This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Urban flooding is becoming a growing concern in densely developed neighborhoods, where paved surfaces limit infiltration and intense rainfall can overwhelm drainage systems. Low impact development measures, such as rain barrels (RBs) and rain gardens (RGs), help manage stormwater close to where it falls.
RBs collect rooftop runoff for later nonpotable use, while RGs use vegetated depressions and soil to encourage infiltration. Although both approaches can reduce runoff, their performance and costs vary with local conditions. Studies often assess flood control, costs and environmental benefits separately, complicating comparisons.
Addressing this challenge, a research team led by doctoral student Jiajing Lin from the Regional Environment Systems, Graduate School of Engineering and Science, Shibaura Institute of Technology (SIT), Japan, along with Hiroyuki Taguchi and professor Hitoshi Nakamura from the College of Systems Engineering and Science at SIT, developed an integrated framework to compare RBs, RGs and their combined implementation (RB + RG) in three flood-prone residential catchments in Saitama City near Tokyo: Miyahara, Higashimiyashita and Motobuto. The team combined the U.S. Environmental Protection Agency's Storm Water Management Model with life-cycle cost assessment, the Benefit Estimation Tool (B£ST) and the Analytic Hierarchy Process (AHP).
Seven experts weighted criteria including runoff reduction, costs, service life and ecosystem benefits. Their findings were published in the journal City and Environment Interactions. The simulations showed that the most effective measure depended partly on the catchment.
In Miyahara, RGs reduced peak runoff by 35.78% and delayed the peak by 20 minutes. The combined approach delivered the largest total runoff reduction there, at 30%. In Higashimiyashita, the combined scenario reduced peak runoff by 3.46%, cut total runoff volume by 10.89% and delayed the peak by 20 minutes.
In Motobuto, it reduced peak runoff by 7.95% and total runoff volume by 8.95%, with a 10-minute peak delay. Across sites, combined measures generally reduced total runoff the most. "RGs can offer more than runoff control because their vegetation also supports neighborhood amenity and other ecosystem services," said Lin.
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