Analysis of Bed Load Equations and River Bed Level Variations Using Basin-Scale Process-Based Modelling Approach

Bed load transport is a key process in maintaining the dynamically stable channel geometry for restoring the form and function of river ecosystems. Bed load consists of relatively large sediment particles that are moved along the streambed by rolling, sliding or saltation. Currently, various empirical correlations are used to estimate bed load transport rates since no single procedure, whether theoretical or empirical, has yet to be universally accepted as completely satisfactory in this aspect. Bed load particles are primarily sourced from river bed materials or banks. The amount of bed load and its spatial distribution contributes significantly to river bed level changes. Hillslope sediment contribution, mostly available to the river in the form of suspended load, also plays an important role in river bed level changes. This study aims to analyse different bed load equations and the resultant computations of river bed level variations using a process-based sediment dynamic model. Analyses have revealed that different bed load equations were mainly deduced from the concept of relating bed shear stresses to their critical values which are highly factored by the slope gradient, water discharge and particle sizes. In this study, river bed level variations are calculated by estimating total surplus or deficit sediment loads (suspended loads and bed loads) in a channel section. This paper describes the application of different widely used bed load equations, and evaluation of their various parameters and relative performances for a case study area (Abukuma River Basin, Japan) using a basin-scale process-based modelling approach. Relative performances of river bed level simulations obtained by using different bed load equations are also presented. This paper elaborates on the modelling approaches for river bed load and bed level simulations. Although verifications were not done due to unavailability of field data for bed load, qualitative evaluations were conducted vis-à-vis field data on flow and suspended sediment loads as well as the bed loads presented in different past studies.     

Evaluation of Sediment Transport Capacity Equations Using Basin Scale Process-Based Sediment Dynamic Modelling Approach

Most process-based sediment dynamic models are based on the concept of sediment transport capacity (TC) of flow. Relationships between sediment TC and its characterized variables are found to vary widely, depending on the characteristics of a watershed and the underlying hydrological processes. This study has aimed to incorporate various widely used sediment transport capacity equations (TCEs) in a process-based sediment dynamic model, and to evaluate their relative performances in estimating suspended sediment dynamics at a river basin scale. The paper describes the modelling approaches and their application to a case study area (Abukuma River Basin, Japan), and then elaborates various parameters used in different TCEs with their useful impacts on modelling outcomes. The results of the case study have demonstrated that some of the TCEs are not suitable for simulating basin scale sediment dynamics. The TCEs that consist of more hydraulic parameters representing the flow and sediment transport processes have produced better outcomes.     

Combination of Runoff Simulation with Sediment Modeling in Rivers and Its Application in the Lower Yellow River

Abstract

Previous research on runoff show flow and sediment movement in rivers, and river bed variations are usually separated. This paper, from the point of view of the basin as a whole system, presents an integrated approach by combining runoff simulation with numerical model of sediment transport in rivers to simulate the whole processes of hydrological variables and flow-caused bed variations from the very upper part of the basin to the river mouth. To accomplish this purpose, BTOPMC, a rainfall-runoff model, and NUSTM-1D, a well-developed numerical model for sediment transport and river bed variations, are selected to form a combined model. The application of the proposed model to the lower Yellow River shows that it can properly simulate rainfall-caused runoff, the change of suspended sediment concentration along the river, and river bed variation.     

基于物理过程的分布式流域水沙预报模型

将分布式水文模型与土壤侵蚀产沙模型相互嵌套,构建了一个分布式流域水沙预报模型。模型基于DEM,将流域离散为“坡面+ 沟道”系统,采用“+ 1 ”分级方法将沟道组织为河网,实现了流域水沙预报的并行计算。坡面单元划分为植被层、地表层、非饱和带和地下水层,模拟了降雨、截留、蒸散发、入渗、地表径流、壤中流和地下水、各种形式的侵蚀产沙及泥沙输移;沟道进行汇流演算以及泥沙输移。模型在李子溪流域对长系列降雨的模拟结果表明,模型的水文模块模拟精度良好,侵蚀产沙模块模拟效果基本令人满意。     

