away by exceptional floods; accumulations of tree trunks and branches. Principal bridges Hautes-Alpes : Pont de Savines on Lac de Serre-Ponçon (on route nationale RN94) (length 924 metres). Alpes-de-Haute-Provence : Old bridge to Baume at Sisteron Viaduct of the A51 autoroute south of Sisteron Dam/bridge at L'Escale (Route nationale RN 85). This replaced the Trébaste Bridge, 1962-3 Railway viaduct on the line from Saint-Auban to Digne Steel girder bridge at Les Mées (road D4a) Pont de La Brillanne (road D4b) Aqueduct at Villeneuve (canal EDF). Pont de Manosque (road D907) Between the Vaucluse and the Bouches-du-Rhône : Viaduct on the A51 autoroute between Beaumont-de-Pertuis and Cadarache Pont de Mirabeau (road ex-RN96) Suspension bridge at Pertuis Suspension bridge at Mallemort Three viaducts for LGV Méditerranée at Cavaillon (length - 940, 900 et 1500 metres) Twin viaducts for Route nationale RN7 and for the A7 autoroute at Bonpas Suspension bridge at Rognonas (road D970) to the south of Avignon Rail viaduct for the old Paris - Marseille line south of Avignon. Management of the course Dams and canals Dams have been built since the Middle Ages to prevent flooding. At first they were often boxes of wood filled up of stones, but these do not resist the floods for long. Dams have also long been used for irrigation. The first known irrigation canal is the , dug in 1171 by the Marquis de Forbin. It was followed by the Adam de Craponne canal, long, dug in nine months in 1554 from to Arles), the canal des Alpilles, the canal de Marseille, the , the , the canal de Ventavon, and the hundreds of other smaller ones, totalling dug between the end of the 16th century and the end of the 19th century. Marseille Canal From 1839 to 1854, the engineer Franz Mayor de Montricher built a canal to supply the city of Marseille with drinking water. It is long with underground. The canal is made out of concrete, and the aqueducts out of stone or stone and brick. The volume of water flowing through the canal is with the slope of . The width across the surface of the canal is , and at its base. The water was first abstracted near the bridge of Pertuis, at an elevation of , from Marseilles. From there the canal diverges to the west from the Durance to Le Puy-Sainte-Réparade. Following the construction of the