Morphodynamic assessment of side channel systems using a simple one‐dimensional bifurcation model and a comparison with aerial images |
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| Authors: | R Pepijn van Denderen Ralph M J Schielen Astrid Blom Suzanne J M H Hulscher Maarten G Kleinhans |
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| Affiliation: | 1. Faculty of Engineering Technology, University of Twente, Enschede, The Netherlands;2. Ministry of Infrastructure and Water Management Rijkswaterstaat, Utrecht, The Netherlands;3. Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, The Netherlands;4. Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands |
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| Abstract: | Side channel construction is a common intervention applied to increase a river's conveyance capacity and to increase its ecological value. Past modelling efforts suggest two mechanisms affecting the morphodynamic change of a side channel: (1) a difference in channel slope between the side channel and the main channel and (2) bend flow just upstream of the bifurcation. The objective of this paper was to assess the conditions under which side channels generally aggrade or degrade and to assess the characteristic timescales of the associated morphological change. We use a one‐dimensional bifurcation model to predict the development of side channel systems and the characteristic timescale for a wide range of conditions. We then compare these results to multitemporal aerial images of four side channel systems. We consider the following mechanisms at the bifurcation to be important for side channel development: sediment diversion due to the bifurcation angle, sediment diversion due to the transverse bed slope, partitioning of suspended load, mixed sediment processes such as sorting at the bifurcation, bank erosion, deposition due to vegetation, and floodplain sedimentation. There are limitations to using a one‐dimensional numerical model as it can only account for these mechanisms in a parametrized manner, but the model reproduces general behaviour of the natural side channels until floodplain‐forming processes become important. The main result is a set of stability diagrams with key model parameters that can be used to assess the development of a side channel system and the associated timescale, which will aid in the future design and maintenance of side channel systems. © 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd. |
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| Keywords: | side channel bifurcation morphodynamic modelling stability river morphodynamics |
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