Flooding solution found for Flockton

The Christchurch City Council hopes a $26.2m flood mitigation plan will help avoid scenes like this in Flockton Basin.
IAIN MCGREGOR/FAIRFAX NZ

The Christchurch City Council hopes a $26.2m flood mitigation plan will help avoid scenes like this in Flockton Basin.

Christchurch City councillors have agreed on a long-term fix for Flockton Basin's flooding woes.

After a lengthy discussion on Thursday they voted unanimously in favour of spending $26.2 million on widening sections of Dudley Creek, adjacent to Stapletons Rd, and building a new underground piped gravity bypass running south along Petrie St and east along Randall and Medway streets, discharging into the Avon River.

The solution– known as Option C – was the least expensive of three options presented to councillors at the meeting and was favoured by council staff because it was the least likely to encounter delays as the route for the bypass did not run over any private or Crown-owned land.

Residents in Randall and Medway streets will face significant disruption during construction of the bypass and the council will need to either buy or get access to some private properties along Stapletons Rd in order to widen parts of Dudley Creek.

The council hopes to do that through negotiation with the affected property owners but will use the statutory powers it has under the Land Drainage Act if required.

About 70 trees will also be lost as a result of the downstream engineering works, which are on top of the $16m worth of upstream works the council is doing to bring the flood risk in the Flockton Basin back to pre-earthquake levels.

Cr Pauline Cotter said staff had done an "incredible job" in coming up with an acceptable solution to the flooding problems that had beset residents in the Flockton Basin since the quakes.

"I think this is going to give a great deal of comfort to people who are vulnerable and who are not sleeping at night when it rains," Cotter said.

Cr Ali Jones said the engineering works would benefit at least 585 properties. 

At the start of the meeting Clarrie Pearce, co-ordinator of the North West Richmond Residents' Association (NWRRA), told councillors the association was worried that not enough attention had been paid to downstream effects of implementing Option C and that it could increase the likelihood of flooding in their area.

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Pearce said the association believed a better option existed but it was being ignored because there was a risk it would not be delivered by the targeted winter 2017 deadline.

"If you chose Option C today you have created a legal situation where if we get flooded in five, 10 or 15 years you put that Flockton problem in our backyard and you are therefore liable for it."

Council staff reassured councillors the modelling work that underpinned the design of Option C was solid and they were confident the problem of downstream flooding raised by the NWRRA would not eventuate. The effects of the scheme on the Avon River were minimal, they said.

The bypass would only be used in extreme weather events and would not adversely affect the ecology of Dudley Creek.

 - Stuff

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