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Shrubby and woody vegetation growing on floodplains profoundly influences hydrodynamic and transport processes in riverine systems. Existing hydrodynamic research is mostly focused on conditions with aquatic plants and rigid model vegetation. To appreciate the different hydrodynamic impacts of submerged floodplain and riverbank vegetation, a novel flume investigation was carried out. We simulated conditions found in riparian environments in terms of vegetation density, plant structure and flexibility, and presence of a grassy understory. Four experimental cases were defined so that vegetation exhibited different degrees of bending and streamlining. Extensive set of velocity measurements allowed reliable description of the double averaged flow. Vegetation morphology, with the flexibility-induced streamlining and dynamic motion controlled the magnitude and distribution of the vegetative drag, shaping the shear penetration within the canopy. The flows were highly heterogeneous, thus calling for spatially averaged approaches for the flow field investigation. The relative importance of dispersive momentum fluxes was high in the canopy bottom region where both Reynolds and dispersive stresses were small. The contribution of dispersive fluxes to momentum transport decreased with increasing reconfiguration. The results revealed the shear layers over floodplain vegetation to be dynamically similar to other environmental flows over porous obstructions. However, the velocity-dependent vegetative drag and deflected height introduced additional complexity in the flow simulation. Altogether our findings implied that accurate description of vegetated floodplain flows can be achieved only when plant morphology and flexibility are appropriately described in drag models. Article highlights: A novel experimental setup with flexible woody plants and grasses was used to model the hydrodynamics of vegetated floodplains. Plant morphology and flexibility controlled the vegetative drag, affecting key shear layer features, including the shear penetration. The spatially heterogeneous flows had higher dispersive stresses at the canopy bottom, where the total fluid stress was small. [ABSTRACT FROM AUTHOR]

Purpose: Riparian vegetation imposes a critical control on the transport and deposition of suspended sediment with important implications for water quality and channel maintenance. This paper contributes (1) to hydraulic and morphological modeling by examining the parameterization of natural riparian vegetation (trees, bushes, and grasses) and (2) to the design and management of environmental channels by determining how the properties of natural floodplain plant stands affect the erosion and deposition of suspended sediment.Materials and methods: Laboratory and field data were employed for enhancing the physical description of flow-plant-sediment interactions with a consideration of practical applicability. A drag force parameterization that takes into account the flexibility-induced reconfiguration, and the complex structure of foliated plants was validated for small natural trees under laboratory conditions, while the data from a small vegetated compound channel demonstrated the approaches at the field scale. Based on the field data, we identified three key vegetative factors influencing the net deposition and erosion on the floodplain. The significance of these factors was evaluated for vegetative conditions ranging from almost bare soil to sparse willows and dense grasses. Overall, the investigated conditions covered flexible and rigid vegetation with seasonal differences represented by foliated and leafless states.Results and discussion: The drag and reconfiguration of woody plants were reliably predicted under leafless and foliated conditions. Subsequently, we present a new easy-to-use methodology for predicting vegetative drag and flow resistance. The methodology is based on a physically solid parameterization for five widely used coefficients or terms (Eqs. (2)-(6)), with the necessary parameter values presented for common riparian species. The methodology was coupled with existing approaches at the field scale, revealing that increasing vegetation density and the associated decreasing flow velocity within vegetation significantly increased net deposition. Further, deposition increased with increasing cross-sectional vegetative blockage and decreasing distance from the suspended sediment replenishment point. Thus, longitudinal advection was the most important mechanism supplying fine sediment to the floodplain, but long continuous plant stands limited deposition.Conclusions: The proposed parameterization (Eqs. (2)-(6)) can be readily implemented into existing hydraulic and morphological models to improve the description of natural vegetation compared to the conventional rigid cylinder representation. The approach is advantageous for evaluating, for example, the effects of both natural succession and management interventions on floodplains. Finally, guidance is provided on how floodplain vegetation can be maintained to manage the erosion and deposition of suspended sediment in environmental channel designs. [ABSTRACT FROM AUTHOR]

To reliably estimate water levels and velocities in vegetated rivers and floodplains, flow resistance models based on physical plant properties are advantageous. The purpose of this study is (1) to assess the suitable parameterization of woody riparian vegetation in estimating the drag forces, (2) to address the effect of plant scale on the drag estimates and reconfiguration, and (3) to evaluate the applicability of three recently developed flow resistance models. Experiments on four tree species in a towing tank together with detailed characterization of tree properties were carried out to establish a novel dataset. Despite the variability in the tree height (0.9 m–3.4 m), the stem, leaf and total areas proved to be suitable characteristic dimensions for estimating the flow resistance at different scales. Evaluations with independent data revealed that the tested models produced reasonable results. The performance of the models was controlled by the parameter values used rather than the model structure or the plant scale. [ABSTRACT FROM AUTHOR]

The authors regret that the article contains a typing mistake in Eq. (5), with an uC2 term accidentally appearing at the right hand side of the squared brackets. [ABSTRACT FROM AUTHOR]

This is the erratum to the article [JALONEN Johanna, JÄRVELÄ Juha, Journal of Hydrodynamics, 2014, 26(4)]. In pages 610 and 621 the drag coefficients are corrected. [ABSTRACT FROM AUTHOR]