The Historic Avalanche that Destroyed the Village of Àrreu in 1803, Catalan Pyrenees

Abstract

The purpose of the present study was to reconstruct the avalanche which destroyed the village of Àrreu in 1803 to solve the unknowns about this historic event, and in a broader context, to improve the knowledge about these low-frequency avalanches in the Pyrenees. To this end, a multidisciplinary approach was carried out by searching in historical sources and databases, reviewing aerial imagery, surveying the site for terrain and vegetation inspection, using dendrogeomorphological analysis, and interviewing local people, to finally apply SAMOS-AT computational simulations and the statistical α-β model. In the Monars avalanche path, 5 major avalanche events were identified, including the one in 1803. Most of these events were dense flow avalanches, but evidence of powder-fraction effects was deduced from the vegetation survey. Frequency analyses assigned a return period of more than 100 years to the 1803 event. Historical information suggests that a succession of avalanches is necessary for an event to reach the hamlet. Simulations indicate that a single avalanche of destructive size 5 would be sufficient to cause the catastrophe, and, at the same time, it would travel 1 km further down along the Àrreu river to the main valley (Noguera Pallaresa).