Hybrid Approach for Excess Stormwater Management: Combining Decentralized and Centralized Strategies for the Enhancement of Urban Flooding Resilience

Abstract

Urban sprawl and soil sealing has gradually led to an impervious surface increase with consequences on the enhancement of flooding risk. During the last decades, a hybrid approach involving both traditional storm water detention tanks (SWDTs) and low-impact development (LID) has resulted in the best solution to manage urban flooding and to improve city resilience. This research aimed at a modeling comparison between drainage scenarios involving the mentioned hybrid approach (H-SM), with (de)centralized LID supporting SWDTs, and a scenario representative of the centralized approach only involving SWDTs (C-SM). Results highlighted that the implementation of H-SM approaches could be a great opportunity to reduce SWDTs volumes. However, the performances varied according to the typology of implemented LID, their parameterization with specific reference to the draining time, and the rainfall severity. Overall, with the increase of rainfall severity and the decrease of draining time, a decrease of retention performances can be observed with SWDTs volume reductions moving from 100% to 28%. In addition, without expecting to implement multicriteria techniques, a preliminary cost analysis pointed out that the larger investment effort of the (de)centralized LID could be, in specific cases, overtaken by the cost advantages resulting from the reduction of the SWDTs volumes.