New radar sensors can be used to see inside avalanches

The data gathered from sensors could be used to build better simulations and offer protection from avalanches

Engineers have developed a radar sensor that remains fully operational even when an avalanche rolls over it, in order to develop better simulations of avalanches.

It is hoped that the simulation results might help to improve the design of avalanche protection devices.

The sensor, developed by a team of engineers at Ruhr-University Bochum (RUB), Germany, headed by Dr Christoph Baer and Timo Jaeschke, has been installed at a test slope in the Swiss canton Valais, where the Swiss Institute for Snow and Avalanche Research intends to use it to perform measurements in winter 2016/17.

The gathered data will be entered into simulations that will reconstruct in fine detail the processes that happen inside of avalanches. “We don’t know what exactly happens when an avalanche moves down a mountain, because avalanches have only ever been observed from the outside,” said Baer.

Currently it is understood that avalanches are made up of several layers that behave like solids, liquids or dust-containing gases. The new sensor records variations in the snow density in the dust layer. The density affects, for example, the impact pressure of the avalanche that determines its destructive force. The avalanche processes can be correctly simulated in terms of fluid dynamics only if the snow density is known.

The system made in Bochum uses a radar to record how many snow particles are contained in the dust layer. The more snow the layer holds, the more slowly the radar wave propagates. This means that researchers will be able to draw conclusions about the snow density and record it in real time.

The sensor is approximately one metre-long, 30cm thick and weighs 70kg. “The avalanche pressure corresponds to 3.5 tons – around two cars – applied to a surface area of a sheet in DIN-A4 format,” said Baer. “It rolls directly over our sensor. Making sure that the sensor remains attached to the test pole and supplies usable measurement results is a real challenge.” The sensor has been made from aircraft-grade aluminium in order to withstand the massive impact pressure it will experience inside an avalanche.

The team at the Swiss Institute for Snow and Avalanche will wait for an avalanche to take place in a closed-off test area at Valée de la Sionne until the end of 2016. If no avalanche occurs naturally, it will be triggered through a controlled detonation.  

The project to develop the sensor was run in collaboration with researchers from Innsbruck, Austria, and Davos, Switzerland.