Belgrand, a French engineer in the middle of the eighteenth century in France, was at the root of sanitation policies enabling significant progress for 150 years in hygiene and public health issues. Nowadays, stakes have changed. Storm watercan no longer be transported the same way as waste water, it must be managed as close as possible to the place where it is generated and copy the naturalcycle of water. Since the last twenty-five years, the Communauté d’Agglomération du Douaisis (CAD) has implemented a sustainable and integrated management of storm water in its territory thanks to a generalized proactive policy. The CAD can assess the numerous technical, regulatory, environmental, financial as well as societal benefits by providing figures. All this leads to more resilient territories responding in a better way to the consequences of climate change.