Hesdin is a commune in the Pas-de-Calais department in northern France.

The river Canche is one of the rivers that flow from the plateau of southern Boulonnais and Picardy, into the English Channel, of which the Somme is the largest example. It is 100.2 km (62.3 mi) long. The basin of the Canche extends to 1,274 square kilometres (492 sq mi) and lies in the south of the département of Pas-de-Calais. Forming an alluvial valley from 1 to 2 kilometres wide, the Canche valley also contains marshes, meadows and small woods. The gentle gradient, averaging 1.5 percent, gives the river a meandering course.