| Summary: | Sustainable urban drainage systems (SUDS) are increasingly implemented to mitigate flood risk and augment environmental quality and wellbeing in cities. Vegetated swales are one of the most common SUDS components, yet they are among the least studied in cold climates. The goal of this research was to assess the performance of a grass swale in a cold maritime climate characterized by frequent freezing and thawing, rain-on-snow events, and repeated midwinter snowmelt. Synthetic runoff experiments, single-ring infiltration measurements, and continuous monitoring of soil and meteorological conditions were undertaken over two years in the BREEAM-certified neighborhood of Urriðaholt, Iceland. The grass swale infiltrated water during all seasons but at a lower rate in winter. Sparsely vegetated and barren areas were more susceptible to concrete frost formation and heave than well vegetated areas during repeated freeze-thaw. The dense vegetation in the grass swales and the intertwined root system aided the hydrological performance of the grass swale by enhancing the near-surface soil porosity while providing soil binding that resists structural deformation. Soil frost modeling indicated that while soil frost has decreased in the last 70 years, the freezing season shifted towards midwinter to coincide with the largest rain-on-snow events. This, combined with increasing rain-on-snow volume, suggests that the risk of urban flooding during winter may increase in the next decades with climate warming. Greenifying urban areas is essential to improve resilience and mitigate the adverse impacts of climate change. Blágrænar ofanvatnslausnir (BGO) eru í auknum mæli innleiddar til þess að draga úr flóðahættu, auka umhverfisgæði og vellíðan í borg. Gróðurrásir eru algeng útfærsla á BGO, en minnst kannaðar í köldu loftlagi. Markmið þessarar rannsóknar var að meta virkni gróðurrásar í köldu sjávarloftslagi, sem einkennist af tíðum umhleypingum frost og þíðu, regn-á snjó atburðum og snjóbráð á miðjum vetri. Framkvæmdar voru ...
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