Based on the analysis of forces acting on non-cohesive sediment particle under non-equilibrium con- dition,a vectorial equation of coarse particle movement on arbitrarily riverbed and the mathematical model used to si...Based on the analysis of forces acting on non-cohesive sediment particle under non-equilibrium con- dition,a vectorial equation of coarse particle movement on arbitrarily riverbed and the mathematical model used to simulate river width adjust are developed,some flume experiments for the time evolution of straight river channel are done.展开更多
The power-function exponent b of at-a-station hydraulic geometry(AHG)depicts the temporal response of river hydraulic parameters to changing discharge and is crucial for hydraulic modeling,habitat assessment,and river...The power-function exponent b of at-a-station hydraulic geometry(AHG)depicts the temporal response of river hydraulic parameters to changing discharge and is crucial for hydraulic modeling,habitat assessment,and river management.However,previous research,limited by field measurements,offers only a fragmentary understanding of the AHG exponent b in confined areas.Additionally,it remains challenging to establish the correlation between b and the climatic regime of a river.To offer a more comprehensive scope of AHG,this study assesses the width-discharge AHG exponents of 1,568 river reaches by pairing multi-temporal river width data from 1.19 million Landsat images with discharge observations from>17,000 gauge stations worldwide.The results show that b has a median value of 0.213,consistent with values reported in previous regional studies,but it exhibits complex relationships with 3 spatial dimensions-latitude,elevation,and drainage area.We further analyze the spatial variations in b against>200 physiographic and climatic factors,and find that reaches characterized by cohesive soil,high forest coverage,and less anthropogenic influences typically exhibit lower values of b,indicating a weaker response of width to discharge changes.By labeling 4 planimetric river morphologic types globally,we show that braided reaches exhibit the highest median of b,followed by straight,anabranching,and meandering reaches.The differences can be well explained by the climatic conditions of the river reaches as shown on the Budyko curve.This study lays the foundation for AHG research in ungauged regions using satellite remote sensing,expanding global hydraulic data and enhancing the understanding of the spatial variability and influencing factors of hydraulic geometry worldwide.展开更多
Bed morphology is the result of a dynamic response to a complex meandering river system. It is an important factor for the further development of river. Based on the meandering river characterized by a large depth-to-...Bed morphology is the result of a dynamic response to a complex meandering river system. It is an important factor for the further development of river. Based on the meandering river characterized by a large depth-to-width ratio, a theoretical model is established with the coupling of Navier-Stokes （N-S）~ sediment transport, and bed deformation equations. The flow characteristics and bed response of river are obtained with the perturbation method. The research results show that, under the effect of two- dimensional flow disturbance, the bars and pools present the regular response. For a given sinuousness, the amplitude of the bed response can be used as a criterion to judge the bedform stability. The effects of the Reynolds number, disturbance wavenumber, sinuousness, and bed morphology gradient on the bed response development are described.展开更多
基金Supported by National Natural Science Fund (50279024,50479029)Open Fund of State Key Laboratory of High Speed Flow,Sichuan University (200301)
文摘Based on the analysis of forces acting on non-cohesive sediment particle under non-equilibrium con- dition,a vectorial equation of coarse particle movement on arbitrarily riverbed and the mathematical model used to simulate river width adjust are developed,some flume experiments for the time evolution of straight river channel are done.
基金supported by the National Natural Science Foundation of China(42371481)the Beijing Nova Program(20230484302)the Yunnan Provincial Science and Technology Project at Southwest United Graduate School(grant no.202302AO370012).
文摘The power-function exponent b of at-a-station hydraulic geometry(AHG)depicts the temporal response of river hydraulic parameters to changing discharge and is crucial for hydraulic modeling,habitat assessment,and river management.However,previous research,limited by field measurements,offers only a fragmentary understanding of the AHG exponent b in confined areas.Additionally,it remains challenging to establish the correlation between b and the climatic regime of a river.To offer a more comprehensive scope of AHG,this study assesses the width-discharge AHG exponents of 1,568 river reaches by pairing multi-temporal river width data from 1.19 million Landsat images with discharge observations from>17,000 gauge stations worldwide.The results show that b has a median value of 0.213,consistent with values reported in previous regional studies,but it exhibits complex relationships with 3 spatial dimensions-latitude,elevation,and drainage area.We further analyze the spatial variations in b against>200 physiographic and climatic factors,and find that reaches characterized by cohesive soil,high forest coverage,and less anthropogenic influences typically exhibit lower values of b,indicating a weaker response of width to discharge changes.By labeling 4 planimetric river morphologic types globally,we show that braided reaches exhibit the highest median of b,followed by straight,anabranching,and meandering reaches.The differences can be well explained by the climatic conditions of the river reaches as shown on the Budyko curve.This study lays the foundation for AHG research in ungauged regions using satellite remote sensing,expanding global hydraulic data and enhancing the understanding of the spatial variability and influencing factors of hydraulic geometry worldwide.
文摘Bed morphology is the result of a dynamic response to a complex meandering river system. It is an important factor for the further development of river. Based on the meandering river characterized by a large depth-to-width ratio, a theoretical model is established with the coupling of Navier-Stokes （N-S）~ sediment transport, and bed deformation equations. The flow characteristics and bed response of river are obtained with the perturbation method. The research results show that, under the effect of two- dimensional flow disturbance, the bars and pools present the regular response. For a given sinuousness, the amplitude of the bed response can be used as a criterion to judge the bedform stability. The effects of the Reynolds number, disturbance wavenumber, sinuousness, and bed morphology gradient on the bed response development are described.
