Stormwater management plans needed, DCC hears

Stormwater management plans for housing developments are crucial to help mitigate the dangers of flooding on the Taieri Plain, a Dunedin City Council (DCC) hearing panel heard yesterday.

Otago Regional Council (ORC) staff members presented its submission to the second generation plan variation 2 panel, with flood management the central concern presented.

ORC policy and planning manager Anita Dawe said her council broadly supported the DCC’s position with regards to infrastructure, and were in favour of applying new development mapped area (NDMA) overlays in rezoned areas.

She said it was important that the panel understood that the ORC’s infrastructure was designed for land drainage and flood management, and was not designed for stormwater.

"For us one of the benefits of NDMAs is that that stormwater management plan comes in with the application rather than being a condition of consent."

The ORC position was that all developments should have a stormwater management plan.

"At the moment the rule is to have one where appropriate, we consider always its appropriate."

ORC natural hazards manager Dr Jean-Luc Payan presented a series of photographs to the panel to illustrate the ORC’s network of flood banks, spillways and ponds on the Taieri Plain.

Dr Payan said that while the system was not designed for stormwater, a lot of stormwater outlets still discharged into it.

In written evidence he tabled to the panel Dr Payan said subdivision, use and development of land impacted on stormwater runoff, particularly on greenfield sites.

Generally, such activities would result in increased peak flows, runoff volumes and runoff speeds.

It was important that the stormwater management approach ensured personal safety, minimised the risk of surface flooding, protects property from inundation, ensured the resilience of infrastructure and minimised adverse environmental effects from stormwater runoff, and did so for likely future climactic conditions.

The hearing will reconvene at 10am this morning for the DCC reporting officers’ right of reply.


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