Selun — Wikipedia

The Sélune
THE Source.
Sélune cours.
Features
Length	84.7 km [ first ]
Bowl	1 038 km 2 [ first ]
Collector	The Sélune
Medium flow	11 m 3 /s [Ref. necessary]
Diet	rainy oceanic
Course
Source	La Luatareière
· Localisation	Saint-Cyr-du-Bailleul
· Altitude	180 m
· Contact details	48 ° 33 ′ 41 ″ N, 0 ° 46 ′ 37 ″ o
Mouth	The Channel
· Localisation	Baie du Mont-Saint-Michel
· Altitude	0 m
· Contact details	48 ° 38 ′ 50 ″ N, 1 ° 24 ′ 00 ″ o
Geography
Main tributaries
· Left Bank	Airon, Lair, Beuvron
· Right bank	CANCE, Guike, Argonce, because
Country crossed	France
Department	Some
Regions crossed	Normandy
Main localities	Saint-Hilaire-du-Harcouët, Ducey
Sources : Sandre: ‘ I9–0200 » , Géoportail, OpenStreetMap
modifier

The Sélune is a French coastal river flowing in the Manche department, in the Normandy region.

He has his source in Saint-Cyr-du-Bailleul and throws himself into the Bay of Mont-Saint-Michel.

The Celtic origin of the hydronym has been described in a study of a learned society of Avranches: “[…] formerly called Se-Onna or Seunna, Sée-on, Water Water or the meeting of several waters. »» ^{[ 2 ]} .

Topography [ modifier | Modifier and code ]

The length of its course is 84.7 km ^{[ first ]} or 68 km ^{[ 3 ]} .

The Sélune has its source at around 175 meters above sea level at the southeast limit of the town of Saint-Cyr-du-Bailleul and west of the Normandie-Maine regional natural park. It flows freely to the west to Saint-Hilaire-du-Harcouët at an altitude of 64 meters. It then forms two artificial lakes: the large lake and the small lake. After La Roche-Qui-Boit, it is at an altitude of 19 meters. She then headed northwest and passes at the foot of the town of Ducey where she separated into several arms. She finished her race in Pontaubault before throwing herself into the bay of Mont Saint-Michel.

Municipalities and cantons crossed [ modifier | Modifier and code ]

Watershed [ modifier | Modifier and code ]

The Sélune watershed extends over an area of ​​1,009 km ² . Although the Sélune itself flows only in the Manche department (Normandy region), its watershed extends over 13 municipalities in Ille-et-Vilaine (Brittany region) and 9 in Mayenne (Pays de la Loire region ), in addition to 57 municipalities in the Manche ^{[ 3 ]} . This basin borders that of the Sée to the north, that of the Loire (by its sub-pests La Varenne, the Colmont and the Ernée) to the east and southeast and the Basin du Couesnon in the southwest.

Manager [ modifier | Modifier and code ]

The main tributaries of the selune are, upstream downstream:

La Sélune is regularly reassembled by a mascaret ^{[ thirty first ]} .

The hydrological regime of the selune is called ocean rainfall.

This river had the status of border between the Kingdom of Brittany and the Duchy of Normandy until 1009. On that date, the border was moved a few kilometers to the Southwest, to the Couesnon ^{[ 32 ]} .

The July 30, 1944 , American troops landed on the beaches of Normandy discover a bridge over the selune which has not been destroyed ^{[ 33 ]} . Americans protect the German counterattack bridge. Important US troops under the command of General Patton crossed him during the three days.

Hydroelectric dams [ modifier | Modifier and code ]

Two hydroelectric dams were built on the selune in the first half of the XX ^{It is} Century: the La Roche-Boit dam and the Vezins dam.

They arrived at the end of the concession in the 2010s, with three options envisaged: continuity of the production of hydroelectric energy as it is done; Stopping the production of hydroelectric energy and maintaining dams to preserve the two artificial lakes; Destruction and restoration of pre -construction to allow several species of migratory fish (salmon, trout, alleys, lampreys, eels, throats) to go back to the source and effective them, without the need for heavy arrangements. An economic study made the June 9, 2012 By the State in the context of new choice of development and economic development for the Sélune valley once the Vezins and La Roche-Qui-Boit dams are erased, whose size and positioning made two obstacles to the ascent migrants. Shortly before the rendering of this study, WWF-France asked ^{[ 34 ]} to the Minister of Ecology to quickly confirm the end of the concessions announced by Chantal Jouanno then Secretary of State responsible for ecology (the November 13, 2009 ^{[ 35 ]} ).

The sediments accumulated by this type of dam generally contain heavy metals, metalloids, organic pollutants and nitrates and phosphates, pesticide residues, which can pollute downstream (to the detriment of fishery and conchyl activities in particular) if they are released in the middle. 4 million euros were provisioned for the treatment of 2009 to mid-2013 of these questions.
The last emptying dated from 1993.

