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Shrinking of Dongting Lake and its weakening connection with the Yangtze river:Analysis of the impact on flooding

International Journal of Sediment Research 2015年第3期30卷 256-262页

作者： Chunhong Hu Chunming Fang Wenhong Cao State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin

In this article,the shrinking of Dongting Lake and its progressively weakening connection with the Yangtze river and their impact on flooding before and after the implementation of the Three Gorges Project are analyzed.In recent decades,human activity combined with natural processes has altered the flow of the middle reach channel of the Yangtze river and interfered with its connection with Dongting Lake.This has resulted in progressively more frequent flooding in the area.This study uses hydrological data to analyze the annual maximum discharge and annual maximum stage development of the middle reach of the Yangtze river and Dongting Lake.In recent decades before the Three Gorges Project became operational in 2003,the annual maximum discharge and the maximum stage recorded in the middle reach of the river downstream of Dongting Lake had increased,a result of the weakening of the flood regulation function of Dongting Lake;the annual maximum stage at Luoshan station(downstream,close to the confluence of the Yangtze river and Dongting Lake) had risen by about 2.0 m during 1955-2005,(1.5 m attributed to annual maximum discharge and 0.5 m to river channel deposition).Observational data recorded after the Three Gorges Project was put into operation in 2003,it can be seen that deposition in the Dongting Lake has nearly ceased and the lake’s connection with the Yangtze river is stable.It is evident that the flood regulation function of Dongting Lake will continue,and that during the lifetime of the Three Gorges Project,the flood situation in the middle reach of the Yangtze river and Dongting Lake will remain stable.

关键词： Dongting Lake Yangtze river The Three Gorges Project Flood situation

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Erosion-control mechanism of sediment check dams on the Loess Plateau

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International Journal of Sediment Research 2021年第5期36卷 668-677页

作者： Zhaoyin Wang Zuyu Chena Shu Yu Qiang Zhang Yu Wang Jianwei Hao State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower Research

Severe soil erosion occurs on the Loess Plateau in China, which makes the Yellow river the most sediment-laden river in the world. Construction of about 60,000 sediment check dams has remarkably controlled soil erosion on the Loess Plateau and reduced the sediment load of the middle and lower Yellow river. Nonetheless, little is known about the mechanism of erosion control and vegetation development of sediment check dams. The function of a single check dam mainly is trapping sediment,while the function of a train of check dams comprising dozens of or over hundreds of check dams in a gully encompasses controlling bed incision and reducing erosion energy. A formula was proposed to calculate the potential energy of bank failure and slope failure in a gully, which essentially constitutes the erosion energy. The erosion energy increases when gully incision occurs, which is induced by the incision of the Yellow river and its tributaries on the Loess Plateau. Sediment deposition in many gullies due to construction of check dams reduces the erosion energy to almost zero, which in turn greatly reduces soil erosion and sediment yield. Construction of check dams promotes vegetation development. The vegetation-erosion dynamics model was used to study the effect of check dams on vegetation development. simulation results show that reforestation without check dam construction might result in an increase of vegetation cover in the first ten years and then a drop of vegetation cover to less than 10% in the later years. The check dams provide a foundation for vegetation development.

关键词： Loess plateau Check dam Energy of soil erosion Vegetation-erosion dynamics Gully incision

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Predicting Net Cross-Shore Total Load Transport: A Phase-Averaging, Quasi-Steady Approach Incorporating Undertow Contribution

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China Ocean Engineering 2016年第5期30卷 703-717页

作者：王玉海 State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower Research

Wave shapes that induce velocity skewness and acceleration asymmetry are usually responsible for onshore sediment transport, whereas undertow and bottom slope effect normally contribute to offshore sediment transport. By incorporating these counteracting driving forces in a phase-averaged manner, the theoretically-based quasi-steady formula of Wang （2007） is modified to predict the magnitude and direction of net cross-shore total load transport under the coaction of wave and current. The predictions show an excellent agreement with the measurement data on medium and fine sand collected by Dohmen-Janssen and Hanes （2002） and Schretlen （2012） in a full-scale wave flume at the Coastal Research Centre in Hannover, Germany. The modified formula can predict the net onshore transport of fine sand in sheet flows. In particular, it can predict the net offshore transport of medium sand in rippled beds through enlarged bed roughness, as well as the net offshore transport of fine-to-coarse sand in sheet flows with the aid of a new criterion to judge the occurrence of net offshore transport.

