Role of Nature-Based Solutions in Mitigating Urban Flooding: A Case Study of Driminagh Neighbourhood in Dublin, Ireland

Urbanisation has a significant impact on the hydrological cycle, primarily through the replacement of natural, permeable surfaces with impermeable, constructed materials. This rapid increase in imperviousness, coupled with ongoing changes in precipitation patterns, has led to both an increased frequency and severity of urban flooding, especially in densely populated areas with limited green spaces. Residential gardens account for a significant proportion of a city’s total urban green spaces. These gardens can offer a promising opportunity for integrating nature-based solutions (NBS) to mitigate urban flooding by enhancing infiltration and reducing surface runoff. Therefore, this study evaluates the role of domestic gardens as NBS for flood mitigation within the highly urbanised Drimnagh neighbourhood in Dublin, Ireland. In particular, we consider diverse vegetation types, permeable and impermeable yard surfaces, and roof structures to assess their effects on flood dynamics during an extreme rainfall event on June 20, 2023. The neighbourhood covers an area of 69 hectares with 260 residential buildings. Using a hydrodynamic model, we simulate inundation depths, streamflow, runoff, and infiltration under four different scenarios for the same neighbourhood during this storm. Our results show that the best-case scenario, with improved garden vegetation and green roofs, could facilitate up to 1650 m³ of water infiltration water compared to the worst-case scenario, where all surfaces are paved. This scenarios with improved permeable surfaces can also reduce flood extents (up to 30%), mean inundation depths (8.3%), and flood peaks (5.6%) in the neighbourhood. This analysis highlights the potential of NBS implementation in domestic gardens in building urban flood resilience.