Environment Waikato is supporting setting up a landslide hazard project team to manage the dangers of a landslide at Hipaua above Little Waihi village near Taupo.
Land movement has been continuing in the area for more than 150 years along the Waihi fault, causing deaths and road closures. Over the last few decades, the Taupo District Council and Environment Waikato have been studying the risk of the landforms, which sit above State Highway 41 and the town of Little Waihi.
Taupo’s Emergency Management Subcommittee asked that a working party be set up to lessen the risks for the local community and motorists on State Highway 41.
Environment Waikato Hazards Analyst Lamorna Cooper said one of the main problems was that there were a number of different scales of failure, such as the massive mudflows that created the hectares of land where Braxmere Lodge now sat, and small mudflows beside the highway.
In 1846 a landslide destroyed a Maori settlement and killed 60 people, another person was killed by a large landslide in 1910 and since 1989 there had been a number of slips closing the highway. Further instability was likely and the District Council had written to all landowners and held public meetings identifying the risks.
Two infrared surveys of the Hipaua Steaming Cliffs and Waihi Springs undertaken in 1991 and 2001 showed very little change but a study in 2001 indicated a northward movement along the Waihi fault of about eight metres a year. As this movement was a prime trigger for the larger scale cliff-face failures, more work was needed to clarify what was happening.
Greatest risks were from rock falls at Little Waihi village, debris flows into the Waimatai Valley and across the highway, slope failures in the Omoho and Waimatai Valleys and gullying across slopes below the cliffs from rain, she said.
Taupo’s Emergency Management Subcommittee has recommended asking the Ministry of Civil Defence and Emergency Management for a statutory hazard warning for the area and appropriate warning signs on Waihi Road after notifying owners. Environment Waikato has agreed to support this initiative. Significant predicted rain should also be monitored and passed onto stakeholders as a danger warning.
The two councils are intending to design a public warning sign below the Waihi Village turn-off, more signs on the highway, and undertake further community consultation.