Based on measured hydrological data by using ship-mounted Acoustic Doppler Current Profiler （ADCP） instrument, we analyzed shapes of river cross sections of the middle Yangtze River basin （mainly focusing on Makou ...Based on measured hydrological data by using ship-mounted Acoustic Doppler Current Profiler （ADCP） instrument, we analyzed shapes of river cross sections of the middle Yangtze River basin （mainly focusing on Makou and Tianjiazhen river reach）. Hydrodynamic properties of river channels were also discussed. The research results indicate that nonlinear relationships can be identified between river-width/river-depth ratio （W/D ratio）, sizes of cross section and mean flow velocity. Positive relations are detected between W/D ratio and mean flow velocity when W/D〈1; and negative relations are observed when W/D〉1. Adverse relationships can be obtained between W/D ratio and cross-section area. Geomorphologic and geologic survey indicates different components of river banks in the wider and narrower river reaches respectively. These may be the main driving factors causing unique hydrological properties of river channels in the middle Yangtze River basin. Narrower river cross sections tend to raise water level in the upstream river reach near narrower river channel, giving rise to backwater effects. River knots can cause serious backwater effects, which is harmful for flood mitigation. However river knots will also stabilize river channel and this will be beneficial for river channel management. The results of this paper may be helpful for flood mitigation and river channel management in the middle Yangtze River basin.展开更多
To understand the non-equilibrium morphological adjustment of a river in response to environmental changes,it is essential to(i)accurately identify how past conditions of water and sediment have impacted current morph...To understand the non-equilibrium morphological adjustment of a river in response to environmental changes,it is essential to(i)accurately identify how past conditions of water and sediment have impacted current morphological adjustment of the river,and(ii)establish a corresponding simulation for non-equilibrium conditions.Based on discharge and suspended sediment concentration(SSC)as well as 82 cross-sectional data items for the Huayuankou-Lijin reach of the Lower Yellow River in the period 1965-2015,the process of adjustment of the geometry of the main channel(area,width,depth,and geomorphic coefficient),and its responses to changes in discharge and SSC for different reaches are statistically analyzed.Following this,a delayed response model(DRM)of the geometry of the main channel subjected to variations in discharge and SSC is established using a multi-step analytical model,with the discharge and SSC as the main controlling factors.The results show that the area,width,and depth of the main channel decreased initially,then increased,decreased again,and finally increased again.These features of the geometry of the channel were positively correlated with the 4-year moving average discharge and negatively with the 4-year moving average SSC.The geomorphic coefficient for the Huayuankou-Sunkou reach exhibited a trend of decrease,whereas that of the Sunkou-Lijin reach decreased initially,then increased,decreased again,and finally increased again.Except for the Huayuankou-Gaocun reach in 1965-1999,the coefficient was negatively correlated with the 4-year moving average discharge and positively with SSC.The simulated values of the morphological parameters of the main channel for all sub-reaches obtained using the DRM agreed well with the measured values.This indicates that the DRM can be used to simulate the process of response of the cross-sectional geometry of the main channel to variations in the water and sediment.The results of the model show that the adjustment of the geometry of the main channel was affected by the discharge and the SSC at present(30%)as well as for the previous 7 years(70%).The proposed model offers insights into the mechanism whereby past water and sediment influence the current morphological adjustment of the river,and provides an effective method for predicting the magnitude and trend of the geometry of the main channel under different flow conditions.展开更多
基金National Natural Science Foundation of China,No.40701015Key Project of National Natural Science Foundation of China,No.40730635
文摘Based on measured hydrological data by using ship-mounted Acoustic Doppler Current Profiler （ADCP） instrument, we analyzed shapes of river cross sections of the middle Yangtze River basin （mainly focusing on Makou and Tianjiazhen river reach）. Hydrodynamic properties of river channels were also discussed. The research results indicate that nonlinear relationships can be identified between river-width/river-depth ratio （W/D ratio）, sizes of cross section and mean flow velocity. Positive relations are detected between W/D ratio and mean flow velocity when W/D〈1; and negative relations are observed when W/D〉1. Adverse relationships can be obtained between W/D ratio and cross-section area. Geomorphologic and geologic survey indicates different components of river banks in the wider and narrower river reaches respectively. These may be the main driving factors causing unique hydrological properties of river channels in the middle Yangtze River basin. Narrower river cross sections tend to raise water level in the upstream river reach near narrower river channel, giving rise to backwater effects. River knots can cause serious backwater effects, which is harmful for flood mitigation. However river knots will also stabilize river channel and this will be beneficial for river channel management. The results of this paper may be helpful for flood mitigation and river channel management in the middle Yangtze River basin.
基金Key Program of National Natural Science Foundation of China,No.51639005Central Public-interest Scientific Institution Basal Research Fund of China,No.CKSF2019214/HL,No.CKSF2019411/HL。
文摘To understand the non-equilibrium morphological adjustment of a river in response to environmental changes,it is essential to(i)accurately identify how past conditions of water and sediment have impacted current morphological adjustment of the river,and(ii)establish a corresponding simulation for non-equilibrium conditions.Based on discharge and suspended sediment concentration(SSC)as well as 82 cross-sectional data items for the Huayuankou-Lijin reach of the Lower Yellow River in the period 1965-2015,the process of adjustment of the geometry of the main channel(area,width,depth,and geomorphic coefficient),and its responses to changes in discharge and SSC for different reaches are statistically analyzed.Following this,a delayed response model(DRM)of the geometry of the main channel subjected to variations in discharge and SSC is established using a multi-step analytical model,with the discharge and SSC as the main controlling factors.The results show that the area,width,and depth of the main channel decreased initially,then increased,decreased again,and finally increased again.These features of the geometry of the channel were positively correlated with the 4-year moving average discharge and negatively with the 4-year moving average SSC.The geomorphic coefficient for the Huayuankou-Sunkou reach exhibited a trend of decrease,whereas that of the Sunkou-Lijin reach decreased initially,then increased,decreased again,and finally increased again.Except for the Huayuankou-Gaocun reach in 1965-1999,the coefficient was negatively correlated with the 4-year moving average discharge and positively with SSC.The simulated values of the morphological parameters of the main channel for all sub-reaches obtained using the DRM agreed well with the measured values.This indicates that the DRM can be used to simulate the process of response of the cross-sectional geometry of the main channel to variations in the water and sediment.The results of the model show that the adjustment of the geometry of the main channel was affected by the discharge and the SSC at present(30%)as well as for the previous 7 years(70%).The proposed model offers insights into the mechanism whereby past water and sediment influence the current morphological adjustment of the river,and provides an effective method for predicting the magnitude and trend of the geometry of the main channel under different flow conditions.
