Preprints
https://doi.org/10.5194/os-2021-76
https://doi.org/10.5194/os-2021-76

  06 Sep 2021

06 Sep 2021

Review status: this preprint is currently under review for the journal OS.

Responses of estuarine circulation to the morphological evolution in a convergent, microtidal estuary

Rui Zhang1, Bo Hong2, Lei Zhu1,3,4, Wenping Gong1,3, and Heng Zhang1,3,4 Rui Zhang et al.
  • 1School of Marine Sciences, SunYat-sen University, Guangzhou, China, 510275
  • 2School of Civil and Transportation Engineering, South China University of Technology, Wushan RD., Tianhe District, Guangzhou 510641, China
  • 3Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519000, China
  • 4Pearl River Estuary Marine Ecosystem Research Station, Ministry of Education, Zhuhai, 519082, China

Abstract. The Huangmaohai Estuary (HE) is a funnel-shaped microtidal estuary in the west of the Pearl River Delta (PRD) in southern China. Since China's reform and opening up in 1978, extensive human activities have occurred and greatly changed the estuary's topography, and modified its hydrodynamics. In this study, we examined the morphological evolution by analyzing remote sensing data with ArcGIS tools and studied the responses of hydrodynamics to the changes in topography from 1977 to 2010 by using the Delft3d model. We took the changes in estuarine circulation during neap tides in dry seasons as an example. The results show that human reclamation caused a narrowing of the estuary, and channel dredging deepened the estuary. These human activities changed both the longitudinal and lateral estuarine circulations. The longitudinal circulation was observed to increase with the deepening and narrowing of the estuary. The lateral circulation experienced changes in both the magnitude and pattern. The momentum balance analysis shows that when the depth and width changed simultaneously, the longitudinal estuarine circulation was modulated by both the channel deepening and width reduction, in which the friction, pressure gradient force, and advection terms were altered. The analysis of the longitudinal vortex dynamics indicates that the changes in the vertical shear of the longitudinal flow, lateral salinity gradient, and vertical mixing were responsible for the change in the lateral circulation. The changes in water depth are the dominant factor affecting lateral circulation intensity. This study has implications for sediment transport and morphological evolution in estuaries heavily impacted by human interventions.

Rui Zhang et al.

Status: open (until 01 Nov 2021)

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Rui Zhang et al.

Rui Zhang et al.

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Short summary
1. The intensity of the longitudinal estuarine circulation kept increasing as the estuary width continued to decrease. 2. The changes in water depth were the dominant factor affecting lateral circulation intensity. 3. The changes in the estuarine circulation were dominated by the changes in the baroclinic pressure gradient force and advection.