The two branches are separated by an island, the Île de la Barthelasse. The southernmost tip of the Île de la Barthelasse once formed of a separated island, the L'Île de Piot. The banks of the Rhone and the Île de la Barthelasse are often subject to flooding during autumn and March. The publication Floods in France since the 6th century until today – research and documentation by Maurice Champion tells about a number of them (until 1862, the flood of 1856 was one of the largest, which destroyed part of the walls). They have never really stopped as shown by the floods in 1943–1944 and again on 23 January 1955 and remain important today – such as the floods of 2 December 2003. As a result, a new risk mapping has been developed. The Durance flows along the southern boundary of the commune into the Rhone and marks the departmental boundary with Bouches-du-Rhône. It is a river that is considered "capricious" and once feared for its floods (it was once called the "3rd scourge of Provence" as well as for its low water: the Durance has both Alpine and Mediterranean morphology which is unusual. There are many natural and artificial water lakes in the commune such as the Lake of Saint-Chamand east of the city. Artificial diversions There have been many diversions throughout the course of history, such as feeding the moat surrounding Avignon or irrigating crops. In the 10th century part of the waters from the Sorgue d'Entraigues were diverted and today pass under the walls to enter the city. (See Sorgue). This watercourse is called the Vaucluse Canal but Avignon people still call it the Sorgue or Sorguette. It is visible in the city in the Rue des teinturiers (street of dyers). It fed the moat around the first defensive walls then fed the moat on the newer eastern city walls (14th century). In the 13th century (under an Act signed in 1229) part of the waters of the Durance were diverted to increase the water available for the moats starting from Bonpas. This river was later called the Durançole. The Durançole fed the western moats of the city and was also used to irrigate crops at Montfavet. In the city, these streams are often hidden beneath the streets and houses and are currently used to collect sewerage. The Hospital Canal (joining the Durançole) and the Crillon