Aa River (France)

Upper reaches of Aa in the Pas -de- Calais

The Aa is a river in northern France, in the Nord -Pas -de -Calais.


It rises at an altitude of about 120 meters, 25 km east of the coast of the English Channel in the municipality of Bourthes in the Pas -de -Calais. From the source it winds through a hilly landscape in the Regional Natural Park Caps Marais d' Opale et mainly in a northeasterly direction and reached Saint- Omer. There, the channeled and thereby strongly straightened underflow begins. It reaches 10 km from the coastal marsh and heads to the north-north -west to its confluence with the North Sea in the city of Gravelines in the department of Nord, 89 river km from the source. In the channelized section the boundary between the two departments runs partly along the river embankments, partly in the river itself.


In Arques Aa meets the Canal de Neuffossé and is downstream from Saint- Omer as channelized river itself part of the commercial shipping route Dunkirk -Scheldt. It is associated with following navigation channels:

  • Canal de Neuffossé

Places on the river

  • Bourthes
  • Verchocq
  • Fauquembergues
  • Wavrans -sur- l'Aa
  • Lumbres
  • Esquerdes
  • Hallines
  • Wizernes
  • Blendecques
  • Arques
  • Saint- Omer
  • Watten
  • Holque
  • Gravelines
  • Grand-Fort -Philippe


The river gained some notoriety in 1940 because Hitler had ordered it as a stop line during the advance on Dunkirk. This has made it possible the British during the Battle of Dunkirk to evacuate over 300,000 men.

Division commander Sepp Dietrich occupied on May 24, 1940 without authorization a hill beyond the Aa (Mount Watten, 235 ft), because this such a good view ( and possibly shot ) bot. Heinz Guderian approved this in hindsight.