Arly

The Arly is one of the affluents of the Isere. It is thrown to it (Right Bank) to Albertville.

Geography

Arly is formed downstream from Megève with the confluence of water of two torrents: the brook of Planay and the brook of Glapet, which take their source both on the northern slope of the Mont Jolly and the Aiguilles Eighth notes, upstream of the Joux Plan.
Its course follows the communes of Praz-sur-Arly then, crosses the limit Savoy/Haute-Savoie to the Panloup locality, then continuous on Flumet, where it receives water of the Arrondine and more far from Flon, continues through the Barrage of Mottets towards Ugine. There, it transfers in the south after having joined the Chair, passes the commune of Marthod then receives the Doron of Beaufort before being thrown in the Isere.

The Throats of Arly, very boxed and dark, are famous for their road, RN 212, which is closed as often as it is opened, because of the frequency of the crumblings. A road of deviation borrowed formerly by the barouches, but malcommode, passes by the northern slope of the throats through the hamlets of Rafforts and the commune of Héry-on-Ugine.

Principal affluents

the Arrondine, which runs since the Plan of Giettaz and the Col of Aravis;
the Flon;
the Chair, which takes its source towards Faverges;
the Doron of Beaufort, resulting from water of the lake of the Dam Roselend.

Etymology

Following the example much of hydronymes in Ar (Arve, Arrondine…) , the origin of the name Arly is unknown but preceltic - i.e., for want of anything better, Ligurian or older.

Flon drift on the other hand directly of Latin fluvium , river.

Hydrology

The interannual medium flow of Arly was observed and calculated over one 11 years period to Ugine. It is assembled to 8,2 m ³ a second for a surface of basin of 225 km ², that is to say only one third of its catchment area (668 km ²). The river present of the seasonal fluctuations of flow typical of a nival mode, with high waters of spring due to the snow melt and carrying the average monthly flow on the level of 14,6 to 19 m ³ in April - May (with an in May maximum), and a double low water level, the first at the beginning of autumn (4,9 m ³ a second in September - October) and the second in winter, involving a fall of the monthly medium flow up to the level of 3,2 m ³ in January.

The VCN3 can fall until 0,285 m ³, in the event of dry decennial period. The VCN3 is the past minimal quantity or minimal flow over three days consecutive.

As for the risings, they can be very important. Indeed, the QIX 2 or calculated flow of rising biennial and QIX 5 calculated for a quinquennial rising are worth respectively 100 and 151 m ³ a second. The QIX 10 or calculated flow of decennial rising is of 185 m ³ a second, the QIX 20 and the QIX 50 available, because is not calculated being given the insufficiency of the period of observation (see note).

Instantaneous maximum flow recorded in Ugine east of 235 m ³ a second, while the daily maximum flow is worth 132 m ³ a second.

The Lame of water past in the catchment area of the river is of 1.148 millimetres annually, which is very high but completely normal in Savoy. The specific flow (Qsp) is assembled thus at 36,4 liters a second and per square kilometer of basin.

Crossed communes and cities

Megève ~ Praz-sur-Arly ~ Flumet ~ Saint-Nicolas-the-Vault ~ Crest-Voland ~ Héry-on-Ugine ~ Cohennoz ~ Ugine ~ Marthod ~ Albertville.

References

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