Marker of the 2001 Somme Valley RPP and tributary flood marker

The inventory and setting of flood markers is essential to raise awareness, maintain and transmit a collective memory of the floods of a watercourse. Poor knowledge of flooding often leads either to minimise the risk by forgetting past events or to mystifying an ancient flood, which left terrible memories, because no data, source or reference allowed it to be relativised. Flood markers, whether they are from the Highest Known Waters (PHEC) or not, are therefore part of the knowledge heritage of floods and are an essential source of information to strengthen risk awareness, and therefore our resilience. They also allow, as part of the hydraulic knowledge of rivers, to refine the assets and expertise of historical floods. The PPR is a regulatory prevention dossier that informs populations and planners of risk areas and defines measures to reduce vulnerability. It was established by the Act of 22 July 1987, as amended by the Act of 2 February 1995. The PPR procedure is defined by Articles L.562-1 to L3562-9 of the Environmental Code.