Navigating the novel design and implementation pathway of the Amity Point flow slide barrier

Abstract

The township of Amity Point is located at the north-east of Minjerribah (North Stradbroke Island), Queensland, Australia. Redland City Council engaged Water Technology (WT) to conduct a Shoreline Erosion Management Plan (SEMP) with a 20-year planning horizon at the site. The foreshore is subject to retrogressive flow slides, while still the subject of significant research efforts, it is understood that these are due to the shifting nature of the 20m deep Rainbow Channel adjacent to the shoreline, causing a underwater bank steepening and eventual trigger of a flow slide event. Private property owners have historically defended their properties by placing (mainly) rocks from a local quarry at the foreshore into the breach created by the retrogressive flow slides. The SEMP recognises this historic protection, and its effectiveness of halting the ingress of retrogressive flow slides. As such, the SEMP recommends continuing to formalise, upgrade and maintain the structure to appropriate engineering standards. The structure is known as the Flow Slide Barrier (FSB), and is thought to be the first purposeful engineering design of a coastal structure intended to halt retrogressive flow slides in Australia. The complexity around the implementation of the FSB is due to the many stakeholders involved, as well as inclusion of legal implications around Native Title determination and maintenance obligations of the FSB. During this process specialised disciplines such as coastal law, community engagement and coastal engineering must collaborate to cover all aspects. A technical and legal review was conducted to ensure the engineering works are feasible and suitable as well as manageable for all involved stakeholders. The plan recommends for the local residents to manage the Flow Slide Barrier individually rather than managed by Council, however with Council assistance on delivering preliminary approvals and design documentation for local residents to utilise. The presentation will discuss the key design and approvals decisions made to implement the FSB.