The Sionne is a

Swiss Swiss most commonly refers to: * the adjectival form of Switzerland * Swiss people Swiss may also refer to: Places * Swiss, Missouri * Swiss, North Carolina * Swiss, West Virginia * Swiss, Wisconsin Other uses * Swiss Café, an old café located ...

river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

, and a

tributary A tributary, or an ''affluent'', is a stream or river that flows into a larger stream (''main stem'' or ''"parent"''), river, or a lake. A tributary does not flow directly into a sea or ocean. Tributaries, and the main stem river into which they ...

of the

Rhône The Rhône ( , ; Occitan language, Occitan: ''Ròse''; Franco-Provençal, Arpitan: ''Rôno'') is a major river in France and Switzerland, rising in the Alps and flowing west and south through Lake Geneva and Southeastern France before dischargi ...

Course

This torrential has a nival regime and is a right-bank tributary of the

. Its source is in the Chamossaire region at an altitude of 2,310 m. It crosses the

Savièse Savièse is a municipality in the district of Sion in the canton of Valais in Switzerland. History Savièse is first mentioned in 1200 as ''Saviesi''. In 1224 it was mentioned as ''Savisia''. The municipality was formerly known by its German ...

and

Grimisuat Grimisuat is a municipality in the district of Sion in the canton of Valais in Switzerland. History Grimisuat is first mentioned around 1001-1100 as ''Grimisoch''. The municipality was formerly known by its unknown name ''Grimslen'', however, ...

plateaus and, after a course of around 11 km, flows into the

at 490 m, after passing through the town of Sion. Its catchment area is 27.6 km. Its main tributary is the Drahin. The Swiss Federal Institute carries out

avalanche An avalanche is a rapid flow of snow down a Grade (slope), slope, such as a hill or mountain. Avalanches can be triggered spontaneously, by factors such as increased precipitation or snowpack weakening, or by external means such as humans, othe ...

measurements on the right bank.

Notable floods

Following major floods, the Sionne was covered over almost 400 m across the town of Sion in several phases between 1657 and the end of 1740, leading to the creation of the Rue du Grand-Pont. The Sionne has often caused flooding, particularly in the lower reaches of the Valais capital. About twice a century, a catastrophic event is observed, accompanied by severe damage. The last two major floods occurred in November 1944 and July 1992. To prevent further major damage, measures have been taken upstream of Sion and in the town of Sion at the Place des Tanneries. An EPFL study carried out prior to this work determined that a 100-year flood could reach a discharge of 39 m³/s. On August 6, 2018, a violent thunderstorm caused the river to overflow its banks, with flows reaching 8 m³/s. On July 26, 2019, the previous year's scenario was repeated, albeit with less virulence. The maximum flow rate measured was 6.3 m³/s.{{Cite news , last=Gabbud , first=Jean-Yves , date=July 26, 2019 , title=Caves inondées et routes coupées en Valais , work=Le Nouvelliste Cellars in the town of Sion were still flooded. From September 2019, Sion will own 440 m of mobile dikes that can be deployed by the fire department.

References

Rhône International rivers of Europe Rivers of Switzerland

Course

Notable floods

See also

References