与Peck公式进行反演计算,并考虑隧道间隔和埋深的影响提出修正Peck公式,再结合叠加原理建立适用于双线隧道开挖引起地面沉降的修正叠加公式。结果表明:隧道开挖扰动地层将引起超静孔隙水压力现象;数值模拟与理论计算得到隧道间隔为4 m时,地面沉降曲线呈现“V”型,隧道间隔为8 m、12 m时,则沉降曲线呈现“U”形;粉土内开挖双线地铁隧道,地面容易受到扰动且沉降量大,随着隧道间距的增加,隧道上方土体沉降量逐渐减小;基于修正Peck公式计算结果与数值模拟结果基本一致,相对误差在3%左右,表明该公式具有很好的实用性。研究可为粉土地区隧道及地下工程建设提供理论依据和技术支撑。

龙羊峡水库后汛期入库径流特征及可蓄水量分析

以1956—2022年唐乃亥水文站实测水文数据为基础,采用数理统计方法,重点分析黄河源区后汛期径流特征,并结合龙羊峡水库满负荷发电流量,对龙羊峡水库在后汛期可蓄水量进行不同情景的分析讨论。研究表明:1)唐乃亥水文站后汛期径流量年际变化较大,丰枯不均,以正常偏枯为主,多年平均后汛期径流量占汛期径流量的29.1%;2)唐乃亥水文站后汛期日平均流量在1000 m^(3)/s以上的径流量平均为8.96亿m^(3),年际变化极大,以1000 m^(3)/s发电流量运用,龙羊峡水库蓄至正常蓄水位的保证率仅为10%,多数年份汛期结束后水位无法达到正常蓄水位2600 m。建议根据后期来水,适时调整进入后汛期的时机,优化和调整龙羊峡水库年度调度方案,为高效合理利用黄河源区后汛期水资源奠定基础。

黄河下游花园口至孙口河段高效输沙洪水阈值研究

河流能量耗散率变化反映了河道水沙输移能力以及河床形态的调整规律。本文研究区域为黄河下游花园口至孙口河段,从能量耗散角度出发,结合对实测资料的统计分析,探究了河流边界阻力能耗率与来水来沙、断面形态以及河床稳定性之间的定量关系,并基于边界阻力能耗率与河床稳定性双重指标,确定了花园口至孙口河段的高效输沙洪水阈值。研究结果表明:流量是影响边界阻力能耗率的主要因素,并与边界阻力能耗率的幂次呈线性相关;随着流量增大到2000 m^(3)/s以上,边界阻力能耗率随含沙量增加呈先减弱后增强的趋势。大流量条件下边界阻力能耗率与宽深比呈负相关关系,花园口与夹河滩断面形态复杂,相关性较弱;相比之下高村与孙口断面形态简单,相关性增强。非恒定水沙条件下的河床大多处于失稳状态,在综合考虑河床形态稳定及边界阻力能耗率最低的前提下,计算得出花园口至孙口河段的洪水高效输沙临界流量约为1500 m^(3)/s,含沙量约为23 kg/m^(3)。

黄河下游花园口以上河道滞沙指标研究

水沙搭配关系是影响黄河下游河道冲淤调整的重要因素,局部河段滞沙则是改善下游水沙关系的有效手段之一。小浪底水库运用后,河槽沿程冲刷不均衡,河床粗化,细沙补给不足,输沙效率明显降低。分析黄河下游河道冲淤特性及水沙演进规律,建立不同类型洪水滞沙河段(花园口以上河段)与排洪瓶颈河段(高村—艾山河段)的冲淤关系。基于滞沙对河道行洪和稳定性的影响,以排洪瓶颈河段不淤积为约束,提出洪水滞沙的水沙优化配置指标。中泥沙洪水滞沙指标为:洪水平均流量为1800~3700 m^(3)/s,平均含沙量为66~235 kg/m^(3)。

黄河防汛抢险技术虚拟试验场构建技术研究

黄河防汛抢险技术试验场由“虚”“实”两部分组成,虚拟平台是实体试验场的数字孪生体。以建设黄河防汛抢险技术虚拟试验场为目标,依托总体布置方案对场地结构进行分解,针对7组模块化构件,通过实体尺寸参数驱动三维模型,同时根据附加材质对不同构件分别进行多边形建模和曲面建模;采用C4D等工具构建三维场景;采用光滑粒子流体动力学(Smoothed Particle Hydrodynamics,SPH)方法求解纳维—斯托克斯方程组,基于Realflow软件在蓄水池内生成流体粒子和网格,在时间、空间两个维度获取粒子水力要素;采用Octane render对三维场景和流体网格进行渲染。最终构建完成强真实感、高可信度的试验场虚拟场景。

