Potential of mitigation strategies to compensate climate change impacts on the urban drainage network and pluvial flood hazard

ABSTRACT Urban flooding is a growing global challenge, driven primarily by climate change and rapid urban development, which place increasing pressure on urban drainage networks. This study investigates the impacts of climate change and mitigation strategies in Innsbruck, Austria. Future periods are represented by design rainfall events scaled using climate change factors derived from bias-corrected convection-permitting simulations, while mitigation strategies are modelled by reducing the impervious connected area by 10, 20, and 30%. The results show climate change factors that indicate a strong intensification of short-duration, frequent rainfall and an increase by more than 31% in sewer surcharge and surface flooding under future conditions. Reducing the impervious connected area by 30% effectively counteracts the negative impacts of climate change in extreme events. However, the benefits of decoupling strategies are more pronounced for moderate precipitation events than for extreme ones and vary from <50 to >350 m3/ha surcharge reduction between districts. The analysis highlights that a spatially heterogeneous strategy is more effective, as decoupling is more effective in districts with high hydraulic pressure. These findings demonstrate a clear potential of decoupling measures to mitigate climate change impacts on urban drainage, but underscore the need for strategic implementation to maximize effectiveness.