Avelon

The Avelon is a French Rivière which runs in the department of the Oise (60). It is an affluent of the Thérain out of Right Bank, therefore a tributary of a tributary of the the Seine by Thérain and the Oise.

Geography

Avelon is born in the Pays from Bray, where the essence of its basin is, between the localities of Senantes and Villembray, i.e. with the Western borders from the department from the Oise close to the Seine-Maritime. It is thrown in the Thérain (Right Bank) with Beauvais.

Common crossings

Avelon crosses the communes of Senantes, Villembray, Blacourt, Saint-Aubin-in-Bray, Lachapelle-with-Pots, Ons-in-Bray, Saint-Germain-the-Pottery, Saint-Paul, Rainvillers, With-Marsh, Goincourt and Beauvais, all located in the department of the Oise.

Hydrology

Avelon is a fairly abundant river. Its flow was observed during 40 years (between 1968-2007), with Goincourt, very close to its confluence with Thérain. The catchment area of the river is there of 171 km ², i.e. its quasi totality.

The interannual medium flow or module of the river with Goincourt is of 1,12 m ³ a second.

Avelon presents seasonal fluctuations of flow moderated, with high waters of winter carrying the average monthly flow on a level located between 1,46 and 1,92 m ³ a second, from December to March included (with an in February maximum). As of April, the flow decreases gradually to the low waters of summer which occur from July to October, involving a fall of the monthly medium flow going up to 0,474 m ³ in September. However the fluctuations can be more marked over moreover short periods, and the levels fluctuate according to the years.

The VCN3 can fall until 0,17 m ³, in the event of dry period quinquennial, which is not yet really severe, but contrast strongly with the VCN3 of the Petit Thérain which, for a module higher of less than 50% than that of Avelon, preserves a flow of 830 liters a second in the worst of the cases, is 400% of more than Avelon (see note).

As almost all the affluents of Oise out of Right Bank, close to High-Normandy or the Sum thus of the ocean, Avelon presents risings very little important. The QIX 2 or calculated flow of biennial rising and QIX 5 (calculated flow of quinquennial rising) are worth respectively 5,7 and 7 m ³. The QIX 10 or calculated flow of decennial rising is of 7,9 m ³ a second and the QIX 20 of 8,7 m ³. As for the QIX 50, it is assembled only to 9,8 m ³ a second (see note). That means that, for example, every five years, one must expect a rising of about 7 cubic meters, and every twenty years a rising from 8 to 9 cubic meters must statistically occur.

The recorded maximum instantaneous flow was of 11,8 m ³ a second on February 15th, 2007, while the maximum daily output was of 10,9 on February 12th, 1988. By comparing the value of the maximum instantaneous flow on a QIX scale of the river, it appears that this rising was much stronger than that determined by the QIX 50, and was thus very exceptional.

On the whole, Avelon is a fairly abundant river. Blade of water past in its area catchment is of 206 millimetres annually (against 243 for the Oise), which is average enough for the area, and is worth definitely less than the overall average of France, all confused basins. This figure is also lower than the blade of the totality of the basin of the Seine (240 millimetres). The specific Flow of the river (or Qsp) reached the figure of 6,5 liters a second and per square kilometer of basin.

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