'Substantial' sea wall needed for shared pathway to protect Eastbourne

Wednesday, 3 May 2023

Work at Windy Point on Tupua Horo Nuku Eastern Bays shared pathway.

It has been talked about since the 1980s and when construction began last year, there were high hopes for the shared pathway around Lower Hutt’s eastern bays. The $79m path is a 4.4-kilometre walking and cycling path between Point Howard and Eastbourne. Locals are also hoping Tupua Horo Nuku will protect them from climate change. Nicholas Boyack looks at the project and asks will it protect Eastbourne?

Pink is not normally a colour associated with bad news but if you live in Lowry Bay it spells very bad news.

Last May, Victoria University of Wellington Professor and SeaRise programme co-leader Tim Naish said time was running out to make the changes needed to combat rising sea levels in Wellington Harbour.

Lowry Bay and the only road to the Lower Hutt seaside suburb of Eastbourne, could be permanently disrupted by flooding in less than 30 years, he said. The suburb will also suffer more frequent inundation by storm surges, likely to mean substantial damage.

“That is now widely recognised by those of us working in climate change.”

Lowry Bay is sinking at 3.8mm a year, whilst the sea is rising by 3.5mm a year - that means Lowry Bay will experience sea-level rise at twice the global average.

Stuff packaged the data to show what areas will be impacted first by climate change with pink, representing areas most at risk. Lowry Bay is very pink.

The suburb contains some of the most expensive properties in Wellington but is one of the lowest points in Wellington Harbour and is increasingly under threat from storms and high tides, which close the road.

Both the city and regional councils are aware of the climate change data, as is Waka Kotahi NZ Transport Agency. By the end of the century, the road around Lowry Bay would be under a metre of water and subject to annual storms that are the equivalent of one in a hundred year events today.

So what can be done to protect Lowry Bay and the Eastbourne suburbs?

Professor Tim Naish, of the Antarctic Research Centre, based at Victoria University, says the latest research on climate change is not good news for the Lower Hutt suburb of Lowry Bay. Within 30 years, residents can expect the road to Lowry Bay, the only road to Eastbourne, to be under water. Eastbourne will also be subjected to annual storms, causing significant damage.

A substantial seawall could be a solution. And that is now part of the 4.4km Tupua Horo Nuku Eastern Bays shared pathway that’s being built from Eastbourne to Petone.

It was initially planned primarily for walkers and cyclists, but its design was modified so it could act as a seawall.

Work at Windy Point on Tupua Horo Nuku Eastern Bays shared pathway.

But will it be enough?

Long-time community board chair and environmentalist Virginia Horrocks thinks not.

“It will mitigate sea level rise to some extent, but you can’t stop the sea. It will give us some time,” she said last August.

Barriers being erected for a shared pathway in Eastbourne were mangled recently by a heavy swell.

Work began at the southern end of Days Bay. Barriers were erected but didn’t last long and it became clear a re-think was needed on the design.

After the problems in Days Bay, the focus moved to Windy Point, where construction restarted. Six weeks ago, a large swell left only a pile of twisted metal.

Jon Kingsbury, the Hutt City Council’s head of transport, said the wall of metal was just the skeleton of the barrier and it would not have failed, if workers had had the chance to fully set it up with additional weights.

But Peter Wylie, in a recent letter to the editor, wasn’t so confident about the future of the new structure.

“While a shared path from Eastbourne to Petone would be nice to have, is nature trying to say no? Twice now the initial works at Windy Point to build this have been destroyed in slightly rough weather.

Professor Tim Naish, of the Antarctic Research Centre, based at Victoria University, in Wellington. (File pic)

“When the real storms come, what chance has a path of a) being used by pedestrians and cyclists and b) of surviving the storms and rising sea levels?”

Mayor Campbell Barry declined to be interviewed on whether or not the current project is fit for purpose. Instead, we were directed to Harbour Ward councillor and deputy mayor Tui Lewis.

She said Stuff had raised valid questions about the viability of the shared pathway/seawall and the impact climate change would have on it. Residents in Eastbourne, like other harbourside communities, need to start thinking about future options, she said.

Building a shared pathway is a major engineering challenge.

“I would like to know what the residents want to do. I really think we need to have that discussion and we need to have it soon.”

In a written statement, Barry said it was clear the “project would offer improved resilience and a greater level of protection” than currently exists.

Lowry Bay gets a battering from large waves and wind in 2018.

“Importantly, the seawall design is future-proofed to make it easier to increase protection over time. Ultimately this means the initial construction will boost resilience, while also allowing us to further increase protection in the future as it is required.”

“Protecting our assets through infrastructure like seawalls – which is at the heart of the Tupua Horo Nuku project.”

The Ngāūranga to Petone shared pathway is part of a longer path called Te Ara Tupua that will eventually allow people to walk or bike around the whole harbour. (First published in July 2022).

Building a substantial seawall would be expensive which raises the issue of who should pay?

As little as six months ago, the project had a budget of $30m. But now it is costed at $79m. In the draft annual budget, the council has increased its contribution from $7.5m to a capped $25.5m.

Waka Kotahi had committed to putting in $7.5m and central government would contribute $15m. The council is now negotiating with central government and the transport agency over the $31m shortfall.

A section of the shared pathway under construction at Windy Pt. Concrete foundations are being put in place to provide a stable base for the next stage of construction.

On the other side of the harbour $312m is being spent on the shared path between Petone and Ngāūranga. It’s a similar length but the design is very different. It will be protected by 144,000 tonnes of rock and 6800 concrete blocks each weighing 2.6 tonnes.

In December Kingsbury noted that storms last year had resulted in the council taking another look at the design. In the long term, the council might look at an offshore breakwater to take some force out of the waves smashing into the sea wall, he said.

The council’s website says construction is “currently picking up” and concrete foundations being put in would provide a stable base for the next stage of construction, pre-cast concrete seawall units.

“The vertical curved seawalls were chosen for the design of the shared path due to being more effective at deflecting wave energy offshore in comparison with other options, as well as their reduced footprint on the foreshore.”

It is hoped they would reduce coastal erosion and the impact of sea surges. “The design is also future-proofed, with the ability to be adapted to accommodate for sea level rise.”

Naish warned that “time is running out” and decisions on how to protect areas like Lowry Bay and Petone, as well as other low-lying areas in the harbour, need to be made soon.

He is pleased that the design of the shared pathway allows for a bigger seawall in the future, as climate change gets worse but doubts it is a long term solution.