Modelling of bar morphological changes around Narrowneck artificial reef

Supervisor: Rodger Tomlinson (Grifith University, Australia)
Storms are frequent on the East coast of Australia, and waves induced by these events dissipate on the long sandy beaches of Gold Coast, creating erosion episodes which decrease the width of beach, impacting the tourist activity and the economy of the region. In 1999, Narrowneck artificial reef was built to address this problem and stabilise beach nourishment and limit the erosion of the coast under storm. Delft3D software and long term observation and measurement data were used together to model the behaviour and the morphology of sand bars at Narrowneck beach. Using ADCP in-situ data, deployed for two periods of three weeks each in April and May 2011, the model has been successfully calibrated in terms of wave and current features. The lack of available beach profile survey data with regards to space and time limited the opportunity for adequate morphological calibration. Therefore, two bathymetry surveys, 39 days spaced apart, have been conducted in the vicinity of the reef, in an area 850m offshore from the shoreline and 1.8km alongshore. Boat measurements were conducted using Ceescope surveying instrumentation and beach measurements were collected using a Leica RTK-GPS system for the creation of two reliable bathymetries of the area, suitable for sediment calibration. The model was configured for sediment transport, using the Bijker formulation associated with Bailard approach and the model was evaluated in 2 and 3 dimensions. Results from the sediment calibration using this recently collected field data are still being processed and reliable results are anticipated. The validation of this model will allow further projects studying the impact of storms on the beach, and inform management decisions regarding future maintenance of the artificial reef.