Abstract. This paper aims at presenting different topographic analysis conducted with GIS software in order to detect flood protection structures, natural or artificial, in river floodplains but also in coastal zones. Those computations are relevant because of the availability of high-resolution lidar digital terrain model (DTM). An automatic detection permits to map the footprint of those structures. Then detailed mapping of structure crest is achieved by implementing a least cost path analysis on DTM but also on other terrain aspects such as the curvature. On coastal zones, the analysis is going further by identifying flood protected areas and the level of protection regarding sea level. This article is illustrated by examples on French Mediterranean rivers and coastal areas.

Following recent catastrophic floods, France issued in 2007 a first regulation on the safety of dams and levees. In 2014 a new competence has been attributed to local authorities: the management of aquatic environments and flood prevention (abbreviated as "GEMAPI" in French), applied since 2018. Intermunicipal authorities have therefore become legally managers of flood protection systems, with the possibility of transferring or delegating all or part of their new competence to catchment authorities. To be able to fulfil their role, the GEMAPI authorities can raise a specific tax. This change was accompanied by an evolution of the regulation on dams and levees. It makes the distinction between dams, levee systems and the newly identified "hydraulic installations for the temporary retention of water". The performance of structures has now to be clearly defined by the manager. We will present the history of this regulation and analyse what it introduces in the management of the structures, of their safety and of flood risk. We will detail governance and organization, inspection and maintenance, regular risk assessments, flood event management and generally decision for risk management. We will conclude by presenting our point of view on what could still be improved in the future.