关键词： cross-shore net total load transport phase-lag phase-averaged undertow

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Exploring impact of street layout on urban flood risk of people and vehicles under extreme rainfall based on numerical experiments

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中国科学:技术科学英文版 2023年第9期66卷 2561-2574页

作者： MEI Chao LIU JiaHong SHI HongYuan WANG Hao WANG Jia DONG LiRong SONG TianXu ZHANG HaiJia State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower ResearchBeijing 100038China key laboratory of river basin Digital Twinning of Ministry of water Resources(Preparation) Beijing 100038China Beijing key laboratory of Urban water cycle and Sponge City Technology Beijing Normal UniversityBeijing 100875China

Urban street layout is an important factor in the formation process, characteristics, and risk level of urban flooding;therefore, this study numerically investigates the impact of street layout on urban flood risk to people and vehicles. Four typical street-layout scenarios with areas of 3 km × 3 km are established based on a block-scale investigation. The layout types are regular grid,irregular grid, radial, and annular. Urban inundation models are then constructed for these typical street layouts based on the twodimensional(2D) hydrodynamic method. Two historic, extreme rainfall events, which occurred in Beijing on July 21, 2012 and in Zhengzhou on July 20, 2021, are used as rainstorm scenarios for urban inundation modelling. The flood risks to people and vehicles are then calculated. Results show that, for an extreme rainstorm on the block scale, the street layout impacts the spatial and temporal distributions of the inundation variables, which include the water depth, flow velocity, flood volume, and inundated area. Moreover, for the same extreme-rainfall scenario, the greatest differences in the total flood volume, maximum street-water depth, and maximum street-flow velocity caused by street-layout differences are 17.22%, 60.25%, and 61.50%, respectively.Among the four street layouts considered in this study, the annular street layout exhibits the lowest degrees of inundation and flood risk. For the same extreme-rainfall scenario, the proportions of high-risk road sections for adults and children in this layout are 58.89% and 62.28% smaller than those for the layout with the largest proportion of high-risk road sections, respectively;the proportions of high-risk road sections for the Honda Accord and Audi Q7 were 55.31% and 53.04% smaller, respectively. The findings of this study may aid scientific understanding and development of “flood-sensitive” block-scale street layouts and urban planning in the context of the changing environment.

关键词： urban inundation street layout urban form flood risk hydrodynamic simulation

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Influences of retrogressive erosion of reservoir on sedimentation of its downstream river channel——A case study on Sanmenxia Reservoir and the Lower Yellow river

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International Journal of Sediment Research 2017年第3期32卷 373-383页

作者： Jianguo Chen Wenhao Zhou Shanshan Han Gaohu Sun State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin Institute of water Resources and Hydropower Research

Retrogressive erosion, a widespread phenomenon of sediment transport in reservoirs, often impacts on both the reservoir capacity and the sedimentation in the downstream river channel. Based on field data from the Sanmenxia Reservoir and the Lower Yellow river over the past decades, three courses of retrogressive erosion with distinctive features were analyzed. The results indicate that retrogressive erosion,especially caused by rapid reduction in the water level till the reservoir is empty, often results in the serious siltation of the lower Yellow river and threatens the safety of the flood control in the Lower Yellow river. Unreasonable operation of the reservoir and incoming hyperconcentrated floods accompanied by retrogressive erosion also aggravate the siltation of the main channel of the river. However, a reasonable operation mode of the reservoir so named "storing the clear(low sediment concentration)water in the non-flood season, and sluicing the muddy(high sediment concentration) water in the flood season" was found, which might mitigate the deposition in both the reservoir and the Lower Yellow river. This operation mode provides important experience for the design and operation of large reservoirs in other large rivers carrying huge amounts of sediment.

关键词： Retrogressive erosion river sedimentation Reservoir operations

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Safe operation of inverted siphon during ice period

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Journal of Hydrodynamics 2015年第2期27卷 204-209页

作者：付辉杨开林郭新蕾郭永鑫王涛 State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower Research

Sixteen inverted siphons are in operation at the Beijing-Shijiazhuang section in the Middle Route of the South-to-North water Diversion Project. Their safe operation is closely related to the safety and the water diversion efficiency of the whole project during an ice period. The ice accumulation process at the inlet of the inverted siphon is modeled under a real ice condition, and then the hydraulic conditions of the ice jam prevention are confirmed. According to the experimental results and the design sizes of the inverted siphons, the detailed safe water diversion discharge and the operational water level are studied. Analysis results of these inverted siphons provide references for the safe operation and the reasonable regulations during the ice period.

关键词： inverted siphon,ice period,safe operation,real ice experiment,water diversion project

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On the Increased Precipitation Recycling by Large-Scale Irrigation over the Haihe Plain

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Journal of Meteorological Research 2022年第3期36卷 450-461页

作者： Yunpeng GUI Qingming WANG Yong ZHAO Mengyang MA Haihong LI Jiaqi ZHAI Enchong LI Department of Hydraulic Engineering Tsinghua UniversityBeijing 100084 State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin Institute of Water Resources and Hydropower ResearchBeijing 100038

Irrigation not only plays an important role in global food security,but it also affects aspects of the regional climate,including precipitation.In this study,we proposed a simple and convenient method to quantify the contribution of large-scale irrigation to precipitation by distinguishing the amount of evaporation generated by irrigation from local evaporation based on the precipitation recycling method.A case study was presented to show the increased precipitation recycling ratio and the contribution of irrigation to precipitation during the main irrigation period in the Haihe Plain from 1961 to 2016.We found that the average precipitation recycling rates in the Haihe Plain are 8.32%,9.74%,and 10.36%in April,May,and June,respectively.The contribution rates of irrigation to precipitation in the Haihe Plain are 3.76%,5.12%,and 2.29%in April,May,and June,respectively.The total contribution of irrigation to precipitation during the main irrigation period is 3.77 mm;the respective contributions in April,May,and June are 0.72,1.70,and 1.35 mm.The contribution of irrigation to local precipitation is relatively small as the inflow of atmospheric moisture during the irrigation period is still the main factor affecting local precipitation.Nevertheless,this part of the precipitation during the irrigation period alleviates the water shortage in the Haihe Plain to some extent.

