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• Bed-load capacity through emerging vegetation depends on two dimensionless parameters only: modified dimensionless bed load and modified flow intensity parameter. • The above two parameters are modified to account for vegetation density, the relative size of vegetation and the dimensionless diameter. • The new general formulation is valid with and without of vegetation. The paper deals with bed-load rates in a mobile bed channel with emerging vegetation. We have adapted the probabilistic/deterministic sediment transport model of Armanini et al. (2015) to account for changes in the flow field induced by vegetation. In addition to the two dimensionless parameters proposed by Einstein (1950) , Φ and Ψ, the new adapted model also depends on a third dimensionless parameter representative of vegetation size and density. The adaptation requires two major changes to the original model by Armanini et al. (2015). Firstly, the presence of vegetation reduces the bed area that is active with processes of sediment entrainment and deposition. To account for this, we propose reducing the net unit area useful for the exchange of sediments between bed and flow in proportion to vegetation density. This hypothesis implies redefining Einstein's parameter Φ, which represents the dimensionless sediment transport rate. Secondly, the presence of vegetation modifies some important parameters that, according to the adopted model, contribute to the formation of the bed load, (i.e. probability distributions of the particle hop length and detachment). Instead of adapting the bed-load formula to account for vegetation, we propose redefining both of Einstein's dimensionless parameters, Φ and Ψ, so that they are functions of the vegetation characteristics. This formulation is compared with a wide range of experimental data obtained in a laboratory channel, where the plants were represented by rigid emerging cylinders of different sizes and distribution densities within the channel. Under statistically homogenous and stationary conditions, these tests provided solid flow rates and hydrodynamic characteristics for 93 configurations with different values of hydrodynamic, granulometric and stem parameters. The comparison between experimental results and theoretical predictions shows the validity of the approach. [ABSTRACT FROM AUTHOR]

This paper describes a new, public-domain interface for modeling flow, sediment transport and morphodynamics in rivers and other geophysical flows. The interface is named after the International River Interface Cooperative (iRIC), the group that constructed the interface and many of the current solvers included in iRIC. The interface is entirely free to any user and currently houses thirteen models ranging from simple one-dimensional models through three-dimensional large-eddy simulation models. Solvers are only loosely coupled to the interface so it is straightforward to modify existing solvers or to introduce other solvers into the system. Six of the most widely-used solvers are described in detail including example calculations to serve as an aid for users choosing what approach might be most appropriate for their own applications. The example calculations range from practical computations of bed evolution in natural rivers to highly detailed predictions of the development of small-scale bedforms on an initially flat bed. The remaining solvers are also briefly described. Although the focus of most solvers is coupled flow and morphodynamics, several of the solvers are also specifically aimed at providing flood inundation predictions over large spatial domains. Potential users can download the application, solvers, manuals, and educational materials including detailed tutorials at www.-i-ric.org . The iRIC development group encourages scientists and engineers to use the tool and to consider adding their own methods to the iRIC suite of tools. [ABSTRACT FROM AUTHOR]

In this paper we present a probabilistic/deterministic model for the evaluation of the sediment transport rate in a stream. Starting from Einstein’s theory, the approach was obtained by trying to overcome some of the intrinsic limitations. The approach is based on two distinct probability functions, one relevant to the detachment of grains and the second relevant to the length of particle jumps. The sediment transport rate is obtained by integrating the distribution of the ranges of the particle jumps multiplied by the average particle velocity. The relationship for the average ranges of particle jumps is an opportune combination of the Einstein and Yalin expressions. The final formulation was calibrated by means of a large number of experimental data and also by comparison with some of the most widely-used empirical formulas. The results show a better agreement between theory and experiments than do the other theories analyzed. [ABSTRACT FROM AUTHOR]

Abstract: Longitudinal dispersion is one of the most important transport processes in fluvial ecosystems. It affects the transport of chemicals, nutrients, seeds, and wood debris along a river. The focus of this work is on the impact of riparian vegetation on the dispersion coefficient. The investigation considers stochastic forcing due to the river discharge randomness and its interplay with vegetation dynamics. A stochastic bio-hydrodynamical model is proposed and the probability distribution of the dispersion coefficient is obtained. The model allows one to elucidate the influence of (i) the vegetation characteristics, (ii) the probabilistic structure of the discharge time series, and (iii) the hydraulic characteristics of the transect. The work demonstrates the high variability of dispersion coefficients and the remarkable impact of riparian vegetation when medium/high discharges flow. [Copyright &y& Elsevier]

Abstract: A flume experiment on entrainment of woody debris is carried out. Woody debris is modeled using smooth, cylindrical dowels, in touch with the flume bed. The water depth and velocity are evaluated that initiate the motion of the partially submerged dowels. On the basis of the experimental finding, a theoretical model of log entrainment is developed, providing in dimensionless form the equilibrium equation for incipient motion. The experiment shows that the equilibrium equation must keep into account the modification of the local water profile, affecting the force balance at incipient motion. This issue has been apparently neglected in the wood entrainment models so far developed. The entrainment model is less sensitive to the choice of the apparent drag coefficient. The capability of the model in predicting the critical log diameter for initiation of motion is discussed and compared with that from the recent entrainment model from Braudrick and Grant, 2000. The comparison shows interesting results and provide evidence of the needs for further studies on wood entrainment in rivers. [Copyright &y& Elsevier]

• Low and high bar modes originate from water discharge variations. • In turn, this induces complex compound bar formation. • Sediment sorting patterns differ between unit and compound bar patterns. • Sediment sorting does not modify bar morphodynamics if sediment mobility is high. • Floods decrease the degree of sediment sorting. Bars are large sediment deposits alternating with deeper areas that arise from alluvial river bed instability and forcing. The present study aimed at investigating the combined influence of flow and longitudinal width variations on the co-evolution between bar pattern and sediment sorting in a sandy-gravel river reach. To this goal, a fully non-linear 2D numerical model was developed to reproduce the morphodynamic behavior of bars in a reach of the Loire River consisting in a typical channel expansion/contraction. Numerical results showed that varying water discharge promoted a competition between low and high bar modes: i.e., from alternate to multiple bar patterns. Low bar modes were associated with coarse sediment over bar tops and fine sediment in pools, and this sorting pattern was inverted for higher bar modes. Surface sediment was coarser and the degree of sediment sorting was greater after periods of low than high flow. Due to high sediment mobility, sediment sorting did not significantly modify bar morphodynamics. [ABSTRACT FROM AUTHOR]