Numerical modelling of riverbed grain size stratigraphic evolution  

作　　者：Peng HU Zhi-xian CAO Gareth PENDER Huai-han LIU 

机构地区：[1]Ocean College,Zhejiang University [2]State Key Laboratory of Water Resources and Hydropower Engineering Science,Wuhan University [3]Institute for Infrastructure and Environment Heriot-Watt University Institute for Infrastructure and Environment,Heriot-Watt University [4]State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University [5]Yangtze Waterway Planning,Design and Research Institute

出　　处：《International Journal of Sediment Research》2014年第3期329-343,共15页国际泥沙研究（英文版）

基　　金：funded by the Natural Science Foundation of China(Grant No.11172217 and 10932012);the Fundamental Research Funds for Central Universities(Grant No.2013QNA4041);the Natural Science Foundation of Zhejiang Province(Grant No.LQ13E090001),China

摘　　要：For several decades,quantification of riverbed grain size stratigraphic evolution has been based upon the active layer formulation（ALF）,which unfortunately involves considerable uncertainty.While it is the sediment exchange across the bed surface that directly affects the riverbed stratigraphy,it has been assumed in the ALF that the sediment fraction at the lower interface of the active layer is a linear function of the sediment fraction in the flow.Here it is proposed that the sediment fraction of the sediment exchange flux is used directly in estimating the sediment fraction at the lower surface of the active layer.Together with the size-specific mass conservation for riverbed sediment,the modified approach is referred to as the surface-based formulation（SBF）.When incorporated into a coupled non-capacity modelling framework for fluvial processes,the SBF leads to results that agree as well or better than those using ALF with laboratory and field observations.This is illustrated for typical cases featuring bed aggradation and degradation due to graded bed-load sediment transport.Systematic experiments on graded sediment transport by unsteady flows are warranted for further testing the modified formulation.For several decades,quantification of riverbed grain size stratigraphic evolution has been based upon the active layer formulation（ALF）,which unfortunately involves considerable uncertainty.While it is the sediment exchange across the bed surface that directly affects the riverbed stratigraphy,it has been assumed in the ALF that the sediment fraction at the lower interface of the active layer is a linear function of the sediment fraction in the flow.Here it is proposed that the sediment fraction of the sediment exchange flux is used directly in estimating the sediment fraction at the lower surface of the active layer.Together with the size-specific mass conservation for riverbed sediment,the modified approach is referred to as the surface-based formulation（SBF）.When incorporated into a coupled non-capacity modelling framework for fluvial processes,the SBF leads to results that agree as well or better than those using ALF with laboratory and field observations.This is illustrated for typical cases featuring bed aggradation and degradation due to graded bed-load sediment transport.Systematic experiments on graded sediment transport by unsteady flows are warranted for further testing the modified formulation.

关 键 词：Bedload Riverbed grain size stratigraphy Active layer formulation Surface-based formulation Numerical modelling 

分 类 号：TV147[水利工程—水力学及河流动力学]