关键词： irrigation precipitation recycling contribution of irrigation to precipitation Haihe Plain

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Time-averaged sub-layer concentration profiles in oscillatory sheet flows

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International Journal of Sediment Research 2018年第4期33卷 433-440页

作者： Yuhai Wang Wenhong Cao Wen Lu Huifeng Liu Gauhu Sun Chonghao Wang Fei Liu State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower Research

Although thin on the order of several to tens of millimeters, sheet flows normally comprise a lower pickup sub-layer and an upper contact-load sub-layer, separated at the bed level(z = 0). The time-averaged concentration profile in the pick-up sub-layer shows a ’convex upward’ curvature, but ’concave upward’shape characterizes the time-averaged concentration profile in the contact-load sub-layer. The timedependent concentration in the contact-load sub-layer is approximately in-phase with the free stream flow velocity, whereas it is nearly in anti-phase with the free stream flow velocity, in the pick-up sublayer. Two distinct analytical expressions of the time-averaged concentration profiles for the respective sub-layers are proposed. The expressions are validated with detailed observation datasets collected in the Groper Wellenkanal(GWK) prototype wave flume in Hannover, Germany. The agreement between the predicted and the measured values is excellent. Interparticle collisions in the pick-up sub-layer and convective lifting processes associated with vortex shedding in the contact-load sub-layer are considered responsible for the opposite curvatures and in-phase/anti-phase concentration variations. Both transitional boundary and reference concentration are also elaborated.

关键词： Sheet flow Sub-layer Time-averaged concentration profile Suspension mechanism

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Non-equilibrium concentration profile formulas of suspended sediment and their preliminary applications

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International Journal of Sediment Research 2022年第4期37卷 505-513页

作者： Zipu Ma Qingchao Guo Jianzhao Guan Maohua Le State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of water Resources and Hydropower Research Yellow river Institute of Hydraulic Research Yellow River Conservancy Commission of the Ministry of Water Resources

The vertical concentration profiles in non-equilibrium sediment transport processes generally deviate from the equilibrium concentration distribution of suspended sediment. The non-equilibrium concentration profile formulas currently available are those of Han and Brown, respectively. However, the complexity of these formulas limits their use in practical calculations. To improve the usefulness of these formulas, the unknown parameters in Han’s formula are reduced from three to two, and the three different forms of Brown’s formula are transformed into one. These formulas then are proved to be essentially the same to some extent, and only different in the expression form of the exponent. Han’s formula then is improved, based on which the theoretical calculation methods and distribution characteristics of non-equilibrium profiles are presented. Han’s and Brown’s formulas are verified qualitatively and quantitatively. Finally, these formulas are applied in the investigation of the characteristics of certain physical quantities, such as the recovery factor of sediment concentration, near-bottom sediment flux, and the non-equilibrium P eclet number in the non-equilibrium sediment transport process. These results clearly reveal that the magnitude of these physical quantities decreases in the erosion process and increases in the deposition process. The results also show that the formulas are largely applicable for the non-equilibrium sediment transport conditions.

关键词： Suspended sediment Vertical concentration profiles Non-equilibrium sediment conditions Non-saturation parameter Péclet number

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Effect of sediment particles on the velocity profile of sediment-water mixtures in open-channel flow

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International Journal of Sediment Research 2023年第3期38卷 361-373页

作者： Lei Zhang Jianzhao Guan Deyu Zhong Yousheng Wang State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin China Institute of Water Resources and Hydropower Research Joint Sponsored state key laboratory of Plateau Ecology and Agriculture Qinghai University state key laboratory of Hydroscience and Engineering Tsinghua University

The presence of sediment particles in open-channel flow has an important effect on turbulence; thus, an empirical, turbulent eddy viscosity formula was established for application in the limit for low concentrations. The current study establishes a theoretical relation for the mixture viscosity based on the two-phase mixture model. The percentage contribution of the three mechanisms of mixture viscosity,namely, fluid turbulence(FT), particle turbulence(PT), and inter-particle collisions(IPCs), was calculated under different conditions. The study results indicate that the contribution of FT is dominant, whereas those of PT and IPCs are not significant when the particle inertia(PI) is small, suggesting that the movement of sediment-laden flows is mainly controlled by the fluid properties. The effects of PT and IPCs increase with increases in sediment concentration and PI. Specifically, the effect of collisions among particles generally becomes dominant near the bed surface. A good agreement between the calculated velocity profile of the mixture and available experimental data for large particle sizes and high concentrations proves that the proposed relation for mixture viscosity is more reasonable than the previous empirical relation owing to the consideration of the effects of PT and IPCs, and, thus, can be applied to both dilute and dense suspensions.

关键词： Velocity profile Sediment particles Viscosity Collisions Turbulence

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