This study examines the problem of flow resistance due to rigid vegetation in open channel flow. The reliability of the conventional flow resistance equations (i.e. Keulegan, Manning and Chézy-Bazin) for vegetated flows at high submergence, i.e. h/k >5, (where h = flow depth and k = vegetation height) is assessed. Several modern flow resistance equations based on a two-layer approach are examined, showing that they transform into the conventional equations at high submergences. To compare the conventional flow resistance equations at high submergences, an experimental methodology is proposed and applied to the experimental data reported in the literature and collected for this study. The results demonstrate the reliability of the Keulegan equation in predicting the flow resistance. Based on the obtained results, a model to evaluate the Nikuradse equivalent sand-grain roughness, k N , starting from the vegetation height and density, is proposed and tested.

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In a variety of environmental settings, including vegetated channel banks and rivers, and their associated floodplains and riparian areas, vegetation occurs along river margins, partially obstructing the cross-section. In these systems, referred to as partly vegetated channels, the long regions of finite width of emergent vegetation laterally interact with the flow, deeply altering the mean and turbulent flow structure with implications on the conveyance capacity of the channel, the water levels, and the mass and momentum exchange processes (

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