10 meter uncertainty band PPRi Vitry-le-François — Marne sector

The studies carried out in the context of the development of the Vitry-le-François PPRi (map of hazards) were carried out on the scale of 1/10 000th, and mapped on a background IGN scan25 enlarged to 1/10 000th. Since regulatory zoning stems from the intersection of the hazard map and the stake map, the accuracy of this mapping cannot be greater than that of the hazards. Consequently, the scale of use of the regulatory zoning is that of 1/10 000 and exploitation on a smaller cadastral scale (1/5000 or 1/2000) is not recommended. However, municipalities wishing to do so may transpose the regulatory map into their planning documents provided that they comply with operating principles in order to take account of the uncertainty associated with the expansion of the zoning, particularly at the boundary of the area. Indeed, it is not possible to improve the accuracy of the initial data which presents uncertainty about its contours of the order of 10 metres, which is relatively important on the scale of a plot in an urbanised area. The transposition of the regulatory map into a cadastral planning document cannot therefore be limited to a mere enlargement, which would result in a false precision of the contours. Therefore, a guide defines the principles that would allow municipalities who wish to do so, a transposition into an urban planning document (PLU, municipal map) taking into account the uncertainties between each area. It must also make it possible to define the area regulation to be applied when considering planning permissions.