Print Email Facebook Twitter River Flow Induced Nonlinear Modulation of M4 Overtide in Large Estuaries Title River Flow Induced Nonlinear Modulation of M4 Overtide in Large Estuaries Author Guo, Leicheng (Shanghai Estuarine and Coastal Science Research Center) Zhu, Chunyan (Shanghai Estuarine and Coastal Science Research Center) Cai, Huayang (School of Ocean Engineering and Technology; Sun Yat-sen University) Wang, Zhengbing (TU Delft Hydraulic Engineering; TU Delft Coastal Engineering; Deltares) Townend, Ian (University of Southampton) He, Qing (Shanghai Estuarine and Coastal Science Research Center) Department Hydraulic Engineering Date 2023 Abstract River discharge is known to enhance tidal damping and tidal wave deformation in estuaries. While the damping effect on astronomical tides has been well documented, river impact on tidal wave deformation and associated overtide generation (shallow water harmonics of one or more astronomical constituents, such as M4) remains insufficiently understood. Overtides affect tidal asymmetry, extreme water levels, and subsequent sediment transport and flooding management, thus meriting in-depth examination. Being inspired by unusual overtide changes in the landward and seaward parts of the Changjiang Estuary under low and high river discharges, in this work, we use a schematized tidal estuary model to systematically explore overtide variations under different river discharges. Model results show enhanced overtide generation in the case with river discharge compared with that without river impact. The M4 amplitude decreases in the landward parts of the estuary, but increases in the seaward parts under increasing river discharges. The potential energy of M4 integrated throughout the estuary shows nonlinear variations and reaches a transitional maximum when the river discharge to tidal mean discharge (R2T) ratio at the mouth is close to unity. Similar nonlinear behaviors are observed for compound tides like MS4 when more astronomical constituents are prescribed and triad tidal interactions are enabled. The space-dependent overtide variability is more profound in large estuaries with high river discharges like the Amazon and Changjiang estuaries. It is ascribed to the inherently nonlinear river-tide interactions, specifically the twofold effects of river discharge in enhancing bottom stress, which simultaneously enhances dissipation of astronomical constituents and reinforces the energy transfer to overtides. These findings highlight the profound nonlinear impact of river discharge on overtides, and inform the study of tidal asymmetry and compound flood risk in large estuaries and deltas. Subject Bottom stressEstuaryOvertideRiver discharge To reference this document use: http://resolver.tudelft.nl/uuid:0e623f20-7ec1-46bf-866a-f97415d0da93 DOI https://doi.org/10.1007/s12237-023-01183-0 Embargo date 2023-08-21 ISSN 1559-2723 Source Estuaries and Coasts, 46 (4), 925-940 Bibliographical note Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public. Part of collection Institutional Repository Document type journal article Rights © 2023 Leicheng Guo, Chunyan Zhu, Huayang Cai, Zhengbing Wang, Ian Townend, Qing He Files PDF s12237_023_01183_0.pdf 5.42 MB Close viewer /islandora/object/uuid:0e623f20-7ec1-46bf-866a-f97415d0da93/datastream/OBJ/view