A Multicriteria Framework for Prioritizing Urban Flood Adaptation Strategies: An Integrated PCSWMM-PROMETHEE II Approach

Conventional stormwater systems were not designed to manage the increasing intensity and frequency of extreme rainfall events driven by climate change, prompting municipalities to seek investment strategies that deliver the greatest overall value at the watershed scale.

The objective of this study is to evaluate and rank eight stormwater adaptation strategies under an equivalent 1M CAD$ investment scenario, identifying options that provide the most effective performance to support municipal decision-makers. A multicriteria decision-making framework is developed to compare grey and blue-green stormwater strategies across technical, environmental, financial and social dimensions, based on 14 evaluation criteria. A calibrated PCSWMM model is applied to a 535-hectare urban watershed in Montreal, Canada, allowing direct extraction of several performance indicators, including flood volumes, outfall discharges for regulatory compliance, evapotranspiration and water quality, ensuring a consistent evaluation across strategies. The evaluated options include (1) oversized pipes, (2) underground chambers, (3) permeable pavements, (4) blue roofs, (5) green roofs, (6) rain gardens, (7) bioretention systems and (8) sponge parks. The PROMETHEE II multicriteria method is used to determine the overall ranking of each strategy.

Results indicate that bioretention systems, sponge parks and rain gardens achieve the highest overall rankings across all dimensions considered, while oversized pipes rank lowest. These findings demonstrate that blue-green strategies provide greater integrated value than conventional grey systems. This study provided the first application of this method within a standardized investment framework, supported by PCSWMM simulations at the urban watershed scale.

The proposed framework offers an adaptable and transparent tool to support municipal stormwater planning and investment decisions under increasing climate uncertainty. It also highlights how the combined use of PCSWMM and Python enables the extraction of hydraulic and environmental performance metrics at the watershed scale, facilitating their direct integration into a multicriteria decision-making analysis.

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