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Cracks in road network revealed

Rocks fell onto Cape Palliser Rd after a storm in June 2021. PHOTO/FILE

A new report has outlined the cracks in Wairarapa’s vulnerable road network that could appear after major storms and earthquakes.

The report commissioned by Wairarapa Engineering Lifelines Association [WELA], with input from Wairarapa’s three district councils, outlined areas at risk of being cut off in the region.

This report comes as Hinakura Rd was swept away in an enormous landslide last month.

The landslide, half a kilometre long and 134m wide, destroyed the road and forced residents to commute for two hours along a narrow and winding route to reach Martinborough.

The trip had previously taken about 20 minutes.

The resilience study found that many of the region’s roads were susceptible to closure because of flooding, landslides, damage to road structures, and liquefaction.

Damage-causing road closures were expected to impact a range of terrain, with roads near floodplains and roads near deep-seated landslides listed as at risk.

“The local road network in the Wairarapa region runs through a variety of terrain, including steep ranges and rolling hill country, as well as river valleys and broad plains.

“As recorded in past events, many of these roads are vulnerable to closure in significant storms or earthquakes, due to flooding, landslides, damage to road structures and liquefaction.”

The report said storms causing flooding would only worsen as climate change ramped up.

It said that with significant parts of the road network in hilly country, many roads were vulnerable to damage from slips, and in a large event, it was likely that multiple failures would occur.

It said failures could lead to long-term road closures.

Roads in the flatter areas of the region could be affected by large storms or earthquakes, causing flooding, liquefaction, and subsequent closures.

“Climate change is likely to result in more frequent extreme weather events, and this is likely to result in more frequent closures on the local road network due to flooding and slips caused by heavy and, or prolonged rainfall and storm surge in coastal areas.”

The report said the time taken for flood waters to subside in the lower Wairarapa valley could increase as sea levels continue to rise, possibly increasing closures.

It said many sections with hillsides couldn’t be practically mitigated to enhance route resilience in large earthquake and storm events because of the size of some of the slopes.

WELA said the good news from the report was that many of Wairarapa’s major roads were expected to remain passable.

WELA chair Adrienne Staples said some of the more remote areas were lucky to have more than one access, but many others didn’t.

“It is important that those likely to be cut off for extended periods know who they are so they can plan their emergency preparedness. This study will help identify those who are most at risk.”

Access in and out of Wairarapa on both SH2 and local roads was identified as at risk, meaning Wairarapa could be cut off from the rest of New Zealand for several weeks.

The report gave 10 recommendations, including that the district councils and WELA review and consider the resilience of roads and include them in emergency response planning.

It also suggested the resilience of the bridges and large culverts be considered to understand the resilience of the transport network.

Grace Prior
Grace Prior
Grace Prior is a senior reporter at the Wairarapa Times-Age with a keen interest in environmental issues. Grace is the paper’s health reporter and regularly covers the rural sector, weather, Greater Wellington Regional Council, and coastal stories.

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