However, it appears unlikely to be endorsed as a quick fix.
The Dunedin City Council might instead look to divert some stormwater directly to the Portobello pump station, increase the size of the Forbury Rd aqueduct, and disconnect the Hillside Rd mains to instead push stormwater to the Orari St outfall through a new pump station.
Or it may hold off on adding interim remedies to the capital programme until a climate adaptation plan is finalised in 2026.
A long-term approach for responding to climate change and boosting resilience is being worked on through the South Dunedin Future programme, but adaptation options have yet to be selected, and implementation is not due before 2027.
This seemed to beg questions about what might be done in the meantime to alleviate flooding risk, so long as this did not compromise what might be done in the medium or long term.
A series of options covering possible measures in the short term has been put in front of councillors ahead of a meeting this week about the council’s 2025-34 draft long-term plan.
A report for the council highlighted South Dunedin was exposed to natural hazards and climate change would likely increase flooding risk over time through sea-level rise, rising groundwater and increased frequency and severity of storms.
A risk assessment and adaptation options are due to be presented to the city council and Otago Regional Council in March.
"While it will be a further two years until completion of the South Dunedin adaptation plan, sufficient technical work has now been undertaken to identify some short-term actions that could support flood alleviation irrespective of what long-term option is eventually adopted," the report for the city council said.
The council used computer modelling to test nine options against a base scenario of a one-in-10-year rainfall event lasting six hours in a future time period after further climate change.
A detention pond at the former Forbury Park raceway, bought by the council last year for $13.2m, could reduce flooding volume by 21% and flooding area by 15%, the modelling indicated.
However, there would be high cost for the benefit achieved, the report noted.
A $25m detention pond at Bathgate Park would have about half the impact.
The report suggested there was some potential for government funding, although a regional infrastructure fund provided mainly loans, rather than grants.
The fund "could be a potential part-funding source for some of the options presented in this report, including water detention at Bathgate and Forbury Parks".
The council grouped together three options as a plausible short-term package that could cost $29.2m.
Diverting water from the Bay View Rd and New Rd stormwater systems to a new pipe directly to the Portobello pump station was considered the most cost-effective option, although its impact would be minor.
Doubling the size of the Forbury Rd aqueduct from Hillside Rd to the outfall at Second Beach could reduce flood volume by 9% and flood area by 8%, modelling indicated.
Disconnection of the Hillside Rd mains and pumping to the Orari St outfall would be more complex and would require installation of a new pump station.
This $15.3m option could reduce flooding volume by as much as 19% and flood area by 11%, the modelling suggested.
Council staff put up two broad options for councillors to consider - one was to provide additional funding to implement short-term options, and the other was to wait for the South Dunedin Future adaptation plan.
