South Dunedin councils split flood plan into two tracks

Dunedin City Council and Otago Regional Council have outlined the next phase of the South Dunedin Future programme, splitting the work into near-term infrastructure planning and longer-term adaptation planning.

The revised approach follows council decisions to examine an engineering-focused "pipes and pumps" option and to account for government direction on climate adaptation planning.

Under the first workstream, the councils plan to prepare a 30-year infrastructure investment package for South Dunedin. It would build on stormwater work already under way and identify priority projects for the next five to 10 years.

This stage would include additional modelling, design work and constructability assessments. The goal is to refine a list of 10 to 15 flood protection projects already identified through the South Dunedin Future programme.

It would also sit alongside Dunedin City Council's existing three waters work, including three stormwater projects in a NZ$29.2 million package approved by the city council. The aim is a sequenced, costed programme setting out the level of flood protection each project would provide and how projects could be staged over time.

The investment package is also intended to remain compatible with a range of longer-term adaptation approaches. It is expected to inform deliberations on future long-term plans, as well as the city council's Infrastructure Strategy and Water Services Strategy.

Two tracks

The second workstream would examine adaptation pathways beyond the first 30 years. It would revisit and refine the longer-term futures already developed through the programme to reflect council feedback and government policy direction.

Those revised futures are expected to represent different approaches based on infrastructure investment, nature-based solutions and land-use change. They would also include the proposed engineering-focused "pipes and pumps" option, either as a supplement to or replacement for one of the three futures previously developed.

The revised options would be tested against a range of climate scenarios. The assessment is expected to provide more detail on benefits, costs, levels of protection and any potential property acquisition.

Another aim is to show how infrastructure spending over the next 30 years could support different long-term pathways. The link between immediate works and longer-term adaptation has become a central issue in the debate over how South Dunedin should respond to flood risk.

South Dunedin has faced repeated concern over flooding and climate exposure, prompting years of planning on how to manage water, infrastructure and land use in one of the city's lowest-lying urban areas. The South Dunedin Future programme has been considering options for the area across councils and communities.

Dunedin Mayor Sophie Barker said the split approach would allow progress on immediate work without closing off longer-term choices.

"South Dunedin communities have told us they want to see progress on reducing flood risk while also ensuring longer-term adaptation options are thoroughly tested. This approach allows both to happen at the same time. Councils can continue progressing work on immediate infrastructure needs while taking the time to carefully assess longer-term options and understand their costs, benefits and implications," Barker said.

Decision path

A proposed infrastructure investment package for the next 30 years, including priority projects for the first five to 10 years, is expected to go before Dunedin City Council councillors as part of long-term plan deliberations. If backed, it could then be included in a draft long-term plan for public consultation.

Advice on the second workstream is also being prepared for both councils. It is expected to cover how the long-term adaptation futures should be revised and how the engineering-focused option should be included.

Otago Regional Council Chair Hilary Calvert said elected members were seeking fuller analysis of the trade-offs involved.

"Councillors need more information about the options available to reduce flood risk in South Dunedin, the benefits and costs involved, and the trade-offs associated with different approaches. This next phase of work will provide that information, enabling councillors to make informed decisions about both near-term infrastructure investment and longer-term adaptation planning," Calvert said.

The revised programme marks a shift in emphasis rather than a complete reset. Existing flood protection work remains in place, but the councils are now trying to separate decisions about projects that can be advanced in coming years from decisions about what the area may need over a much longer timeframe.

That distinction may prove important as local authorities across New Zealand grapple with climate adaptation, infrastructure costs and the question of how much protection can be provided in vulnerable urban areas. In South Dunedin, the next stage will test whether councils can advance practical flood works now while preserving room for different long-term responses, including major engineering intervention, nature-based measures or land-use change.