Hydrodynamic, Water Quality and Sediment Transport Modeling of Estuarine and Coastal Waters on the Gold Coast Australia

There is an increasing demand for knowledge about hydrodynamic, morphological and water quality processes within the estuarine waterways of the Gold Coast. This study describes the development of a suite of hydrodynamic, sediment transport and water quality models for the Gold Coast tidal waterways. The modeling framework described was developed to provide a strategic understanding of waterway behaviour at a level appropriate for planning and environmental impact assessment in addition to guiding strategic decision making. The model simulations are based on DHI’s two-dimensional flexible mesh code, MIKE21 FM. The hydrodynamic equation is linked to a set of transport-dispersion (transport module) equations that are solved using the flow field generated by the hydrodynamic model. This transport module establishes connection between heat, salinity, tracers and turbulence parameters and hydrodynamic. It also provides a base for water quality and sediment transport modeling. Water quality modeling is achieved through development of required process module. Process module is constructed using templates that the ECOLab interface provides. The process module describes the flow of N, P and C between the various trophic forms. The external factors, such as salinity and temperature, which govern the variations of the components in time and space, are made available to processes through a link with the hydrodynamic module. The current induced sediment transport and the associated morphological evolution in the study area were simulated by the sediment transport module of the software. The transport rates and the morphological evolution are calculated on the same flexible mesh that was used for hydrodynamic and water quality modeling. The resulting estuarine model framework has been applied to a number of specific issues such as recycled water discharge and waterway assimilative capacity. Future applications include modeling of extreme events under climate change.