Stormwater solutions to protect south of city

STORMWATER from Dunedin’s hill suburbs could be diverted away from lowlying South Dunedin and water could be stored before it reaches the stormwater system to reduce pressure on the network.

Wetlands could be created, larger pipes installed or increased pumping provided as part of widespread improvements to reduce the risk of flooding.

The Dunedin City Council has budgeted $36.6 million for the next 10 years to reduce flooding risk in the greater South Dunedin area.

This includes $33.5 million of new capital expenditure.

It was not yet clear how that money would be spent, but groundwater and technical data was being gathered before decisions would be made.

Otago Regional Council and GNS Science were contributing to that work.

Dunedin City Council infrastructure services general manager Simon Drew said areas around Forbury Rd and Portobello Rd were key parts of the stormwater system that might need upgrades.

‘‘However, new information has shown that these areas are not the only bottlenecks in the system as previously thought, and therefore wider investigation is needed before any improvements in those areas are actioned,’’ he said.

The council had made some improvements since widespread flooding in South Dunedin in 2015, including replacing and improving infrastructure and better maintenance practices.

‘‘This includes a new $300,000 filter screen at the Portobello stormwater pumping station and the improved inspection, cleaning and maintenance of mud tanks.’’

South Dunedin was built on land reclaimed from a coastal wetland.

‘‘This means that groundwater is already close to the surface and that can make it hard for water to drain away when it rains,’’ Mr Drew said.

Climate change was expected to increase the flooding risks for the area.

‘‘The climatechange challenges are large and complex, but we believe there is time to respond and reduce the flooding risks in a careful and considered way,’’ Mr Drew said.

‘‘Investigations are under way into all the options and we hope to have an initial list of solutions in the 202223 year.’’