Speeds in the flooding area by hydraulic and hydrogeomorphological approach to the rivers Dordogne and Rhue, municipality of Bort-les-Orgues en Corrèze

L_ZI_DORDOGNE_HRUE_2009_V_S_019 The study determined the flooding areas of the Dordogne and the Rhue in the crossing of the municipality of Bort-les-Orgues by hydrogeomorphological approach to the natural areas and by a hydraulic approach on the areas with stakes (urbanised areas crossed by the Dordogne up to the confluence with the Rhue and the area of the aid centre by the work of the Willow bordered by the Rhue). The mapping from this study replaces the mapping of the flooding area of the Dordogne established in 2000 only on the Plantade sector. The hydrogeomorphological study is a naturalistic approach based on the morphology and sedimentology of the alluvial plain. It makes it possible to identify the different river beds shaped by past floods (minor, medium, major, or even exceptional) in order to map the ordinary river bed, very frequent flood areas (annual return, here marnage zone of the hydro dam holding), frequent (return from 5 to 15 years) and exceptional (higher water). The hydraulic approach seeks to reproduce the reference flood by integrating flood and flow parameters. The reference flood for the Dordogne is the 1944 flood with an estimated return period of 150 years; for the Rhue the reference flood is the estimated centennial flood. Hydraulic modelling was carried out using Hec-ras (EU) software