The Sélune must regain its ecological value, and for regional planning within the framework of the territorial coherence scheme of the country of the bay and the regional green and blue frame and therefore of the future SRCE scheme which prefigures it in 2012.

The decision to destroy the two dams dates from 2009, presented as before “putting the site in accordance with European law” then in 2014, Minister Ségolène Royal requests that we study alternative solutions to allow the circulation of migratory fish out of 90 km of rivers (salmon and eel) ^{[ 36 ]} .

Dract, sludge management and leveling of works were scheduled from 2015 to 2018 ^{[ 37 ]} .

However, the local opposition remains strong against the destruction of the dams. The mayors of the riparian municipalities, as well as the deputy for the constituency of Avranches, refuse demolition, in order to preserve tourist employment, carnivorous fishing and the beauty of the site. The Artificial Lake in Vezins is the only large-scale lake in the South Manche region. An association, Friends of the Vezins dam , federates citizen actions against the government project ^{[ 38 ]} .

In 2016, Valorem was a candidate for the resumption of the Vezins dam following the search for an alternative to the leveling by the Minister of the Environment Ségolène Royal ^{[ 39 ]} . In 2017, the Minister of Ecological Transition Nicolas Hulot revived the biodiversity restoration project, with stalement work before starting in spring 2018 ^{[ 40 ]} . In August 2022 , the destruction of the two dams is almost finished ^{[ 41 ]} .

The Vezins dam [ modifier | Modifier and code ]

This dam, built on the limit of the municipalities of Vezins (associated with Isigny-le-Buat) and Saint-Laurent-de-Terregatte, is multiple vaults, with reinforced concrete buttresses and measures 35 meters high and 278 of long ^{[ 42 ]} .

Eight times more powerful than that of La Roche-Qui-Boit, it belongs to the West Hydraulic Operating Group with the Guerlédan dam, the Saint-Adrien dam, the Rance factory, the La-Roche- Quotation and the Rabodanges Dam ^{[ 43 ]} .

Its potential was identified during the intense stock market speculation of the 1920s on hydroelectricity. It was then built from 1929 to 1932 by the Sélune Motor Forces Society.
The engineers were Louis Pelnard-Considère and Albert Caquot ^{[ 44 ]} .

During the Second World War, he fueled the Arsenal of Cherbourg and the Atlantic Wall. A sabotage destroyed two transformers, which delayed the construction of part of these fortifications.

At the beginning of XXI ^{It is} A century, the Mazure leisure center is installed by the lake. We practice fishing, kayaking, rowing, canoeing, etc.

The dam was to be destroyed in 2018, following the decisions of Chantal Jouanno and Nathalie Kosciusko-Morizet. At the time, an opposition was organized to protect “800 direct or induced jobs” ^{[ 45 ]} . In addition, the emptying of the Vezins dam (May – September 2018 ) has uncovered nearly 500,000 m ³ Sediments suspected of being polluted because the previous emptying, in 1993, caused significant pollution of the Baie du Mont-Saint-Michel. These vases were confined in situ, which cost approximately 20 millions d’E euros ^{[ 36 ]} .

The destruction of the Vezins dam begins in April 2019 . The authorization decree as well as that of La Roche-Qui-Boit were signed at the end October 2018 ^{[ 36 ]} .

The piercing of the vault is effective in June 2019 . The site will spread out until April 2020 at a cost of 4.25 million euros including tax ^{[ forty six ]} .

While dismantling has started, the case is not definitively decided by justice ^{[ 47 ]} .

The Roche-Qui-Boit dam [ modifier | Modifier and code ]

Located downstream from the Vezins dam, of which it has become a compensation work after the construction of it, this dam produced 4 million kilowatt hours annually. It restores at the river a minimum flow of 2 m ³ /s. The restraint lake is 5 km , 40 hectares and 4 million cubic meters of water.

The authorization for the construction of the dam was granted by prefectural decree in August 1914. The work began during the First World War, in 1916 to end in 1919.
The dam is 129 meters long and 16 meters high. It connects the territories of Ducey and Saint-Laurent-de-Terregatte, but almost all of the lake of restraint is shared between the territories of Vezins and Saint-Laurent.

Its emptying should be made from 2020/2021, as decided in 2017 ^{[ 36 ]} .

Fishing [ modifier | Modifier and code ]

The selune waters are rich in salmon. The Sélune is classified by fishermen in the first category. It is also populated by sea trout, eels, fario or rainbow trout, pike, tanches, roach, pike perch, poles and carp.

: document used as a source for writing this article.

Notes [ modifier | Modifier and code ]

References [ modifier | Modifier and code ]

Resource relating to geography :