Ternoise

The Ternoise is a French Rivière of the area Nord-Pas-de-Calais. It runs in the Département of the Pas-de-Calais. It is the principal affluent of the Canche which it joins out of Right Bank.

Geography

It takes its source with Ligny-Saint-Flochel, passes to Saint pol. on Ternoise and is thrown in the Canche with Huby-Saint-Leu, locality very close to the town of Hesdin.

Common crossings

Ternoise crosses the following communes, all located in the Département of the Pas-de-Calais (of upstream downstream):

Ligny-Saint-Flochel, Roëllecourt, Saint-Michel-on-Ternoise, Saint-Pol.-on-Ternoise, Gauchin-Verloingt, Hernicourt, Wavrans-on-Ternoise, Monchy-Cayeux, Anvin, Content, Érin, Tilly-Capelle, Blangy-on-Ternoise, Blingel, Rollancourt, Auchy-lès-Hesdin, Parcq, Grigny and Huby-Saint-Leu.

Affluents

Its principal affluent is the Forgery out of Right Bank.

Hydrology

Ternoise is a very regular river, following the example its neighbors of the Pas-de-Calais and Sum. Its flow was observed during one 44 years period (1964-2007), with Hesdin, locality of the Département of the Pas-de-Calais located at the level of its confluence with Canche (ref.: ). Surface thus studied is of 342 km ², i.e. it quasi totality of the catchment area of the river.

The interannual medium flow or module of the river with Hesdin is of 4,45 m ³ a second.

Ternoise introduces seasonal fluctuations of flow very little marked, just like Canche or the Sum, her neighbors. The high waters are held at the end of the winter and in spring, and are characterized by average monthly flows included/understood in a fork located between 4,94 and 5,36 m ³ a second, from January to May included, with a maximum little Net in February (5,23 m ³) and in March (5,36 m ³ a second). From June, the flow drops very gently to the low waters which take place from August at October included, involving a light fall of the monthly flow average energy to the floor of 3,44 m ³ in September.

With the low water levels, the VCN3 can fall until 2,3 m ³ a second, in the event of dry period quinquennial, which remains very consistent. This fact is frequent among the rivers of the area as the Sum, Authie, Thérain, water of the rains infiltrating almost completely in basement, before being restored with the rivers, by sources and seepages, and are thus retained a long time before running out (see note).

As for the risings, they are generally not very important. The QIX 2 and QIX 5 are worth respectively 11 and 15 m ³ a second. The QIX 10 or calculated flow of decennial rising is of 17 m ³ a second, the QIX 20 of 20 m ³, while the QIX 50 is assembled to 23 m ³ a second (see note).

The recorded maximum instantaneous flow with Hesdin was of 28,8 m ³ a second on July 4th 2005, while the value maximum day laborer was of 23,5 m ³ a second the same day. If one compares the first of these values on a QIX scale of the river, one notes that this rising of July 2001 largely higher than raw the cinquantennale was defined by the QIX 50, and thus very exceptional.

Ternoise is an extremely abundant river. The Lame of water past in its catchment area is of 411 millimetres annually, which is definitely higher than the overall average of France, all confused basins. The specific Flow (or Qsp) reached the high figure of 13,0 liters a second and per square kilometer of basin.

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