Investigating Nature-based Solutions Potential to Mitigate Urban Pluvial Flooding

Global warming is associated with rising precipitation intensities, challenging urban drainage systems, and policymakers worldwide. Densely populated, highly sealed cities face high pluvial flooding risks. Nature-based Solutions have been identified as a promising and multifunctional approach to mitigating pluvial flooding impact. This study investigates the flood mitigation potential of various Nature-based Solutions scenarios and a green-grey infrastructure hybrid solution in a neighbourhood in Bochum, Germany. Using an integrated 1D-2D drainage model in PCSWMM, different sub-hourly storm events were simulated for current and future periods. The green-grey hybrid solution was the most effective in reducing flood area and depth. Among Nature-based Solutions, permeable pavement had the greatest impact, followed by rain gardens and tree pits. All Nature-based Solutions were able to prevent pluvial flooding in design storms with return intervals of 10 years. Runoff reduction rates exhibited relatively stable behavior throughout different precipitation intensities, suggesting that Nature-based Solutions’ potential to reduce runoff exceeds the standard design applications. The results suggest Nature-based Solutions are effective against pluvial floods in Bochum. Extensive, holistic Nature-based Solutions implementation is crucial for adapting sewer systems and enhancing city-wide resilience. While individual interventions can protect vulnerable infrastructures, city-level resilience must be prioritized to effectively address urban pluvial flood challenges.