INFLUENCE OF SEA－AIR INTERACTION ON THEDISCHARGE OF FLOOD SEASON IN THEUPPER REACHES OF THE CHANGJIANG RIVER

On the method of correlation analysis the poper begins with searching theSST (Sea Surface Temperature) and circulation features of some regions with close correlation to the discharge of the flood season (from June to September) in the upperreaches of the Changjiang (Yangtze) River, then discusses the characteristics of sea-airinteraction and the relations between the sea-air interaction and the discharge of theflood season,after that analyzes the possible mechanisms through which the main searegions affect atmospheric circulation, and of the influence of the circulation changes onthe discharge of the flood season.

Downstream Decreasing Channel Capacity of a Monsoon-dominated Bengal Basin River: A Case Study of Dwarkeswar River, Eastern India

Downstream changes in channel morphology and flow over the ephemeral Dwarkeswar River in the western part of the Bengal Basin, eastren India were investigated. The river stretches from the Proterozoic Granite Gneiss Complex to the recent Holocene alluvium, forming three distinctive geomorphological regions across the river basin: the pediplane and upper and lower alluvial areas. Sixty cross-sections from throughout the main trunk stream were surveyed and the bankfull width, depth, cross-sectional area, and maximum depth were measured. Sediment samples from each location were studied and the flow velocity, stream power, Manning’s roughness coefficient, and shear stress were estimated. The results show that the bankfull channel cross-section area, width, width-to-depth ratio, and channel capacity increased between the beginning and middle of the river. Thereafter, the size of the river started to decrease in the lower alluvial area. This was characterized by gentle gradients, cohesive bank materials with grass cover, and channel switching. Within the lower part of the river, the channel capacity was observed to diminish as the drainage area increased. This increased the bankfull flow frequency and accelerated large floodwater losses in the floodplain via overbank flows and floodways.

POLLUTION TREND IN THE TUMEN RIVER AND ITS INFLUENCE ON REGIONAL DEVELOPMENT

The Tumen River had failed to meet Grade Ⅲ and Ⅳ levels in the environmental quality standard for surface water, and had exceeded Grade Ⅴ level. Surface water pollution is serious. The major excessive standard pollutants were COD Mn and SS. After taking effective treatment steps, the worsening trend of water pollution will be basically under control. But the change of runoff in the Tumen River is large in a year, especially during as long as five month freezing period, smaller flow and lower temperature of river waters led to weak dilution and self purification capacity. The water quality of the Tumen River will not reach the appoint functional water quality standards, even if sewage meets discharge standard, which will influence water resources utilization in the lower reaches of the Tumen River and regional economic development. Therefore water pollution has become the major restrictive factor of the development of the Tumen River area.

Response of flood discharging capacity to the deterioration of the lower Yellow River

Based on the clarifications of the deterioration characteristics of the lower Yellow River (LYR), the influence of river deterioration on flood discharging capacity is studied through theoretical derivation and analysis of field data. This study indicates that response of flood discharging capacity to river deterioration is nonlinear. Sediment depositions in the main channel cause the reductions of dominant discharge and thus the increase of initial flood stage. Reductions in the channel width result in the increases of the rising rate of flood stage and the decrease of flood discharging capacity.

Evaluation of Dredging Operations for Tigris River within Baghdad, Iraq

River Tigris divides Baghdad, capital of Iraq, in two parts. The reach of the river within Baghdad is about 60 km long. Many islands and bars are obstructing the flow of the river within Baghdad. To overcome this problem, dredging operations started along most of Tigris River inside Baghdad City to remove many islands and side bars, which reduced the flooding capacity and the efficiency of water intakes. An examination for the dredging plan under process and two proposed additional plans was performed using the Hydrologic Engineering Centers River Analysis System software (HEC-RAS) for a 50 km long river reach to investigate whether they can recover the designed flooding capacity of the river or just improving it. Calibration and verification processes were implemented in the model using observed water levels at Sarai Baghdad gauging station and along the last 15 km of the river reach. Comparisons of computed water levels were conducted with those of previous studies and historical data. Some improvement of flood capacity was achieved based on the recorded data of the last three decades. Cautions about the water intakes should be considered to maintain their function with the expected drop in water level due to dredging operations.

Hazardous Events on the Black Sea Rivers, Their dynamics and Regulation

The historical, informational and literary sources regarding flooding have been studied. Based on the statistical processing of multiyear stationary observation data the river maximal discharge parameters are specified. According tendency of their dynamics the flooding strengthening has been revealed on rivers nourished by glaciers, on the contrary in other rivers they reduced, in some regions evaporation has been increased and desertifieation has been detected. For mitigation negative impacts of those processes the recommendations of prevention measures are drafted.

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.

