Atlas of flood zones (AZI) of the Loire Estuary — flood zone

The data of this layer correspond to the flood zones of l' Loire Estuary defined according to the \#x27; hydrogeomorphological approach. They represent the maximum envelope of flood zones. The hydrogeomorphological method used in the Loire Estuary and described in the production process of the sheet was supplemented by an analysis of historical documents, geological elements and topography. This method of d’#x27; elaboration of the atlas allowed to identify the minor bed and flood areas (medium bed and major bed and exceptional major bed). The minor bed corresponds to the area where all the flow before overflow flows. It contains the annual floods. The average bed corresponds to l' all the low areas near the minor bed regularly flooded by the Loire (period of return 1 to 5 years) as well as to the old arms and ancient islands of the Loire. The major bed and exceptional major bed correspond to l' all floodable areas outside the middle bed, flooded for medium to rare floods or very rare (return period between 5 and 100 years or even beyond) Territory concerned: River Loire de Couéron to Saint Nazaire on the right bank and from the Pellerin to Saint Brévin les Pins on the left bank (Loire-Atlantique) __Origin__ The method used for the development of this atlas is the hydrogeomorphological approach recommended by the ministry. This method was developed in the Mediterranean to define the flood zones of rivers with significant solid transport (materials transported by watercourses) and therefore had to be adapted to the estuarine context subjected to marine submersions and river floods where it is not possible to; clearly identify slopes or slope breaks that delimit the different beds of the alluvial plain. In contrast to the classical hydrogeomorphological method, which uses stereoscopic analysis to identify slope breaks and slopes, the definition of flood zones in the &atlas of l’'estuary was carried out from a numerical precision field model, called Litto 3D, which allowed to analyse slope breaks with level curves. __Partner organisations__ DDTM Loire-Atlantique __Links annexes__ * [report, map atlas and map on web portal of services of the Loire-Atlantique State](http://www.loire-atlantique.gouv.fr/Politiques-publiques/Risques-naturels-et-technologiques/Prevention-des-risques-naturels/Atlas-des-zones-inondables/Atlas-des-zones-inondables-de-l-Estuaire-de-la-Loire) [See this page on geo.data.gouv.fr](https://geo.data.gouv.fr/fr/datasets/2ee9eb770525629439f0693f38a700fb961fb796)