The hydraulic response of urban drainage networks equipped with green roofs

The rapid growth of urbanisation profoundly affects the urban hydrological cycle by augmenting stormwater runoff, reducing surface roughness, and increasing impermeable surfaces. In these circumstances, sewer networks may become overwhelmed, resulting in pressurised flows and backwater effects occurrences in the sewer conduits. Sustainable Drainage Systems (SuDSs) can represent a valid strategy to mitigate these effects. In this regard, the present study investigates the impact of green roof installations on the reduction of pressurised flow conditions within sewer networks. Numerical simulations were performed by simulating the flow behaviour of an urban drainage network with a basic topology and serving urban subcatchments with an increasing percentage of green roof extension. At this aim, the software EPA SWMM 5.2 was used. Preliminary findings show that green roofs can improve the hydraulic functioning of urban drainage systems by reducing filling ratios, mitigating pressurisation risks and the flood occurrence.