A debris flow sprawls across SH1 and the rail line north of Kaikoura – heavy rain from Cyclone Gita sluiced 300,000 cu m of material down the fragile slopes
Kaikoura’s resilient defence systems
New defence systems to protect the narrow rail and road corridor north and south of Kaikoura have survived the full force of ex-cyclone Gita and a battering from other summer storms that swept across New Zealand.
The hard yakka behind tens of thousands of work hours paid off and slopes engineered over the past year to reduce the risk of slips performed as expected,
says Tim Crow, the New Zealand Transport Agency’s (NZTA) earthquake recovery manager for the North Canterbury Transport Infrastructure Recovery (NCTIR)
Tim Crow, NZTA earthquake recovery manager for NCTIR: “It’s going to be beautiful travelling alongside the Pacific Ocean, one of the world’s great journeys, a bit of a wow factor”
Gita, he says, was NCTIR’s toughest test. “Heavy rain sluiced 300,000 cu m of material down some pretty fragile slopes still recovering from the Kaikoura
earthquake. In engineering terms, we were dealing with debris flows, not slips, made up of unreachable material high up on coastal slips and flushed
down existing creeks and streams,” Tim says.
“Given the fragile geography along the Kaikoura coast, it’s always going to be at risk from extreme natural events. But what we were pleased about is that where we had undertaken remediation work on slips caused by the earthquake – we’d used water or earthworks to remove loosened material, cut benches, planted vegetation, and put in rockfall protection like gabion walls – these slips performed as expected despite high rainfall,” he notes.
“All this meant our crews could quickly access sites where the rain had triggered debris flows and start clearing the mess.”
Remediation work on slips caused by the earthquake includes installing rockfall protection like gabion walls
Tim says the outcome was not only good news for NCTIR’s geology and engineering crews who worked long hours to protect the corridor, but also for communities along the north Canterbury coast and wider New Zealand.
“Locally, we’re confident as time goes on and our work is completed that the route will be more resilient during future storms. Nationally, the lessons learned on the recovery programme by the contractors, KiwiRail and the NZTA will be used in future strategic planning around transport resilience to keep networks open and communities connected.”
Managing risks triggered by events like Gita is one of three main phases of work to complete NCTIR’s recovery programme. The others are finishing core recovery work caused directly by the earthquake, and delivering safety and tourism improvements along the north Canterbury corridor.
The NCTIR alliance includes KiwiRail and the NZTA for the NZ government, and four main contractors – Downer, Fulton Hogan, HEB and Higgins. There are also around 175 subbies on NCTIR’s books. The alliance was established shortly after the earthquake.
Most of central New Zealand was woken just after midnight on 14 November 2016 by a 7.8 magnitude earthquake centred some 60 km southwest of the seaside town of Kaikoura. Two terrifying minutes left a trail of damage to the road and rail corridor between Picton and Christchurch and the impact on communities was unprecedented in this country.
The earthquake triggered some 5000 landslides, and 3300 road and rail items needed repair. Add to that the disrupted lives of those with damaged homes, businesses closed, farms left with damaged land and no access to markets for their goods, and communities devastated by the loss of trade from passing traffic and tourists.
The Kaikoura earthquake disrupted the lives of many who made their home along the northeast Canterbury coast, and not just humans
The level of devastation was described at the time as though “a dinosaur had walked through that corridor along the coast, smashing its tail everywhere!”
Eighteen months on and the landscape along what Tim Crow describes as “a complex national strategic corridor” is still recovering, presenting a daunting challenge for NCTIR and its team of around 800 workers.
Turning adversity into opportunity
Many slips still remain, scattered along the unstable coast. One of the biggest, and most troublesome, is located at Waipapa Bay, north of Kaikoura. Known as Slip Nine, it is still on the move.
While clearing spoil and cutting back rock faces is reducing the risk elsewhere, at Waipapa Bay teams have been busy shifting the highway and the railway closer towards the sea and further from the unstable cliff.
Convoys of earthmoving trucks have rumbled up and down State Highway 1 shifting 80,000 cu m of stockpiled slip material from nearby Ohau Point to Waipapa Bay to be used as the foundation for the new alignment.
“Reusing spoil from a destructive earthquake has turned adversity into opportunity,” Tim says. “It’s great that we have been able to use slip material on the realignment to better protect the rail and road corridor for local communities and those travelling between Picton and Christchurch.”
It may seem an unlikely choice of words to use in the aftermath of the earthquake, but ‘wow factor’ is exactly what Tim has in mind for this year.
When rail and road links and the Kaikoura marina reopened last year, the Ministry of Business, Innovation and Employment estimated that tourism spending in the seaside town rose by $9 million in December alone. Improved traffic flows helped to boost the town’s December visitor spend to $12 million, up from the $3 million the previous year when access was severely limited after the earthquake.
There is still some way to go to get back to pre-quake levels, but NCTIR plans to build on that positive economic start.
One of the world’s great journeys
The north Canterbury coast is a place of cultural, environmental and recreational significance – historically important to iwi, home to one of the world’s rarest plants, the Ohau Point daisy, and to the thousands of seals that shelter along the coast, and offshore the Pacific Ocean delivers great surfing.
NCTIR will enhance the corridor significantly for all travellers, with safer places to stop along the way, constructing a 15 km long shared cycle footpath north of Kaikoura and making improvements to SH1 road tunnels.
Contractors work to repair one of the earthquake-damaged rail tunnels
“Whether you’re driving or cycling, it’s going to be beautiful travelling alongside the Pacific Ocean, one of the world’s great journeys, a bit of a wow factor,” Tim says.
He predicts the upgrades can lead to wider economic benefits for Kaikoura and its neighbouring communities. “We’ve already had one enquiry for a food outlet along the way, and other businesses might leverage off the improvements as well. Although it’s early days, that’s great news.”
Treading lightly in sensitive areas
Tim acknowledges that behind NCTIR’s achievements are two important groups – its committed workforce, and a supportive north Canterbury community. Collaboration with the community remains critical, and NCTIR extends its reach through the Restoration Liaison Group (RLG) that includes iwi, local government, the Department of Conservation (DOC), the tourist industry and others.
“Community groups have a stake in the recovery and our programme is more effective by including them in our outcomes,” says Tim. “Given the importance of Kaikoura and the wider area, this group’s inputs help us tread lightly in sensitive areas.”
A successful rescue story involves the Ohau Point daisy. Most of the rare plants had been swept away by slips. DOC, however, was able to recover enough seeds from the six plants that had survived to produce 200 seedlings for replanting.
And even after 18 months of challenging work night and day and in all conditions, Tim says the level of engagement from the alliance teams remains extraordinarily high. “That sense of commitment and responsibility is still there. Our latest staff engagement survey hit 85% – that’s huge, through the roof! Everyone gets our vision and our purpose to help the communities who are our neighbours and a wider New Zealand as well,” he concludes.
“That attitude is a perfect fit with the legacy NCTIR wants to leave when its work ends, carving enduring connections.”