made the length of the Aa from Saint-Omer to the junction with the Dunkirk-Escaut waterway unnavigable since the 1970s. References External links Aa river guide - Navigation on the canal, including Gravelines as an entry port into the French waterways network. Rivers of France Rivers of the Pas-de-Calais Rivers of Nord (French department) Rivers of Hauts-de-France 0Aa