The Plaine des Wateringues occupies the natural depression of the ancient Aa River Delta for nearly 850 km² between Calais, Dunkirk and Saint Omer. The natural context of this territory makes it particularly vulnerable to flooding by flooding, or in case of difficulty in the gravity evacuation of water during periods of high tide, as well as to the risk of marine submersion in the event of a combination of high tide and storm. The Intercommunal Wateringues Institution, as part of the Aa Delta PAPI, has programmed about twenty operations to be carried out in a global manner. 13 water level management works are involved in this work programme. These programmes also concern project management studies. In order to carry out its entire work programme, the IIW undertakes an overall construction and not by managing station-by-station operations. In fact, as part of its financial requests under the ERDF, an annual programme will be carried out which will include studies or work-type actions depending on the progress of the projects. With reference to the objective of priority investment 5a — OS1, this first phase of work aims at the long-term protection of nearly 836 inhabitants, pro rata to the target of 30 360 people protected throughout the Aa Delta PAPI.