The Yser (Dutch: IJzer, French: Yser) is a river that originates in French Flanders (the north of France), enters the Belgian province of West Flanders and flows into the North Sea at the town of Nieuwpoort.
The source of the Yser is in Buysscheure (Buisscheure), in the Nord département of northern France. It flows though Bollezeele (Bollezele), Esquelbecq (Ekelsbeke), Bambecque (Bambeke) and approximately 30 of its 78 kilometers run through France before it enters Belgium. It then flows through Diksmuide and out into the North Sea at Nieuwpoort.
During the Battle of the Yser in the First World War, the river was deliberately flooded between Nieuwpoort and Diksmuide to provide an obstacle to the advancing German Army and keep westernmost Belgium safe from German occupation.
Read more about Yser: Tributaries