Author(s): D. Alan Ervine; Hasan K. Jasem

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Abstract: Recent media reports on river flooding in Bangladesh and Sudan have concentratedon the complex causal nature of such floods including deforestation,sediment movement,urbanisation and changes in weather patterns. Even at the level of flood analysis,including stage-discharge estimation and velocity and shear stress distribution,hydraulicianshave been unable to provide convincing analyses for the case of river flooding when floodplains are inundated.The main reason for this is the breakdown of conventionalformulae,such as Manning's equation,whenever a river bank is over-topped andfloodplain flow occurs. The method of sub-dividing the main river channel from theflood plain sections and summing the discharges in each sub-section simply does not work.The main reason being that large turbulent interactions between the main river channelflow and flood-plain flows,which generate very significant additional energy losses overand above bed friction,require to be simulated by additional turbulence terms preferablyin the form of a simple turbulence model such as that of Vreugdenhil and Wijbenga(Ref.10).

DOI:

Year: 1989