Enough talking in circles — action needed

In winter 2015, a series of storms caused significant St Clair dune retreat between July 22 (left...
In winter 2015, a series of storms caused significant St Clair dune retreat between July 22 (left) and September 2. A black line of deteriorating sand sausages can be seen towards the esplanade, providing very limited protection for the longer beach. Photos: Stephen Jaquiery
Unsightly, limited patches of sea defences along South Dunedin’s beaches have stopped a rising tide rolling inland — so far. Mary Williams investigates the magnitude of the threats and need for a funded, sustainable solution.

A massive truck rumbles over the dune. It reverberates through the sand to the Stedmans’ house. It feels like an earthquake and adds to the tension in the air.

Peter and Pat Stedman are in full flow, complaining about a "talk fest" that has gone on for years about how to protect the thinning dune that slopes up behind their house and down again to the raging Pacific Ocean.

"Different people pop up and profess they know the answer. Then they have done their damage and gone, and we just go round in circles and nobody does anything," Mr Stedman says.

The single dune offers decreasingly slim protection. A path that led along the seaward side, up to a lookout at the top, has been washed away.

The lookout, and a plaque commemorating a former mayor, can still be found by scrambling up, but his legacy has a wobbly future. A few steps leading back towards the beach end mid-air.

There is a double whammy too — a toxic landfill starts about here and goes as far east as Marlow Park. It is at high risk of spilling its guts into the ocean and people’s lungs any stormy day now, because of the degrading sand at its edge.

The truck is part of a construction crew frantically placing long sand bags, often called sand sausages, in front of it.

The bags don’t protect the Stedmans and are only a short-term solution. More radical, and much more expensive, measures are needed. Climate change means more frequent storms at higher sea levels, but this isn’t just a future problem.

Storm surges happen now. Ocean Beach dune erosion is happening now. Efforts to prevent it are incurring costs now — and the acute threat of an environmental disaster from the toxic landfill is now.

Three beaches with three problems

Anyone who imagines the dune as fortress-like protection for South Dunedin along the whole of Ocean Beach is sadly misguided. Ocean Beach is three beaches, all backed by variably slim and shaky sandbanks.

At St Clair Beach in the west, from where the esplanade’s seawall ends, the dune rises only briefly before sloping down to houses along Victoria Rd, where the Stedmans live.

At Middle Beach, commonly called Middles, there is no natural dune, just the thin wall of sand in front of the noxious landfill, topped by the domain’s Kettle Park and Marlow Park.

The landfill has asbestos in it and other nasties including, possibly, munitions.

The wedge-shaped landfill is up to 8m deep and up to 150m wide. The sand in front of it gets as thin as 4m.

At the edge of St Kilda Beach, John Wilson Ocean Dr has been built on rubble such as bricks, glass and metal that has already been exposed in storms. The council says this is a low-risk area for now, but it is only a matter of time before it becomes problematic too.

The speed of erosion

The erosion of the dune along Ocean Beach, with its potentially terrifying consequences, is understood and broadly happens like this. Marram grass was historically planted to stabilise the top, but the side gets eroded by the Pacific Ocean’s magnificent waves. The dune becomes more vertical, then undercut.

Inevitably, a slab of sand slips down like a melting iceberg. Repeat. The threat to South Dunedin increases.

A council-commissioned survey, undertaken in a 2007 storm, found the dune receded by around 10m at St Clair Beach and up to 20m at Middle Beach.

About 100,000cu m of sand was estimated to be lost from the St Clair dune but only about 13,000cu m added back by the council, using imported sand. Another 100,000cu m were lost in front of Kettle Park and 8000cu m added back, plus a 90m-long reno mattress — wire cages filled with rocks. Sand bags shaped like Santa sacks have also been tried here.

In winter 2015, South Dunedin suffered storms and a catastrophic flood because of rain and shallow groundwater. While people were clearing drains, the dune at St Clair was receding 15m between the end of July and September.

Bill Brown has been campaigning to save the beach and protect the community for more than a...
Bill Brown has been campaigning to save the beach and protect the community for more than a decade and demands action now.
Another Victoria Rd resident, Bill Brown, can be thanked for the 2015 data. He paid a surveyor to evidence the dune’s retreat and rammed his point home to the council with aerial photography using a helicopter he also paid for.

The ‘disappointing’ response

In 2016, sand sausages — technically called geobags — were placed by the council in front of the St Clair dune from where the seawall ends. They replaced previous, similar incarnations attempting to hold back the erosion.

The bags only stretched 200m — not as far as the Stedmans’ house. The three beaches stretch more than 2km.

Mr Brown calls the bags, and the panic installation of 500m more bags further down the beach in front of the landfill, a "disappointing" response to a problem he has campaigned about for more than a decade.

"The council needs to do the job 100%, rather than half measures that fail.

"How many of the current councillors have walked the beach? I would be happy to take them."

The St Clair geobags don’t look healthy. Piled on top of each other, they slump seawards, shedding plastic netting and presenting a safety risk. People walk on top of them to get from the esplanade to the beach. A child could roll off and plummet 4m. There is a warning sign about sea lion danger, but not slipping off the geobags.

Just beyond the end of the St Clair bags, a tree has fallen from the summit, because of the land beneath its roots disappearing. It lies upside down, its leaves still green.

The expert opinion

University of Otago coastal expert Associate Prof Mike Hilton worries about maintenance and replacement costs of the geobags at St Clair, describing them as a "real mess", but says the potential mess at Middle Beach is the big worry. The sand in front of the landfill is a "trivial" sand scar, not a dune, and the "odds are not that long" for one or more terrible storms to happen, worse than any before. It just requires a coinciding of spring high tides, low atmospheric pressure, and strong on-shore winds and waves.

