Le ravin de la boulette

This ravine, upstream from Barles, is a favorite observation ground for geologists and surprises hikers by its sheer size. In 1973, it had far-reaching consequences. That summer, a massive collapse of gypsum materials occurred in the upper part of the ravine. Destabilized by pockets of dissolution, thousands of cubic metres of this soluble rock broke away and tumbled down the slope. A torrential lava then obstructs the bed of the Bès and cuts across the departmental road, forming a natural dam. But when the torrent's water finally breaks through, muddy waves laden with material rush down the Bès to join the Bléone, which is already in flood. In Digne, one of the arches of the large bridge failed to withstand the raging waters. The bridge had to be completely rebuilt, and was not reopened to traffic until 1975. The Boulette torrent is still very active and is subject to regular monitoring and intervention.