Coastline retreat favoured

Some retreat from Dunedin’s coastline is emerging as a favoured long-term approach for managing the beach between St Clair and St Kilda.

However, engineering work will be needed in the short term.

Broad approaches and options for management interventions have been outlined in the draft plan for the coast between St Clair and St Kilda, which was released for public feedback yesterday.

The plan signals the part of the coastline most urgently in need of attention is beside the old landfill under Kettle Park, at Middle Beach.

Old materials there are at risk of being exposed by erosion.

Middle Beach has been identified as the area that will likely first need to depart from existing approaches, described as temporary fixes and largely reactive.

The plan described four high-level management approaches for the coast between St Clair and St Kilda and two appeared to be unsuitable — simply allowing nature to take its course or carrying out works to push the coast seawards.

One approach was called ‘‘coastal setback’’, described as undertaking works to accommodate coastal processes and allowing the sea to move landward.

‘‘We are not suggesting that the entire stretch of coast needs to be set back soon, but rather that in time some form of coastal setback is likely to be of value,’’ the draft plan stated.

‘‘The coastal setback approach most closely aligns with the vision and management objectives established in this plan and offers the best option to develop a natural and resilient coast for the long term.’’

An approach labelled ‘‘hold the line’’ would be needed in places, at least in the interim.

‘‘This approach potentially commits to a future of maintenance and engineering work, but could meet the needs and aspiration for improved access and amenity over a shorter time scale.’’

Council coastal specialist Tom Simons-Smith said key short-term actions proposed in the draft plan included improving public access points to the beach, plantings and sand stockpiling to help in storm responses.

There would also be ongoing monitoring and modelling to help shape longer-term management decisions.

Management options have been critiqued in the draft plan.

Existing defences ‘‘do not meet the needs of the community and the effects of climate change will increase the risk’’.

A new or upgraded seawall at St Clair could improve access, but would require ongoing maintenance and upgrades.

Offshore structures could be costly to construct and could affect surf amenity.

Multiple groynes might be needed to be effective in retaining sufficient sand.

Importing sand to replenish beaches could be expensive and disruptive.

Enhancing dunes would support resilience, but some retreat would be needed.

Coastal setback, considered to be the approach most closely aligned with community aspirations, would allow more space for the coast to respond to natural events.

However, it would require changes to land use and substantial lead-in time to implement.

Dunedin Mayor Aaron Hawkins said the draft plan had been shaped by extensive community engagement and input from technical experts over the past two years.

‘‘The St Clair to St Kilda coastline is highly valued by many different people for many different reasons,’’ Mr Hawkins said.

‘‘How the coast is managed in the future ideally needs to align as closely as possible with how people value the space and want to use it.’’

grant.miller@odt.co.nz