Calculating sediment contributions from highly modified catchments to a tidal inlet – Broadwater, Gold Coast, Australia

Ms Jemma Purandare1, Dr Nick Cartwright2, Professor Rodger  Tomlinson1, Dr Mark Gibbs3

1Griffith Centre For Coastal Management, Griffith University, Southport, Australia, 2School of Engineering, Griffith University, Southport, Australia, 3Institute for Future Environments, Queensland University of Technology, Brisbane, Australia

Abstract

The Broadwater is a semi-enclosed tidal inlet located on the northern Gold Coast, Queensland, Australia. The Broadwater is connected to the Coral Sea by the Gold Coast Seaway – a constructed entrance originally the mouth of the Nerang River, and is fed by the Nerang, Coomera, Pimpama, and Albert-Logan River catchments. These catchments are highly modified with extensive urbanisation and constructed canal estates in the lower reaches of the Nerang and Coomera Rivers, water control from weirs and dams, including the Hinze Dam in the upper Nerang River catchment, agriculture, including grazing and cane farming, and dense urbanisation of the lower catchment around Southport and Labrador. The Broadwater itself is a highly modified coastal environment, with the fixing of the Nerang River entrance, construction of the Gold Coast Seaway and sand bypass system on the Southport Spit, and continuous dredging of navigational channels, all contributing to significant hydrological and sediment transport dynamics over the past 40 years. The urbanisation and intense modification of the catchments and surrounding coastal environment have impacted sediment dynamics, and while the Broadwater, particularly the Gold Coast Seaway and nearshore coastal environments, have been relatively extensively studied, analysis of literature indicates that the sediment dynamics and contribution from catchments is relatively poorly understood.

This paper details an investigation into the sediment contribution of the catchments to the Broadwater, with the aim of providing a quantitative assessment and analysis of catchment sediment dynamics. The paper provides a summary of the literature reviewed in determining the gap in knowledge, methodologies employed for gathering data and conducting analysis, summary of the data collected and quantitative statistical analysis and associated results, and a discussion and conclusions relating to the findings.

Biography

Jemma is a Coastal Scientist with more than 13 years’ experience in coastal and estuarine geomorphology, sedimentology, and restoration. She is currently halfway through her PhD research investigating the changes to sediment transport dynamics in a highly modified tidal inlet that is subject to a sand bypass pumping system. Jemma also works with Gold Coast City Council as the lead scientist on multiple estuarine monitoring projects, and is also the Queensland State Chair of the Australian Coastal Society.

About the Association

The Australian Coastal Society (ACS) was initiated at the Coast to Coast Conference in Tasmania in 2004. The idea was floated as a means for those interested in coastal matters to communicate between conferences and where possible take resolutions of the conference to appropriate levels of government.

The idea was discussed further at the Coast to Coast Conference in Melbourne in 2006 and it was agreed that Bruce Thom develop a constitution of a company limited by guarantee that would operate on a national basis.

This plan was accomplished and in 2008 at the Coast to Coast Conference in Darwin the constitution was ratified and an Executive appointed. The company received charitable status in 2011.

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