Ã“engus II del Picts

The Dranse is a French river , department of Haute-Savoie which is thrown in the Lac Léman.

The name Dranse comes from old * a Drantia , based on the hydronyme Dur-, gilded and the suffix - antia .

Geography

It is resulting from the meeting, approximately nine to ten kilometers upstream of the delta, about at the same place, of three rivers of mountain coming from the mounts of Haut-Chablais.

in the east, the Dranse d' Abondance which irrigates the Val of Abundance and crosses the communes of Abondance and of Châtel;
in the south, the Dranse de Morzine which cross, Morzine, Saint-Jean-with Aulps and the Gorges of the Bridge-of-Devil;
in the west, the Brevon, also called Dranse de Bellevaux which come from the Roc of Hell and cross the Lac of Small valley and the village of Bellevaux.

Dranse d' Abondance is regarded as upper part of the course of the Dranse river. Dranse de Morzine is consequently its affluent (see note).

Dranse is thrown in the Lac Léman by forming a delta, integrated in the Natural reserve of the delta of Dranse, located at the east of Thonon-the-Baths, on a small surface of 53 hectares, but offering an incomparable botanical richness.

Hydrology

Dranse is a very abundant river, like all the rivers resulting from the solid masses préalpins. Its flow was observed over one period of 97 years (1906-2003), with Reyvroz, locality of the department of Haute-Savoie located on southern bank of the Lac Léman at the level of its outlet in the lake. The catchment area of the river is there of 495 km ² (either its totality) what does not exceed the equivalent of three times the surface of the commune of Paris.

The interannual medium flow or module of the river with Reyvroz is of 20,1 m ³ a second.

Dranse has a typically nival mode, with however a small rain component. It presents seasonal fluctuations of flow marked well, like rule within the alpine rivers. The high waters are held in spring and are due primarily to the snow melt. They are accompanied by average monthly flows going from 30 to 40 m ³ a second, from April at June included (with an in May maximum). As of at the end of June, the flow drops abruptly what leads very quickly to low waters. Those take place of at the end of July at the end of February and post a flow always solid, oscillating between 12,7 and 17,1 m ³ a second, with a floor of 12,7 m ³ in August, and cut of light a " sommet" in November, related to the rains of autumn. But the fluctuations are much more marked over short periods and according to the years.

With the low water level, the VCN3 can fall until 2,5 m ³ a second, in the event of period quinquennial dry, which is rather low, but perfectly normal in the area of the Alps and the préalpes (see note).

As for the risings, they can be very important, though without common measurement with certain rivers of midday, like the Cevennes rivers. The QIX 2 and QIX 5 or calculated flows of biennial and quinquennial rising are worth respectively 180 and 220 m ³. The QIX 10 or calculated flow of decennial rising is of 250 m ³ a second, the QIX 20 of 270 m ³ and the QIX 50 of 310 m ³ (see note).

The maximum instantaneous flow recorded at the station of Reyvroz was of 273 m ³ a second on June 1st, 1963, while the value maximum day laborer was of 229 m ³ a second on September 22nd, 1968. By comparing the first of these values on a QIX scale of the river, it arises that this rising of June 1963 was of a vicennial nature, and thus at all exceptional.

Dranse is an extremely abundant river, supplied with such abundant precipitations they, in the area of the Alps of north. The Lame of water past in its catchment area is of 1 285 millimetres annually, which is very high, more than three times superior to the overall average of France. The specific Flow of the river (or Qsp) reached the very high figure of 40,7 liters a second and per square kilometer of basin.

Random links: