The City conducts bi-annual coastal monitoring profiles at several key locations within the City, including Tern Bank, the Bent Street Navigation Channel and the Safety Bay Foreshore. Monitoring is conducted prior to, and after the winter season to determine the volumes of sand that have accreted (accumlated) over the winter period and to determine the best actions for the management of Tern Bank.
Tern Bank is a naturally accreting sandbar extending from the Safety Bay Foreshore. It's name comes from the Fairy Terns which nest on the bank, typically in the warmer months of November and December.
Fairy Tern feeding on Tern Bank
Sediment sources for the formation of Tern Bank are still uncertain with limited studies conducted on the potential sediment transport pathways.
The sandbar typically experiences rapid growth over the winter months with prevailing north to northwesterly winds, and remains relatively stable over the summer period with the prevailing southeasterly wind.
Tern Bank falls within the Shoalwater Islands Marine Park and is managed by the Department of Biodiversity, Conservation and Attractions (DBCA). Under an agreement between the City and the DBCA, the City manages the body of water between Tern Bank and the Safety Bay Foreshore (the Pond) and the Bent Street boat ramp navigation channel footprint.
The City conducts bi-annual coastal monitoring profiles at several key locations within the City, including Tern Bank, the Bent Street Navigation Channel and the Safety Bay Foreshore. Monitoring is conducted prior to, and after, the winter season to determine the volumes of sand that have accreted (accumulated) over the winter period and to determine the best actions for management of Tern Bank.
Furthermore, in 2024/2025, the City undertook the Warnbro Sound Modelling Project to improve understanding of coastal processes and to develop sustainable management solutions for the Warnbro Sound coastline, including Tern Bank.
In 2024/25, the City undertook the Warnbro Sound Modelling Project, drawing on long-term shoreline movement data, metocean and seabed analysis, and advanced numerical modelling. The study concluded the following:
- Continued excavation of Tern Bank to support boat launching and retrieval is not sustainable.
- Regardless of future excavation or dredging of the Tern Bank/Bent Street navigation channel, the condition of 'The Pond' will continue to deteriorate and eventually infill with sediment.
Based on these findings, the City Council has recommended discontinuing boating operations at the Bent Street Boat Launching Facility and repurposing the area to align with natural coastal processes.
Tern Bank previously provided sheltered waters for recreational activities such as kite surfing and boat launching. The City has managed the sandbar through a combination of land-based excavation and dredging using a cutter suction dredge. However, continued accretion of the sandbank has led to the closure of the Bent Street Jetty. Furthermore, recent numerical modelling of the area predicts a possible closure of the pond in the near future due to ongoing sedimentation.
Sand inundation into the Bent Street Boat Ramp Navigation Channel reduces channel depth, creating navigational safety hazards. To maintain operational requirements, periodic civil dredging works were necessary. Sustaining access to the boat ramp requires sediment removal at an average excavation rate of 20,000 m³ per year to keep pace with ongoing accretion.
However, dredging is costly and disrupts the natural littoral sediment transport system, which otherwise contributes to the resilience of the Rockingham coastline. Based on findings from the recent numerical modelling study, the City has opted to allow natural coastal processes to proceed without further intervention. As a result, the Bent Street Boat Ramp will no longer remain operational, and the facility will be removed and repurposed.
Sand accretion and growth of Tern Bank is expected to continue. The rate at which this occurs will be determine by weather patterns, in particular the frequency and strength of winter storm events. Future management of Tern Bank falls under the City’s Community Plan and associated strategies.
The City of Rockingham engaged a coastal modelling consultant to investigate the unique processes of accretion and erosion occurring within Warnbro Sound. The modelling results indicate that, over the long term and irrespective of management interventions, the spit will degrade, the Pond will infill, and sediment from Tern Bank will redistribute along the northern shoreline of Warnbro Sound, ultimately smothering the Bent Street Boat Ramp. Given the projected evolution of Tern Bank and in line with the recommendations of the modelling report, the City has resolved to remove or repurpose the Bent Street Boat Ramp, allowing natural coastal processes to proceed unimpeded at that location.