Effectiveness of smart rain barrels for urban pluvial flood mitigation in densely built-up residential areas: a case study of Saitama City near Tokyo

Abstract In recent years, rain barrels (RBs) have emerged as effective stormwater management tools for mitigating urban flooding. Our previous study in Saitama City revealed that traditional RBs performed poorly in the densely populated residential areas compared to other low-impact development solutions. This study investigated the effectiveness of smart RB, comprising water pumps. These SRBs can be controlled online using smart switches that rely on local weather forecasts, to ensure that barrels are emptied before rainfall. We aimed to assess how SRBs can reduce urban pluvial flooding during continuous rainfall in Saitama City using the PySWMM model. We varied the drainage values of the RBs in simulations to control the activation of the smart switches, enabling us to evaluate the effectiveness of SRBs in flood reduction. The results showed that SRBs reduced total runoff volume by 2–10% compared to traditional RBs. Moreover, although the runoff reduction effect of the RBs was found to be independent of their size, the effectiveness of the SRBs increased proportionally with their capacity.