La servitude de sur-inondation : un mécanisme capable de penser les solidarités entre espaces ruraux de fonds de vallées et espaces urbains inondables ? Le cas du bassin-versant de l’Oudon

For several years in France, flood risk management policy has focused on the preservation and even the restoration of flood expansion zones in areas where the stakes are low in order to better control hazards upstream of urbanised areas. Projects for the development of water retention areas (also called flood expansion zones) are multiplying. In 2003, a public utility easement known as «over-flooding» was created and tends to become a tool used by watershed managers to ensure the proper implementation of their operations. Nevertheless, the question arises as to the future of the activities, particularly agricultural, already present on these sites and the conciliation methods to be envisaged on a larger territorial scale, with regard to the effects of this instrument of environmental public action. These developments are most often designed to protect relatively vulnerable urban areas located downstream of the impacted agricultural sectors. In the field of spatial and urban planning, and drawing more specifically on references from the sociology of public action, this article reviews the application of this easement under the Environmental Code, its rules of application and the initial questions that institutional actors using it are now facing. Based on the case of the easements established in recent years in the Oudon catchment area (Mayenne/Maine-et-Loire), we show how this easement is an important tool in the land strategy of flood risk managers, but that its implementation requires time for consultation with potentially affected owners and occupants, as well as the formalisation of local arrangements or memoranda of understanding negotiated between the various parties and allowing for the constraints suffered.