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COASTAL ENGINEERING NOMINEES
MAROOCHY GROYNE PROJECT
Sunshine Coast Council
Sunshine Coast Council’s $2 million Maroochy Groyne Renewal Project (Stage 1) renewed two groyne structures and the seawall surrounding the Cotton Tree Holiday Park at Maroochydore. Driven by failing assets the project was the result of extensive planning by Sunshine Coast Council, including a 10-year Shoreline Erosion Management Plan (SEMP) developed in 2014. The project was required to protect the iconic park and other valuable assets in the surrounding Cotton Tree precinct (including recreation areas, businesses, accommodation and residential properties) from erosion, and was an Australian first for using 9 tonne geotextile bags. Over 2,000 sand-filled geotextile containers were used. Facing significant community and political interest in groyne replacement options, the project involved extensive community consultation including establishment of a community reference group (the Maroochy River Estuary Consultation Group) which continued to work with Council after the initial consultation period on design options and testing, and wider community engagement. The project was delivered by a cross organisational team, with continuity of involvement for each project phase drawing on project management and coastal engineering expertise throughout. It employed a design which was informed by comprehensive research and physical modelling of different design structures and onsite testing, undertaken with industry specialists at the Water Research Laboratory at the University of New South Wales. This research, combined with coastal engineering principles and a sound understanding of the Maroochy River’s natural migration processes, delivered a successful project and infrastructure that will serve the community for decades to come.
SURFERS PARADISE SAND BACKPASS PIPELINE PROJECT
City of Gold Coast Council
The Surfers Paradise Sand Backpass Pipeline project is a 7.8 kilometre sand delivery pipeline which is due for completion in November 2021. This pipeline will deliver natural sand from The Spit and deposit it on the Gold Coast’s iconic northern beaches to provide protection from coastal erosion and maintain beach amenity for residents and visitors. Once completed, 6.3 kilometres of permanent pipe will run underground and connect to 1.5 kilometres of temporary above-ground pipe to deliver sand from the existing Gold Coast Waterway Authority’s Sand Bypass Jetty at The Spit onto the upper northern beaches from Surfers Paradise to Main Beach. The Gold Coast northern beaches are regularly impacted by large waves, storms and king tides, compromising foreshore infrastructure and beach amenity. This pipeline will enable the City to conduct annual renourishment campaigns, proactively increasing the resilience of this section of coastline. The pipeline is able to redirect up to 20 per cent or approximately 120,000 cubic metres of the sand transported via the sand bypass jetty to South Stradbroke Island each year. The Surfers Paradise Sand Backpass Pipeline is an important long-term investment in maintaining our beaches and supports all of the strategic outcomes of the City’s Ocean Beaches Strategy.
Moreton Bay Regional Council
MBRC have successfully delivered a technically innovative, environmentally friendly, and aesthetically sympathetic coastal cliff stabilisation solution on the Redcliffe peninsular. The Scarborough Cliffs Stabilisation Project was initiated by MBRC to address persistent coastal cliff erosion, including public safety risks plus risks to infrastructure, along a 320m stretch of the Redcliffe coastline. MBRC also identified the need to protect the character of the cliffs given that the Redcliffe peninsular name, given by Lieutenant Matthew Flinders in 1799, derives from its iconic red cliffs. Long-term monitoring, including periodic terrestrial laser scanning, identified lower cliff erosion, due to the actions of tides and waves, as a key driver of the persistent erosion and subsequent localised cliff failures. Multiple options were investigated to address the lower cliff erosion, ranging from conventional rock armour seawalls to novel largescale precast blockwork walls. An innovative concept solution was put forward by MBRC’s design consultant, entailing a coloured and textured, soil-nailed, glass-fire reinforced polymer (GFRP) reinforced shotcrete seawall. This innovative solution was designed to best mimic the natural form and aesthetic of the natural cliff, whilst protecting the lower-cliff from erosion, minimising the footprint of the structure and maximising the durability and resilience of the wall. The design was further developed by the design consultant in close collaboration with MBRC and other project stakeholders. The construction works, which occurred predominantly within the environmentally significant Moreton Bay Marine Park, were successfully completed in 2020.
HOLLOWAYS BEACH STABILISATION
Cairns Regional Council / BMT / GHD
Holloway’s Beach has historically experienced coastal erosion that has progressed to levels prompting protective works and increased shoreline erosion management. These previous measures have included a rock revetment, installation of a geotextile sandbag groyne and multiple beach nourishment campaigns. However, the threat of erosion to Holloways Beach persists, with long-term recession trends apparent in some areas, indicating that these measures are no longer effective and need to be improved or replaced with more suitable options. As a result of this, Cairns Regional Council have implemented an updated and improved shoreline erosion management plan. This plan included the construction of two 30m rock groynes, combined with an updated nourishment plan. The end product of these actions helps to maintain shoreline position south of the groynes and maximise the benefits of future nourishment campaings at Holloways Beach. The chosen action plan has also been tailored to minimise damages to land, community disruption and short and long-term costs, as well as maintaining recreational use of the beach. Sand recycling south of the two groynes will maximise the potential benefit while also reducing the initial quantity of sand required. This change in sand nourishment methodology resulting from the construction of the groynes offers both increased flexibility and a significant reduction in ongoing operational costs.