When asked why waves gouge out sand but can’t easily deposit it again, Assoc Prof Hilton gives the headline — "there’s no room".

The landfill, placed dangerously close to the ocean, replaced a sandy lagoon that the sea previously naturally washed into, dissipating its wave energy more gently over more space. Now the sea is angrily hammering on a flimsy door to get back home. It is a tough combatant that never gives up.

Humans also contributed to a lack of sand in front of the landfill by removing it from the beach way back in the 1880s for land reclamation in the northerly harbour. Sand is also now whipped up by, and lost to, the wind and can often be seen scattered across the domain.

A council management plan for the area from the early 1990s, shortly after the council had taken over its management from a previous Ocean Beach Domain Board, claimed the planting of marram grass had "corrected" instability. If only.

Hope for action

South Dunedin Future programme manager Jonathan Rowe, who leads the climate adaptation planning for South Dunedin, has sympathy with people desperate for action to protect the beach and agrees the status quo is inadequate.

"One-off and short-term solutions at the coast are typically costly, ineffective over an extended period, degrade the visual appeal of the beach and can create other risks and issues.

"We want to break out of the circle of short-term, sub-optimal fixes."

A St Clair to St Kilda coastal plan was published in February 2022 after a process of community consultation. It was more of a vision and a plan for a plan, and enthusiastically envisaged an enhancement of the beaches as a natural amenity for people and wildlife, resilient to climate change and safe to access. The document showed images of boardwalks in dunes.

A coastal protection implementation plan for the beaches is now being worked on by council coastal expert Dr Raphael Krier-Mariani who is modelling what could be done, using data already collected. He stresses it is important to get it right first time.

"You can’t just implement options and take them back. It’s really costly."

For obvious safety reasons, he is hoping to fast-track remediation options for Middle Beach and stresses the benefits of "dune reprofiling" as a likely front-runner solution. A larger area of rolling dunes would be created, further inland where the landfill and domain sit. It would enable waves to dissipate their energy more gently and as nature intended. The concept could also enable the envisaged boardwalks in dunes.

The dump would have to be emptied at a significant cost, but disaster risk would be eliminated.

Sports clubs and other activities that happen in the bay’s domain would have to be relocated. A similar approach could be extended east to St Kilda, with the loss of John Wilson Ocean Dr, reconnecting the golf course to the ocean. The internationally lauded St Andrews Golf Course in Scotland springs to mind.

Assoc Prof Hilton gives a local comparison.

"You could come out with a much better landscape that is not expensive to sustain, includes biodiversity goals and is more pleasant to meander through, like the Timaru foreshore at Caroline Bay."

A need to end the ‘disgrace’

The St Clair Action Group is dedicated to improving the whole bay, which its Facebook page describes as a "disgrace".

Co-chairman Richard Egan praises the council for its community engagement and intelligent planning process but fears the risk at Middle Beach could cause a disaster on the scale of Fox River, where an old dump washed into the river during a storm.

He calls the sand sausages at Middle Beach "expensive stop gaps".

"The council is probably hoping the government is going to come in and help them because it is such a huge issue.

"When we hear from people, there is cynicism and sadness the sand seems to be getting worse. Evidence-informed approaches take time but that is not always understood or accepted.

"Some people have been coming to meetings for 20-years plus and feel they have heard it all. I do think there is potential for change though."

Local Kim McKenzie steps gingerly down the Middle Beach geobag construction site to walk with her dog, Ra. She has brought up her two children here and they like to jump on the half-filled sausages that can be bouncy like a trampoline, but it’s definitely not all fun and games. They also spend time picking up rubbish, including plastic netting from the geobags further west.

"Watching the deterioration of the beach is sad.

"You see people climbing up the dune and children sliding down, making it worse.

"We are so exposed."


Remnants of former groynes at St Clair Beach.
Remnants of former groynes at St Clair Beach.

Groynes, seawalls not suitable to protect dunes: prof

Back in 2010, the council commissioned a report by University of Otago Emeritus Prof Blair Fitzharris that called for dune protection to prevent flooding because of climate change.

An "issues and options" report by Tonkin and Taylor, also commissioned by the council, came hot on its heels in 2011.

The report provided a long list of what could be considered for the whole of Ocean Beach, including hefty engineering options, such as buried seawalls, and the more cheap and cheerful option of groynes.

Groynes, the pier-like structures that aim to stop sideways sand migration along a beach, were most recently promoted by Dunedin Mayor Jules Radich.

Prof Hilton said there was no persistent trend of sand transport along the shore "which is why groynes won’t work".

Mostly, sand is washed into the sea then brought back forwards, but a lot sits in a big area underneath the waves and up to 800m offshore, not on the beach.

The sand eroded from the dunes was "minuscule compared to the sand volume across the intertidal beach and in bars and seabed deposits under and beyond the surf".

However, residents of Victoria Rd behind St Clair Beach understandably do not want their homes replaced by rolling dunes to accommodate the ocean.

Various engineering options are still floated in the council’s 2022 plan for this particular stretch and options still include groynes and offshore structures.

There is one significant engineering measure already here — the seawall at St Clair.

It has required ongoing repairs and is built on reclaimed land where the ocean naturally wants to flow. It would need to be bigger and stronger in the future if it is to remain — and stands as evidence that engineering solutions bring ongoing challenges.

A seawall for the whole bay was dismissed as out of hand by Prof Hilton.

It would be "impossible, too expensive".

"You can easily get yourself on to a path of bigger works, walls, geotubes, but this city can’t afford that."