Saône

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For other uses, see Saone (disambiguation).
Coordinates: 45°43′39″N 4°49′4″E / 45.72750°N 4.81778°E / 45.72750; 4.81778
Saône (Sona)
River
Lyon-quais-Saône-pont-La-Feuillée-nord-nuit.jpg
The Saône in Lyon by night.
Countries France, Switzerland
Tributaries
 - left Doubs, Lanterne
 - right Azergues, Morgon
Source Vioménil
 - location Vosges
 - elevation 392 m (1,286 ft)
 - coordinates 48°05′40″N 6°10′55″E / 48.094444°N 6.181944°E / 48.094444; 6.181944
Mouth Rhône
 - location Lyon, France
 - elevation 158 m (518 ft)
 - coordinates 45°43′39″N 4°49′4″E / 45.72750°N 4.81778°E / 45.72750; 4.81778
Length 473 km (294 mi)
Area 29,950 km2 (11,564 sq mi)
Discharge
 - average 410 m3/s (14,479 cu ft/s)
Scenic view of the banks of the Saône in Lyon, showing Lyon Cathedral, the Basilica of Notre-Dame de Fourvière, and the Tour métallique de Fourvière

The Saône (French pronunciation: ​[soːn];[1] Arpitan Sona, Latin: Arar) is a river of eastern France. It is a right tributary of the River Rhône, rising at Vioménil in the Vosges department and joining the Rhône in Lyon, just south of the Presqu'île.

The name "Saône" derives from that of the Gallic river goddess Souconna, which has also been connected with a local Celtic tribe, the Sequanes. Monastic copyists progressively transformed "Souconna" to "Saoconna", which ultimately gave rise to "Saône". The other recorded ancient names for the river were Brigoulus and Arar.

Geography[edit]

The Saône rises at Vioménil at the foot of the cliff of the Faucilles in the Vosges at an altitude of 392 m, and flows into the Rhône at Lyon at an altitude of 158 m. Its length is 480 km.[2] Its largest tributary is the Doubs; upstream of receiving the Doubs at Verdun-sur-le-Doubs in Saône-et-Loire, the Saône is called the "Petite Saône" (lesser Saône), which reflects the large contribution of the Doubs to the Saône. In fact the Doubs' mean annual flow rate is slightly stronger than that of the Petite Saône (175 vs. 160 m³/s); some thus assert that it is in fact the Saône that flows into the Doubs. Nonetheless the Saône has a substantially larger watershed than the Doubs, at 11500 vs. 7500 km².

At 30,000 km² the Saône has the largest watershed of any French river which does not flow directly into the sea, covering approximately 1/18 of metropolitan France.

In pre-Roman times the river's name was "Arar", a doubling of the Indo-European root ar (water). According to Caesar's Gallic Wars this doubling reflected the idea that it was difficult to identify the direction of the river due to its slow rate of flow. Its current name came from a sacred spring, Sauc-Onna, located at Chalon, which was used by Roman legionnaries to refer to the entire river.

Departments and cities traversed by the Saône[edit]

Course of the Saône
View over the Saône, Lyon, France

Main tributaries of the Saône[edit]

Bridge over the Saône at Tournus

R indicates a right tributary, L indicates a left tributary.

Navigation[edit]

Saint Albin tunnel at Scey-sur-Saône-et-Saint-Albin

The Saône is classed as navigable after its confluence with the Côney at Corre in the north of Haute-Saône all the way to its confluence with the Rhône (itself a navigable river) at la Mulatière, in Lyon. The navigable stretch is over 365 km long, of which 167 km is European large gauge (from Verdun-sur-le-Doubs to Lyon).

The Saône is linked with the Loire by the Canal du Centre, with the Yonne by the Canal de Bourgogne, with the Marne by the Canal entre Champagne et Bourgogne (previously the Canal de la Marne à la Saône), with the Meuse by the Canal de l'Est, whose southern branch has been renamed the Canal des Vosges, and with the Rhine by the Canal du Rhône au Rhin. All the canals are Freycinet gauge.

Also navigable are the small Canal de Pont-de-Vaux (3 km), the Seille, navigable in a 40 km stretch up to Louhans, and the lower part of the Doubs. None of these three connect the Saône to any other body of water, however.

Hydrology[edit]

The lesser Saône[edit]

Source of the Saône at Vioménil
The Saône at Gray
The main bridge at Gray

The lesser Saône has a tendency to flood (sometimes influenced by snow), with a very strong oceanic effect. The soils are not susceptible to much infiltration, so that they saturate quickly which contributes to surface runoff. The flow rate grows very quickly, and after receiving the waters of the Lanterne, the Saône already becomes a powerful river.