基于MIKE FLOOD的杜家台分蓄洪区运用调度研究

运用MIKE平台建立杜家台蓄洪区行洪道MIKE11一维河道模型,模拟并分析了红星垸堤刨毁前后的分洪道行洪能力。同时搭建MIKE21分洪区二维模型,并利用MIKE FLOOD动态耦合一、二维模块,以此为平台研究杜家台分蓄洪区分蓄汉江夏、秋洪水与长江洪水时的调度工况。结果表明:红星垸堤刨毁后分洪道宽度增加,显著降低了该处分洪道上游的洪水水位,提高了分洪道分洪能力;汉江低量级来水情况下,杜家台只需运用南区1~4垸分洪,而高量级来水下杜家台需运用1~7垸分洪;长江分洪时,处于下游的第6垸分洪能力显著,最终可解除第7、9垸的风险,只需运用1~6垸。现有防洪工程中第5、6垸分洪速度较慢且分洪量小,而处于最上游的第2垸分洪量大且分洪较快,导致与其相临的1~4垸洪水超高,危及7、9垸,故7、9垸堤顶亟待加高,同时5、6垸分洪能力需要增强。

基于MikeFlood的行洪区调度运用研究

行蓄洪区承担着分泄洪水,保护堤防的重任,历年以来行蓄洪区的科学调度运用都是困扰着水利部门的一大难题。本文以《淮河干流行蓄洪区调整规划》实施后的正阳关至峡山口河段为研究对象,利用DHI MIKE系列软件建立规划河道的一、二维耦合水动力学模型。设置行洪区闸门不同开启次序,及该段行洪区开启时间和启用次序组合的不同调度运用工况,分析不同工况下行洪区行洪效果对淮河干流影响效果。结果表明:对于正峡河段,先开启董峰湖行洪区,且适当的延后行洪区的开启时间和退洪闸的开启时间,更有利于发挥行洪效果。本文研究内容可为行洪区调度运用提供参考。

基于MIKE FLOOD耦合模型的洪水淹没风险分析:以北京市某科学城为例

为科学制定城市空间发展及相关规划,对城市暴雨洪水进行精细化模拟,以北京市某科学城为例,利用MIKE FLOOD平台,基于基础地理、河道断面、闸坝工程、暴雨洪水、防洪规划及调度等数据构建了河道一维、研究区二维的大尺度、高精度耦合模型,模拟范围包括山区120 km^(2)、平原区267 km^(2)。根据设计洪水和2021年潮白河生态补水实测数据进行了模型参数率定和验证,准确模拟了现状和规划情景下的河道洪水漫溢及洪水淹没情况。结果表明:模拟水位与率定及验证水位差均不大于0.20 m,纳什系数接近于1,均方根误差较小。模型对包含山区和平原区的大区域范围及精细化河道断面和网格尺度模拟结果较好,适用于科学城洪水淹没风险分析。现状条件下,科学城内仅沙河牤牛河基本满足20 a一遇防洪标准,20 a、50 a和100 a一遇洪水条件下科学城淹没面积分别为0.45 km^(2)、0.76 km^(2)和3.06 km^(2),淹没主要集中在沙河中游部分河段以及沙河、雁栖河下游入河口处两岸。规划条件下,科学城内河道基本满足防洪标准,未发生洪水淹没。

Impact of dams on flood occurrence of selected rivers in the United States

A significant large number of dams have been constructed in the past two centuries in the United States. These dams＇ ability to regulate downstream flooding has received world-wide attention. In this study, data from 38 rivers distributed over the entire conterminous Untied States with extensive pre- and post-dam annual peak discharge records, were collected to research the impacts of various dams on the flood behaviors at a national scale. The results indicate that dams have led to significant reductions in flood magnitude for nearly all of the sites; the decrease rate in the mean of annual peak discharge varies between 7.4% and 95.14%, except for the Dead River, which increased by 1.46%. Because of dams＇ effective- ness, the probability density curve of annual peak flow changes from a flat to peaked shape because both the range and magnitude of high discharges are decreased. More- over, the potential impact of dams on flood characteristics were closely related to the dam＇s geographic location and function, the ratio of the storage capacity of the dam to the mean annual runoff of the river （C/R）, and the ratio of reservoir storage capacity to the area of its drainage （C/D）. Specifically, the effects of dams on annual peak flows were more related to latitude than longitude. Compared with dams built for other purposes, the dam exclusively used for flood management cut off more flood peaks. Increases in the ratios of C/R and C/D increased the degree of modification of annual maximum discharge.

