Minister welcomes new lahar warning system

More than 50 years on from the tragedy at Tangiwai, a lahar early warning system is finally in place and operational on Mt Ruapehu.
The multi-million-dollar system, which includes volcanic flood sensors and automatic gates, was tested for the first time yesterday during a multi-agency civil defence response exercise.
Conservation Minister Chris Carter, who was in the Ruapehu district yesterday to observe the exercise, said the results of the system test were "very positive".
He said lahars from Ruapehu had been a hazard for more than a century, but now people living in the Ruapehu district had early warning of and protection from emergencies on one of the most active lahar paths in the world.
Fifteen eruptions had produced lahars since the 1953 disaster when a lahar swept away the Tangiwai rail bridge causing 151 deaths when the Wellington-Auckland express train plunged into the Whangaehu River.
An eruption in 1975 had created a lahar of similar size to the Tangiwai event. An even larger lahar is expected to spill from Mt Ruapehu's Crater Lake before January next year.
Councils from districts around the mountain had asked the Government to try and prevent the predicted lahar, which is expected to release hundreds of millions of litres of water trapped inside the volcano's lake.
However, Mr Carter said it was "absurd" that debate in recent years had revolved around digging a trench on top of Mt Ruapehu when excavation would do nothing to prevent future lahars.
Instead, the Government decided to install an early warning system to give people time to clear the area in the event of a lahar.
"When you are doing flood protection work you don't wait for the storm before starting it... you take steps based on the history of the area," he said.
Mr Carter said the technology tested yesterday had been available since it was put in place on Mt St Helens, in North America, in the early 1990s, but successive New Zealand Governments had done nothing until now to apply that technology on Ruapehu.
The overall lahar response plan includes an electronic alert system to provide 90 minutes' warning before the lahar reaches the Tangiwai Bridge; a 300m-long stopbank on the Whangaehu River to minimise the risk of the lahar spilling into the Taupo catchment and closing off at-risk sites such as bridges, roads and railway lines.
The raising of the road bridge on SH49 at Tangiwai is also part of the protection plan, is still under way and is scheduled for completion in November.
That project, along with the automatic gates and warning lights on SH49 and the Desert Rd, will have an all-up cost around $4.5 million.
The electronic lahar sensing equipment high on Mt Ruapehu and building of the stopbank have already cost more than $500,000.