The mean annual flow rate, or discharge, of the Saône has been measured over 50 years (as of 2013) at the Ray-sur-Saône hydrological station, situated about 30 km after the Lanterne confluence between Port-sur-Saône and Gray. The figure is 59.7 m³/s for a watershed area of 3,740 km² (the upper basin of the lesser Saône), and has an annual maximum of 64.5 and minimum of 54.8 m³/s.

The river exhibits seasonal variations in flow rate, with winter floods from 84 to 108 m³/s from December to March inclusive, and summer reductions in July/August/September falling to a monthly average of 16.9 m³/s in August.[3]

The runoff curve number in the upper basin of the lesser Saône is 505 mm annually (cf. 687 mm for the Lanterne), an elevated figure resulting from the very high rainfall in the Vosgian part of its watershed. The specific flow rate rises to 16.0 litres per second per square km of watershed.

The maximum instantaneous recorded flow rate was 930 m³/s on December 19, 1982.

The greater Saône[edit]

The greater Saône is formed by the confluence of the Doubs and the lesser Saône at Verdun-sur-le-Doubs. The Doubs brings a mean annual flow rate of 175 m³/s, and the lesser Saône, 160 m³/s.

The greater Saône has only modest tributaries which have little effect on floods or other hydrological properties. It flows in a vast plain approximately 3 km wide as far as Lyon in the basin of the former Bressan lake. The slope is very gradual, and without hydraulic projects up to the north of Chalon aimed at guaranteeing a deep navigation channel, overflows would be more frequent.

At the Couzon-au-Mont-d'Or hydrological station, located where the river enters the Lyon area, measurements taken between 1969 and 1986 revealed a mean annual flow rate of 473 m³/s, with a 100-year flood flow rate of 3,180 m³/s.[4] The runoff curve number from the river's entire watershed is 501 mm, and the specific flow rate rises to 15.8 litres per second per square km of watershed.

Average flow rate[edit]

Mean monthly discharge (in m3/s)
Hydrological station : Couzon-au-Mont-d'Or (date unknown)

Source : Banque Hydro – Station U4710010

Overall, the average flow rate in Lyon is 475 m³/s, with a minimum of 153 m³/s, in August, and a maximum of 954 m³, in February.[5]

Historic floods[edit]

When the Saône floods, the impact varies considerably over the course of the river. A large flood with a strong flow rate upstream can be largely attenuated in the Bressan plain so as to have only moderate impact at Mâcon, particularly if it carries a limited volume of water. By contrast, a medium-sized flood of the lesser Saône can turn into a significant flood downstream, if the Doubs brings in a similar contribution at about the same time.

Historic floods include:

  • The Lyon flood of 580
  • The floods of 1602 during the autumn equinox[6] and of 1711
  • The flood of November 1840, with an estimated flow rate of almost 4,000 m3/s, destroyed numerous habitations along the river valley. Many plaques marking this serious event are still visible in the villages affected. The high water measured at flood scales reached 8.05 m at Mâcon and 7.28 m at Chalon (or about 6 m and 5.5 m respectively above normal levels).
  • The flood of May 1856
  • The largest floods in the last 50 years as of 2006: January 1955, March 1970, December 1981 and 1982, May 1983, March 2001 and 2006.

The reference flood in town planning is the 100-year flood. This reference was in the course of being modified as maps linked to modelling the 1840 flood in modern town planning conditions were distributed to local mayors in December 2008, and as new prevention plans were ordered for 2012.

See also[edit]

References[edit]

  1. ^ (French) Jean-Marie Pierret, Phonétique historique du français et notions de phonétique générale, Peeters, Louvain-la-Neuve, 1994, p. 104.
  2. ^ Sandre. "Fiche rivière la saône (U—0000)" (in French). Retrieved July 19, 2008. 
  3. ^ (French) Banque Hydro – Station U0610010 – La Saône à Ray-sur-Saône (Synthèse) (Do not tick the box "Station en service")
  4. ^ (French) Drainage basin of the Saône
  5. ^ (French) Banque Hydro – Station U4710010 – La Saône à Couzon-au-Mont-d'Or (Do not tick the box "Station en service")
  6. ^ (French) Floods of the Rhône and all its tributaries, Volume 4

External links[edit]