is a river
, northern France
. The name Somme
comes from a Celtic
word meaning tranquility
. The department Somme
was named after this river.
The river is 245 km long, from its source in the high ground of the former Forest of Arrouaise at Fonsommes
, to the Bay of the Somme, in the English Channel
. It lies in the geological syncline
which also forms the Solent
. This gives it a fairly constant and gentle gradient.
Départements and towns along the river
The river is characterized by a very gentle gradient and a steady flow. The valley is more or less steep-sided but its bottom is flat with fens
and pools. These characteristics of steady flow and flooded valley bottom arise from the river's being fed by the ground water
in the chalk
basin in which it lies. At earlier, colder times, from the Günz
to the Würm
(Beestonian or Nebraskan to Devensian or Wisconsinian) the river has cut down into the Cretaceous geology
to a level below the modern water table
. The valley bottom has now therefore, filled with water which, in turn, has filled with fen
. This picture
, of the source of the Somme in 1986, shows it when the water table had fallen below the surface of the chalk in which the aquifer
lies. Here, the flow of water had been sufficient to keep the fen from forming.
This satellite photograph shows the fenny valley crossing the chalk to the sea on the left. The sinuous length at the centre of the picture lies downstream from Péronne.
One of the fens, the Marais de l'Île is a nature reserve in the town of St.Quentin. The traditional market gardens of Amiens, the Hortillonages are on this sort of land but drained. Once exploited for peat cutting, the fen is now used for fishing and shooting.
The construction of the Canal de la Somme began in 1770 and reached completion in 1843. It is 156 km long, beginning at St.Simon and opening into the Bay of the Somme. From St.Simon to Froissy (near Bray sur Somme, south of Albert), the canal is alongside the river. Thence to the sea, the river is partly river and partly navigation. From Abbeville, it is diverted through the silted, former estuary, to Saint-Valéry-sur-Somme, where the maritime canal, once called the canal du Duc d'Angoulême enters the English Channel.
The St.Quentin Canal, famous for the 1918 battle, links the Somme to northern France and Belgium and southward to the Oise. The Canal du Nord also links the Somme to the Oise, at Noyon, thence to Paris.
In 2001, the Somme valley was affected by particularly high floods, which were in large part due to a rise in the water table of the surrounding land.
Flow-rate data (external links)
Monthly flow rates (mean over 43 years)
Catchment area 5560 km².
Daily flow rates compared with mean rates for the time of year at Hangest-sur-Somme (m³/s)
Catchment area 4835 km².
2000 2001 2002 2003 2004 2005
Mean flow rates monthly and daily at Péronne (m³/s)
Catchment area 1294 km².
1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
- Delattre, Ch., Mériaux, E. and Waterlot, M. Guides Géologiques Régionaux: Région du Nord, Flandre Artois Boulonnais Picardie (1973)