Durance

Management of the course

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 Canal Saint-Julien, dug in 1171 by the Marquis de Forbin. It was followed by the Adam de Craponne canal, 50 kilometres (31 mi) long, dug in nine months in 1554 from Silvacane to Arles), the canal des Alpilles, the canal de Marseille, the canal de Carpentras, the canal de Manosque, the canal de Ventavon, and the hundreds of other smaller ones, totalling 540 kilometres (340 mi) dug between the end of the 16th century and the end of the 19th century.

Hydrology

The river is considered "capricious", alternating between the feared flash floods (called the third plague of Provence) and low water levels. The upper Durance is an alpine river with a flow ranging from 18 to 197 cubic metres per second (640 to 6,960 cu ft/s). Its total drainage area is 14,225 square kilometres (5,492 mi2). At the confluence with Ubaye, salmon used to thrive, and trout were found up as far as Sisteron, before the development of the river. Later it becomes a Mediterranean river with the characteristic morphology.

The sources of the water are a combination of melting snow and the drainage of rain from the surrounding hills and plateaux which have a Mediterranean climate.

History

The Durance played a very important part in the history of Provence, and largely contributed to the economic growth and population of the Marseilles area, after having been an obstacle for centuries. From Antiquity until the 19th century, the Durance was famous for the difficulty of crossing it, its massive floods and an inconstant flow. The width of its bed, the force and depth of its current, and the changes of course after the floods hindered crossing by ford. The only durable fords are those of Mirabeau and Pertuis, obviously unusable in periods of floods. The changes in the flow also limited river navigation (in spite of size of the river in periods with a high flow. It sometimes needed several ferries to cross the various arms or channels.

Ecology

Along the river there are many habitats of both regional and European importance that are naturally governed by the varying flow of the river. These habitats include both mountain and Mediterranean types. The river with its valley is an important biological corridor, within the national green infrastructure and the Pan-European ecological network. Consequently, it is classified as a Natura 2000 protected area.

Currently there are between 150 and 200 species of benthic macroinvertebrates, but with few plant species (due to the greatly changing flow of the river).