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.
Highlights
The objective of this analysis was to assess the ability of hybrid approach for excess stormwater management (H-SM) approaches to reduce the excess stormwater volumes and, the storage volumes required
While considering that low-impact development (LID) cannot completely solve the problem of urban flooding phenomena on their own, the hybrid and diffuse approach allows reducing the excess stormwater volumes discharged into stormwater detention tanks (SWDTs)
Several studies focused on the assessment of the most suitable location of SWDTs as a traditional and cost-effective solution to improve the overall performance of the urban drainage system [14,15]
Summary
Drainage networks seem undersized, and critical rainfall events make them responsible for natural disasters and widespread water pollution [4,5]. Structural measures such as drainage facilities systems, including pump stations and detention reservoirs, are usually adopted to prevent and mitigate urban stormwater runoff excess [6]. Throughout Europe and North America, stormwater detention tanks (SWDTs) are of particular importance in controlling the negative impact of stormwater discharges. Several studies focused on the identification of SWDTs volumes distribution, mainly aiming at cost-effective solutions able to minimize flood, pollutant load, and storage cost [13,14,15]. According to [16,17], private/residential allotment SWDTs, directly connected with roofs, can potentially reduce runoff peaks to downstream stormwater drainage systems during rare, long-duration storms, especially if implemented using smart systems approaches that enable rainwater tanks to be emptied, maximizing available retention storage
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