明清时期黄河下游决泛区的时空变化及其人地关系规律

明清黄河下游决泛水沙对颍河沿岸平原地区的环境和地表塑造的影响相对较轻,颍河两岸未形成显性决口扇地貌,历次黄泛水沙一般未越过颍河向西南漫溢,颍河干流长期作为黄泛水沙的良好容受体及其向西南蔓延扩张的界隔线。涡河沿岸地区受到明清黄河独流干道决口水沙向南泛滥及涡河本身被黄水夺溜时决泛水沙的双重影响,黄河主故道南岸核心决口扇的边缘带与沿涡次级决口扇相互交集,在涡河地区形成叠加型决口扇地貌,涡河干流长期作为黄泛重灾区与影响轻微地区的分界线。大型湖泊洼地的积水面通常与黄泛决口扇的前缘互为进退,鱼台县的土壤分布及农作物结构特征,较好地证明了南四湖洼地长期作为黄泛决口扇的边界,南四湖是明清时期黄泛水沙向北蔓延扩张的重要蓄洪区和调剂区。

新形势下黄河下游控导工程建设思路探讨

2021年黄河中下游发生历史罕见秋汛洪水,下游控导工程经受了长历时中常洪水过程的检验。针对部分控导工程在洪水过程中暴露出来的坝顶高度不够、根石不足、裹护段长度不够、抢险道路交通能力不足等问题,从工程设计、管理上进行分析,认为水沙条件变化、控导工程设计流量降低、河道下切、平滩流量增大、抢险机械设备大型化等是出现这些问题的原因,并提出了今后避免类似问题发生的措施和建议。

干旱区与湿润区旱涝急转演变特征对比研究

以长江、黄河和淮河流域为研究对象,基于标准化旱涝急转指数,利用趋势分析、变点检验、小波分析、随机森林等方法探究典型干旱区与湿润区旱涝急转演变特征及其驱动因子。结果表明:湿润和半湿润区是极端旱涝急转事件的高频发生区,干旱区是极端旱转涝事件的高频发生区;干旱区的突变发生在1998年,湿润区的突变在1978年,未来干旱区更易发生旱转涝事件,湿润区则相反;气象因子在湿润区对旱涝急转的贡献度更大,大气环流对干旱区的影响突出,旱涝急转与不同驱动因子间存在非线性关系。

黄河流域防洪形势与对策

在全球极端暴雨频发背景下,黄河流域防洪安全对保障全面建设社会主义现代化国家具有十分重要的意义。分析了黄河流域防洪安全现状及存在问题,剖析了保障黄河长治久安面临的严峻挑战,以确保堤防不决口、确保河床不抬高、让黄河成为造福人民的幸福河为目标,提出了新时期黄河流域防洪减灾体系的对策措施,论证了黄河长治久安的前景和保障思路。

黄河秋汛洪水防御实践与思考

黄河秋汛洪水相比夏汛洪水,具有洪峰低、持续时间长、含沙量低的特点。2021年黄河发生严重秋汛,干支流、中下游汛情多区域交织,多场次叠加,洪量之大、历时之长,历史罕见。文章以2021年黄河秋汛洪水为例,从水库群精细联合调度、洪水防御工作部署、防洪调度成效等方面回顾了秋汛洪水防御工作,总结了此次洪水防御过程中的技术支撑及组织保障经验,展望了新形势下秋汛洪水防御工作重点,为今后秋汛洪水防御工作提供借鉴参考。

黄河源区汛期降水径流序列多尺度小波分析

基于黄河源区15个地面站点日降水数据、唐乃亥水文站逐日径流数据以及小波分析方法,分析了黄河源区1961—2020年汛期降水和径流的周期规律、变化趋势及相关关系。结果表明,1)黄河源区近60 a汛期降水、径流均存在多时间尺度的变化特征,且不同时间尺度汛期降水、径流丰枯变化趋势均不同;2)汛期降水、径流序列均具有63 a左右、35 a左右特征时间尺度的主周期,两个时间尺度下的平均周期分别为41、25 a左右,汛期降水、汛期径流具有一定的正相关性;3)在63 a特征时间尺度可预测2020年之后未来5~10 a内黄河源区汛期降水、径流整体均呈减小趋势。