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Long-term modelling of fluvial systems at the watershed scale: Examples from three case studies

  • To date, many numerical approaches are available in studying water flow and sediment dynamics along rivers from the reach to the watershed scale, based on various simplifications. The aim of the present research is to demonstrate how the so-called “morphodynamic quasi-equilibrium hypothesis” is effective in modelling riverine landscape morphodynamics evolution at the watershed scale, focussing on the long-term changes of longitudinal profile and bed grainsize composition of large alluvial rivers. A lumped 0-D, two-reach, two-grainsize model based on the Local Uniform Flow hypothesis and originally developed for reproducing fluvial changes at the historical time-scale, has been applied to three large watercourses to reproduce their long-term evolution, performing a sensitivity analysis based on the present conditions. Three morphometric parameters were analysed, aiming to describe the evolution of the longitudinal profile (concavity and aggrading) and the grainsize composition of the river bed (fining). Though the 0-D approach does notTo date, many numerical approaches are available in studying water flow and sediment dynamics along rivers from the reach to the watershed scale, based on various simplifications. The aim of the present research is to demonstrate how the so-called “morphodynamic quasi-equilibrium hypothesis” is effective in modelling riverine landscape morphodynamics evolution at the watershed scale, focussing on the long-term changes of longitudinal profile and bed grainsize composition of large alluvial rivers. A lumped 0-D, two-reach, two-grainsize model based on the Local Uniform Flow hypothesis and originally developed for reproducing fluvial changes at the historical time-scale, has been applied to three large watercourses to reproduce their long-term evolution, performing a sensitivity analysis based on the present conditions. Three morphometric parameters were analysed, aiming to describe the evolution of the longitudinal profile (concavity and aggrading) and the grainsize composition of the river bed (fining). Though the 0-D approach does not allow for a spatial distribution of the input parameters, namely the liquid and solid discharge, the modelling outcomes show reasonably good qualitative trends. At the scale of analysis (centuries to millennia) and for the chosen large sedimentary systems (thousands of kilometres long), which show high inertia to geomorphological changes likely owing to their longitudinal scale, the model can be helpful in detecting where the present conditions reflect a big disturbance to the “natural” trend. This initial detection method can provide additional insights in evaluating the capability of actual rivers to respond to the present external forcing, eventually reaching a quasi-stable configuration.show moreshow less

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Metadaten
Author: Arianna VarraniORCiD, Michael Nones, Remika Gupana
DOI:https://doi.org/10.1016/j.jhydrol.2019.05.012
ISSN:0022-1694
Title of the source (English):Journal of Hydrology
Document Type:Scientific journal article peer-reviewed
Language:English
Year of publication:2019
Tag:0-D model; Congo River; Large rivers; Mississippi River; Morphodynamic equilibrium; Orinoco River; River concavity; Riverbed aggrading; Riverbed fining
Volume/Year:574
First Page:1042
Last Page:1052
Faculty/Chair:Fakultät 2 Umwelt und Naturwissenschaften / FG Hydrologie
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