Preprints
https://doi.org/10.5194/hess-2021-75
https://doi.org/10.5194/hess-2021-75
26 Feb 2021
 | 26 Feb 2021
Status: this preprint was under review for the journal HESS but the revision was not accepted.

River-enhanced non-linear overtide variations in river estuaries

Leicheng Guo, Chunyan Zhu, Huayang Cai, Zheng Bing Wang, Ian Townend, and Qing He

Abstract. Tidal waves traveling into estuaries are modulated in amplitude and shape due to bottom friction, funneling planform and river discharge. The role of river discharge on damping incident tides has been well-documented, whereas our understanding of the impact on overtide is incomplete. Inspired by findings from tidal data analysis, in this study we use a schematized estuary model to explore the variability of overtide under varying river discharge. Model results reveal significant M4 overtide generated inside the estuary. Its absolute amplitude decreases and increases in the upper and lower parts of the estuary, respectively, with increasing river discharge. The total energy of the M4 tide integrated throughout the estuary reaches a transitional maximum when the river discharge to tidal mean discharge (R2T) ratio is close to unity. We further identify that the quadratic bottom stress plays a dominant role in governing the M4 variations through strong river-tide interaction. River flow enhances the effective bottom stress and dissipation of the principal tides, and reinforces energy transfer from principal tide to overtide. The two-fold effects explain the nonlinear M4 variations and the intermediate maximum threshold. The model results are consistent with data analysis in the Changjiang and Amazon River estuaries and highlight distinctive tidal behaviors between upstream tidal rivers and downstream tidal estuaries. The new findings inform study of compound flooding risk, tidal asymmetry, and sediment transport in river estuaries.

Leicheng Guo, Chunyan Zhu, Huayang Cai, Zheng Bing Wang, Ian Townend, and Qing He

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2021-75', Xiao Hua Wang, 08 Apr 2021
    • AC1: 'Reply on RC1', Leicheng Guo, 16 Apr 2021
      • RC2: 'Reply on AC1', Xiao Hua Wang, 17 Apr 2021
        • AC2: 'Reply on RC2', Leicheng Guo, 28 May 2021
  • RC3: 'Comment on hess-2021-75', Anonymous Referee #2, 27 Apr 2021
    • AC3: 'Reply on RC3', Leicheng Guo, 28 May 2021
  • RC4: 'Comment on hess-2021-75', Anonymous Referee #3, 29 Apr 2021
    • AC4: 'Reply on RC4', Leicheng Guo, 28 May 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2021-75', Xiao Hua Wang, 08 Apr 2021
    • AC1: 'Reply on RC1', Leicheng Guo, 16 Apr 2021
      • RC2: 'Reply on AC1', Xiao Hua Wang, 17 Apr 2021
        • AC2: 'Reply on RC2', Leicheng Guo, 28 May 2021
  • RC3: 'Comment on hess-2021-75', Anonymous Referee #2, 27 Apr 2021
    • AC3: 'Reply on RC3', Leicheng Guo, 28 May 2021
  • RC4: 'Comment on hess-2021-75', Anonymous Referee #3, 29 Apr 2021
    • AC4: 'Reply on RC4', Leicheng Guo, 28 May 2021
Leicheng Guo, Chunyan Zhu, Huayang Cai, Zheng Bing Wang, Ian Townend, and Qing He
Leicheng Guo, Chunyan Zhu, Huayang Cai, Zheng Bing Wang, Ian Townend, and Qing He

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Short summary
Overtide is a shallow water tidal component and its interaction with astronomical tides induces tidal wave deformation, which is an important process that controls sediment transport. We use a numerical tidal model to examine overtide changes in estuaries under varying river discharges and find spatially nonlinear changes and the threshold of an intermediate river that benefits maximal overtide generation. The findings inform management of sediment transport and flooding risk in estuaries.