Spatialisation de l'information : une aide à l'analyse hydraulique et paysagère développée lors de la réhabilitation des sites post-industriels - Cas des réaménagements des gravières en eau en milieu alluvionnaire

The aim was to create a set of methods to evaluate redevelopment projects for water gravel pits in an alluvial medium which is in agreement with the legislator in vigour particulary regarding the impact of future gravels pits on groundwater, streams and landscape modification. Today, successful rehabilitation of the used exploited domains still depends on the well known principles of integrated redevelopment of gravel pits. The hydraulic and hydrodynamic models, coupled to a Geographical Data Base (GIS), can simulate the aquifers reponses to the modification concerned, thus highlighting the key parameters to be taken into account. The environmental parameters, resulting from landscape ecology, are given by using the topological and geometrical properties of the geographical objects. A multicriterion analysis makes it possible to break down this complex system studied into its components essentially of a diverse nature, and then to make a hierarchical classification by taking into consideration direct relationships. The weighting of each parameter's contribution is taken into consideration, therefore it is impossible to give a accurate mathematical measurement. Thus constituted, this structure is a base for the evaluation of the adequation between the future vocation of the domain as considered by the site manager and the real "ecological" potential. The studied case is located on the banks of the river Loire, in the heart of an alluvial plain : the "plaine du Forez " (department Loire in France). In this zone, two differents groups found an consensus, a gravel pit exavation company left the minor bed for the major bed of the river Loire while a nature conservation group rehabilitated the exploited domain.