Envelopes approaching Potential Floods (EAIP) of Auvergne rivers

As part of the Preliminary Flood Risk Assessment (EPRI), DREAL Auvergne carried out all basins covering the Nearly Flood Envelopes Region (EAIP) taking into account river overflow flooding (EAIPce). This envelope was developed with a view to approaching the contours of extreme events. In this sense, the effect of hydraulic structures (bars and protective dams) is not considered. Except in particular cases, protection dams are considered transparent. The watercourse EAIP represents the potential right of way for overflows of all streams, y including small and intermittent, torrents, talweg. Since the dikes are not taken into account, the resulting right-of-way may be considered, as a first approximation, as incorporating the effect of failure of protective structures. However, it does not integrate runoff by pouring (sludge flows and runoff located outside the talwegs) or the specific phenomena associated with local saturation of urban sanitation systems. EAIPs are intended to be the subject of a more precise analysis of phenomena during the following stages of the Flood Directive for the territories concerned by an IRR or a local strategy. The method used to construct EAIPs led to the fusion of variable scale and precision information sources. It generates uncertainties that can be occasionally important (overestimate of right-of-way or, on the contrary, underestimate). EAIPs are therefore not a mapping of flood zones and should not be confused with: — plans to prevent the foreseeable natural risks of floods or coastal areas; — the atlas of flooding or submersible areas; — mapping of submersible areas and flood risk of the Territories to Significant Flood Risks (TRI). EAIPs cannot be used to identify flood zones in administrative or regulatory procedures. Moreover, given the scales of the data mobilised, their graphic exploitation has no meaning only for scales greater than 1/100 000e.