TEN YEARS OF AVALANCHE FORECASTING ON BONAIGUA AND BERET ROADS, ARAN VALLEY, SPAIN

The Aran Valley, located on the northern side of the Central Pyrenees, is one of the areas with the highest avalanche risk rate in the whole mountain range (52% of the Aranese territory is affected). The exposed areas include not only high mountain terrain but also 6 population clusters and 3 main roads. On the roads with which this paper is concerned, a combination of temporary and permanent mitigation measures has been set up. Over a total of 31.5 kilometers there are 82 avalanche prone areas. Most of the slopes affecting the road are south faces, with heights between 1600 and 2300 meters. Until the year 2003, the avalanche risk management on these roads was based upon the regional avalanche danger advisory. In the winter of 2003/2004 a local forecasting system was set up. In order to do so, a snow and weather observation network was implemented and a specific danger scale was developed -adapted to the particular management needs of these roads. In the winter of 2008/2009, a helicopter-based triggering system using Daisybell was put in practice. Overall, it has proved to be a highly effective system but the operations are largely dependent on the weather conditions. A quick and visual interpretation bulletin is issued to the road managers and other interested groups (ski resort, person in charge of Civil Protection, police...) three times a week -or on a daily basis whenever there is the possibility of avalanches affecting the road. The implementation of an avalanche prevention system and the close collaboration between the forecasting center and the road managers has resulted in an improvement of the viability and of the safety management of the roads.