HYDRAULIC CRITERIA IN A HOLISTIC DECISION SUPPORT TOOL FOR SUSTAINABLE URBAN STORMWATER MANAGEMENT

Urban development modifies the natural hydrologic patterns by producing higher and more rapid peak discharges with higher runoff volumes. Sustainable Drainage Systems (SuDS) aim at minimizing the impacts on local hydrology by reducing the amount of impervious surfaces promoting infiltration and disconnecting flow paths to reduce runoff volumes and peak flows. Recovering natural hydrology by sustainable stormwater management produces clear benefits in the urban water cycle, like reduction of combined sewer overflows (CSO), mitigation of flood risk by detaining and reducing stormwater discharges, and reduction of stormwater inflows into sewer systems, hence reducing the costs and energy consumption in treating and pumping runoff. The EU-MED Programme (ESTORMED)-S-2 project (improvement of energy efficiency in the water cycle by the use of innovative storm water management in smart Mediterranean cities, www.e2stormed.eu) has developed a holistic Decision Support Tool (DST) that includes energy efficiency and environmental criteria in the decision making process for stormwater management. Within this tool, guidance is provided to estimate the hydraulic performance of drainage infrastructures, especially SuDS. With this data, economic benefits and energy savings produced by runoff infiltration and detention are quantified. They include flood protection benefits, aquifer recharge and savings in treating and pumping runoff. The (ESTORMED)-S-2 Decision Support Tool introduces these results in a multi-criteria analysis to support the decision making process in storm water management. The paper focuses on the hydraulic features of the DST. The main purpose of the tool is to compare and evaluate different drainage options for stormwater management, analyzing different drainage system scenarios. Each scenario is defined by different drainage infrastructures from a catalogue of several types of conventional infrastructures and SuDS. Hydraulic criteria are based on the estimation of runoff produced, runoff reduction, peak flow reduction and CSO mitigation. Finally, a case study in Spain is presented to compare two different drainage strategies (conventional vs SuDS). As the DST results show, hydraulic performance of SuDS provides stormwater management benefits like lower runoff volumes to be treated.