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。

河湖幸福指数——安澜之河评价研究

水安全是人民群众生存发展的最基本要求之一,是影响社会经济发展的重要因素。防洪安全是沿河人民获得和提升幸福感的基本保障。本研究分析了安澜之河与“幸福河”的关系、安澜之河的内涵,从洪涝灾害严重程度、洪涝灾害防御能力、洪涝灾害恢复能力等三方面构建了安澜之河的评价指标体系,提出了指标标准计算方法,并对全国10个水资源一级区安澜之河指标进行计算评价。结果显示,全国安澜之河总体水平已接近良好,太湖流域、黄河区、松花江区、淮河区和长江区等5个水资源一级区均高于全国水平。本次研究成果较为合理的反映了全国安澜之河的总体情况,可为水利行业开展“幸福河”建设与评估等工作提供参考。

三峡大坝运行20年泄洪安全评价

近年来国内外高坝泄水建筑物破坏事故时有发生,三峡大坝泄洪流量和落差大,泄洪功率居世界第一,其泄洪安全备受关注。结合三峡大坝自2003年蓄水以来的历次水力学原型观测和以往水工模型试验结果,围绕泄水建筑物布置、泄流能力、动水压强、水流空化、水流掺气与通气风速、空蚀磨损、消能防冲7个要素指标,依据有关技术标准和工程经验建立了一套完整的高坝泄洪安全评价方法,提出了定性标准和量化阈值,并据此对三峡大坝深孔、表孔、排沙孔和排漂孔进行泄洪安全评价。结果表明:大坝泄水建筑物布置是合理的;大坝实际泄流量与设计值符合良好;大坝泄洪流道未见空蚀磨损破坏;三峡大坝运行20 a,泄水建筑物和坝下消能区运行性态正常,泄洪安全可靠。

四川金阳县2023年“8·21”山洪泥石流灾害成因分析

2023年8月21日凌晨,四川金阳县芦稿林河流域受短时强降雨影响暴发山洪,位于下游的沿江高速JN1(金宁一)标段项目部钢筋加工场民工驻地板房被冲毁,造成52人死亡失联。灾害发生后,四川省委、省政府高度重视,派出专家对灾害过程进行调查评估。结合现场调查情况,通过水文气象分析计算、河道行洪能力计算等,分析了灾害形成过程及致灾原因,可供类似项目山洪灾害防御工作参考。

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)。

汛期与非汛期水沙条件对黄河下游不同河段过流能力的影响

20世纪80年代以来黄河下游水沙输移特性显著改变,下游河道经历强来沙作用下的持续淤积与小浪底水库调控下的持续冲刷过程。基于黄河下游1986—2020年实测水沙数据与固定断面地形,计算了河段尺度的平滩流量,量化了汛期与非汛期水沙过程对各河段过流能力的相对贡献。结果表明:①小浪底枢纽运行前水流冲刷强度随时间减弱,下游河道呈汛期淤积、非汛期冲刷的整体淤积态势,平滩流量持续减小,最小过流能力小于2000 m^(3)/s。②小浪底枢纽运行后水流冲刷强度显著增大,尤其在非汛期,对河床冲刷产生重要影响;各河段过流能力显著恢复,其中游荡段恢复最为迅速。③各河段平滩流量与前5 a汛期、非汛期平均水流冲刷强度呈良好的幂律关系,该关系能较好地反映汛期与非汛期累积水沙过程对过流能力的综合影响。④小浪底枢纽运行后,非汛期水沙条件对平滩流量的贡献率增大,尤其是对游荡段具有重要影响(占比53%),对过渡段与弯曲段贡献则较小(占比不到20%)。

洪潮影响下潭江流域安全行洪阈值研究

为研究洪潮叠加影响下潭江流域下游感潮河段河道洪水演进动态与行洪能力,构建了一维水动力模型,通过多组洪潮组合工况模拟计算,量化了不同潮位、控制水位、持续泄流时间下潭江流域控制性节点安全行洪阈值以及涨落潮情形下的行洪能力,揭示了洪潮影响下潭江流域水文变化规律,并结合随机森林模型,绘制了高精度安全行洪阈值图谱。结果表明:以潮动力为主的潭江流域下游感潮河段,干流水位主要受下游潮位影响,高潮位的洪潮顶托效应更为强烈,安全行洪阈值受潮位和泄流时间影响;落潮时段行洪能力较涨潮时段明显增强,且落潮时段行洪能力与控制断面水位基本呈线性变化。

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。

海河“23·7”流域性特大洪水北京市拒马河洪水调查分析与河道治理建议

受2305号台风“杜苏芮”北上影响,2023年7月29日至8月2日京津冀地区连续降雨,海河流域发生“23·7”流域性特大洪水,造成严重的人员伤亡和财产损失。对北京市境内拒马河进行洪水调查,在深入分析拒马河治理现状的基础上,采用天然河道恒定流水面线计算和均匀流计算方法推求洪痕对应的流量,并以此复盘分析洪水频率。根据洪水分析成果及水毁情况,从拒马河水域空间划定、河道治理及建筑物设计等方面提出规划治理建议,以期为后续河道整治提供参考。