at Caumont), at the end of the 12th century until its destruction by the Count of Toulouse in 1241; at Mirabeau, the beginning of the 13th century, close to Sainte-Madeleine-du-Pont; at Savines, the most used bridge on the Upper Durance (built in the 15th century) the ancient bridge of Sisteron which was rebuilt in 1365. 19th century In 1843, 1856, 1882 and 1886 there were catastrophic floods. The 1852 floods affected the entire basin of the Durance, from Sisteron to its confluence in Avignon. It washed away many cultivated alluvial terraces, broke dams and destroyed canals. The irrigation syndicates and the local services that maintained the roads and bridges requested exceptional help from the State. A service to monitor the river was created, the Service spécial de la Durance, in order to study the hydrology of the river, using the kilometre-long divisions from 1868 between the confluence with the Verdon with that with the Rhône. This division allows surveying and mapping of the land at risk. The construction of the Marseille canal in the middle of the 19th century allowed the metropolitan area of Marseille to develop quickly. 20th century The Durance was ceased to carry freight because of competition from road and rail. There were only 10 raftmen remaining in 1896 and only one in 1908. Hydroelectric installations and chains of locks on the Durance, and its tributaries the Verdon, Buëch and Bléone had the most significant economic impacts and are the most visible change in the landscape. The major part of the flow was diverted into canals downstream from Serre-Ponçon, and the flow in the river's natural bed is a minimal flow of , which is only 1/40 of its natural flow. The silt in the river bed has become stabilised by vegetation and this also reduces the flow. Thanks to the reservoirs at Serre-Ponçon and Sainte-Croix, which together can hold more than 2 billion tonnes of water, irrigation remains possible in summer even during the driest years. The predictable water levels have also allowed development of the local economy through summer tourism. Beginning in the 1950s, aggregate was extracted from the river bed for road surfacing and wear-resistant concrete. The majority of the quarries have closed or are closing. The few factories that used the river's energy have closed (an aluminium factory at L'Argentière-la-Bessée) or are being closed (Arkema at Saint-Auban). At Cadarache an experimental nuclear fusion