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Field Measurements

We have been very unlucky so far in that 2009-10 and 2010-11 are the first two consecutive winters ever where the conditions have not been right for a controlled avalanche release. Hence, we have not been able to validate our radar against the other instruments at Vallee de la Sionne.
 
However, we do have data from spontaneous avalanches on the path. The image below shows an avalanche that released on 7th December 2010. This was a wet avalanche, which flowed relatively slowly. The flow clearly followed two main gullies down the mountainside, with the smaller flow stopping at an elevation just upslpe of the instrument tower, while the larger flow carried on to the bottom of the mountain.
 
The range-time plot shown below is from one of our 8 receivers and uses the longest period of our chirps that we generate. The slow moving wet avalanche is clearly still moving at the end of the recording window. But the bright band that fades with time at 1500 m is the decelerating material in the smaller gully. The resolution of our data is sufficient to detect roll-waves behind the main flow front (e.g. at ~ 60 s and 1000 m).
 
This is the first time that data with sufficient resolution to resolve such features have been collected for a geophysical mass flow. 
 
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