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Is “Morphodynamic Equilibrium” an oxymoron?

Is “Morphodynamic Equilibrium” an oxymoron?
Is “Morphodynamic Equilibrium” an oxymoron?
Morphodynamic equilibrium is a widely adopted yet elusive concept in the field of geomorphology of coasts, rivers and estuaries. Based on the Exner equation, an expression of mass conservation of sediment, we distinguish three types of equilibrium defined as static and dynamic, of which two different types exist. Other expressions such as statistical and quasi-equilibrium which do not strictly satisfy the Exner conditions are also acknowledged for their practical use. The choice of a temporal scale is imperative to analyse the type of equilibrium. We discuss the difference between morphodynamic equilibrium in the “real world” (nature) and the “virtual world” (model). Modelling studies rely on simplifications of the real world and lead to understanding of process interactions. A variety of factors affect the use of virtual-world predictions in the real world (e.g., variability in environmental drivers and variability in the setting) so that the concept of morphodynamic equilibrium should be mathematically unequivocal in the virtual world and interpreted over the appropriate spatial and temporal scale in the real world. We draw examples from estuarine settings which are subject to various governing factors which broadly include hydrodynamics, sedimentology and landscape setting. Following the traditional “tide-wave-river” ternary diagram, we summarize studies to date that explore the “virtual world”, discuss the type of equilibrium reached and how it relates to the real world.
0012-8252
257-267
Zhou, Zeng
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Coco, Giovanni
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Townend, Ian
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Olabarrieta, Maitane
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Van Der Wegen, Mick
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Gong, Zheng
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D’alpaos, Andrea
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Gao, Shu
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Jaffe, Bruce E.
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Gelfenbaum, Guy
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He, Qing
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Wang, Yaping
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Lanzoni, Stefano
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Wang, Zhengbing
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Winterwerp, Han
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Zhang, Changkuan
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Zhou, Zeng
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Coco, Giovanni
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Townend, Ian
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Olabarrieta, Maitane
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Van Der Wegen, Mick
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Gong, Zheng
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D’alpaos, Andrea
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Gao, Shu
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Jaffe, Bruce E.
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Gelfenbaum, Guy
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He, Qing
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Wang, Yaping
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Lanzoni, Stefano
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Wang, Zhengbing
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Winterwerp, Han
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Zhang, Changkuan
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Zhou, Zeng, Coco, Giovanni, Townend, Ian, Olabarrieta, Maitane, Van Der Wegen, Mick, Gong, Zheng, D’alpaos, Andrea, Gao, Shu, Jaffe, Bruce E., Gelfenbaum, Guy, He, Qing, Wang, Yaping, Lanzoni, Stefano, Wang, Zhengbing, Winterwerp, Han and Zhang, Changkuan (2017) Is “Morphodynamic Equilibrium” an oxymoron? Earth-Science Reviews, 165, 257-267. (doi:10.1016/j.earscirev.2016.12.002).

Record type: Article

Abstract

Morphodynamic equilibrium is a widely adopted yet elusive concept in the field of geomorphology of coasts, rivers and estuaries. Based on the Exner equation, an expression of mass conservation of sediment, we distinguish three types of equilibrium defined as static and dynamic, of which two different types exist. Other expressions such as statistical and quasi-equilibrium which do not strictly satisfy the Exner conditions are also acknowledged for their practical use. The choice of a temporal scale is imperative to analyse the type of equilibrium. We discuss the difference between morphodynamic equilibrium in the “real world” (nature) and the “virtual world” (model). Modelling studies rely on simplifications of the real world and lead to understanding of process interactions. A variety of factors affect the use of virtual-world predictions in the real world (e.g., variability in environmental drivers and variability in the setting) so that the concept of morphodynamic equilibrium should be mathematically unequivocal in the virtual world and interpreted over the appropriate spatial and temporal scale in the real world. We draw examples from estuarine settings which are subject to various governing factors which broadly include hydrodynamics, sedimentology and landscape setting. Following the traditional “tide-wave-river” ternary diagram, we summarize studies to date that explore the “virtual world”, discuss the type of equilibrium reached and how it relates to the real world.

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equilibriumESRrev2 - Accepted Manuscript
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Accepted/In Press date: 1 December 2016
e-pub ahead of print date: 18 December 2016
Published date: 1 February 2017
Organisations: Ocean and Earth Science, Geology & Geophysics

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Local EPrints ID: 406579
URI: http://eprints.soton.ac.uk/id/eprint/406579
ISSN: 0012-8252
PURE UUID: 4bdc0b9b-86f7-47bc-aaac-0ead7eb1e9bb
ORCID for Ian Townend: ORCID iD orcid.org/0000-0003-2101-3858

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Date deposited: 18 Mar 2017 02:23
Last modified: 09 Jan 2022 03:08

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Contributors

Author: Zeng Zhou
Author: Giovanni Coco
Author: Ian Townend ORCID iD
Author: Maitane Olabarrieta
Author: Mick Van Der Wegen
Author: Zheng Gong
Author: Andrea D’alpaos
Author: Shu Gao
Author: Bruce E. Jaffe
Author: Guy Gelfenbaum
Author: Qing He
Author: Yaping Wang
Author: Stefano Lanzoni
Author: Zhengbing Wang
Author: Han Winterwerp
Author: Changkuan Zhang

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