Hydro-morphological modelling of small, wave-dominated estuaries. (5th November 2017)

• Record Type: Journal Article
• Authors: Slinger, Jill H.
• Is Part Of: Estuarine, coastal and shelf science. Volume 198:Part B(2017)
• Page Start: 583
• Page End: 596
• Publication Date: 2017-11-05
• Subjects: Intermittently open estuary -- Episodic closure -- Parametric modelling -- Bar-built -- Tidal inlet -- Freshwater flows -- Climate change -- South Africa; Estuarine oceanography -- Periodicals; Coasts -- Periodicals; Estuarine biology -- Periodicals; Seashore biology -- Periodicals; Coasts; Estuarine biology; Estuarine oceanography; Seashore biology; Periodicals; 551.461805
• DOI: 10.1016/j.ecss.2016.10.038
• Languages: English
• ISSNs: 0272-7714

Abstract

Abstract: Small, intermittently open or closed estuaries are characteristic of the coasts of South Africa, Australia, California, Mexico and many other areas of the world. However, modelling attention has tended to focus on big estuaries that drain large catchments and serve a wide diversity of interests e.g. agriculture, urban settlement, recreation, commercial fishing. In this study, the development of a simple, parametric, system dynamics model to simulate the opening and closure of the mouths of small, wave-dominated estuaries is reported. In the model, the estuary is conceived as a basin with a specific water volume to water level relationship, connected to the sea by a channel of fixed width, but variable sill height. Changes in the form of the basin are not treated in the model, while the dynamics of the mouth channel are central to the model. The magnitude and direction of the flow through the mouth determines whether erosion or deposition of sediment occurs in the mouth channel, influencing the sill height. The model is implemented on the Great Brak Estuary in South Africa and simulations reveal that the raised low water levels in the estuary during spring tide relative to neap tide, are occasioned by the constriction of the tidal flow through the shallow mouth. Freshwater inflows to the estuary are shown to be significant in determining the behaviour of the inlet mouth, a factor often ignored in studies on tidal inlets. Further it is the balance between freshwater inflows and wave events that determines the opening or closure of the mouth of a particular estuary. Graphical abstract: Highlights: A simple, parametric, model is developed for small, bar-blocked estuaries. The opening and closure of the estuary mouth is simulated. Estuary low water levels are characteristically higher during spring than neap tide. Freshwater inflows are significant in determining the inlet behaviour. More frequent severe storms lead to more frequent, persistent mouth closure.