Scientists Plan Aerial Laser Survey of Lahar Path

NEWS RELEASE from GNS Science, 17 FEBRUARY 2006

Scientists Plan Aerial Laser Survey of Ruapehu Lahar Path

A state-of-the-art aerial survey of the path of the predicted break-out lahar from Mt Ruapehu's Crater Lake is scheduled to be flown from Saturday onwards, weather permitting.

GNS Science, in association with Massey University, has commissioned the survey as part of a broader research plan designed to capture maximum scientific value from this event.

Mt Ruapehu hosts one of the most active volcanic crater lakes in the world and the Whangaehu River, which drains the lake, has carried more than 45 lahars (flash floods involving volcanic debris) since the 1953 Tangiwai tragedy.

The survey is to be carried out by NZ Aerial Mapping Ltd and its Australian partner Fugro Spatial Solutions, who are providing the US$1 million LiDAR (light detection and ranging) mapping system.

This equipment uses digital laser technology to take up to 83,000 measurements of the land surface per second with sub-metre accuracy. Combined with high resolution digital photography, the method produces a highly accurate 3D snapshot of the land surface.

"The steep and unstable terrain in close proximity to an active volcano makes this a very challenging project from both a technical and operational perspective," said Fugro project manager John Lazarus. "The experience we recently gained working in the jungle-clad highlands of Papua New Guinea will be very useful."

GNS Science lead scientist for the project, Vern Manville, said LiDAR offered the most cost-effective method of producing a highly accurate 3D map of the upper Whangaehu River. "Comparison of the results of this survey with a duplicate mission flown immediately after the lahar happens will allow us to work out what changes it made to the river bed," Dr Manville said.

The 3D topographic model of the lahar channel will also be used for numerical modelling of lahar behaviour conducted by volcanologist Shane Cronin and his team from Massey University.

GNS Science and Massey are also planning to install an array of monitoring instruments at key locations along the lahar path to measure its properties as it flows past.

"This is a unique opportunity to capture the secrets of a life-sized lahar," said Dr Cronin. "The more we can learn about this event, the better prepared we will be in the future."

ENDS

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