Zone of uncertainty of the regulatory zoning of the risk prevention plan for landslides of the Côte d’Île-de-France sector Vallée de la Marne Tranche 1 & 2

The studies carried out in the context of the development of the PPRN GT of the Côte d’Île-de-France (map of hazards) were carried out at 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. The accuracy of the initial data therefore presents uncertainty about its contours in the order of 10 metres. Genealogy: The boundaries of a restricted area are shown on the graphical documents of the RPP. Regulatory limits are generally set on natural phenomena, which do not follow cadastral or administrative boundaries. A RPP determines the boundaries of the different restricted areas based on the calculated right-of-way of the site’s hazardous events. Some RPPs may sometimes contain regulations associated with linear or point configurations (cavitates, runoff axis, etc.). Linear and point graphic primitives are to be used in these cases respectively.