Incidence des modes alternatifs de gestion des eaux de ruissellement sur les flux d'eau ef de contaminants

Three watersheds, with sustainable urban drainage systems (SUDS), were compared to a reference watershed drained by classical separate sewer, in terms of hydraulic behavior and of discharged contaminants fluxes. A runoff model and contaminant production functions have been developed to overcome land use differences. It has been shown that control systems smooth rainfall variations and reduce water discharges from 43 to 55 % depending on the site. This work also demonstrated that SUDS significantly reduce pollutant discharges in stormwater. The level of reduction is related to the type of substances and to the type of systems, and is especially tightly related to the reduction in runoff volume. Indeed results have shown reduction in mass but not always in concentrations. Moreover, deposits of contaminants in the studied SUDS are not very contaminated, in comparison with combined sewer sediments.