Hypsometric and geometric controls on hydrodynamics, tidal asymmetry, and sediment connectivity in shallow estuarine systems
type: CreativeWork
description: Estuaries and tidal basins are highly dynamic coastal systems that serve as a transition zone between the river and the ocean. The morphological evolution of these diverse environments is modulated by non-linear feedbacks between tides, meteorological forcing, and sediment transport processes. This thesis focuses on the fundamental links between these physical processes, and the geomorphologic characteristics of shallow estuarine systems, specifically: (i) how shallow basin geometries and hypsometries affect hydrodynamics and tidal asymmetry, (ii) how wind-induced currents modify velocity asymmetry in shallow basins, and (iii) defining the relationships between geometry, hypsometry, and sediment connectivity inside shallow estuarine systems. Linking geomorphological characteristics and tidal processes in shallow tidal basins The links between tidal basin geometry and hypsometry, bed shear stress patterns, tidal velocity- and slack water asymmetry, and hypsometric profile shapes were explored for six shallow microtidal basins of Tauranga Harbour, New Zealand. Model results, obtained from a depth-averaged numerical model developed in Delft3D for the full estuarine system, indicated that tidal distortion increases with distance from basin entrance. A simple ratio between tidal basin width and entrance width was defined to describe the planform shape of the basin. This metric, termed the ‘basin dilation factor’ indicates whether a basin can be designated as a divergent or convergent geometry. Shallow basins with a constricted geometry and relatively deep entrance channels were found to be associated with small bed shear stress values and high rates of flood-directed tidal velocity asymmetry in the sheltered basin centres. These results suggest substantial potential for sediment deposition of larger particles. Moreover, slack water asymmetry within these basins was weakly ebb-directed, indicating a small potential for export of fine sediments. These divergent, deposition…
abstract: Estuaries and tidal basins are highly dynamic coastal systems that serve as a transition zone between the river and the ocean. The morphological evolution of these diverse environments is modulated by non-linear feedbacks between tides, meteorological forcing, and sediment transport processes. This thesis focuses on the fundamental links between these physical processes, and the geomorphologic characteristics of shallow estuarine systems, specifically: (i) how shallow basin geometries and hypsometries affect hydrodynamics and tidal asymmetry, (ii) how wind-induced currents modify velocity asymmetry in shallow basins, and (iii) defining the relationships between geometry, hypsometry, and sediment connectivity inside shallow estuarine systems. Linking geomorphological characteristics and tidal processes in shallow tidal basins The links between tidal basin geometry and hypsometry, bed shear stress patterns, tidal velocity- and slack water asymmetry, and hypsometric profile shapes were explored for six shallow microtidal basins of Tauranga Harbour, New Zealand. Model results, obtained from a depth-averaged numerical model developed in Delft3D for the full estuarine system, indicated that tidal distortion increases with distance from basin entrance. A simple ratio between tidal basin width and entrance width was defined to describe the planform shape of the basin. This metric, termed the ‘basin dilation factor’ indicates whether a basin can be designated as a divergent or convergent geometry. Shallow basins with a constricted geometry and relatively deep entrance channels were found to be associated with small bed shear stress values and high rates of flood-directed tidal velocity asymmetry in the sheltered basin centres. These results suggest substantial potential for sediment deposition of larger particles. Moreover, slack water asymmetry within these basins was weakly ebb-directed, indicating a small potential for export of fine sediments. These divergent, deposition…
author: de Ruiter, Peter Jaap
keywords: Oceanography, Coastal science, Estuaries, Sediment transport, Numerical modeling, Hydrodynamics, Tidal asymmetry, thesis with publication
license: https://researchcommons.waikato.ac.nz/bitstreams/42357c14-3714-446c-9334-bbcef99288dc/download
date published: 2022
date modified: 2026-07-24T05:57:38Z
provider: University Waikato
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: The University of Waikato