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1.
三峡工程下游宜昌至沙市河段河床冲刷预测 总被引：1，自引：1，他引：0
在已建水库下游河床冲刷泥沙数学模型的基础上针对宜昌－沙市河段的河道特性,修改并建立了能够反映该河段水沙运动特性的一维水流泥沙数学模型,在此基础上,进行了三峡建库后,前２０年内宜昌－沙市河段的一维水沙运动及河床冲淤计算。 相似文献
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在冲积河流上,各类河道整治工程的实施一定程度上会影响河床的演变过程.本文通过改进现有的一维水沙数学模型,重点研究护岸及护滩(底)这类限制河床进一步冲刷的整治工程对水沙输移及河床冲淤变形的影响.首先对固定断面的各节点采用特定的代码进行标记,以此区分河漫滩、有或无整治工程的主槽区域.然后对悬沙输移及河床冲淤变形模块进行改进:当断面发生淤积时,其形态调整不受整治工程的影响,淤积量将在整个断面上进行分配;当发生冲刷时,断面形态调整仅发生在未实施工程的位置或者受工程限制但形成了一定厚度淤积层的区域;在实施了整治工程且无法提供沙源的区域,河床冲刷则不会发生.最后长江中游荆江段2016年的模拟结果表明:考虑整治工程情况时,改进模型计算的河道冲刷量偏小且与实测值更为接近;河槽断面形态与实测结果也更为吻合. 相似文献
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以三峡工程为核心的梯级水库群联合调度运用显著改变水沙条件,坝下游河段出现长时间、长距离的冲淤调整,长江中下游沙量平衡分析是合理评估水库群修建对河道影响的重要依据,是河湖管理与保护的关键支撑.本文基于长时间序列原型观测资料,采用沙量平衡法分析长江中下游不同时空尺度泥沙沿程恢复特征,对比断面地形法计算结果,结合河道空间区域性特征,从临底悬沙测验误差、断面代表性及断面间距、河道采砂等多角度深入揭示两种方法计算冲淤量产生差异的主要原因.结果表明:(1)2003-2018年宜昌至大通河段冲刷泥沙10.76亿t,其中粒径d<0.125 mm的泥沙冲刷量占比达90.9%.以螺山为界,宜昌至螺山段"粗细均冲",螺山至大通河段则"细冲粗淤";(2)宜昌至大通河段2003-2018年沙量平衡法与断面地形法计算冲淤量相对偏差为71%,从沿程差异分布来看,距离三峡大坝坝址较近的宜昌至沙市河段两方法计算绝对差值较小,而沙市至大通河段差值较大,占宜昌至大通全河段绝对偏差的近86%;(3)宜昌至沙市河段河道采砂量占实测河床冲刷量的比例约为20%,临底悬沙对输沙量的改正比例为13.2%~26.7%(平均约为20%),修正后,沙量平衡法、断面地形法计算结果吻合相对较好;沙市至大通河段泥沙测验、固定断面布设、河道采砂等是导致沙量平衡法与断面地形法出现差异的主要原因. 相似文献
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以往关于三门峡水库的研究多关注库区年际间的冲淤变化,而对汛期和非汛期库区冲淤分布研究较少。本文基于三门峡水库蓄清排浑运用以来1974 2018年实测水沙、断面及冲淤数据,研究汛期和非汛期库区冲淤重心的迁移、冲淤速率及其对潼关高程的影响。结果表明,蓄清排浑运用以来库区河道基本遵循汛期冲刷、非汛期淤积的演变规律。分别定义汛期最大冲刷速率和非汛期最大淤积速率发生的相邻两断面间的子河段为冲刷重心和淤积重心,汛期冲刷重心与非汛期淤积重心出现的位置基本对应,1974 2010年冲淤重心由距坝约90 km逐渐向坝前移动,平均下移速率约1～2km/a;2010年后冲淤重心逐渐上移,2017年位于坝上游约60～70 km,但冲淤强度明显减弱。淤积重心的位置主要受水库回水长度影响,冲刷重心主要与汛期水流能量相关,淤积重心位置迁移滞后于影响因子的变化约5年,而冲刷重心滞后时间约2年。潼关高程与潼关至太安段（潼太段）比降呈反比关系,比降越大,潼关高程越低,而当冲刷重心迁移至潼太段并影响其下段时,潼太段比降增大,利于潼关高程降低。1985年后回水范围和冲淤重心均位于潼关以下,潼关高程受冲淤重心影响较小。 相似文献
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三峡工程运用后城陵矶-武汉河段河床调整及崩岸特点 总被引：1，自引：1，他引：0
为研究近期城汉河段河床调整及崩岸特点,利用实测水沙及地形等资料,采用河段平均的方法,计算了城汉河段断面形态的调整过程,主要包括平滩河槽形态调整及其与前期水沙条件之间的关系.计算结果表明：城汉河段平滩河宽由2003年的1710 m增加至2016年的1732 m,增幅为1.28%,平滩水深由2003年的16.47 m增加至2016年的17.95 m,增幅为9.0%;白螺矶、界牌、簰洲及武汉等河段河床调整以纵向冲深为主,但陆溪口河段河床调整横向展宽与纵向冲深同步发展;2006-2016年城汉河段多年平均崩退速率为5.5 m/a,崩岸总长19.6 km,占岸线总长的8.3%,右岸占55.3%.簰洲河段岸线崩长占城汉河段岸线崩退总长的75.9%.此外还分析了河床边界与水沙条件等因素对重点河段（簰洲河段）崩岸过程的影响,来水来沙条件占主导地位,局部区域崩岸的发生依赖于河床边界条件;建立了典型断面平滩河宽与前期水沙条件之间的经验关系,较好地反映了水沙条件变化对崩岸过程的影响. 相似文献
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受上游水库运行的影响,自2003年后长江中游河段河床调整,引起河道自身过流能力的变化.本文选取长江中游城陵矶-汉口河段作为研究对象,根据实测资料计算了2003-2016年两个水文断面的水位-流量关系及特征流量变化,并采用一维水动力学模型计算了河段尺度的平滩流量.结果表明:(1)螺山站及汉口站2003-2016年的水位-流量关系呈现枯水流量下水位降低、洪水流量下水位抬升的特点;(2)两站年最大流量下对应的水位整体抬升,警戒水位下对应的流量分别减小9%和16%;(3)2003-2016年城汉河段平滩流量有增有减,无明显单向变化趋势,2014年后呈减小趋势.分析断面的过流能力变化,发现螺山站与汉口站警戒流量与动床阻力呈明显的反比关系,过流能力由于河道阻力的增大而减小;床沙粗化、河道相对水深的减小及洲滩植被覆盖度的增大是引起河道阻力增大、过流能力减小的原因. 相似文献
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针对现有的河道水流洪水演算模型只能模拟单一变量(流量或水位)的问题,以水流连续方程和河段蓄水量的两种不同表达形式(蓄水量等于平均过水断面面积与河段长乘积,蓄水量等于河段平均流量与传播时间的乘积)为基础,对马斯京根模型进行了通用性改进,提出了双变量耦合通用演算模型.选取了四大水系(包括内陆河流和入海河流)的16个河段汛期洪水资料进行模型检验,模型验证考虑了地理范围、不同的河段特征和水力特征、洪水量级等因素,全面地检验了模型结构的合理性和模拟实际洪水的有效性.将双变量耦合通用演算模型与传统的马斯京根法进行了效果比较,结果表明双变量耦合通用演算模型的模拟精度高于马斯京根法,模拟效果比马斯京根法稳定一些,而且具有较好的通用性. 相似文献
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强烈下渗条件下天然河道洪水演进模拟方法 总被引：2，自引：0，他引：2
河道洪水演进模拟是河道洪水预报与汇流计算的主要内容和关键.对于常年断流、河水与地下水长期处于脱节状态的河道,一旦行洪下渗非常强烈,渗漏量很大.不考虑河道下渗洪水演进模拟模型,无法准确模拟真实的洪水运动行为,不能用于洪水模拟预报.本文采用土壤下渗理论描述河道下渗,推导出了河道下渗流量计算公式,建立了基于霍顿下渗公式的河道下渗模拟方法;并把下渗当做单位区间出流,与基于马斯京根康吉法天然河道洪水演进模型进行耦合,构建了强烈下渗条件下天然河道洪水演进模拟模型.针对天然河道水力特性复杂特点,研究了洪水演进模型参数确定方法和波速计算方法.海河流域漳卫河水系岳城水库-蔡小庄段的典型场次洪水应用结果表明,模型能很好反映强烈下渗条件下洪水演进实际情况,具有很高模拟精度,基于土壤下渗理论的下渗量计算公式和模拟方法可以很好地模拟河道下渗过程.这一模型具有计算简便、参数确定简单、适合于洪水预报等特点,在干旱和半干旱地区河道洪水演进模拟预报与河道汇流计算中也具有一定的推广应用价值. 相似文献
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三峡工程运行后,坝下游河道发生持续冲刷。本文研究了长江中游(955 km)不同河段沿程演变差异及其原因。总体而言,河床形态调整幅度自上而下减弱,这是因为在河床持续冲刷过程中,水流含沙量沿程恢复,故越往下游冲刷相对缓慢。平面形态方面,长江中游岸线崩退及洲滩变形的强度均呈沿程减弱趋势,且在荆江河段最为显著。断面形态方面,河床冲深幅度在宜枝下段>荆江河段>宜枝上段>城汉河段>汉湖河段。理论上距离三峡工程最近的河段冲刷应最为剧烈,但由于宜枝上段床沙粗化显著,限制了冲刷的进一步发展。过流能力方面,宜枝河段由于距洞庭湖较远,并未受到入汇顶托作用,故其平滩流量的调整基本由进口水沙条件控制,并随着河床冲深下切而增大;对于荆江、城汉和汉湖河段,河床冲刷虽显著,但支流或湖泊的入汇顶托对平滩流量产生的影响大于前者,故平滩流量总体随上下游水位差同步波动。 相似文献
