Oral Presentation 9th Australian Stream Management Conference 2018

Predicting opening duration of intermittently open/closed estuaries in victoria (#56)

Sarah L McSweeney 1 , Justin C Stout 2 , Ian D Rutherfurd 1 , David M Kennedy 1
  1. The University of Melbourne, Melbourne, VICTORIA, Australia
  2. Australian Rivers Institute, Griffith University, Brisbane, QLD, Australia

The Victorian government spends tens of thousands of dollars artificially opening Intermittently Open/Closed Estuaries (IOCE) that have been closed by sediment. IOCE close when wave driven deposition exceeds the capacity of the ebb-tidal prism to remove sediment from the entrance channel. Entrance closures often persist for months to years and can present a range of challenges for management including flooding and the deterioration of estuary water quality. Despite providing short-term flooding relief, artificial openings do not always persist for more than a day or two as large quantities of sediment are redistributed landward to rapidly rebuild the beach berm. Infill of the channel commences following removal of the hydraulic head between the estuary and the ocean following lagoon drainage. After drainage, the opening duration is controlled by the subsequent geomorphic conditions, specifically the balance between on and offshore sediment transport as a function of waves, tides, and river discharge. This study uses historical records of entrance opening duration at IOCE in Victoria to develop a method of predicting the probable entrance opening duration given the marine and fluvial conditions. The model is site specific and is validated against existing records of entrance monitoring. Predictive models are developed from historic data at each individual site and a Monte Carlo simulation is used to populate the model by simulating the possible combination of conditions that could occur. The outcome of this is a predictive tool that managers can use to input both the current and forecast conditions to predict entrance opening duration. This method will form a decision support tool for estuary entrance management that will also have the capacity to learn and improve in future. It can also provide a complimentary module to work alongside existing entrance management strategies.

Download Full Paper