On the stability relationships between tidal asymmetry and morphologies of tidal basins and estuaries |
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| Authors: | Zeng Zhou Giovanni Coco Ian Townend Zheng Gong Zhengbing Wang Changkuan Zhang |
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| Institution: | 1. State Key Laboratory of Hydrology‐Water Resources and Hydraulic Engineering, Hohai University, Nanjing, China;2. Jiangsu Key Laboratory of Coast Ocean Resources Development and Environment Security, Hohai University, Nanjing, China;3. School of Environment, University of Auckland, New Zealand;4. Ocean and Earth Sciences, University of Southampton, UK;5. College of Harbour, Coastal and Offshore Engineering, Hohai University, Nanjing, China;6. Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, Netherlands;7. Deltares, Delft, Netherlands |
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| Abstract: | Simple stability relationships are practically useful to provide a rapid assessment of coastal and estuarine landforms in response to human interventions and long‐term climate change. In this contribution, we review a variety of simple stability relationships which are based on the analysis of tidal asymmetry (TA). Most of the existing TA‐based stability relationships are derived using the one‐dimensional tidal flow equations assuming a certain regular shape of the tidal channel cross‐sections. To facilitate analytical solutions, specific assumptions inevitably need to be made, for example by linearizing the friction term and dropping some negligible terms in the tidal flow equations. We find that three major types of TA‐based stability relationships have been proposed between three non‐dimensional channel geometric ratios (represented by the ratio of channel widths, ratio of wet surface areas and ratio of storage volumes) and the tide‐related parameter a/h (i.e. the ratio between tidal amplitude and mean water depth). Based on established geometric relations, we use these non‐dimensional ratios to restate the existing relationships so that they are directly comparable. Available datasets are further extended to examine the utility of these TA‐based relationships. Although a certain agreement is shown for these relationships, we also observe a large scatter of data points which are collected in different types of landscape, hydrodynamic and sedimentological settings over the world. We discuss in detail the potential reasons for this large scatter and subsequently elaborate on the limited applicability of the various TA‐based stability relationships for practical use. We highlight the need to delve further into what constitutes equilibrium and what is needed to develop more robust measures to determine the morphological state of these systems. Copyright © 2018 John Wiley & Sons, Ltd. |
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| Keywords: | tidal basins estuarine morphologies tidal asymmetry stability relationships |
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