Les bassins versants sensibles aux 'crues rapides' dans le Bassin Parisien - Analyse de la structure et de la dynamique de systèmes spatiaux complexes

摘要

“Flash floods” occurring on the loamy plateaux of the Paris Basin, in the north of France, are the most original and dangerous form of floods encountered in this area because of their torrential nature. The human impact on these events is indisputable as they usually originate in agricultural ploughed areas. The increasing urbanization as well as the road network located in the thalweg of the valleys leads to faster water flows and a higher vulnerability of societies. To better assess occurrence of these events, watersheds have been located thanks to the French CatNat data base. The morphological organization of the watershed between forms, slopes and drainage networks, plays a key role on the “flash floods” dynamics and on the water flow concentration along pathways. Therefore, the traditional quantitative methods usually describe separately each morphological component (index of compacity of Gravelius, Horton ratio ordination, longitudinal profile section, hypsometric curve, etc), and none of them enables to estimate, in a synthetic and dynamic ways, the influence of the spatial organization of those three morphological component. Based on the complex systems theory, it is now possible to measure the 3D organization of the catchment area. The methodological implications of this work are very relevant as the tools involved were not currently used by geomorphologists or hydrologists at the beginning of this research. The results obtained and the validity of these spatial analysis methods will have to be discussed at the end of this work, progressively integrating other variables in simulations. All these results encourage maps of sensibility in these areas.