A study on limit velocity and its mechanism and implications for alluvial rivers

查看全文 作　　者：Yanhong [1]Jia;Zhaoyin [2]Wang;Xiangmin [1]Zheng;Yanfu [3]Li

机构地区：[1]East China Normal University,Shanghai 200241,China;[2]State Key Laboratory of Hydroscience and Engineering of Tsinghua University,Beijing 100084,China;[3]Nanjing Hydraulic Research Institute,Nanjing 210029,China

出　　处：《International Journal of Sediment Research》索引2016年第31卷第3期,共7页

基　　金：supported by National Natural Science Foundation of China(Nos.51309102,51179089,44108140,51309154) 摘　　要：Observations from field investigations showed that flow velocity greater than 3 m/s rarely occurs in nature,and high flow velocity stresses the bio-community and causes instability to the channel.For alluvial rivers without strong human disturbance,the flow velocity varies within a limited range,generally below 3 m/s,while the discharge and wet area may vary in a range of several orders.This phenomenon was studied by analyzing hydrological data,including daily average discharge,stage,cross sections,and sediment concentration,collected from 25 stations on 20 rivers in China,including the Yangtze,Yellow,Songhua,Yalu,Daling,and Liaohe Rivers.The cross-sectional average velocity was calculated from the discharge and wet area using the continuity equation.For alluvial rivers,the wet cross section may self-adjust in accordance with the varying flow discharge so that the flow velocity does not exceed a limit value.In general,the average velocity increases with the discharge increase at low discharge.As the discharge exceeds the discharge capacity of the banks,any further increase in discharge does not result in a great increase in velocity.The average velocity approaches an upper limit as the discharge increases.This limit velocity,in most cases,is less than 3 m/s.Human activities,especially levee construction,disturb the limit velocity law for alluvial rivers.In these cases,the average velocity may be approximately equal to or higher than the limit velocity.The limit velocity law has profound morphological and ecological implications on alluvial rivers and requires further study.Rivers should be trained and managed by mimicking natural processes and meeting the limit velocity law,so as to maintain ecologically-sound and morphological stability. 关键词：极限速度冲积河流平均速度机理人为干扰生态意义自然过程连续性方程

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A study on limit velocity and its mechanism and implications for alluvial rivers

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