Hydraulic Response of SuDS-Equipped Urban Drainage Networks

Growing urbanization significantly influences the urban hydrological cycle by increasing impervious surfaces, reducing surface roughness, and increasing stormwater runoff. Consequently, urban drainage networks may be forced beyond their hydraulic capacity, leading to anomalous pressurized flow conditions, stormwater geysering, and urban flooding. Under this scenario, sustainable drainage systems (SuDSs), such as green roofs, can offer an alternative approach to managing stormwater runoff and alleviating the urban drainage systems. How can SuDS improve the hydraulic behavior of drainage infrastructure? This paper aims to reply to this question by assessing the effect of green roof installation on the operation of urban drainage systems. The hydraulic behavior of an idealized urban drainage network, derived from literature, was modeled using EPA SWMM 5.2. The network, with variable conduit slopes and hydraulic roughness, served fully impervious urban subcatchments, which were interested by the installation of green roofs with an increasing extension across the urban subcatchments. Moreover, the effect of the rainfall temporal variability was investigated through the application of both a uniform and a Chicago hyetograph. Results indicate that green roofs significantly enhance the hydraulic performance of the urban drainage network by reducing filling ratios, mitigating pressurization risks, and delaying the occurrence of pressurized conditions. Some equations were also provided to calculate the performance indexes as a function of the cross-sectional sewer conduits and the green roof extension.