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The slip in Karangahake Gorge closed the road for several hours last week. Photo: SHARON KATE MCHARDIE-ROYCROFT

Karangahake Gorge under stress

State Highway 2 through the Karangahake Gorge is under closer scrutiny from Waka Kotahi NZ Transport Agency, following a spate of major slips in the area.

The main highway, which traverses the length of the gorge, was closed earlier this year due to slips caused by Cyclone Gabrielle.

Another closure came last week when a section of dirt and vegetation plummeted down the hill and blocked both lanes near Crown Hill Rd. The highway remained closed into the night, forcing travellers to detour along SH25 through Thames, or south into the Bay of Plenty.

The road was also reduced to one lane during the storm on May 9, when the Crown Hill Rd slip moved again. 

Waka Kotahi said the road through Karangakake Gorge was a vulnerable section of highway, and would benefit from increased resilience works. The agency has increased patrols by its roading contractors, as well as stepping up monitoring by geotech engineers.

“Further stabilisation of the bank will be carried out this year on SH2 near Crown Hill Rd,” Waka Kotahi system manager Cara Lauder said.

“We have been assessing what can be done to improve drainage in the gorge in the immediate future, and have already completed all our usual maintenance works since the big storm. Larger improvement works are currently being scoped, for further resilience work.”

Ms Lauder said the increased frequency and extreme nature of weather events across the country is putting pressure on Waka Kotahi’s capacity and funding.
“Climate change and its effects are impacting the condition of the roading network,” she said.

“While the overall annual rainfall total has not increased by much, the intensity has, resulting in much higher numbers of intense rainfall events affecting both local roads and state highways.”

Waka Kotahi’s ongoing resilience programme aims to protect New Zealand’s roading network against the impacts of climate change, including rising sea levels and severe weather.

By ALICE PARMINTER, Public Interest Journalism funded by NZ on Air