Strategic prioritization of sewersheds to mitigate combined sewer overflows under climate change

• CSOs pose significant environmental and public health challenges. • Increased precipitation under climate change must be considered in CSO management. • A predictive model was used to predict CSOs under climate change. • CSOs will increase exponentially over time under climate change. • Results inform municipalities on prioritizing sewersheds to mitigate future CSOs. The impact of combined sewer overflows (CSOs) on water bodies is well documented: they pose severe threats to water quality, ecosystems, and public health. Exposure to contaminants from overflows can lead to waterborne diseases, emphasizing the critical need for effective stormwater management. Mitigating the effects of CSOs can be achieved through various solutions, including blue-green infrastructure (BGI). However, the implementation of these solutions often occurs opportunistically rather than strategically, depending on the opportunities that arise. In addition, simulations under climate change predict a surge in extreme events, necessitating adaptation in urban planning and infrastructure design. This paper proposes a prioritization index to support the location choice for mitigation measures under current conditions and projected climate scenarios. The model's effectiveness is validated, and simulated precipitations generated by the Canadian Regional Climate Model version 5 (CRCM5) are used, revealing an exponential increase in CSO events over time due to climate change. The importance of spatial location in prioritizing urban catchments for mitigation measures implementation is emphasized, providing valuable insights for urban planners to navigate climate-induced challenges and protect water bodies.