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Upstream perturbation and floodplain formation effects on chute‐cutoff‐dominated meandering river pattern and dynamics

A sustained dynamic inflow perturbation and bar–floodplain conversion are considered crucial to dynamic meandering. Past experiments, one‐dimensional modelling and linear theory have demonstrated that the initiation and persistence of dynamic meandering require a periodic transverse motion of the in...

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Autores principales: Weisscher, Steven A. H., Shimizu, Yasuyuki, Kleinhans, Maarten G.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6774324/
https://www.ncbi.nlm.nih.gov/pubmed/31598027
http://dx.doi.org/10.1002/esp.4638
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author Weisscher, Steven A. H.
Shimizu, Yasuyuki
Kleinhans, Maarten G.
author_facet Weisscher, Steven A. H.
Shimizu, Yasuyuki
Kleinhans, Maarten G.
author_sort Weisscher, Steven A. H.
collection PubMed
description A sustained dynamic inflow perturbation and bar–floodplain conversion are considered crucial to dynamic meandering. Past experiments, one‐dimensional modelling and linear theory have demonstrated that the initiation and persistence of dynamic meandering require a periodic transverse motion of the inflow. However, it remains unknown whether the period of the inflow perturbation affects self‐formed meander dynamics. Here, we numerically study the effect of the inflow perturbation period on the development and meander dynamics of a chute‐cutoff‐dominated river, which requires two‐dimensional modelling with vegetation forming floodplain on bars. We extended the morphodynamic model Nays2D with growth and mortality rules of vegetation to allow for meandering. We tested the effect of a transversely migrating inflow boundary by varying the perturbation period between runs over an order of magnitude around typical modelled meander periods. Following the cutoff cascade after initial meander formation from a straight channel, all runs with sufficient vegetation show series of growing meanders terminated by chute cutoffs. This generates an intricate channel belt topography with point bar complexes truncated by chutes, oxbow lakes, and scroll‐bar‐related vegetation age patterns. The sinuosity, braiding index and meander period, which emerge from the inherent biomorphological feedback loops, are unrelated to the inflow perturbation period, although the spin‐up to dynamic equilibrium takes a longer time and distance for weak and absent inflow perturbations. This explains why, in previous experimental studies, dynamic meandering was only accomplished with a sustained upstream perturbation in flumes that were short relative to the meander wavelength. Our modelling of self‐formed meander patterns is evidence that scroll‐bar‐dominated and chute‐cutoff‐dominated meanders develop from downstream convecting instabilities. This insight extends to many more fluvial, estuarine and coastal systems in morphological models and experiments, which require sustained dynamic perturbations to form complex patterns and develop natural dynamics. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd.
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spelling pubmed-67743242019-10-07 Upstream perturbation and floodplain formation effects on chute‐cutoff‐dominated meandering river pattern and dynamics Weisscher, Steven A. H. Shimizu, Yasuyuki Kleinhans, Maarten G. Earth Surf Process Landf Research Articles A sustained dynamic inflow perturbation and bar–floodplain conversion are considered crucial to dynamic meandering. Past experiments, one‐dimensional modelling and linear theory have demonstrated that the initiation and persistence of dynamic meandering require a periodic transverse motion of the inflow. However, it remains unknown whether the period of the inflow perturbation affects self‐formed meander dynamics. Here, we numerically study the effect of the inflow perturbation period on the development and meander dynamics of a chute‐cutoff‐dominated river, which requires two‐dimensional modelling with vegetation forming floodplain on bars. We extended the morphodynamic model Nays2D with growth and mortality rules of vegetation to allow for meandering. We tested the effect of a transversely migrating inflow boundary by varying the perturbation period between runs over an order of magnitude around typical modelled meander periods. Following the cutoff cascade after initial meander formation from a straight channel, all runs with sufficient vegetation show series of growing meanders terminated by chute cutoffs. This generates an intricate channel belt topography with point bar complexes truncated by chutes, oxbow lakes, and scroll‐bar‐related vegetation age patterns. The sinuosity, braiding index and meander period, which emerge from the inherent biomorphological feedback loops, are unrelated to the inflow perturbation period, although the spin‐up to dynamic equilibrium takes a longer time and distance for weak and absent inflow perturbations. This explains why, in previous experimental studies, dynamic meandering was only accomplished with a sustained upstream perturbation in flumes that were short relative to the meander wavelength. Our modelling of self‐formed meander patterns is evidence that scroll‐bar‐dominated and chute‐cutoff‐dominated meanders develop from downstream convecting instabilities. This insight extends to many more fluvial, estuarine and coastal systems in morphological models and experiments, which require sustained dynamic perturbations to form complex patterns and develop natural dynamics. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd. John Wiley and Sons Inc. 2019-04-23 2019-09-15 /pmc/articles/PMC6774324/ /pubmed/31598027 http://dx.doi.org/10.1002/esp.4638 Text en © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd. This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
spellingShingle Research Articles
Weisscher, Steven A. H.
Shimizu, Yasuyuki
Kleinhans, Maarten G.
Upstream perturbation and floodplain formation effects on chute‐cutoff‐dominated meandering river pattern and dynamics
title Upstream perturbation and floodplain formation effects on chute‐cutoff‐dominated meandering river pattern and dynamics
title_full Upstream perturbation and floodplain formation effects on chute‐cutoff‐dominated meandering river pattern and dynamics
title_fullStr Upstream perturbation and floodplain formation effects on chute‐cutoff‐dominated meandering river pattern and dynamics
title_full_unstemmed Upstream perturbation and floodplain formation effects on chute‐cutoff‐dominated meandering river pattern and dynamics
title_short Upstream perturbation and floodplain formation effects on chute‐cutoff‐dominated meandering river pattern and dynamics
title_sort upstream perturbation and floodplain formation effects on chute‐cutoff‐dominated meandering river pattern and dynamics
topic Research Articles
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6774324/
https://www.ncbi.nlm.nih.gov/pubmed/31598027
http://dx.doi.org/10.1002/esp.4638
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