Evolution of tidal inlet geometries in a restored coastal wetland — ASN Events

Evolution of tidal inlet geometries in a restored coastal wetland (#218)

Jamie E Ruprecht 1 , William C Glamore 1 , Stefan Felder 1
  1. UNSW Australia, Water Research Laboratory, Manly Vale, NSW, Australia

Over the past two decades, the restoration of coastal wetlands has increased globally.  The recognition of the environmental and ecological values of coastal wetlands has resulted in a shift from destruction for agriculture and development, to restoration and preservation. 

Continuously, tidal inlets to coastal wetlands and estuaries exhibit a dynamic stability, changing in response to variations in the controlling hydrodynamic forcing functions (e.g. floods, variations in the spring-neap tidal amplitudes, sedimentary regimes) and anthropogenic perturbations (e.g. dredging, entrance training). The formation of equilibrium conditions of these tidal inlets is typically estimated using an empirical approach based upon field observations of tidal prism and marsh area.  However, little is known about the evolution of tidal channels in restored wetlands.

Herein, field data was collected over a consecutive 3-year period from several tidal inlet channels within the Hunter Wetland National Park, a coastal wetland undergoing restoration in Southeast Australia.  The collected data included depth, top width and cross-sectional area of nine channels of varying sizes ranging from approximately 10 to 200 ha, as well as the corresponding marsh areas.  The observations provided a novel data set characterising the evolution of tidal inlet channels.  The present field data were compared with existing empirical predictions for equilibrium conditions in tidal inlets, as well as with a simplified theoretical model of equilibrium inlet conditions, known as Escoffier analysis.  The comparative analysis showed that most channels were out of equilibrium, but the largest of all channels surveyed appeared to be close to its equilibrium channel morphology. 

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