Dunkirk is in the heart of the coastal Flanders, a part of the embanked North Sea area which is vulnerable to floods but also deeply farmed and equipped. At the end of the 19th Century, the city is becoming an expanding industrial and cargo port, but its spatial and demographic growths are limited by its fortifications. The Dunkirk urban development area therefore spreads in its suburban towns. This essay addresses the evolution of the drainage projects and their governance in these urban and suburban areas. The work emphasises the role of the wateringues (water boards) associations of landowners and their interaction with the civil engineers and the municipal authorities. Since the 12th Century, landowners collaborate to ensure themselves the maintenance and construction of sluices and the repair and digging of canals and ditches to drain the coastal plain. They are facing the takeover of environmental management by the Second French Empire and then the Third French Republic national governments. Wateringues are therefore subject to bureaucratic and technical control embodied by the Ponts et Chaussées civil engineers. These associations were formed during the preindustrial era and therefore need to adapt to the modern period issues while they still are affected by frequent floods. The great urban development projects, especially focused on the port from 1879, impact the hydraulic installations and flood control. This complex technical, political and economic system of multiple interactions between the landowners, the engineers and the administrative authorities then stands out for its stability and efficiency. ; Dunkerque est située au cœur de la plaine maritime flamande, espace vulnérable aux inondations mais également cultivé et profondément aménagé et mis en valeur. La ville devient à la fin du 19e siècle un port industriel et de marchandises en expansion, mais son développement spatial et démographique est limité par ses fortifications, et a donc lieu dans les communes suburbaines. Ce mémoire étudie ...