The avalanche of la Tartera de la Pica (Andorra)

Abstract

The great extension of the avalanche path of "la tartera de la Pica" was identified during a systematic avalanche cartography in Andorra (Pyrenees). There are witnesses who, around 1930, saw the avalanche going down around 1200 m (vertical drop) and reaching a zone that, at present, is included in the city of Andorra la Vella and have a dense settlement. The altitude (2295 m at the top of the path), the aspect (SE) and the information about the meteorological characteristics of this zone suggest that, while the long return period extreme avalanches can reach the inhabited area, in general there are not avalanches in this path or they are very small. As a consequence, the population do not have a sense of danger and there is not any prevention or protection measure or control against this avalanche. In this paper we present the study of this avalanche path. The aim of this work is to characterise the extreme avalanches in order to protect this area of high vulnerability. The results of the present study come from the comparison and combination of different techniques and methods: expert criteria, photointerpretation, application of a statistic model and a dynamic model and use of ancient photographs from historical archives.