Editing Saône (section)

== Hydrology ==
=== The lesser Saône (Petite Saône) ===
[[File:Source de la Saone.jpg|thumb|Source of the Saône at Vioménil]]
[[File:Saone at gray.jpg|thumb|The Saône at Gray]]
[[File:Puvis de Chavannes Personification of the Saone.jpg|thumb|Personification of the Saône by [[Pierre Puvis de Chavannes]], 1883–1886, [[National Museum, Warsaw|National Museum]] in [[Warsaw]], a study for decoration of the stairwell in the new wing of the [[Museum of Fine Arts of Lyon|Palace of Fine Arts]] in [[Lyon]], a city at the confluence of the Saône and [[Rhône]] rivers]]
The lesser Saône has a tendency to flood (sometimes influenced by snow), with a very strong oceanic effect. The [[soil]]s are not susceptible to much [[infiltration (hydrology)|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 {{convert|30|km|mi}} after the Lanterne confluence between [[Port-sur-Saône]] and [[Gray (Haute-Saône)|Gray]]. The figure is {{convert|59.7|m3/s|cuft/s}} for a watershed area of {{convert|3740|km2|mi2}} (the upper basin of the lesser Saône), and has an annual maximum of {{convert|64.5|m3/s|cuft/s}} and a minimum of {{convert|54.8|m3/s|cuft/s}}.

The river exhibits seasonal variations in flow rate, with winter floods from {{convert|84|to|108|m3/s|cuft/s}} from December to March inclusive, and summer reductions in July/August/September falling to a monthly average of {{convert|16.9|m3/s|cuft/s}} in August.<ref>{{in lang|fr}} [http://www.hydro.eaufrance.fr/selection.php Banque Hydro – Station U0610010 – La Saône à Ray-sur-Saône (Synthèse)] (Do not tick the box "Station en service")</ref>

The [[runoff curve number]] in the upper basin of the lesser Saône is {{convert|505|mm|in}} annually, ''cf.'' {{convert|687|mm|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 {{convert|930|m3/s|cuft/s}} on December 19, 1982.

=== The greater Saône (Grande Saône) ===
[[File:La Saône à Neuville-sur-Saône.jpg|thumb|The Saône at [[Neuville-sur-Saône]]]]
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 {{convert|175|m3/s|cuft/s}}, and the lesser Saône, {{convert|160|m3/s|cuft/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 {{convert|3|km|mi|0}} wide as far as Lyon in the basin of the former [[Bresse|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, where the river enters the Lyon area, measurements taken between 1969 and 1986 revealed a mean annual flow rate of {{convert|473|m3/s|cuft/s}}, with a 100-year flood flow rate of {{convert|3180|m3/s|cuft/s}}<ref>{{in lang|fr}} [http://www.eptb.asso.fr/dyn/eptb-asso/fichiers/monographie/pj/Saone.pdf Drainage basin of the Saône] {{webarchive|url=https://web.archive.org/web/20071013222622/http://www.eptb.asso.fr/dyn/eptb-asso/fichiers/monographie/pj/Saone.pdf |date=October 13, 2007 }}</ref> The runoff curve number from the river's entire watershed is {{convert|501|mm|in}}, and the specific flow rate rises to 15.8 litres per second per square km of watershed.

==== Average flow rate ====
{{River discharge
|station=[[Couzon-au-Mont-d'Or]]
|date=date unknown
|unit=m<sup>3</sup>/s
|source = [http://www.hydro.eaufrance.fr/selection.php Banque Hydro – Station U4710010]
|max discharge = 1000
|main scale = 200
|secondary scale = 50
|jan1=747
|feb1=954
|mar1=679
|apr1=565
|may1=462
|jun1=306
|jul1=197
|aug1=153
|sep1=159
|oct1=303
|nov1=439
|dec1=745
}}

Overall, the average flow rate in Lyon is {{convert|475|m3/s|cuft/s}}, with a minimum of {{convert|153|m3/s|cuft/s}}, in August, and a maximum of {{convert|954|m3/s|cuft/s}}, in February.<ref>{{in lang|fr}} [http://www.hydro.eaufrance.fr/selection.php Banque Hydro – Station U4710010 – La Saône à Couzon-au-Mont-d'Or] (Do not tick the box "Station en service")</ref>

=== Historic floods ===
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 (Northern Hemisphere)|autumn equinox]]<ref>{{in lang|fr}} [http://91.121.162.160/BIB/champion/tomes/tome4/Tome4.htm Floods of the Rhône and all its tributaries, Volume 4]</ref> and of 1711
* The flood of November 1840, with an estimated flow rate of almost {{convert|4000|m3/s|cuft/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 {{convert|8.05|m|ft}} at Mâcon and {{convert|7.28|m|ft}} at Chalon, or about {{convert|6|and|5.5|m|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 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.

<gallery>
File:SAONE1840.jpg|A plaque commemorating the flood of 1840 at [[Quincieux]]
File:Saône - échelle des inondations à Ecuelles.JPG|Historic floods since 1950 [[Écuelles, Saône-et-Loire|Écuelles]], north [[Saône-et-Loire]]
File:Niveau crue Saône Belleville.jpg|Indicators of the level of historic floods of the Saône on the Church of Notre-Dame de [[Belleville-sur-Saône|Belleville]]
</gallery>