 Forming an alluvial valley from wide, the Canche valley also contains marshes, meadows and small woods.The gentle gradient, averaging 1.5 percent, gives the river a meandering course.The river rises at Gouy-en-Ternois and passes Frévent, Hesdin, and Montreuil-sur-Mer before leaving the chalk to flow to the coast between Étaples and Le Touquet-Paris-Plage.