Simulation of Runoff and Suspended Sediment Transport Rate in a Basin with Multiple Watersheds

Accurate runoff and suspended sediment transport rate models are critical for watershed management. In this study, a physiographic soil erosion–deposition (PSED) model is used in conjunction with GIS, to simulate the runoff and sediment transport process during storm events in a multi-watershed basin. This PSED model is verified using three typhoon events and 33 storm events in Cho-Shui River Basin, located in central Taiwan. Cho-Shui River Basin has 11 sub-watersheds displaying a variety of hydrologic and physiographic conditions as well as high concentrations of suspended sediment in river flow and a steep average channel bed slope of 2%. The results show the capability, applicability, and accuracy of the PSED model for multi-watershed basins.     

悬移质近底参考面平衡浓度的一个计算公式--对Lane与Kalinske模式的改进

根据推移质与床沙交换、悬移质主要与推移质交换的物理背景，采用Einstein床面泥沙的起动概念及推移运动概率函数表征床面泥沙起动及推移运动，采用Lane与Kalinske提出的泥沙因水流垂向脉动而进入悬浮运动的模式表征推移质进入悬浮运动的过程，建议一个床面层高度，建立了一个悬移质近底平衡浓度的一个计算公式。公式的参数由实测资料确定，公式经过了独立资料的检验，计算精度在可以接受的范围内。基于本文建议的床面层高度及参考面平衡浓度公式，建立了悬移质输沙率计算方法，取得了满意的输沙率计算精度。对于细颗粒泥沙的悬移质输沙率计算，本文公式克服了Einstein方法的缺陷。     

长江河口涨潮槽泥沙运动规律

30年来，在对涨潮槽性质和水沙条件有所了解的基础上，于2001年洪季和2003年枯季又一次对长江口新桥水道和南小泓两条典型涨潮槽及与其相邻的南支和南港主槽(落潮槽)的水流、泥沙和河床沉积物进行观测，并进行了专题研究。结果表明：潮流历时涨潮比落潮短；潮流和单宽潮量涨潮比落潮大，优势流小于50％，净水流向槽顶方向：涨潮含沙量、单宽输沙量大于落潮，优势沙小于50％，净输沙向槽顶方向；悬沙粒径组成较细，河床泥沙粒径组成较粗，河床存在推移质泥沙运动，并形成微地貌沙波。     

Two Dimensional Heavy Metal Transport Model for Natural Watercourses

This work presents the development and calibration of a two‐dimensional (depth‐averaged) river flow, sediment transport and heavy metal transport model in natural watercourses. Because heavy metals occur in dissolved and adsorbed phases, implementing the active‐layer concept for sediment transport computation enabled the development of a heavy metal transport model that accounts for pollutant moving in dissolved phase, adsorbed on suspended sediment, adsorbed on bed‐load, deposited in the active‐layer of the river bed or adsorbed on sediment in deeper strata. The proposed concept also enables the modelling of pollutant exchange processes using accessible sediment particle surface area for suspended and bed sediment separately. The presented heavy metal transport model is able to manage sediment mixtures found in natural watercourses using an arbitrary number of sediment size‐classes, distinguishing in this way smaller size‐classes that engage in interaction with the pollutant. Using field measurements for a reach of the Danube River, simulations were conducted for water flow, sediment transport and heavy metal transport. While some discrepancies between measured and computed values for pollutant concentrations were observed, the model reproduced the water and sediment contamination quite reasonably with acceptable mass conservation errors. The simulations also gave an insight in the general behaviour of the monitored heavy metals in the considered river reach. Therefore, it can be concluded that the developed model is suitable for simulating complex flow, sediment transport and heavy metal transport conditions in natural watercourses. Copyright © 2015 John Wiley & Sons, Ltd.     

