Is “Morphodynamic Equilibrium” an oxymoron?

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• 作者：Zeng Zhou^a ; ^b ; ^{zhouzeng@hhu.edu.cn} ; Giovanni Coco^b ; Ian Townend^c ; Maitane Olabarrieta^d ; Mick van der Wegen^e ; ^f ; Zheng Gong^g ; Andrea D&rsquo ; Alpaos^h ; Shu Gaoⁱ ; Bruce E. Jaffe^j ; Guy Gelfenbaum^j ; Qing Heⁱ ; Yaping Wang^k ; Stefano Lanzoni^l ; Zhengbing Wang^f ; ^m ; Han Winterwerp^f ; ^m ; Changkuan Zhang^g
• 关键词：Morphodynamic equilibrium ; Estuaries and coasts ; Sediment transport ; Static equilibrium ; Dynamic equilibrium ; Numerical modelling
• 刊名：Earth-Science Reviews
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：165
• 期：Complete
• 页码：257-267
• 全文大小：1320 K
• 卷排序：165

文摘

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.