ABSTRACT Quantifying flow resistance in open channels with mixed‐height vegetation is essential for predicting stage–discharge relationships and assessing conveyance and habitat conditions in vegetated floodplains. In staggered tall–short vegetation, strong lateral velocity contrasts and inter‐patch momentum transfer alter the flow structure and hinder the direct use of conventional roughness formulations. Based on flume experiments with rigid cylindrical surrogates arranged as laterally adjacent tall and short patches in a staggered layout, this study develops a physics‐based procedure to estimate the drag coefficient and the equivalent Manning coefficient across emergent to submerged conditions. A two‐patch momentum‐balance model is formulated by explicitly accounting for the measured water‐surface slope, vegetation drag within each patch and an apparent shear stress representing interfacial momentum exchange between the tall and short patches. Closed‐form expressions are then derived to invert patch‐averaged drag coefficients from readily measurable hydraulic variables and flow‐facing area metrics, providing a tractable alternative to purely empirical calibration. The analytically inverted drag coefficients are further consolidated with literature data recast under consistent definitions of Reynolds number and a density descriptor, yielding an empirical predictor C d ( R e, λ ) for rigid vegetation in staggered canopies. Finally, a practical linkage between the mean vegetation drag coefficient and Manning coefficient is established by incorporating vegetation area density and hydraulic‐radius scaling, enabling computation of an equivalent Manning coefficient for mixed‐height, staggered vegetation within the tested parameter range. The proposed framework offers a parameter‐consistent basis for resistance estimation in laterally heterogeneous vegetated channels and supports hydraulic assessment and management of vegetated floodplains.
Yameng et al. (Fri,) studied this question.