冲积河流推移质输沙最优河道形态影响因素理论分析

为从理论上确定水沙动力、阻力和边界条件对冲积河流推移质输沙最优河道形态和最小比降的影响,基于 水力半径分割方法将河床整体糙率划分为河岸糙率和河底糙率;采用河道形态自动调整变分方法,以等腰梯形为 河道过水断面,推导推移质输沙率与河道形态的关系,分析河岸与河底相对糙率、河岸坡角、流量、输沙率、中值 粒径和河底糙率对最优河道形态和最小比降的影响。结果表明：最优河道形态和最小比降随河岸与河底相对糙 率的增大而减小,随河岸坡角的增大而增大。流量或者河底糙率的增加将使最小比降减小,同时造成最优河道形 态趋向窄深。输沙率或者中值粒径的增加将使最小比降增大,但两者对最优河道形态演变的影响不同,输沙率增 大将使最优河道形态向宽浅发展,而中值粒径增加将使最优河道形态向窄深发展。     

Suspended sediment load estimation in an ungauged river in south‐eastern Australia

Soil erosion poses a significant threat to river health as well as the sustainability of soil resources. Management of this issue requires catchment‐specific data to be developed; however, many large catchments are poor in terms of hydrological and sediment transport data. Regional scale (thousands of square kilometres), computer‐based modelling methods are a way to generate such data. This study aims to apply the SedNet model to estimate a sediment budget for a 575 km², ungauged, agricultural catchment of south‐eastern Australia. The model results are then compared with field measured erosion rates for the catchment, in order to assess the sustainability of soil loss and redistribution across the catchment. SedNet estimated average suspended sediment concentrations between 70 and 120 mg/L, under conditions deemed most representative of the river. These model estimates were comparable with monitoring data, showing suspended sediment concentrations between 30 and 350 mg/L. It was found that soil loss and redistribution across the catchment is low; however, the estimated base sediment loads indicate that river health may be negatively impacted by this. SedNet accurately represented current catchment and river conditions and provided a reliable estimation of sediment yield, demonstrating the ability to estimate sediment loss and redistribution across data‐poor catchments using a multifaceted modelling approach. Methodologies, such as the one presented here, offer the ability to better assess the impacts of erosion on sediment loads to develop strategies to effectively manage excess suspended sediment.     

An Estimation of the Suspended Sediment Load Using Adaptive Network Based Fuzzy Inference System,Support Vector Machine and Artificial Neural Network Models

Sediment transport in streams and rivers takes two forms as suspended load and bed load. Suspended load comprises sand + silt + clay-sized particles that are held in suspension due to the turbulence and will only settle when the stream velocity decreases, such as when the streambed becomes flatter, or the streamflow into a pond or lake. The sources of the suspended sediments are the sediments transported from the river basin by runoff or wind and the eroded sediments of the river bed and banks. Suspended-sediment load is a key indicator for assessing the effect of land use changes, water quality studies and engineering practices in watercourses. Measuring suspended sediment in streams is real sampling and the collection process is both complex and expensive. In recent years, artificial intelligence methods have been used as a predictor for hydrological phenomenon namely to estimate the amount of suspended sediment. In this paper the abilities of Support Vector Machine (SVM), Artificial Neural Networks (ANNs) and Adaptive Network Based Fuzzy Inference System (ANFIS) models among the artificial intelligence methods have been investigated to estimate the suspended sediment load (SSL) in Ispir Bridge gauging station on Coruh River (station number: 2316). Coruh River is located in the northern east part of Turkey and it is one of the world”s the fastest, the deepest and the largest rivers of the Coruh Basin. In this study, in order to estimate the suspended sediment load, different combinations of the streamflow and the SSL were used as the model inputs. Its results accuracy was compared with the results of conventional correlation coefficient analysis between input and output variables and the best combination was identified. Finally, in order to predict SSL, the SVM, ANFIS and various ANNs models were used. The reliability of SVM, ANFIS and ANN models were determined based on performance criteria such as Root Mean Square Error (RMSE), Mean Absolute Error (MAE), Efficiency Coefficient (EC) and Determination Coefficient (R²).     

