Predicting the Ruapehu lahar path

An aerial survey of the path of the predicted lahar from Mt. Ruapehu's Crater Lake has been conducted by scientists from GNS Science and Massey University.

GNS Science 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.

Volcanologist Dr Shane Cronin and his team from Massey will use the survey results to make a 3D topographic numerical model of the lahar channel.

This is a unique opportunity to capture the secrets of a life-sized lahar , Dr Cronin says.

The more we can learn about this event, the better prepared we will be in the future.

Fugro Spatial Solutions has provided the LiDAR (light detection and ranging) mapping system, worth US$1 million. The 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, Dr 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.

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.

Created: 21 February, 2006

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