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Variations in the effective and bankfull discharge for suspended sediment transport due to dam construction

Frontiers of Earth Science 2022年第2期16卷 446-464页

作者： Fan CHEN Li CHEN Wei ZHANG Jing YUAN Kanghe ZHANG State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan UniversityWuhan 430072China Changjiang Institute of Survey PlanningDesign and ResearchWuhan 430010China Bureau of Hydrology Changjiang Water Resources CommissionWuhan 430010China

A varied class method is applied to calculate the effective discharges and their variations after the Three Gorges Dam(TGD)construction based on the mean daily flow discharge and suspended sediment concentration field data from 1981 to *** comparison,the bankfull discharges are also determined according to the cross-section profiles and flow discharge-stage *** results show that a bimodal effective discharge curve usually exists at the fixed sites,which generates two effective discharges(Q_(e1) and Q_(e2))within the moderate flow *** the quasi-equilibrium circumstances of the pre-dam period,effective discharges are closely related to the mean annual runoff,with a narrow range of regional variations in occurrence *** analyses draw the conclusion that the relatively higher unsaturation degrees of the pre-dam effective discharges caused by dam interception and riverbed coarsening are the primary cause of the increase in effective discharges from Yichang to Shashi,while the more frequent low and medium discharges due to flow regulation drive the decrease in effective discharges from Jianli to *** slightly elevated flood levels and descending bankfull levels collaboratively result in the decrease of bankfull discharges from Yichang to Shashi,while the lowered bed elevation causes the increase in bankfull discharges from Luoshan to ***,the bankfull discharge in the Middle and Lower Yangtze River is larger than effective discharge and approaches the 1.5-year recurrence interval discharge.

关键词： effective discharge bankfull discharge unsaturation degree flow-sediment regimes Middle and Lower Yangtze River Three Gorges Dam

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Multiple temporal scale relationships of bankfull discharge with streamflow and sediment transport in the Yellow River in China

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International Journal of Sediment Research 2013年第4期28卷 496-510页

作者： Yan-yan ZHANG De-yu ZHONG Bao-sheng WU State Key Laboratory of Hydroscience and Engineering Tsinghua University Pearl River Hydraulic Research Institute Pearl River Water Resources Commission

This paper presents a study on the characteristics of multiple time scales of bankfull discharge and its delayed response to changes of tlow conditions using continuous wavelet analysis for data from selected hydrologieal stations in the Yellow River *** showed that bankfull discharge series had one or two dominant lime *** example,the Huayuankou station in the lower reach of the Yellow River had two dominant time scales of 19 20 years and 5 6 *** dominant time seales of the bankfull discharge series were generally consistent with the dominant time scales of water discharge and sediment concentration series,indicating thai the channel morphology inherits the characteristics of the hydrologieal system in terms of multiple time *** addition,the wavelet coefficients of the bankfull discharge series had a phase difference in relation to those of the sediment concentration series,with a delay time that varied from 3 to 16 years at different *** delay time or relaxation lime is a result of the delayed response of bankfull discharge to How conditions,which was significant for channel adjustments in response lo changes of tlow *** findings of the multiple lime scales and the delayed response are of importance for further study of channel morphology of fluvial systems.

关键词： Multiple time scales wavelet analysis bankfull discharge river morphology fluvial processes Yellow River

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Delayed response model for bankfull discharge predictions in the Yellow River

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International Journal of Sediment Research 2011年第4期26卷 445-459页

作者： Baosheng WU and Lingyun LI 1 Prof.,State Key Laboratory of Hydroscience and Engineering,Tsinghua University,Beijing 100084,China, 2 Ph.D.and Research Hydraulic Engineer,Changjing River Scientific Research Institute,Wuhan 430010,China Prof. State Key Laboratory of Hydroscience and Engineering Tsinghua University Beijing 100084 China Ph.D. and Research Hydraulic Engineer Changjing River Scientific Research Institute Wuhan 430010 China

Delayed response means that channels cannot achieve a new equilibrium state immediately following disruption;the channel requires a response time or relaxation time to reach *** follows that the morphological state of fluvial system represents the cumulative effects of all previous disturbances and environmental conditions.A unique feature of the delayed response model for bankfull discharge is that the model is capable of representing the cumulative effects of all previous flow conditions when applied to predict the path/trajectories of bankfull discharge in response to altered flow *** this paper,the delayed response model was modified by readjusting the weight for the initial boundary conditions and introducing a variableβwith respect to *** modified model was then applied to the bankfull discharge calculations for three selected river reaches of the Yellow River,with each reach having different geomorphic settings and constraints. Results indicated that the modified model can predict accurately the bankfull discharge variation in response to changes in flow discharge and sediment load conditions that have been dramatically altered in the *** also demonstrated the strong dependence of current bankfull discharge on the previous years’ flow conditions,with the relaxation time varied from 2 to 14 years,meaning that the bankfull discharge was not only affected by the flow discharge and sediment load in the current year,but also by those in previous 1 to 13 ***,the relaxation time of bankfull discharge adjustment was inversely proportional to the long-term average suspended sediment concentrations,and this may be explained by fact that high sediment concentrations may have a high potential to perform geomorphic work and there is more sediment readily available to shape the channel boundary and geometry.

