How Substrate and Drainage Layer Materials Affect the Hydrological Performance of Green Roofs: CHEMFLO-2000 Numerical Investigation

Green Roofs (GRs) are a promising solution for the reduction of flooding risk in urban areas. Reproducing on the traditional roofs the drainage pattern typical of natural soils, these infrastructures are able to mitigate the stormwater discharged into sewers. Their retention capacity depends on both climate and design variables, among which the substrate and drainage materials seem to play a fundamental role in the enhancement of the efficiency of the roof. This research aimed at analyzing the hydrological behavior of five 15-cm GRs modules, characterized by different substrate and drainage layers soil composition and thickness, using CHEMFLO-2000. Specifically, among the substrate materials particular attention was paid to the biochar, a fertilizer known for its ability to filter pollutant, to assess its effect on the green roof retention capacity. Simulations under different rainfall inputs were carried out to compare the performance of each system.