Hydraulic-Hydrologic Invariance effectiveness of SuDS techniques: Italian case study

In this paper, the contribution of the Sustainable Drainage Systems (SuDS) to the achievement of the Hydraulic-Hydrological Invariance (HHI) principle and their hydrological and hydraulic performance are assessed for an urban catchment sited in southern Italy. Green roofs and permeable pavements are the selected SuDS techniques, and different land use conversions are supposed. The numerical simulations are conducted using the software Storm Water Management Model (SWMM). This paper pays attention to the evaluation of the green roofs and permeable pavements performance in reducing stormwater runoff through the definition of two parameters: the peak reduction and the volume reduction indexes. Moreover, two other parameters are defined to evaluate the role of the selected SuDS in the achievement of the HHI concept. The simulations are carried out by using as input the constant hyetographs derived for three different return periods (T = 5, 10, and 20 years) with three rainfall durations (8, 15, and 30 min) and considering different values of Effective Impervious Area (EIA) reduction. The experimental results confirmed the positive impact of green roofs and permeable pavements in stormwater management, in particular the factor that most influences hydraulic and hydrological performance and the achievement of the HHI principle is the EIA reduction. Moreover, the findings of the present research show that the rainfall characteristics don't strongly influence the SuDS performance.