The Gosford Beaches Coastal Zone Management Plan was prepared in line the state government legislation, and in consultation with the Central Coast community. The plan was certified by the Minister for the Environment in May 2017 and guided coastal management by describing the issues, the relevant actions and assigning responsibilities. Council is currently preparing new Coastal Management Programs as required under the Coastal Management Act 2016.

The Gosford Beaches Coastal Zone Management Plan (2017) included an action M1 – Erosion Protection works for Surf Club which detailed that the works may comprise of engineered rock revetment works constructed along the face of the existing in front of the surf club.

Council initially investigated a design for a typical rock revetment, however due to site constraints and design requirements, it would have extended far onto the beach with a large footprint.

Further consultation with stakeholders and coastal engineers, identified a preference for a temporary structure comprised of rock bags, which could achieve a reduced footprint, provide a cost-effective solution and can be easily modified, repaired or removed as required.

Completing the works would help protect the MacMasters Beach Surf Life Saving Club, existing Norfolk Island Pines and Aboriginal heritage from coastal erosion and storm impacts.

The temporary nature is defined by the relatively short design life and chance the structure being damaged during severe storm events that exceed its design standard. This is in line with guidelines for temporary coastal structures and the compromise was required to reduce the overall size and footprint of the structure and considered the relative ease of completing maintenance and repairs if storm damage were to occur. However, the structure could remain, if not completely damaged by a severe storm, until the bags start to reach the end of their life and show signs of deterioration, which could be decades based on the supplier advice.

Rock bags are an innovative flexible mesh bag made from recycled polyester that can be filled with rock (between 50mm – 175mm) and used for scour and erosion control. Suppliers advise that rock bags have a proven lifespan of over 35 years, and even longer when covered either by water or soil / sand / vegetation. For more information, please visit https://www.bluemont.com.au/erosion/rock-filter-bags/.

Typical rock revetments in open coast locations are sloping structures constructed on the beach to provide protection from erosion caused by wave action, storm surge and currents. Usually, they are constructed with a primary armour, consisting of very large, durable rock, and a secondary armour or filter layer.

To ensure that there are no impacts to Aboriginal heritage, the draft design has been prepared to ensure that no excavation into the existing slope would occur. Additionally, registered Aboriginal parties were consulted and a cultural heritage management plan would outline further construction related measures to mitigate any potential impacts. An Aboriginal Heritage Impact Permit (AHIP) would also be required for the works to proceed.

Due to community concerns about surf amenity and beach access regarding an early design for a typical rock revetment, alternative concepts were investigated by qualified coastal engineers and with the involvement of key stakeholders.

This process involved consideration of a revised rock revetment, temporary solutions and vertical options. However, each of these solutions all have their own limitations:

- Revised sloping/typical rock revetment: although this option could provide a high level of protection over a long design life and the footprint could be slightly reduced from the initial design, this option was not acceptable to stakeholders due to concerns relating to the still extensive footprint required and the seaward position having the potential to impact beach access and coastal processes.

- Vertical wall options, including low and full height concepts: The vertical options would allow the structure to be located further landward and have a reduced impact on access along the beach, however, they are also significantly more expensive. Their application on narrow beaches such as this can also be problematic, potentially creating safety concerns during storms (difficult to escape the beach as waves approach and impact the wall), the more significant visual impact they pose and increased potential for wave reflection and scour in front of the wall.

- Temporary structure comprised of rock bags: Although this option would not provide as much protection to landward assets as the other options, it has a significantly reduced footprint and impact on beach access and amenity (compared to a typical rock revetment), and a reduced risk of wave reflection (compared to vertical structures).

Although there is no perfect solution for managing coastal erosion problems, the temporary structure comprised of rock bags was recognised as the most balanced approach as it would:

- Extend less onto the beach than a rock revetment and therefore be least likely to affect the surf break and beach access.

- Flexible approach that allows for the rock bags to be moved, and maintained with relative ease, or removed if adverse impacts from their installation are experienced.

- Provides a reasonable level of protection to the surf lifesaving club from coastal erosion, except for very severe storms. No option would provide protection to the area landward of the ramp.

- Provides a temporary solution while the longer-term management of MacMasters Beach and risk from coastal hazards can be investigated.