长江流域泥沙输移与概算

泥沙概算是一种通过研究泥沙在流域不同位置和一定时期内的时空分布，从而揭示河流水沙平衡状态的方法。本文通过分析提出了长江泥沙概算方法，探讨长江流域产沙、输沙和泥沙沉积三者的关系。在此基础上，通过流域侵蚀、沉积物和悬移质泥沙粒径级配的对比分析，计算得出每年从长江上游侵蚀下来的泥沙中，粒径大于0．5mm的近12亿t泥沙几乎都沉积在长江流域上游的沟谷和支流中，粒径在0．05-0．5mm范围内的4．92亿t泥沙有3．13亿t沉积在上游沟谷和支流中，而粒径小于0．05mm的5．36亿t泥沙也有2．02亿t沉积在这些区域。当长江上游（宜昌站）和汉江总输沙量超过2．86亿t时，长江中下游将发生淤积，总输沙量超过5亿t时的淤积量超过1亿t；当宜昌输沙量超过1亿t时，洞庭湖区将发生淤积。文章还根据长江干流、部分支流和通江湖泊的水沙关系，建立水沙动态图，研究分析了长江水沙在时空上的分布特点。     

局部冲刷坑发展过程的泥沙输运特性

为揭示水流作用下沙质河床结构物周围床面冲刷过程中的泥沙输运特性,采用三维紊流、考虑推移质和悬移质运动的河床变形数值模拟,研究了清水冲刷和动床冲刷条件下,墩柱型结构物局部冲刷过程中悬移质和推移质泥沙输运贡献及其与马蹄涡流特征量、床面切应力以及泥沙悬浮指数的相关性。研究发现,清水冲刷条件下,悬移质输运占比较小,推移质泥沙输运占优;动床冲刷条件下,悬移质输运的贡献随悬浮指数的减小迅速增大;冲刷过程中悬移质和推移质输沙率与床面切应力变化趋势一致,结构物周围局部切应力的大小与马蹄涡涡量呈正相关关系。     

Digital Yellow River Model

Soil erosion is one of the key concerns in land use management for the Loess Plateau of the Yellow River, where serious soil loss is the root cause of environmental and ecological degradation of the basin. In this paper, a physically-based, distributed-parameter, and continuous erosion prediction model at the river basin scale was developed with the aim of assisting in developing better land use management strategies. The framework, the major supporting techniques, and the typical erosion processes are described. The physical processes of sediment yield and transport in the Loess Plateau are divided into three sub-processes, including the runoff and sediment yield on hillslopes, gravitational erosion in gullies, and hyperconcentrated flow routing in channels. For each sub-process, a physically-based simulation model was developed and embedded into the whole model system. The model system was applied to simulate the runoff and sediment yield in several typical years in the coarse sediment source area of the Loess Plateau, and the simulated results were in reasonably good agreement with the measured values.     

珠江磨刀门河口洪季悬沙与沉积物颗粒度分布及交换过程

基于洪季磨刀门河口实测水沙观测资料和河床表层沉积物数据,通过对不同区域不同时刻悬沙浓度和粒度、沉积物粒径组成分析,运用因子分析和粒度谱等统计计算方法,重点研究近期洪季磨刀门河口及滨海水域悬沙与河床沙交换过程及其动力机制。结果表明:磨刀门河口拦门沙内河道及汊道口区域的动力以径流为主的涨落潮流流系,悬沙与河床沙交换过程较弱;拦门沙浅滩区域泥沙运动表现为"波浪掀沙,潮流输沙"特性,再悬浮泥沙平均量占实测悬沙浓度的32%;拦门沙外滨海水域悬沙组成受径流与潮汐相对强度影响显著,构成上大潮时以再悬浮泥沙为主,小潮时则以径流下泄悬沙沉积为主,而悬沙输运方向受到东南向波浪和沿岸流控制。     

