The nameSaône derives from that of theGallic river goddessSouconna, which has also been connected with a localCeltic tribe, theSequanes.Monastic copyists progressively transformedSouconna toSaoconna, which ultimately gave rise toSaône. The other recorded ancient names for the river wereBrigoulus andArar. The nameArar later gave rise to specific regional terms inhistoriography, created to designate various northern parts ofhistorical Burgundy in relation to the river Saône. Depending on the point of view of a particular author, northern Burgundian lands were thus designated whether "on this side of Saône" (Burgundia Cisararica) or "on the other side of Saône" (Burgundia Transararica).[2]
The Saône rises at Vioménil at the foot of the cliff of theFaucilles [fr] in theVosges at an elevation of 392 metres (1,286 ft); it flows into the Rhône at Lyon at an elevation of 158 metres (518 ft).
Its length is 473 kilometres (294 mi).[3] Its largest tributary is theDoubs; upstream of receiving the Doubs atVerdun-sur-le-Doubs inSaône-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's mean annual flow rate is slightly stronger than that of the Petite Saône, 175 cubic metres per second (6,200 cu ft/s) compared to 160 cubic metres per second (5,700 cu ft/s); some thus assert that it is in fact the Saône that flows into the Doubs. Nonetheless, the Saône has a substantially largerwatershed than the Doubs, at 11,500 square kilometres (4,400 sq mi)vs. 7,500 square kilometres (2,900 sq mi).
At 30,000 square kilometres (12,000 sq mi) the Saône has the largest watershed of any French river that does not flow directly into the sea, covering approximately 1/18 ofmetropolitan France.
In pre-Roman times the river's name was "Arar", a doubling of theIndo-European rootar (water). According toJulius Caesar'sCommentaries on the Gallic War this doubling reflected the idea that it was difficult to identify the direction of the river due to its slow rate of flow. TheBattle of the Arar was the first major battle of theGallic Wars. Its current name came from a sacred spring,Sauc-Onna, located atChalon, which was used byRoman legionaries to refer to the entire river.
Saint Albin tunnel at Scey-sur-Saône-et-Saint-Albin
The Saône is navigable from itsconfluence with the Coney atCorre in the north of thedépartementHaute-Saône all the way to its confluence with theRhône (itself a navigable river) atLa Mulatière, in Lyon. The navigable stretch is 367 kilometres (228 mi) long, of which 206 kilometres (128 mi) has been redeveloped to European high-capacity dimensions fromSaint-Symphorien-sur-Saône to Lyon. It has 5 locks.[4] The 161 km long part upstream from Saint-Symphorien-sur-Saône to Corre, also namedPetite Saône, is navigable forFreycinet gauge ships and has 19 locks.[5]
Also navigable are the smallCanal de Pont-de-Vaux (3 km), the Seille, navigable in a 40-kilometre (25 mi) stretch up toLouhans, as well as the lower part of the Doubs. None of these three connect the Saône to any other waterway.
The lesser Saône has a tendency to flood (sometimes influenced by snow), with a very strong oceanic effect. Thesoils are not susceptible to muchinfiltration, so that they saturate quickly which contributes tosurface 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 theRay-sur-Saône hydrological station, situated about 30 kilometres (19 mi) after the Lanterne confluence betweenPort-sur-Saône andGray. The figure is 59.7 cubic metres per second (2,110 cu ft/s) for a watershed area of 3,740 square kilometres (1,440 sq mi) (the upper basin of the lesser Saône), and has an annual maximum of 64.5 cubic metres per second (2,280 cu ft/s) and a minimum of 54.8 cubic metres per second (1,940 cu ft/s).
The river exhibits seasonal variations in flow rate, with winter floods from 84 to 108 cubic metres per second (3,000 to 3,800 cu ft/s) from December to March inclusive, and summer reductions in July/August/September falling to a monthly average of 16.9 cubic metres per second (600 cu ft/s) in August.[6]
Therunoff curve number in the upper basin of the lesser Saône is 505 millimetres (19.9 in) annually,cf. 687 millimetres (27.0 in) 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 kilometre of watershed.
The maximum instantaneous recorded flow rate was 930 cubic metres per second (33,000 cu ft/s) on December 19, 1982.
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 cubic metres per second (6,200 cu ft/s), and the lesser Saône, 160 cubic metres per second (5,700 cu ft/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 kilometres (2 mi) wide as far as Lyon in the basin of the formerBressan lake. The slope is very gradual, and withouthydraulic projects up to the north of Chalon aimed at guaranteeing a deep navigation channel, overflows would be more frequent.
At theCouzon-au-Mont-d'Or hydrological station, where the river enters the Lyon area, measurements taken between 1969 and 1986 revealed a mean annual flow rate of 473 cubic metres per second (16,700 cu ft/s), with a 100-year flood flow rate of 3,180 cubic metres per second (112,000 cu ft/s)[7] The runoff curve number from the river's entire watershed is 501 millimetres (19.7 in), and the specific flow rate rises to 15.8 litres per second per square km of watershed.
Overall, the average flow rate in Lyon is 475 cubic metres per second (16,800 cu ft/s), with a minimum of 153 cubic metres per second (5,400 cu ft/s), in August, and a maximum of 954 cubic metres per second (33,700 cu ft/s), in February.[8]
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.
The flood of November 1840, with an estimated flow rate of almost 4,000 cubic metres per second (140,000 cu ft/s), destroyed numerous habitations along theriver valley. Many plaques marking this serious event are still visible in the villages affected. The high water measured at flood scales reached 8.05 metres (26.4 ft) at Mâcon and 7.28 metres (23.9 ft) at Chalon, or about 6 and 5.5 metres (20 and 18 ft) 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 intown planning is the100-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.
A plaque commemorating the flood of 1840 atQuincieux
River Saône (Petite Saône) with maps and information on places, ports and moorings on the river from Corre to Saint-Jean-de-Losne, by the author ofInland Waterways of France, Imray
River Saône (Grande Saône) with maps and information on places, ports and moorings on the river from Saint-Jean-de-Losne to Lyon, by the author ofInland Waterways of France, Imray
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