ABSTRACT

Sedigh, M.; Tomlinson, R.; Cartright, N., and Etemad-Shahidi, A., 2016. Morphological evolution of the Nerang River Entrance ebb-tidal delta. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 238–242. Coconut Creek (Florida), ISSN 0749-0208.

The Nerang River entrance is a tidal inlet that connects the Pacific Ocean to the extensive Gold Coast estuarine system known as the Broadwater. Due to relatively fast northward migration of the inlet from 1920 to 1985 and the importance of having a safe navigable channel, the inlet was stabilized with two training walls in 1986. A sand bypassing system was implemented upstream with an average sand bypassing rate equal to the estimated net northward lonshore sediment transport in the area to prevent the formation of a bar across the entrance. However, historical analysis of survey data has shown an ongoing growth of the ebb-tidal delta at the river mouth. Thus, despite the sand bypassing system, costly dredging of the ebb-tidal delta is required to maintain safe navigation through the entrance. A number of studies have been undertaken to investigate sediment transport and hence morphological evolution. However, despite all the previous efforts, the cause of the ongoing ebb-tidal delta accretion is still not known with any degree of certainty. According to recent numerical modeling efforts, there is a considerable amount of longshore sediment transport leakage past the sand bypassing system, particularly during storm events. This paper will present a brief history of the dynamics of the Nerang River entrance since the early 1820s before reviewing historical sand volume analysis based on available survey data. An updated conceptual model will then be developed in order to better understand the morphological change in and around the Nerang River entrance area.

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