The City of Onkaparinga wants your say on the development of a plan for long-term responses to the risks of rising seas in the region, while a council-first project to retreat a clifftop car park gets underway.
The proposed Coastal Adaptation Plan aims to take action to help Onkaparinga’s coastal communities, infrastructure and ecosystems to adjust to the impacts of climate change, particularly sea-level rise.
It will respond to the recommendations of council’s 2021 Coastal Adaptation Study, which detailed the level of risk along 12 distinct sections of Onkaparinga’s coastline.
You can have your say at council’s Your Say Onkaparinga page until Sunday 3 September, and at three public forums at Moana Surf Life Saving Club (Thursday 10 August), Christies Beach Surf Life Saving Club (Wednesday 16 August) and Aldinga Library (Thursday 17 August)—register for your free spot via Your Say.
Following consultation, the council will develop the Coastal Adaptation Plan, with the community to have further opportunities to provide feedback on the draft in early 2024 before the final plan is expected to be released in mid-2024.
Ynys Onsman, Manager Strategy, Sustainability and Economic Growth, says the City of Onkaparinga has been taking action on coastal adaptation for decades.
“The coastal adaptation plan will help us to stay ahead of the game and to work in partnership with other spheres of government and the community,” she says.
“Our 2021 Coastal Adaptation Study shows that, because most of our coastline is elevated, flooding is likely to be limited but our main challenge will be responding to erosion issues.
“It also shows impact is more likely to be on public rather than private assets, especially in the short to medium term.”
The council’s Coastal Adaptation Study, produced by independent coastal experts, identified potential risks to the region’s 31km coastline arising from sea-level rise, which is projected to accelerate after 2050, as well as from storms and sea surges.
While risks vary across the coastline, overall the region faces the following:
- sea-water flooding in a limited number of areas
- some pockets of erosion on a coast that is rated as moderate to high erodibility
- recession of beaches and soft-sediment cliffs
- possible impact on some public assets like reserves or walking trails in the short to medium term
- impact on private infrastructure, public safety and ecosystems in the longer term.
A coastal adaptation plan will address the issues, identify options to manage critical risks and actively monitor other risk areas.
Adaptation may take a number of forms: moving or building assets away from the risk area, modifying services and assets on the coastline, strengthening natural defences through sand and vegetation, building infrastructure such as sea walls, or retreating from damaged areas.
Coastal adaptation action already undertaken by the council includes activities such as replenishing dunes, managing outlet flows from rivers and creeks, revegetating cliffs, installing sandbag groynes, and building geofabric sea walls and rock sea walls.
Carpark retreating project underway in Seaford
One coastal adaptation project already underway is a carpark retreating project on the Esplanade at Seaford, opposite Tiller Drive, which addresses erosion issues impacting the existing clifftop infrastructure.
The project, which began on 14 June and is expected to be completed in early spring, involves:
- retreating infrastructure to allow for cliff erosion
- reduction and relocation of existing carpark, including new kerb and asphalt
- relocation of shared-use path
- relocation of fencing, lookout area, shower, and furniture
- planting of new vegetation.
The project follows community consultation in March and shoreline analysis undertaken in council’s Coastal Scoping Study, which provided evidence that retreat of infrastructure is a viable first option for the area to address the cliff’s long-term erosion.
The erosion over the past 60 years has been caused by waves at the cliff’s base, and groundwater discharge mid-slope, which have increased the steepness and instability of the cliffs, accelerating the erosion.
By retreating the infrastructure, cliff recession will continue and steep slopes can find an equilibrium (less steepness), so the council can maintain the natural and cultural values of this important coastal environment.
The project’s coastal location brings with it particular significance to local Traditional Owners, and council staff have been working with the Traditional Owner members of its First Nations People Advisory Group (FNPAG) to learn more about this significance.
Through this collaborative approach, shared understandings are developing regarding the cultural significance of the coastline and how to protect this as council upholds its responsibilities to also protect public amenities from the ongoing natural threat of coastal erosion.
The final design of the new shared path segment will play a storytelling role in the form of artwork stencilled into the concrete path, recognising the strong Kaurna heritage associated with the location.