Abstract
Abstract. Fully validated numerical models specifically designed for simulating bedload transport dynamics in mountain streams are rare. In this study, the recently developed modelling tool sedFlow has been applied to simulate bedload transport in the Swiss mountain rivers Kleine Emme and Brenno. It is shown that sedFlow can be used to successfully reproduce observations from historic bedload transport events with plausible parameter set-ups, meaning that calibration parameters are only varied within ranges of uncertainty that have been pre-determined either by previous research or by field observations in the simulated study reaches. In the Brenno river, the spatial distribution of total transport volumes has been reproduced with a Nash–Sutcliffe goodness of fit of 0.733; this relatively low value is partially due to anthropogenic extraction of sediment that was not considered. In the Kleine Emme river, the spatial distribution of total transport volumes has been reproduced with a goodness of fit of 0.949. The simulation results shed light on the difficulties that arise with traditional flow-resistance estimation methods when macro-roughness is present. In addition, our results demonstrate that greatly simplified hydraulic routing schemes, such as kinematic wave or uniform discharge approaches, are probably sufficient for a good representation of bedload transport processes in reach-scale simulations of steep mountain streams. The influence of different parameters on simulation results is semi-quantitatively evaluated in a simple sensitivity study. This proof-of-concept study demonstrates the usefulness of sedFlow for a range of practical applications in alpine mountain streams.
Highlights
The rolling, sliding or saltating transport of sediment grains along river beds, which is summarised as bedload transport, represents one of the main morphodynamic processes in mountain streams
The simulated peaks of very coarse grainsize distributions (GSDs) in the upper part of the Kleine Emme are due to the small alluvium thickness, which is in some places washed out completely
We used the model sedFlow to calculate bedload transport in two Swiss mountain rivers. sedFlow is a tool designed for the simulation of bedload dynamics in mountain streams
Summary
The rolling, sliding or saltating transport of sediment grains along river beds, which is summarised as bedload transport, represents one of the main morphodynamic processes in mountain streams. Bedload transport has implications which go beyond mere morphodynamics. It exerts considerable ecological influence by reorganising the bed and potential spawning grounds Bedload fluxes are responsible for damage to engineering structures Badoux et al, 2014) This wide range of implications is reflected in numerous applied engineering projects which evaluate potential bedload transport using one- or twodimensional simulation models. A summary of the applied aspects of bedload transport assessment has been given by Habersack et al (2011)
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