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Dam-break flows usually propagate along rivers and floodplains, where the processes of fluid flow, sediment transport and bed evolution are closely linked. However, the majority of existing two-dimensional (2D) models used to simulate dam-break flows are only applicable to fixed beds. Details are given in this paper of the development of a 2D morphodynamic model for predicting dam-break flows over mobile beds. In this model, the common 2D shallow water equations are modified, so that the effects of sediment concentrations and bed evolution on the flood wave propagation can be considered. These equations are used together with the non-equilibrium transport equations for graded sediments and the equation of bed evolution. The governing equations are solved using a matrix method, thus the hydrodynamic, sediment transport and morphological processes can be jointly solved. The model employs an unstructured finite volume algorithm, with an approximate Riemann solver, based on the Roe-MUSCL scheme. A predictor–corrector scheme is used in time stepping, leading to a second-order accurate solution in both time and space. In addition, the model considers the adjustment process of bed material composition during the morphological evolution process. The model was first verified against results from existing numerical models and laboratory experiments. It was then used to simulate dam-break flows over a fixed bed and a mobile bed to examine the differences in the predicted flood wave speed and depth. The effects of bed material size distributions on the flood flow and bed evolution were also investigated. The results indicate that there is a great difference between the dam-break flow predictions made over a fixed bed and a mobile bed. At the initial stage of a dam-break flow, the rate of bed evolution could be comparable to that of water depth change. Therefore, it is often necessary to employ the turbid water governing equations using a coupled approach for simulating dam-break flows. 相似文献
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1 INTRODUCTION Evolution of the river bed in alluvial channels has been studied by many researchers using analytical and numerical approaches. The use of analytical approach alone is insufficient for solving natural river engineering problems. With rapid growth in computer technology, numerical models have become a popular means for the study of mobile bed hydraulics. During the past decade, several numerical models have been developed. Most of the computer codes, such as HEC2SR (Si… 相似文献
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More frequent extreme flood events are likely to occur in many areas in the twenty‐first century due to climate change. The impacts of these changes on sediment transport are examined at the event scale using a 1D morphodynamic model (SEDROUT4‐M) for three tributaries of the Saint‐Lawrence River (Québec, Canada) using daily discharge series generated with a hydrological model (HSAMI) from three global climate models (GCMs). For all tributaries, larger flood events occur in all future scenarios, leading to increases in bed‐material transport rates, number of transport events and number of days in the year where sediment transport occurs. The effective and half‐load discharges increase under all GCM simulations. Differences in flood timing within the tributaries, with a shift of peak annual discharge from the spring towards the winter, compared to the hydrograph of the Saint‐Lawrence River, generate higher sediment transport rates because of increased water surface slope and stream power. Previous research had shown that channel erosion is expected under all GCMs' discharge scenarios. This study shows that, despite lower bed elevations, flood risk is likely to increase as a result of higher flood magnitude, even with falling base level in the Saint‐Lawrence River. