[DREAL OCCITANIA] Atlas of flooding Languedoc-Roussillon — historical flood limits

Since 1999 DREAL Occitanie (formerly Languedoc-Roussillon) has been carrying out atlases of flooding areas (AZI) which provide knowledge of areas likely to be flooded by flooding of rivers. The method used, the hydrogeomorphological method, gives a description of the functional alluvial plain of the rivers, shaped by their successive floods, by delimiting the different morphodynamic structures that make up it. It therefore allows to map the maximum envelope of the flood zone, and also provides elements relating to the dynamics of the flood. This method is complemented by a historical approach (e.g. flood markers, flood envelopes, archive data or testimonials). These atlases consist of a GIS mapping at the scale of 1/25 000 or even 1/10 000 for urbanised areas, as well as a report on the presentation of the watershed which provides comments on the mapping for each homogeneous sector identified. Knowledge of flood zones is essential both to help inform the public, guaranteed by the Environmental Code and reinforced by the Risks Act of 30 July 2003, but also as a decision-making aid for spatial planning. The atlas mapping of flood zones is an element of information that has no regulatory value but is brought to the attention of elected officials and the general public within the meaning of Article R121.1 of the Urbanism Code. For more information on flood mapping and flood atlas: http://www.occitanie.developpement-durable.gouv.fr/cartographie-des-zones-inondables-r466.html The atlas of flood zones shall consist of the following layers: hydrogeomorphology: — r_azi_unite_hydrogeomorpho_s_r76: hydrogeomorphological units constituting the alluvial plain of a watercourse, — r_azi_unite_hydrogeomorpho_l_r76: hydrogeomorphological limits that can no longer be represented by a surface, — r_azi_entite_hydro_l_r76: hydrographic entities (stream trunctures), — r_azi_zone_inond_pot_s_r76: potential flooding areas, — r_azi_encissant_s_r76: collectors (land outside the flooding area of a watercourse), — r_azi_encissant_l_r76: the boundary between the flooding area of a watercourse and the non-floodable land outside, — r_azi_limite_difference_topo_l_r76: clear limits marking a topographic difference (false, slope, slope), artificial obstacles: — r_azi_obst_anthro_s_r76: anthropogenic elements of land cover that may play a role in the hydraulic functioning of the modern alluvial plain represented as surface objects, — r_azi_obst_anthro_l_r76: anthropogenic elements of land cover that may play a role in the hydraulic functioning of the modern alluvial plain represented as linear objects, — r_azi_obst_anthro_p_r76: anthropogenic elements of land cover that may play a role in the hydraulic functioning of the modern alluvial plain represented as point-type objects, natural obstacles: — r_azi_obst_natural_s_r76: natural elements of land cover that may play a role in the hydraulic functioning of the modern alluvial plain represented as surface objects, — r_azi_obst_natural_l_r76: natural elements of land cover that may play a role in the hydraulic functioning of the modern alluvial plain represented as linear objects, — r_azi_element_geomorpho_second_s_r76: secondary geomorphological elements of the functional alluvial plain represented in surface objects, — r_azi_element_geomorpho_second_l_r76: secondary geomorphological elements of the functional alluvial plain represented in linear objects, — r_azi_element_geomorpho_second_p_r76: secondary geomorphological elements of the functional alluvial plain represented in point-type objects, — r_azi_talus_10_l_r76: slopes represented at 1/10 000, — r_azi_talus_25_l_r76: slopes represented at 1/25 000, historical floods: — r_azi_plus_hautes_eaux_known_p_r76: reference water heights or peak flows, — r_azi_donnees_histo_crues_p_r76: historical data from landmarks, testimony or archives, — r_azi_limites_crues_histo_l_r76: limit of extension of historical floods, — r_azi_points_representatives_p_r76: special points where descriptive elements are attached (photos). In addition, a layer of the sub-sectors of the catchment area on the Languedoc-Roussillon territory makes it possible to access the AZI web pages per catchment area: — r_azi_bv_s_r76.