The joint DCC-ORC South Dunedin Future programme has today released two major reports which analyse the risks facing the low-lying area and options for responding to them. The reports are key building blocks for making a long-term climate adaptation plan. 

South Dunedin Future programme manager, Jonathan Rowe, says “this is a major milestone after several years of technical work and community discussions.”

“Not only do we have a better understanding of the challenges South Dunedin will face in the future, we now have a full suite of potential responses,” Mr Rowe said.

Report 1 – Risk Assessment

The South Dunedin Risk Assessment brings together the first comprehensive picture of the flood-related challenges facing the area. 

It analyses the risks presented by a range natural hazards like surface flooding, coastal inundation, and shallow groundwater, illustrating these down to a city block level. It shows that the overall flood risk is already high for a large part of the area known as The Flat and this will increase over the next 75 years with climate change. 

Half of all South Dunedin buildings are at risk of rainfall flooding now, and this rises to up to almost 70% by 2100. The assessment details what is expected to happen in South Dunedin unless additional action is taken to manage the flooding.

ORC Manager Natural Hazards, Dr Jean-Luc Payan, says “The risk assessment is a snapshot in time using the best available information. It will be updated as new data and information comes to hand. It is primarily intended to support suburb-level adaptation planning, so we can test how effective various adaptation options are at reducing risk.”

Report 2 – Seven Potential Futures

The second report, Potential Adaptation Futures, identifies and analyses seven possible futures for the area, with a status quo ‘doing nothing’ option, and a further six options along a spectrum of ‘fight and flight’. One end of the spectrum involves investing heavily in new infrastructure, the other end involves moving people out of the worst affected areas, with options in between involving a mix of actions.

A visualisation has been created for each future showing what South Dunedin could look like in the year 2100.

“The potential adaptation futures show there are a range of things that we can do to make South Dunedin both safer and better. This includes building new infrastructure, creating streams, parks and wetlands, and moving people out of harm’s way,” Mr Rowe says.

“Some of those options look very different to how South Dunedin is now – and could involve a lot of change. Change would bring challenges, but also some exciting opportunities.  We will talk with the community about the trade-offs involved with each future.”

Future 1 is a continued status quo for the next 75 years. It shows that if we keep doing what we’re doing it is likely to increase the flood risk and lead to the worst overall outcomes, with an estimated cost of about $2 billion by 2100, high risks and negative social effects, with very few benefits.

Futures 2 – 7 each adopt a different mix of infrastructure and managed relocation. The estimated cost of implementing these futures ranges from $2.8 billion to $7.1 billion (over 75 years) and have benefits of up to $4.5 billion. The costs and benefits of these don’t sit just with councils, they would be shared across Government, insurance, banks, businesses, property owners and the people of Dunedin.

In 2023, the South Dunedin Future programme developed 16 approaches that could be used. Following feedback of more than 500 residents and technical analysis, these approaches were combined in different ways to develop the seven potential adaptation futures released this week.

Next steps

Both reports will be put to the Dunedin City Council and Otago Regional Council for consideration next week. Councillors will be asked to endorse the reports for consultation with affected communities, planned for April and early May.

This milestone has been welcomed by the leaders of both councils.

"It’s great to see this important work reach this stage where communities have a clear picture of the risks and a sense of how the future could look for South Dunedin. I look forward to discussing the reports with councillors next week,” said Dunedin’s Mayor Jules Radich.

"It’s pleasing to see latest reports blending technical science and engineering expertise with wide community engagement. This information will empower informed decisions as communities plan for a resilient future,” said ORC Chair, Gretchen Robertson.

Further phases of more detailed technical and economic work are planned to refine the seven futures down to a preferred option, a process that would include further community engagement. A final adaptation plan is on track to be agreed by the end of 2026.

“This is a process which takes time, but it’s important that we hear the community’s views, and use the best available science, engineering, and planning to identify the best way forward. Alongside the long-term focus of the South Dunedin Future programme, there is also more immediate work happening to address more present day issues in South Dunedin,” Mr Rowe says.

Other work to address issues

In the short-term, the DCC is planning to spend $29 million dollars on three pipe and pumping projects around South Dunedin which together are expected reduce the extent of flooding by between 10% to 20%.