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Mathematical modelling of overland flow is a critical task in simulating transport of water, sediment and other pollutants from land surfaces to receiving waters. In this paper, an overland flow routing method is developed based on the Saint‐Venant equations using a discretized hillslope system for areas with high roughness and steep slope. Under these conditions, the momentum equation reduces to a unique relationship between the flow depth and discharge. A hillslope is treated as a system divided into several subplanes. A set of first‐order non‐linear differential equations for subsequent subplanes are solved analytically using Chezy's formula in lieu of the momentum equation. Comparison of the analytical solution of the first‐order non‐linear ordinary differential equations and a numerical solution using the Runge‐Kutta method shows a relative error of 0·3%. Using runoff data reported in the literature, comparison between the new approach and a numerical solution of the full Saint‐Venant equations showed a close agreement. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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For most of the year, a dry‐bed desert wash is void of water flow. Intensive rain events, however, could trigger significant flash floods that bring about highly complicated hydrodynamics and morphodynamics processes within a desert stream. We present a fully coupled three‐phase flow model of air, water, and sediment to simulate numerically the propagation of a flash flood in a field‐scale fluvial desert stream, the so‐called Tex Wash located in the Mojave Desert, California, United States. The turbulent flow of the flash flood is computed using the three‐dimensional unsteady Reynolds‐averaged Navier–Stokes equations closed with the shear stress transport k ? ω model. The free surface of the flash flood at the interface of air and water phases is computed with the level‐set method, which enables instantaneous tracking of the water surface as the flash flood propagates over the dry bed of the desert stream. The evolution of the desert fluvial stream's morphology, due to the action of the propagating flash flood on the mobile bed, is calculated using a Eulerian morphodynamics model based on the curvilinear immersed boundary method. The capabilities of the proposed numerical framework are demonstrated by applying it to simulate a flash flood event in a 0.65‐km ‐long reach of the Tex Wash, the intricate channel morphology of which is obtained using light imaging detection and ranging technology. The simulated region of the stream includes a number of bridge foundations. The simulation results of the model for the flash flood event revealed the formation of a highly complex flow field and scour patterns within the stream. Moreover, our simulation results showed that most scour processes take place during the steady phase of the flash flood, that is, after the flash flood fills the stream. The transient phase of the flash flood is rather short and contributes to a very limited amount of erosion within the desert stream. 相似文献
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Farhad YAZDANDOOST 《国际泥沙研究》2005,20(4):358-365
1 INTRODUCTION Rivers as a source of life can at the same time impose devastating conditions on the environment. It is , therefore, imperative to analyse and predict river behaviour for different given conditions and engineering activities. Therefore, the use of simulation tools in this field has become a necessity. Many computational tools for simulation of sediment transport in rivers are now available that can be used for prediction and design under different flow conditions. However, … 相似文献
