Karitane’s successful seawall made of natural material

A driftwood fence built at Karitane in July has been successful in combating coastal erosion in the area, and could provide a low-cost solution elsewhere, the Dunedin City Council says. Photo: Supplied

The structure at Karitane was built by the Dunedin City Council — led by council coastal specialist Tom Simons-Smith — local runaka and volunteers from the Karitane community in July. Constructing it took two hours.

Since then, the simple sand trap has been successful in combating erosion on the Karitane sand spit and in November earned Mr Simons-Smith a New Zealand Coastal Society national sustainability award.

Soon, replicating the novel approach would be considered as part of wide-ranging planning for the future management of Ocean Beach — the area of coastline stretching from St Clair to Lawyers Head — as erosion threatened.

Council infrastructure services general manager Simon Drew said the approach employed at Karitane was among options to be considered for Ocean Beach when community consultation began later this year.

Mr Simons-Smith, in a statement, said the Karitane project had evolved from a plan to build a ‘‘more formal’’ sand fence, using posts and cloth, to encourage the redevelopment of the sand spit and protect the inland area.

However, after talks with Kati Huirapa Runaka ki Puketeraki and the wider community, the focus shifted to a more ‘‘environmentally friendly’’ approach, using driftwood to build a fence.

Because the sand spit was always changing, ‘‘it was important to recognise that whatever was put in place would be damaged or removed during storms’’, he said.

‘‘The idea is that if it gets washed away nothing gets lost, and no synthetics fabric, wire or tanalised posts enter the environment.

‘‘The driftwood can be re-collected when it washes away and poses no risk of environmental pollution.’’

About 40 members of the community had volunteered to help build the fence, helped by Maori Tours, which used their waka to get people across to the sand spit, while local runaka helped with health and safety.

It was a ‘‘solid community effort’’, Mr Simons-Smith said.

It was also effective, as by late October the 1.5m-high fence was ‘‘almost entirely’’ covered in sand, Mr Drew noted.

The success of the driftwood fence came after Dunedin city councillors last month voted to ask for a report into the viability of returning wooden groynes to Ocean Beach.

Cr Jules Radich had campaigned on the idea, which he said would build up the beach and protect against recurring coastal erosion.

Most recently, up to 13m of sand had been stripped from the area in August, raising fears an old landfill buried behind the dunes, under nearby Kettle Park, could be exposed.

Mr Drew said public consultation on the future management of Ocean Beach was expected to begin in March or April.