AVALDAT

Avaldat was a data processing system for interpreting avalanche speeds and flow depths . The first version of such a program was programmed by Hansueli Gubler in the 80s (in BASIC). Based on this program, I programmed a processing system to interpret the data from the full scale avalanche test site in Vallée de la Sionne. The program allowed the visualisation of the spread of speeds within the avalanche (measured by Doppler radars) and concatenated the outputs of several radars directed at various sections of the avalanche path to provide a calculation of speeds throughout the path of the avalanche.
The program also read the data provided by several under-snow FMCW radars, which provided a cross section of the avalanche as it passed over the top of them.
The data provided by these radars can very easily be falsely interpreted and the dangers of these interpretations were documented along with the software. I programmed this application in 1998/1999 and it is still in use today.

A plot of height (m) against time, showing the reflected signal the FMCW radar. Darker pixels are larger or denser particles. The front of the avalanche shows the erosion of the snowpack during the first few seconds as it passes over the radar.

A plot of the speed of the avalanche, calculated as the modal speed, not the speed of the avalanche front. This data is the result of concatenating speeds from several Doppler radars, each covering a section of the slope.

The frequency spectrum of the Doppler radar output (converted to velocity in the direction of the radar) against time. This shows the distribution of snow mass velocities throughout the slope during the avalanche.

BBC Horizon - Anatomy of an Avalanche - Avalanche from 31:40 and analysis using Avaldat from 35:30

The avalanche deposit immediately following the initial large avalanche in February 1999.

Photos of the initial fieldsite preparation and calibration in 1998: