Hydrogeomorphological Mapping and Recent Floods in France

Christophe Esposito (1) , Sylvain Chave (2) , Jean-Louis Ballais (2) , Virginie Delorme-Laurent (2)

1 Centre d'Etudes Techniques de l'Equipement Méditerranée
2 ESPACE - Études des Structures, des Processus d’Adaptation et des Changements de l’Espace

On November 12th and 13th, 1999, and September 8th and 9th 2002 two uncommon rainfall events occurred in the Mediterranean part of France (400 mm and more in 24 hours). These generated extensive damage (2 billion euros) and loss of human lives (58 dead). These events offered a rare opportunity for comparing the observed flood areas with the boundaries of the flood plain. The hydrogeomorphological approach is rising up in the engineering field relative to the natural hazards forecast. If we superimpose the boundaries, we can mesure an excess length and a non-excess length. We can also proceed to a reasearch on the origins and the process that originate an excess. Thanks to graphical and numerical processing, the results obtained widely show the floods' extent within the floodplain of the twenty-seven rivers studied. Besides, there were no incoherent situations thanks to the principles of the hydrogeomorphological mapping. The contradictions with these principles remain very limited (about 10 %) and clearly delimited. So, this study demonstrates the efficiency and the importance of using field approach.

Mots clés: floodplain; hydrogeomorphological method; flood

Domaines: Sciences de l'environnement; Géographie; Hydrologie; Géomorphologie

Christophe Esposito, Sylvain Chave, Jean-Louis Ballais, Virginie Delorme-Laurent. Hydrogeomorphological Mapping and Recent Floods in France. 9th International Conference on the Mediterranean Coastal Environment (MEDCOAST 09), Nov 2009, Sotchi, Russia. pp.1053-1064. ⟨hal-01570817⟩