Abstract
Abstract. Especially in mountainous environments, the prediction of sediment dynamics is important for managing natural hazards, assessing in-stream habitats and understanding geomorphic evolution. We present the new modelling tool {sedFlow} for simulating fractional bedload transport dynamics in mountain streams. sedFlow is a one-dimensional model that aims to realistically reproduce the total transport volumes and overall morphodynamic changes resulting from sediment transport events such as major floods. The model is intended for temporal scales from the individual event (several hours to few days) up to longer-term evolution of stream channels (several years). The envisaged spatial scale covers complete catchments at a spatial discretisation of several tens of metres to a few hundreds of metres. sedFlow can deal with the effects of streambeds that slope uphill in a downstream direction and uses recently proposed and tested approaches for quantifying macro-roughness effects in steep channels. sedFlow offers different options for bedload transport equations, flow-resistance relationships and other elements which can be selected to fit the current application in a particular catchment. Local grain-size distributions are dynamically adjusted according to the transport dynamics of each grain-size fraction. sedFlow features fast calculations and straightforward pre- and postprocessing of simulation data. The high simulation speed allows for simulations of several years, which can be used, e.g., to assess the long-term impact of river engineering works or climate change effects. In combination with the straightforward pre- and postprocessing, the fast calculations facilitate efficient workflows for the simulation of individual flood events, because the modeller gets the immediate results as direct feedback to the selected parameter inputs. The model is provided together with its complete source code free of charge under the terms of the GNU General Public License (GPL) (www.wsl.ch/sedFlow). Examples of the application of sedFlow are given in a companion article by Heimann et al. (2015).
Highlights
Environmental models typically seek to predict the future state of a system, based on information about its current state and the mechanisms that regulate its evolution through time
Local grain-size distributions have a high influence on the local hydraulic radius rh, which in turn determines bed shear stress and bedload transport capacity
In order to study dynamically evolving grain-size distributions and their effects on hydraulics and bedload transport, together with the effects of an evolving channel slope, sedFlow is optimised for the simulation of fractional bedload transport
Summary
Environmental models typically seek to predict the future state of a system, based on information about its current state and the mechanisms that regulate its evolution through time. The DREAM models feature the simulation of (a) bank erosion during the downcutting of reservoir deposits, (b) transcritical flow conditions, (c) combined bedload and suspended load transport, (d) the details of gravel abrasion and (e) staged dam removal and partial dredging as options in the dam removal scenarios Due to their specific focus, the wider applicability of the DREAM models is limited. Most published model applications used bedload transport calculations for a single grain size In such a situation, all grain sizes and their spatial distribution are constant for the complete simulation. The model sedFlow fills a gap in the range of existing sediment transport models for mountain streams (Table 1) and the goals outlined above have led to the implementation described This implementation represents the current state of the model, and may be extended and adjusted in the future. Examples of sedFlow application are given in a companion article by Heimann et al (2015)
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