Author(s): G. M. Smart

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Abstract: Conditions were investigated under which a given flow may exist at two sub-critical uniform depths, one with flow only in the main channel, one with flow also on the floodplains. Such stage-discharge discontinuities were found only for channels with a narrow, deep central channel and wide rough floodplains. The increase in Manning's n caused by momentum transfer to floodplains was found to be related to a factor representing the ratio of floodplain drag to the main channel driving force. A similar relationship was found for trapezoidal flume data provided the correct location of the interface between main channel and floodplain was chosen. The resulting equation enables correction of the Manning equation to allow for momentum transfer.

DOI: https://doi.org/10.1080/00221689209498912

Year: 1992