A comprehensive risk assessment released by the South Dunedin Future programme paints a sobering picture of vulnerability amid climate change.
Among the findings is about half of South Dunedin is exposed to two or more hazards — such as groundwater, surface flooding, coastal inundation and erosion — and by 2100 most of the area is projected to be exposed to four hazards "under a high-end climate scenario".
"As this exposure and direct physical risk increases, the adverse consequences for South Dunedin’s buildings, infrastructure, and communities also increase to a point where much of the key infrastructure, functions and services experience declining functionality, loss of service, or complete failure," the report warned.
"These risks will have significant adverse effects on the South Dunedin community, Dunedin city and the economy unless appropriate risk mitigation is employed."
At the same time as the risk assessment was released last week, South Dunedin Future unveiled seven options for what might be done about the situation over the next 75 years.
Proposed approaches range from improving stormwater infrastructure to moving homes out of harm’s way.
A mix of responses could include creating space for waterways and wetlands, upgrading pipes and pumps and possibly elevating some land.
Each option has an estimated cost that runs into billions of dollars over 75 years, including for a status quo approach.
All — other than the status quo — would also produce benefits running to billions of dollars.
The status quo was estimated to have benefits tallying just $200 million.
Benefits for the other six options ranged between $2.3 billion and $4.5b, it was estimated by consultants.
The area — mostly low-lying and flat — is home to more than 13,000 people and hundreds of businesses.
Both the risk assessment and options report are to be discussed by both councils this week.
The risk assessment was described as building the case for change.
It was intended to support suburb-level adaptation planning, rather than providing a detailed property-level assessment of risk.
The councils said in a joint statement the assessment detailed "what is expected to happen in South Dunedin unless additional action is taken to manage the flooding".
A parallel mana whenua risk assessment found substantial risk from a "keep doing what we are doing" scenario.
South Dunedin Future programme manager Jonathan Rowe said the reports showed there was no "quick, simple, easy, obvious solution to South Dunedin".
"The challenges are complex, and the solutions are going to be as well."
There were also opportunities to reimagine how the area might best function and to adjust the environment or improve amenity, he said.
"While it might involve a lot of change, there’s enormous opportunity for South Dunedin not just to become safer, but also better."
