Substrate Soil Moisture Impact on Green Roof Performance for an Experimental Site in Tomblaine, France

During the last decades, urbanization completely changed the layout of the cities, increasing the imperviousness and reducing infiltration, evapotranspiration and groundwater recharge. The direct consequence of this is the enhancement of floods in urban context. It is widely known that Nature Based Solutions such as GreenRoofs may represent a successful solution in supporting traditional drainage systems in the management of an ever-increasing stormwater runoff. To the purpose, an improved knowledge of the hydrological behavior of such infrastructures and the relation between their retention capacity and climate or design variable is essential to enhance their effectiveness. Starting from the analysis of 56 rainfall-runoff events, this paper aims at assessing the behavior of a 98 m(2) experimental green roof, located in Tomblaine (Northern-Eastern France), with specific reference to the relation between runoff retention capacity, soil moisture content prior to the triggering rainfall event and the rainfall event properties. For the specific case study, the ANOVA analysis pointed out that soil moisture content appeared to be the best predictor of retention capacity both under moderate and severe rainfall. However, a weak correlation between the two variables was detected with a maximum 0,67 coefficient reached by a single regression of the low retention group.