ORIGINAL RESEARCH article
Front. Mar. Sci.
Sec. Coastal Ocean Processes
Volume 12 - 2025 | doi: 10.3389/fmars.2025.1585285
Subaqueous multiscale bedform morphology dynamics in a mountainous macrotidal estuary
Provisionally accepted- 1East China Normal University, Shanghai, China
- 2Faculty of Geosciences, University of Bremen, Bremen, Bremen, Germany
- 3Institute of Coastal Systems - Analysis and Modeling, Helmholtz Centre for Materials and Coastal Research (HZG), Geesthacht, Schleswig-Holstein, Germany
- 4Center for Marine Environmental Sciences, University of Bremen, Bremen, Bremen, Germany
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Bedforms in macrotidal estuaries and deltas are distinguished from those in rivers and oceans due to the tidally-driven water depth variations and the varying hydrodynamic processes resulting from the interaction between tidal and fluvial flows. The relations between hydrodynamics, sediment transport, and bedform morphology in these estuaries are complex, but research on the morphodynamics of bedforms in such environments is still lacking. This study explores the morphodynamic development patterns of multiscale bedforms in mountainous estuaries and tidal deltas, using the Minjiang Estuary as a representative case. Field observations were conducted in the Minjiang Estuary in the East China Sea in December 2021 (dry season) and August 2023 (flood season) using a multibeam echosounder system and an Acoustic Doppler Current Profiler (ADCP). Bedform presence and characteristics were calculated from bed elevation data. The results indicate that bedforms are widely developed from the underwater delta plain to the delta front channel of the Minjiang Estuary, with large compound bedforms being prevalent. Both primary and secondary bedforms coexist, with wavelengths ranging from 2 to 233 meters and heights from 0.1 to 6 meters. About 60% of primary bedforms exhibit ebb asymmetry, indicating ebb-directed sediment transport in the main channel. The average flood/ ebb lee side angle is 6°, with an average maximum angle of 19°. The maximum side angle of primary bedforms is observed to be on average greater than that of secondary bedforms. Water depth and riverbed slope significantly affect bedform density, with non-sloping riverbeds favoring bedform development. Variations in bed shear stress throughout the tidal cycle drive differences in bedform size and morphology. High clay content in surface sediments correlates with lower bedform density, indicating fine-grained materials may inhibit bedform development. This study highlights a feedback mechanism where structural geology shapes channel morphology, influencing energy distribution and bedform evolution. The findings enhance our understanding of sediment transport and hydrodynamic processes in macrotidal estuaries, offering insights for estuarine management and conservation. Future research should explore how seasonal and tidal variations influence bedform evolution to refine models of estuarine dynamics.
Keywords: Mountainous Macrotidal Estuary, Bedform morphology, Multiscale, Hydrodynamics, Minjiang estuary
Received: 28 Feb 2025; Accepted: 03 Jun 2025.
Copyright: © 2025 Liu, Cheng, Chen, Teng, Ren, Yang, Fan and Lefebvre. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence:
Heqin Cheng, East China Normal University, Shanghai, China
Alice Lefebvre, Center for Marine Environmental Sciences, University of Bremen, Bremen, 28359, Bremen, Germany
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