Capital city surfers seek certainty

Wellington's Lyall Bay has been surfed for more than a century, and locals are worried the airport's runway extension plans could kill some of the city's best waves.

The airport plans to extend the runway another 350m into the water, and that will affect the peakiness of the waves, cutting the number of surf rides in parts of the bay by nearly a third.

"This is a very special place for us here in Wellington," Wellington Boardriders Club president James Whitaker said.

"A lot of people have surfed Lyall Bay, especially the break known as 'The Corner', which is the break that runs parallel to the runway. And there's also a lot of people who on a nice day come down to the beach and watch the spectacle, not just those who take part.

"It would be such a shame if the construction of an extension ruined what's there, because it's a very special thing."

The bay is considered the city's safest, most reliable break, and the shape of the bay helps focus the waves. At just 15 minutes from the central business district by car, it is undeniably convenient.

But it is also quite a particular beach. In 2014, there were only 125 days where the waves were surfable and only 38 of those days had "very good surf".

Mr Whitaker said his life was based around surfing at Lyall Bay. He had been surfing there since he was 14, and had taught his three daughters there.

He and others were worried the runway extension would make things even worse.

"There's other spots around Wellington but they're for the more die-hard surfers who don't mind cracking their head on reefs," he said.

Artificial surfing reef proposed

The airport, in response, has enlisted the help of DHI Hydrology coastal engineer Simon Mortensen.

"What we proposed is to [put in] an artificial surfing reef which acts as a wave focusing structure," Mr Mortensen said. "It would be in the middle of Lyall Bay, or potentially toward the west."

The wave focusing structure consists of a 180m-long mound of rocks, positioned 5m below the surface, 500m out to sea.

"What it does, being a submersed wave focusing structure, is that waves are not going to be breaking on the structure itself. Instead it's going to focus waves into a peak, which are then going to travel a bit further into shore and break (closer to shore)."

Read the draft report prepared for the airport by DHI

Draft documents provided for the airport company show it could cost as much as $3 million to create the wave focusing structure, but Mr Mortensen said by doing it alongside the runway extension, using the same diggers and rocks, that figure could be much lower.

Doubts raised

Surfbreak Protection Society spokesperson Mike Gunson said a more cautious approach was needed.

"The thing is we're talking about 'mights' and 'maybes', and so we're actually in the field of the unknown here," he said. "We just need more assurances, and more commitment to getting some really good science on the ground to see what's going to happen."

Mr Gunson said there needed to be ongoing surf monitoring once the runway and focuser were completed.

To help address doubts, the airport is helping the Wellington Boardriders Club pay for a second surf scientist, Dr Shaw Mead, to peer-review Mr Mortensen's proposal.

Mr Whitaker said there were plans to attach GPS tracking devices to the surfers so the coastal engineers could compare the computer-generated wave models with some real-world data.

"That's the sort of peace of mind we're after - we're not out there to block progress, we just want to make sure if this does go ahead, what we have now is protected," Mr Whitaker said.

The airport is seeking feedback on the runway extension until 12 February.