Abstract
Global warming is associated with rising precipitation intensities, which present a challenge to urban drainage systems worldwide. Highly sealed and densely populated cities and metropolitan regions are at high risk of pluvial flooding. Nature-based Solutions (NbS) have been identified as a promising and multifunctional approach to mitigating the impact of pluvial flooding. This study aimed to investigate the pluvial flood mitigation potential of different NbS implementation scenarios, as well as a green-grey infrastructure hybrid solution, in a neighbourhood scale case study in Bochum Langendreer, Germany. Flood and runoff reduction rates were computed by simulating different sub-hourly storm events for current and future reference periods, and different return intervals, in an integrated 1D-2D drainage model in PCSWMM. The green-grey hybrid solution was the most successful measure in all simulations in terms of flood area and depth reduction. Of the NbS, permeable pavement reduced flood area and depth the most, followed by rain gardens and tree pits. All NbS measures were able to fully prevent pluvial flooding in design storms with return intervals of 10 years. Runoff reduction rates exhibited relatively stable behaviour throughout different precipitation intensities, suggesting that the NbS potential to reduce runoff exceeds the standard design applications. The investigated NbS were most associated with regulating ecosystem services. The variety of cobenefits of rain gardens is higher than the number of co-benefits of permeable pavement, followed by tree pits. The results indicate that NbS are effective measures against pluvial floods in Bochum Langendreer. The study concluded that single NBS, together with technical solutions, can help reducing the exposure of vulnerable infrastructure. However, substantial contributions to urban resilience against pluvial flooding will require the scaling up and mainstreaming of NBS applications in suitable locations throughout the entire city fabric.