Major Helpe

The Helpe Majeure is a French Rivière. It takes its source close to the Belgian border between Ohain and Momignies, to the south of the forest of Trelon, passes to Eppe-Savage, Liessies, Avesnes-on-Helpe, Taisnières-in-Thiérache, Noyelles-on-Sambre, is thrown in the Sambre. Its average slope is of 1,7.

A stopping on Helpe Major with the Valley Jolly, creating a reserve of 1,56 km ², chops the risings and regularizes the flows for the summer period.

Affluents

the brook of Monbliart, the brook of Belleuse out of Right Bank,
Voyon, Turbid Rieu and Rieu de Baquy out of left bank.

Hydrology

Helpe Majeure is a rather abundant river. Its flow was observed over one 46 years period (1962-2007), with Taisnières-in-Thiérache, locality of the Département of North located at little distance from its confluence with the Sambre. The catchment area of the river is there of 320 km ² (either more than 95% of its totality which makes approximately 335 km ²).

The interannual medium flow or module of the river with Taisnières-in-Thiérache is of 3,9 m ³ a second.

Helpe Major present of the seasonal fluctuations of flow marked well, like very often in the basin of Sambre and in Thiérache corresponding to the Western part of the of the Ardennes solid mass, with high waters of winter carrying the average monthly flow on a level located between 5,85 and 7,3 m ³ a second, from December to March included (with an in January maximum), and low waters of summer, June to October included, with a fall of the monthly medium flow going up to 1,14 m ³ in August. But the fluctuations of flow are much more marked over moreover short periods or according to the years.

With the low water level, the VCN3 can fall until 0,200 m ³, in the event of dry period quinquennial, that is to say 200 liters a second, which is rather severe, but normal compared with the other affluents of Sambre of the area. Let us recall that the VCN3 is the past minimal quantity or minimal flow over three days consecutive.

As for the risings, they can be very important relative with the modest size of the river and its catchment area. The QIX 2 and QIX 5 are worth respectively 31 and 45 m ³ a second. The QIX 10 or calculated flow of decennial rising is of 54 m ³ a second, the QIX 20 of 63 m ³, while the QIX 50 is assembled to 74 m ³ a second (see note).

The maximum instantaneous flow recorded with Taisnières-in-Thiérache during this 46 years period, was of 85,5 m ³ a second on July 1st, 1980, while the value maximum day laborer was of 66 m ³ a second on January 16th, 1968. By comparing the first of these values with the scale of the QIX of the river, it appears clearly which this rising was of order more than cinquantennal, undoubtedly centennial, and in all the cases exceptional.

Helpe Majeure is an abundant river, extremely well supplied with relatively strong precipitations in its surface. The Lame of water past in its catchment area is of 384 millimetres annually, which is definitely higher than the overall average of France all confused basins. The specific Flow of the river (or Qsp) thus reached the figure of 12,1 liters a second and per square kilometer of basin.

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