Sasha Alexander Zigic

Modeling the Effect of Flow Structure Selection on Residence Time in an Artificial Canal System: Case Study

A novel modeling approach was used to investigate the residence times of Oyster Cove, an artificial canal system connected to adjacent water bodies by unidirectional and bidirectional flow structures. A field program was carried out to evaluate and quantify the exchange of water through the system of flow structures and to gain an understanding of the mixing dynamics within the artificial canal. Results from the field program were also used to validate a three-dimensional circulation model and a flushing model used to quantify the existing residence time of the canal system. Finally, the model was used to compare several hypothetical design alternatives, to identify the effect on the canals residence time, by changing the positions of the flow structures and using different combinations of structures. The comparison showed the significant improvements in residence times that could be achieved.

Gold Coast Broadwater: Southern Moreton Bay, Southeast Queensland (Australia)

The Gold Coast Broadwater, a large shallow estuarine water body, is a central feature of the Gold Coast City in Southeast Queensland (Australia) and forms the southern part of Moreton Bay. The Broadwater has undergone dramatic changes over the past few decades, including the construction of an extensive number and network of artificial waterways that account for up to 90 % of Australias canal estates. Positioned in one of the fastest growing regions in the developed world, urbanisation surrounding the Broadwater will continue. The region has important biodiversity values that have led to areas of the Broadwater being listed as an international Ramsar site and inclusion to international migratory bird agreements. The Broadwater provides a vital function in the provision of feeding, spawning and nursery sites for recreationally and commercially important finfish species. Key to the protection of the Broadwater is a reduction of pollutant loads from urban and agricultural stormwater run-off, golf courses and industrial infrastructure/areas and replacement of natural habitats with urban development. Collectively, initiatives undertaken by regulatory authorities have been successful to date and demonstrate that future conservation requires the integration of multidisciplinary science and proactive management driven by the high ecological, economical and community values placed on the Broadwater and adjoining waterways.

Modelling the effect of flow structures on canal system residence time

A modelling study was carried out using separate 3-dimensional circulation model and flushing model components of WQMAP to investigate the residence times of Oyster Cove, an artificial canal system connected to the adjacent Saltwater Creek estuary, Gold Coast, Australia. The flow between the canal system and estuary is controlled via a system of uni-directional and bi-directional structures. To validate the circulation model and the influence of the flow structures, a detailed field experiment was carried out using flow meters, tide gauges and fluorescent dye. Following the validation process, the model was used to examine the existing mixing dynamics and residence time of the canal estate. Finally, the model was used to compare a hypothetical design alternative to the existing layout and quantify the effect on the canals residence time by changing the position of the flow structures and using different combinations of flow structures.