Lachlan Swamp, in Sydney’s Centennial Park, is one of the most ecologically significant landscapes in the city. The sensitive wetland environment includes a dense Paperbark Forest that houses Sydney’s largest grey-headed flying fox colony.

When the client Botanic Gardens and Centennial Parklands commissioned JN in 2021 to deliver the structural design for a new pedestrian boardwalk through this landscape, the brief demanded a durable and functional walk that had minimal impact on the existing ecosystem.

Every design decision had to balance structural performance, environmental responsibility and the practical realities of constructing within a live, protected habitat. Forefront was the specific work hours in which work could take place to minimise disturbance to the flying fox colony.

Sam Crawford Architects developed an elegant, curved boardwalk concept that was designed to avoid impacting the existing Paperbark trees. JN was tasked with translating that architectural vision into a structural design that was both efficient and suited to the persistent moisture and ecological sensitivity of the swamp environment.

The team worked through numerous conceptual framing layouts to accommodate the boardwalk’s curved geometry, a process that required close collaboration with the architect and extensive structural analysis before arriving at the final solution. Fibre reinforced plastics (FRP) were ultimately selected for both the floor framing and mesh floor grating, providing the corrosion resistance and long-term durability demanded by the wet swamp conditions while minimising the load and visual impact on the surrounding landscape.

For the foundations, screw piles were identified as the most appropriate solution, allowing the boardwalk to be anchored securely with minimal ground disturbance. This was a critical consideration given the ecological sensitivity of the site and the root systems of the Paperbark trees.

The scope of JN’s civil engineering services on this project extended beyond structural design alone. Detailed coordination with geotechnical specialists and the principal contractor was undertaken to ensure every element of the build could be executed with precision in a challenging and constrained environment.

The boardwalk delivered a safe, accessible and architecturally striking pedestrian experience through one of Sydney’s most remarkable natural environments. Importantly the project was delivered without compromising the integrity of the ecosystem it passes through.

Projects like Lachlan Swamp are a testament to what JN’s multi-disciplinary engineering team can achieve when technical rigour, environmental sensitivity and genuine collaboration come together. Where hydraulic engineering and structural considerations intersect in complex natural environments, JN’s integrated approach ensures that every element of the design is considered in its full context.

Watch a video overview of the swamp.

JN Team

JN Project Manager and Structural Engineer: Mark Williams

JN BIM Technician: Rod Lawrence

Client and Collaborative Partners

Client: Botanic Gardens and Centennial Parklands Sydney

Architect: Sam Crawford Architects

Structural Engineer: JNGeotechnical Douglas Partners

Principle Contractor: Civilcraft Pty Ltd

Screw Piling Contractor: Australian Piling Contractors

FRP supplier: Treadwell Group.