关键词： Yellow River bankfull discharge Delayed response Flow discharge Sediment load Relaxation time

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

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Chinese Geographical Science 2020年第5期30卷 900-920页

作者： MALIK Sadhan PAL Subodh Chandra Department of Geography University of BurdwanBurdwan 713104West BengalIndia

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.

关键词： bankfull channel width bankfull discharge Dwarkeswar River flat alluvial plain channel degradation overbank flow and flood

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Equilibrium relations for water and sediment transport in the Yellow River

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International Journal of Sediment Research 2021年第2期36卷 328-334页

作者： Xujian Chen Yuqi An Zhihao Zhang Chunhong Hu China Institute of Water Resources and Hydropower Research (IWHR) State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin (SKL-WAC) Institute of Disaster Prevention

The equilibrium relations for water and sediment transport refer to the relative balance of sediment transport and the relative stability of river courses formed by the automatic adjustment of riverbeds. This is the theoretical basis for the comprehensive management of sediment in the Yellow River. Based on the theories of sediment carrying capacity and the delayed response of riverbed evolution, in this study, the equilibrium relations for water and sediment transport in the Yellow River are established. These relations include the equilibrium relationships between water and sediment transport and bankfull discharge in the upper and lower Yellow River and between water and sediment transport and the Tongguan elevation in the middle Yellow River. The results reveal that for the Ningmeng reach, the Tongguan reach, and the lower Yellow River, erosion and deposition in the riverbeds are adjusted automatically, and water and sediment transport can form highly constrained equilibrium *** newly established equilibrium relationships can be applied to calculate the optimal spatial allocation scheme for sediment in the Yellow River.

关键词： Yellow River Water and sediment transport Riverbed evolution bankfull discharge Equilibrium relationship

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Shaping and maintaining a medium-sized main channel in the Lower Yellow River

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International Journal of Sediment Research 2012年第3期27卷 259-270页

作者： Chun-hong HU Jian-guo CHEN Qing-chao GUO State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin(SKL-WAC) China Institute of Water Resources and Hydropower Research(IWHR) International Research and Training Center on Erosion and Sedimentation(IRTCES) IRTCES SKL-WAC IWHR

This paper studies relations between bankfull discharge,lateral cross section variation and the incoming flow and sediment condition in the Lower Yellow River using measured data from 1950 to *** 1950 the bankfull discharge has obviously decreased and the ratio of channel width to flow depth has *** critical annual average incoming sediment coefficient（defined as the ratio of sediment concentration to discharge） and discharge at the Huayuankou station are approximately 0.012 and 1,850 m;s;,respectively,for no accumulative deposition occurring in the reach from Huayuankou to *** this basis,a mathematical model is used to study the scale of the main channel in the Lower Yellow River and its corresponding bankfull discharge under possible incoming flow and sediment conditions in the near *** main factors influencing the scale of the main channel are analyzed,and measures to shape and maintain a medium-sized channel are *** results show the effect of various water and sediment combinations released from the Xiaolangdi Reservoir on the shaping of the main channel and suggest that under recent incoming flow and sediment conditions,it is possible to shape and maintain a medium-sized channel with a bankfull discharge of approximate 4,000 m;s;.

关键词： The Lower Yellow River Xiaolangdi Reservoir bankfull discharge Medium size channel Flow and sediment condition

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EFFECTIVE discharge CALCULATION GUIDE

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International Journal of Sediment Research 2001年第4期16卷 445-459页

作者： D. S. BIEDENHARN,C. R. THORNE, P.J.SOAR. ,R.D.HEY, and C. C. WATSONS 1 Engineer, U.S. Army Corps of Engineers, Waterways Experiment Station, Vicksburg, MS 39180, USA. 2Professor School of Geography, University of Nottingham, Nottingham NG7 2RD, UK. 3 Prof Engineer U.S. Army Corps of Engineers Waterways Experiment Station Vicksburg MS 39180 USA. Professor School of Geography University of Nottingham Nottingham NG7 2RD UK. Research Assistant School of Geography University of Nottingham Nottingham NG7 2RD UK. Reader School of Environmental Sciences University of East Anglia Norwich NR4 7T J UK. Professor Department Civil Engineering Colorado State University Fort Collins CO 80523 USA.

This paper presents a procedure for calculating the effective discharge for rivers with alluvial channels. An alluvial river adjusts the bankfull shape and dimensions of its channel to the wide range of flows that mobilize the boundary sediments. It has been shown that time-averaged river morphology is adjusted to the flow that, over a prolonged period, transports most sediment. This is termed the effective discharge. The effective discharge mayo be calculated provided that the necessary data are available or can be synthesized. The procedure for effective discharge calculation presented here is designed to have general applicability, have the capability to be applied consistently, and represent the effects of physical processes responsible for determining the channel. dimensions. An example of the calculations necessary and applications of the effective discharge concept are presented.

关键词： bankfull discharge Effective discharge Hydraulic geometry Regime theory River engineering River management

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