A comparative analysis of different sustainable urban drainage systems to ensure hydraulic invariance

Hydraulic Invariance ensures urbanization does not increase flood flow rates in receiving water bodies or drainage networks. Indeed, urbanization reduces soil permeability, increasing surface runoff and may lead to overwhelm existing sewer systems designed for pre-urbanization conditions. To manage this, measures like Sustainable urban Drainage Systems (SuDS) or Low Impact Developments (LID) are crucial. In this work, using EPA Storm Water Management Model (EPA SWMM), we build the model of an hypothesized drainage network, both in pre-construction conditions and after the construction of a new shopping center, without implementing any mitigation measure. Then, LIDs are introduced either individually or in pairs in the sub-basin with changing impermeabilization, aiming to restore initial flow values, water depth, and maximum fill levels. The optimal solution is selected through the evaluation of total costs, including implementation, installation, and maintenance of each single or combined measure.