$50m Upgrade Underway to Rebuild SH35 Mangahauini Gorge After Cyclone Damage

A major milestone in the East Coast’s recovery from Cyclone Gabrielle is now underway, with extensive reconstruction works beginning in Mangahauini Gorge on State Highway 35 (SH35). The project represents the final and largest phase of recovery efforts in the Tairāwhiti region, according to Transport Minister Chris Bishop.

From Temporary Fix to Long-Term Solution

Since the devastating cyclone struck in February 2023, crews from Transport Rebuild East Coast (TREC) and local contractors have kept a single lane through the gorge open. This temporary lifeline allowed essential travel and goods movement while engineers designed a more permanent solution.

The new programme of works will see the gorge fully restored to two lanes by mid-2026, marking the first time since Cyclone Gabrielle that the route will be fully reopened.

“This is about protecting the highway for the long-term,” Minister Bishop said. “The East Coast communities rely on SH35, and this work will ensure resilience and safety for decades to come.”

Battling a Shifting River

The Mangahauini River, which runs alongside the gorge, has been a constant challenge for engineers. It frequently shifts course, with extreme weather events such as Cyclone Bola in 1988 and Cyclone Gabrielle in 2023 dramatically altering the riverbed by several metres. These shifts cause erosion, slips, and undermining of the highway, often leading to prolonged closures.

To combat this, a key innovation will be introduced: the construction of a “roughened channel”, believed to be the first of its kind in New Zealand.

Innovation: The Roughened Channel

Half a kilometre of the riverbed will be reshaped and stabilised using specially designed interlocking blocks (hanbars), rocks, and other materials. This engineered roughened channel will guide the river along a fixed course, preventing it from cutting into the highway embankments.

“The roughened channel will help keep the river on course and away from the road, ensuring SH35 stays open for East Coast communities,” Bishop explained.

Alongside this, the highway itself will be realigned, repaired, and rebuilt to make it straighter, smoother, and safer for motorists.

Cost, Timeline, and Local Involvement

The programme, valued at around $50 million, will be delivered in phases by East Coast-based contractors, supporting local jobs and the regional economy.

• Early site set-up began this month.

• Major earthworks and river works will commence in September 2025.

• The roughened channel will be constructed during the summer season.

• Final road surfacing and upgrades will follow, with completion scheduled for mid-2026.

Local contractors were praised for their rapid response after Cyclone Gabrielle, when they built a temporary bypass through the gorge that reconnected isolated communities. The upcoming works will upgrade this temporary track to meet full state highway standards, ensuring long-term resilience.

Community Patience and Future Benefits

The Minister acknowledged the patience of local residents who have endured ongoing disruptions. “I want to thank local communities for their patience as the team has worked hard to get us to this point. The final programme of work will provide lasting improvements in safety, reliability, and resilience for SH35.”

The upgrade is expected not only to secure a vital transport link but also to boost regional growth, by enabling safer freight movement, tourism travel, and everyday commuting across the East Coast.

When finished, SH35 through Mangahauini Gorge will represent a nationally significant resilience project, blending innovation with local expertise to future-proof one of New Zealand’s most vulnerable highways.