黄河水沙变化与下游河道改造

20世纪80年代中期以来,进入黄河的水沙量及其过程发生了重大变化,潼关水文站水量和输沙量大幅下降,已由1919~1959年期间的平均水量426亿m3/年、输沙量16亿t/年下降到2000~2012年的231亿m3/年和2.76亿t/年,随着黄河上中游水土保持和生态建设的持续开展,预计未来50~100年潼关站年平均水量和输沙量将逐步稳定在210亿m3/年左右和3亿t/年左右。水沙变化关系到治黄方略的制定,关系到黄河的长治久安。为了顺应黄河水沙的变化,确保黄河防洪安全,实现下游河道不改道、河床不抬高的治理目标,本文提出了新的水沙条件下黄河下游河道治理的总体思路是:改造河道、解放滩区。具体措施包括:稳定主槽、缩窄河道、完建堤防、治理悬河、滩区分类。建议深入研究下游河道改造的方案与河道缩窄的可行性及其影响,为黄河下游河道改造提供科技支撑。     

信江流域水沙变化及其对降雨侵蚀力的响应

信江流域是鄱阳湖的第三大入湖流量支流,其水沙变化直接影响鄱阳湖水文情势。本文基于信江流域7个气象站降雨资料和梅港水文站1960-2014年的径流和输沙资料,采用Mannn-Kendall非参数检验、双累积曲线等方法,研究了流域水沙变化及其对降雨侵蚀力的响应。结果表明：信江多年平均径流量为179.8×108m3,年际呈不显著的上升趋势（P>0.05）。多年平均输沙量为198.9×104t,年际呈极显著下降趋势（P<0.01）。多年平均降雨侵蚀力11 270MJ·mm/（hm2·h）,年际呈不显著的上升趋势。输沙量与降雨侵蚀力双累积关系曲线在1999年出现拐点,与基准期（1960-1998年）相比,变化期（1999-2014年）降雨侵蚀力使年均输沙量增加14.0×104t,对输沙量变化的影响程度为10.8%;人类活动导致年均输沙量减少143.5×104t,对输沙量变化的影响程度为-110.8%,二者综合作用导致输沙量减少。水库建设和大规模水土保持措施的实施是信江流域输沙量减少的主要原因,研究成果可为流域水土流失防治、水土资源利用提供参考。     

远距离输沙干渠的临界纵坡研究

挟沙水流一般要求比同等条件清水水流更大的能坡．才能保持泥抄不淤。本文在非均质输抄水流不淤流速研究基础上，提出输沙平衡条件下渠道临界最小纵坡的确定方法，论证了输沙渠道能坡的两部分组成，可澄清对挟沙水流阻力的分歧认识。经实际资料验证．文中提出的临界纵坡及输-抄渠道断面的确定方法可用于引黄远距离输沙干渠的设计．也为黄河中下游节水减淤的高含抄放淤渠道提供计算依据。文中对影响干渠纵坡的有关因素进行了分析，并附有计算例子。     

乌江流域水沙变化特性及其原因分析

乌江流域是三峡入库水沙来源之一,近年来水沙特性发生了明显变化。1980-2004年与1979年前相比,武隆站年均径流量变化不大,但悬移质输沙量减少了1 140万t,减幅35%。乌江渡电站建成后,乌江干流各站水沙关系均发生显著变化,同径流量下输沙量大幅度减小。水利工程拦沙是武隆站输沙量减少的主要因素,乌江上游东风、普定和乌江渡等电站年均拦沙量为1 500万t左右,导致武隆站输沙量减小约1 030万t。随着乌江干流大型水电站的陆续兴建,流域输沙量在未来一段时期将进一步减小。     

悬移质分选沉降及其在工程上的应用

悬移质泥沙占河流输沙的大部分，由于泥沙的重力作用及水流的紊动混掺的双重作用，悬移质沿垂线的分布呈上稀下浓，上细下粗的规律。在水流的不平衡输沙条件下，趋饱和水流中必然有一部分泥沙沉降落淤，其中较粗的泥沙必然率先沉降，较细的泥沙仍随水流悬浮前进。