Suspended sediment concentrations in the Middle Yangtze River(MYR)reduced greatly after the Three Gorges Project operation,causing the composition of bed material to coarsen continuously.However,little is known about ...Suspended sediment concentrations in the Middle Yangtze River(MYR)reduced greatly after the Three Gorges Project operation,causing the composition of bed material to coarsen continuously.However,little is known about the non-equilibrium transport of graded suspended sediment owing to different bed material compositions(BMCs)along the MYR,and it is necessary to determine the magnitude of recovery factor.Using the Markov stochastic process in conjunction with the hiding-exposure effect of non-uniform bed-material,a new formula is proposed for calculating the recovery factor including the effect of different BMCs,and it is incorporated into the non-equilibrium transport equation to simulate the recovery processes of suspended load in both sand-gravel bed and sand bed reaches of the MYR.The results show that:(i)the recovery rate of graded sediment concentrations at Zhicheng was slower than that at Shashi during the period 2003-2007;(ii)the mean recovery factors of the coarse,medium,and fine sediment fractions in the ZhichengShashi reach were 0.152,0.0012,and 0.0005,respectively,and the coarse sediment recovered up to the maximum sediment concentration of 0.138 kg/m3over a distance of 15 km;and(iii)the results of the new formula that can consider the effect of bed material composition are in general agreement with the field observations,and the spatial and temporal delay effects are inversely related to particle size and BMC.Consequently,the BMC effect on the nonequilibrium sediment transport in different reaches of the MYR needs to be considered for higher simulation accuracy.展开更多
Bed Load Motion and its transport rate is one of the basic issues in river dynamics.In this paper, the authors discussed the stochastic nature of bed load motion in Chuanjiang River in details.Chungjiang lies in the u...Bed Load Motion and its transport rate is one of the basic issues in river dynamics.In this paper, the authors discussed the stochastic nature of bed load motion in Chuanjiang River in details.Chungjiang lies in the upstream reach of Yangtze River.Its stochastic nature is shown in the following four aspects.Firstly, even though all the conditions are the same,due to the fluctuation of the flow,the bed load discharge and the location and width of sediment transport belts are different.Secondly,during the ...展开更多
Given the challenges of re-creating complex bed load(BL)transport processes in rivers,models are preferred over gathering and examining field data.The highlight of the present research is to develop an approach to det...Given the challenges of re-creating complex bed load(BL)transport processes in rivers,models are preferred over gathering and examining field data.The highlight of the present research is to develop an approach to determine the ungauged bed load concentration(BLC_(u))utilizing the measured suspended sediment concentration(SSC)and hydraulic variables of the last four decades for the Mahanadi River Basin.This technique employs shear stress and SSC equations for turbulent open channel flow.Besides,the predicted BLC_(u)is correlated with SSC using a power relation to estimate BLC_(u)on the river and tributaries.Eventually,different BL functions(BLF)efficiency is assessed across stations.The model predicted BLC_(u)is comparable with the published data for sandy rivers and falls within±20%.Outliers in hydraulic and sedimentological statistics significantly influence estimating the BL fraction apart from higher relative ratios and catchment geology.The constants of power functions are physically linked to sediment transport configuration,mechanism,and inflow to the stream.The stream power-based BLF best predicts the BL transport,followed by shear stress and unit discharge approaches.The disparity in the estimation of BLC_(u)results from station-specific physical factors,sampling data dispersion,and associated uncertainties.展开更多
基金the National Natural Science Foundation of China(Grant Nos.51725902,52009095,U2040215,U2240206,and 52109098)supported partly by the Postdoctoral Research Foundation of China(Grant No.BX2021228)Natural Science Foundation of Hubei Province(Grant No.2021CFA029)。
文摘Suspended sediment concentrations in the Middle Yangtze River(MYR)reduced greatly after the Three Gorges Project operation,causing the composition of bed material to coarsen continuously.However,little is known about the non-equilibrium transport of graded suspended sediment owing to different bed material compositions(BMCs)along the MYR,and it is necessary to determine the magnitude of recovery factor.Using the Markov stochastic process in conjunction with the hiding-exposure effect of non-uniform bed-material,a new formula is proposed for calculating the recovery factor including the effect of different BMCs,and it is incorporated into the non-equilibrium transport equation to simulate the recovery processes of suspended load in both sand-gravel bed and sand bed reaches of the MYR.The results show that:(i)the recovery rate of graded sediment concentrations at Zhicheng was slower than that at Shashi during the period 2003-2007;(ii)the mean recovery factors of the coarse,medium,and fine sediment fractions in the ZhichengShashi reach were 0.152,0.0012,and 0.0005,respectively,and the coarse sediment recovered up to the maximum sediment concentration of 0.138 kg/m3over a distance of 15 km;and(iii)the results of the new formula that can consider the effect of bed material composition are in general agreement with the field observations,and the spatial and temporal delay effects are inversely related to particle size and BMC.Consequently,the BMC effect on the nonequilibrium sediment transport in different reaches of the MYR needs to be considered for higher simulation accuracy.
基金Supported by National Key Basic Besearch and Development Program of (~na (ff73 Program) (2003CB415202)Key Project of Chinese Ministry of China(03134)
文摘Bed Load Motion and its transport rate is one of the basic issues in river dynamics.In this paper, the authors discussed the stochastic nature of bed load motion in Chuanjiang River in details.Chungjiang lies in the upstream reach of Yangtze River.Its stochastic nature is shown in the following four aspects.Firstly, even though all the conditions are the same,due to the fluctuation of the flow,the bed load discharge and the location and width of sediment transport belts are different.Secondly,during the ...
基金Ministry of Water Resources,Government of India,No.28/1/2016-R&D/228–245。
文摘Given the challenges of re-creating complex bed load(BL)transport processes in rivers,models are preferred over gathering and examining field data.The highlight of the present research is to develop an approach to determine the ungauged bed load concentration(BLC_(u))utilizing the measured suspended sediment concentration(SSC)and hydraulic variables of the last four decades for the Mahanadi River Basin.This technique employs shear stress and SSC equations for turbulent open channel flow.Besides,the predicted BLC_(u)is correlated with SSC using a power relation to estimate BLC_(u)on the river and tributaries.Eventually,different BL functions(BLF)efficiency is assessed across stations.The model predicted BLC_(u)is comparable with the published data for sandy rivers and falls within±20%.Outliers in hydraulic and sedimentological statistics significantly influence estimating the BL fraction apart from higher relative ratios and catchment geology.The constants of power functions are physically linked to sediment transport configuration,mechanism,and inflow to the stream.The stream power-based BLF best predicts the BL transport,followed by shear stress and unit discharge approaches.The disparity in the estimation of BLC_(u)results from station-specific physical factors,sampling data dispersion,and associated uncertainties.
