Saône

• 1. Introduction

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  The Saône is a river in eastern France that Julius Caesar found nearly impossible to read. In his Commentaries on the Gallic War, Caesar explained that its pre-Roman name, Arar, doubled an Indo-European root meaning water. The doubling, he said, reflected how slowly the river moved, so that no one could easily tell which way it was flowing. That sluggish water rises in the Vosges and slides south through Burgundy until it meets the Rhône at Lyon. Along the way it raises odd questions. How does a river come to carry the name of a goddess? Why do some people claim the Saône actually flows into its own tributary? And how can a river this calm turn violent enough that villagers still mark the height of its waters on plaques?

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• 2. A Goddess Becomes a River

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  The name Saône begins with Souconna, a Gallic river goddess. Her name has also been linked to a local Celtic tribe, the Sequanes. Over the centuries, monastic copyists reshaped the spelling, first into Saoconna and eventually into the Saône of today.

  Another route to the same name runs through a sacred spring called Sauc-Onna at Chalon. Roman legionaries used that spring's name to describe the whole river, and the habit stuck. Older records preserve other names too, including Brigoulus and the Latin-era Arar.

  The Battle of the Arar, the first major battle of the Gallic Wars, took place on this river. Arar also left a mark on how historians describe Burgundy. Writers invented the terms Burgundia Cisararica and Burgundia Transararica, meaning Burgundy on this side of the Saône or on the other side. Which label applied depended on where the author stood.

  The river's later names lead naturally to a puzzle about its size, because one of its tributaries has a surprisingly strong claim to be the main stream.

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• 3. Saône or Doubs

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  Verdun-sur-le-Doubs, in Saône-et-Loire, is where the Saône meets its largest tributary, the Doubs. Upstream of that point the Saône carries the name Petite Saône, the lesser Saône. The name itself admits how much the Doubs adds.

  The flow figures make the argument for the Doubs. Its mean annual flow is 175 cubic metres per second, while the Petite Saône brings 160. Some observers therefore claim that the Saône is the stream flowing into the Doubs, not the other way round.

  The Saône answers with its watershed. It drains 11500 square kilometres, against 7500 for the Doubs. Taken as a whole, the Saône basin covers 30000 square kilometres. That is the largest drainage area of any French river that does not run straight to the sea, and it spans roughly one eighteenth of metropolitan France.

  Below the junction the river is known as the greater Saône, the Grande Saône, and its character changes entirely.

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• 4. From Vioménil to Lyon

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  At Vioménil, in the Vosges department, the Saône starts at the foot of a cliff, 392 metres above sea level. It finishes 473 kilometres later in Lyon, at an elevation of 158 metres. There it joins the Rhône at the southern tip of the Presqu'île, the peninsula between the two rivers.

  In between, the river passes through five more departments, each with its own string of towns. In the Vosges the list includes Darney and Monthureux-sur-Saône. Haute-Saône brings Jussey, Port-sur-Saône and Gray. Côte-d'Or adds Auxonne, Saint-Jean-de-Losne and Seurre.

  Farther south, Saône-et-Loire contributes Chalon-sur-Saône, Tournus and Mâcon. The Ain department offers Thoissey, and the Rhône department offers Villefranche-sur-Saône, Anse and Caluire-et-Cuire before the river reaches Lyon.

  Dozens of smaller streams feed the Saône on the way, from the Ourche and the Lanterne to the Ognon, the Tille and the Ouche. The Azergues is the last major arrival on the right bank before Lyon. Once the river is large enough to carry boats, the story shifts from water to engineering.

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• 5. A Crossroads of Canals

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  Boats can enter the Saône at Corre, in the north of Haute-Saône, where the Coney joins it. From there the navigable channel runs 367 kilometres to La Mulatière in Lyon, where it meets the Rhône, another navigable river.

  The two halves of that route differ. The 206 kilometres from Saint-Symphorien-sur-Saône to Lyon have been rebuilt to European high-capacity dimensions, and they need only 5 locks. The 161 kilometres upstream, back to Corre, form the Petite Saône. It takes Freycinet gauge vessels and has 19 locks.

  Canals tie the river to the rest of the country. The Canal du Centre reaches the Loire, and the Canal de Bourgogne reaches the Yonne. The Canal entre Champagne et Bourgogne, once called the Canal de la Marne à la Saône, leads to the Marne.

  To the east, the Canal de l'Est links the Saône to the Meuse. Its southern branch has been renamed the Canal des Vosges. The Canal du Rhône au Rhin runs on to the Rhine. All of these canals follow the Freycinet gauge.

  Three short waterways also open off the Saône but lead nowhere else. They are the 3 kilometre Canal de Pont-de-Vaux, a 40 kilometre stretch of the Seille up to Louhans, and the lower Doubs.

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• 6. The Rhythm of the Water

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  Fifty years of measurements, as of 2013, at the Ray-sur-Saône station between Port-sur-Saône and Gray give the upper river a mean flow of 59.7 cubic metres per second. That station watches a basin of 3740 square kilometres. The yearly maximum is 64.5 and the minimum is 54.8.

  The Petite Saône is prone to flooding, and snow sometimes plays a part. The soils absorb little water, so they saturate fast and rain runs straight off the surface. The flow rises quickly, and once the Lanterne has joined, the Saône is already a powerful river. Very heavy rainfall in the Vosges part of the Lanterne's watershed explains why that tributary's runoff figure is 687 millimetres a year, compared with 505 for the whole upper basin.

  Seasons shape the numbers. From December to March, winter floods reach 84 to 108 cubic metres per second. In August the monthly average sinks to 16.9. The highest instantaneous flow recorded at Ray-sur-Saône was 930 cubic metres per second, on the 19th of December 1982.

  The greater Saône behaves differently. It crosses a broad plain about 3 kilometres wide, on the floor of the former Bressan lake, with only a gentle slope and modest tributaries. At Couzon-au-Mont-d'Or, where the river enters the Lyon area, readings from 1969 to 1986 gave a mean flow of 473 cubic metres per second. The calculated 100-year flood there reaches 3180.

  In Lyon the long-term average is 475, ranging from 153 in August to 954 in February. Those extremes set the stage for the floods that people still remember.

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• 7. Floods Remembered

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  A flood on the Saône does not hit every town equally. A large surge from upstream can fade out in the Bressan plain and reach Mâcon as a moderate event, especially if the volume is small. A medium flood on the lesser Saône can grow dangerous farther down if the Doubs delivers a similar pulse at about the same time.

  The chronicle of notable floods stretches back to the Lyon flood of 580. Later entries include the floods of 1602, which came with the autumn equinox, and of 1711. The flood of May 1856 is also recorded.

  November 1840 was the worst of them. The flow was estimated at almost 4000 cubic metres per second, and many homes along the valley were destroyed. At Mâcon the water on flood scales stood at 8.05 metres, and at Chalon at 7.28. That is about 6 and 5.5 metres above normal. Plaques recording the event can still be seen in the affected villages.

  The largest floods of the 50 years to 2006 came in January 1955, March 1970, December 1981 and 1982, May 1983, March 2001 and 2006.

  Planners treat the 100-year flood as their reference. In December 2008, local mayors received maps that modelled the 1840 flood under present-day building conditions, and new prevention plans were ordered for 2012.

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