DOC lahar early warning system in perfect working order

The Department of Conservation confirms that its lahar early warning system on Mt Ruapehu is working perfectly.

Criticisms of ERLAWS (East Ruapehu Lahar Alarm Warning System) have been made in relation to a false alarm on 20 February calling for the evacuation of Ohakune.

The ERLAWS system did not trigger a lahar alert on 20 February, DOC scientist Harry Keys said today.

“The system did pick up a flash flood in the Whangaehu river on the slopes of Mt Ruapehu on that day. Our sensors on the mountain are sensitive enough to record vibrations created by heavy rain, as well as a lahar.”

“Small vibration patterns showed that the sensors were picking up a flash flood and not a lahar, which would have produced large, long duration peaks,” Dr Keys said. “This event showed that the system is working perfectly and we at DOC are very pleased with that outcome.”

In any event, a lahar would not have been possible on that date because the lake level was 5m below the pre-1995 hard rock rim, Dr Keys said.

It appeared that a failure in TranzRail’s warning system on 20 February led to an incorrect message being passed on to emergency services, Dr Keys said. This had nothing to do with DOC, or any of DOC’s systems.

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