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One-dimensional numerical simulation of non-uniform sediment transport under unsteady flows 总被引：16，自引：9，他引：7
One-dimensional numerical models are popularly used in sediment transport research because they can be easily programmed and cost less time compared with two- and three-dimensional numerical models. In particular, they possess greater capacity to be applied in large river basins with many tributaries. This paper presents a one-dimensional numerical model capable of calculating total-load sediment transport. The cross-section-averaged sediment transport capacity and recovery coefficient are addressed in the suspended load model. This one-dimensional model, therefore, can be applied to fine suspended loads and to hyperconcentrated flows in the Yellow River. Moreover, a new discretization scheme for the equation of unsteady non-uniform suspended sediment transport is proposed. The model is calibrated using data measured from the Yantan Reservoir on the Hongshui River and the Sanmenxia Reservoir on the Yellow River. A comparison of the calculated water level and river bed deformation with field measurements Shows that the improved numerical model is capable of predicting flow, sediment transport, bed changes, and bed-material sorting in various situations, with reasonable accuracy and reliability. 相似文献
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Modelling extraordinary floods and sedimentological processes in a large channel-floodplain system of the Lower Paran River(Argentina) 总被引：1，自引：0，他引：1
A quasi-2D unsteady flow and sediment transport model suitable for the simulation of large lowland river systems,including their floodplains,is presented.The water flow and sediment equations are discretised using an interconnected irregular cells scheme,in which different simplifications of the 1D de Saint Venant equations are used to define the discharge laws between cells.Spatially-distributed transport and deposition of fine sediments throughout the river-floodplain system are simulated.The model is applied over a 208-km reach of the Parana River between the cities of Diamante and Ramallo(Argentina) comprising a river-floodplain area of 8100 km~2.After calibration and validation,the model is applied to predict water and sediment dynamics during synthetically generated extraordinary floods of100,1000,and 10,000 years return period.The potential impact of a 56-km long road embankment constructed across the entire floodplain is simulated and compared to model results without the embankment.The embankment results in increases in upstream water levels,inundation extent,flow duration,and sediment deposition. 相似文献
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The paper presents a 0-D model of an alluvial watercourse schematized in two connected reaches, evolving at the long time-scale and under the hypothesis of Local Uniform Flow. Each reach is defined by its geometry (constant length and width, time-changing slope) and grain-size composition of the bed, while the sediment transport is computed using a sediment rating curve. The slope evolution is provided by a 0-D mass balance and the evolution of the bed composition is computed by a 0-D Hirano equation. A system of differential equations, solved with a predictor-corrector scheme, is derived and applied to the schematic watercourse to simulate the morphological response to changing initial conditions, and the evolution towards long-term equilibrium conditions. Differently from a single-reach 0-D schematization with uniform grain-size, besides the simplifications adopted, the model proposed here simulates the behaviour of alluvial rivers in a physically-based way, showing a grain-size fining in the downstream direction accompanied by milder slopes, and a tendency to develop concave longitudinal profiles. 相似文献