The ride up to the Col du Tourmalet takes us up the valley of the Bastan, which was the site of a massive flood in the summer of 2013. The Bastan arises on the western slopes of the Col du Tourmalet and flows through Barèges until it joins the Gave de Gavarnie in Luz-Saint-Saveur. These waters flow down into the Gave de Pau through Lourdes and then through Pau.
Over the winter of 2012 to 2013, precipitation was significantly higher than normal, with a very large accumulation of snow in the mountains surrounding the valley. An avalanche on May 31, 2013, blocked up part of the river, setting the stage for the flood in June. Over the weekend of June 15 and 16, a heat wave developed, melting that tremendous snow pack, and on the 17th and 18th, a storm passed through, dropping an additional seven inches of rain in 48 hours. The Bastan left its banks, overwhelmed the dam at Cabadur and flooded the valley down to Lourdes. Barèges was completely devastated by the flood, and Lourdes suffered significant damage as well.