ABSTRACT Urban stormwater systems are facing increased pressure due to climate change and urban densification. Integrated multifunctional stormwater solutions, referred to as Blue-Green Infrastructure (BGI), have gained increasing attention for urban stormwater management. However, planning BGI involves navigating complex challenges, including division of responsibilities and trade-offs associated with different BGI schemes. This study presents a case-based sustainability assessment including stakeholder perspectives and priorities regarding different BGI schemes at an urban catchment scale in Uppsala, Sweden. A multicriteria decision analysis (MCDA) approach was applied to assess economic, environmental, and social benefits, while stakeholder priorities were captured through a structured dialogue workshop with mixed-stakeholder deliberation. The BGI schemes were differentiated by spatial scale (private to public land) and system complexity. The mixed stakeholder groups agreed on the prioritization of environmental values but diverged in how they valued social benefits. The priorities emerged in the deliberative process and did not correlate with formal mandates or group composition. Different BGI strategies were favoured under different sustainability priorities. In the Uppsala case, the performance profile of simple, swale-based schemes aligned well with aspects prioritised by most stakeholder groups.
ABSTRACT Flowchart showing the general methodology of the study, starting from water footprint accounting, water footprint assessment, and then LID allocation based on WFA results. Rapid urbanization and climate change are placing increasing pressure on urban water systems by exacerbating stormwater runoff, flooding, and water quality concerns. In response, low-impact development (LID) controls are increasingly being adopted as a sustainable approach to urban water management; however, their effectiveness depends strongly on strategic spatial allocation. This study applies water footprint accounting (WFA) as a data-driven approach for identifying priority areas for LID implementation in a mixed-use tropical urban catchment. A spreadsheet-based WFA tool was developed to automate the quantification of blue, green, and gray water footprints. The resulting water footprint estimates were mapped to identify hotspots representing critical pressure points within the catchment. Based on these hotspots, selected LID controls, including permeable pavements, rain barrels, and bioretention cells, were allocated and evaluated under varying rainfall percentiles. Simulation results showed that the proposed LID plan reduced runoff volume by up to 9.98% and peak runoff by up to 10.30% across subcatchments with LID controls implemented. These findings demonstrate the potential of integrating WFA with LID planning to improve urban hydrologic performance and support evidence-based stormwater management. Overall, the study highlights WFA as a useful decision-support approach for optimizing the spatial allocation of LID controls in mixed-use urban catchments, particularly in rapidly urbanizing tropical environments.
Plant selection is critical for the performance and long-term functionality of NBS. However, selecting suitable species remains challenging due to factors such as the need to balance multiple performance criteria. This study addressed this gap by proposing a structured decision-making framework for roadside rain gardens (RGs) in cold climates, based on three objectives, thirteen criteria, and sixteen quantitative metrics scored on a 1–5 scale. The framework was tested on five plant species commonly used in RGs in Norway to demonstrate its application and assess data availability for the metrics. Results showed that the evaluated plant species exhibit different strengths across objectives: for instance, Bolboschoenus maritimus excelled in plant procurement and establishment support, while Iris pseudacorus scored highest in functions of interest. Consequently, a combination of high-performing species was recommended for RG vegetation design. While the framework was successfully applied, limited data for some metrics required assumptions, highlighting the need for more comprehensive species-specific databases. Given the critical role of plants in the success of NBS, it is recommended that the framework be integrated into official RG design guidelines, with criteria tailored to local conditions.
ABSTRACT Graphical abstract summarising spatial optimisation in urban stormwater management, highlighting simulation and GIS dominance, design-storm rainfall, catchment-scale applications, common interventions, flood objectives, and governance challenges. Urban stormwater management is increasingly challenged by rapid urbanisation, climate change, and the declining performance of conventional drainage systems. This decline can result from capacity exceedance, pipe and pump failures, blockages, sediment accumulation, inadequate maintenance, and long-term asset deterioration. These pressures have accelerated interest in spatially distributed stormwater-management approaches, including nature-based solutions (NBS) and blue–green infrastructure (BGI). However, despite the growing body of research, no critical review systematically examines how spatial optimisation methods guide the allocation, configuration, and prioritisation of stormwater interventions across urban areas. In this systematic review, 102 simulation-optimisation studies were analysed to examine spatial optimisation of NBS placement and deployment in urban water management systems. The review examined the main elements of spatial optimisation frameworks, including simulation models, optimisation techniques, intervention types, objective functions, and spatial and temporal configurations. This review indicates that spatial optimisation can greatly improve urban stormwater management, though its transition from modelling studies to implementation-ready planning is still incomplete. By integrating current methods, applications, and limitations, this review provides a structured foundation for future methodological development and helps practitioners, policymakers, and decision-makers apply spatial optimisation more effectively when planning urban stormwater management at the catchment scale.
ABSTRACT Diagram summarizing the study methodology. Eight stormwater management alternatives were hydraulically simulated using PCSWMM under a standardized $1 million investment, evaluated with PROMETHEE II across 14 quantitative and qualitative criteria, and ranked according to their net flow. Nature‑based solutions provide the greatest overall value. Traditional drainage infrastructures were not designed to manage the increasing intensity and frequency of rainfall events caused by climate change, prompting municipalities to seek investment strategies that deliver the best value at the watershed scale. This study evaluates and ranks eight stormwater adaptation strategies under an equivalent 1M CAD$ investment scenario to support municipal decision-making. A multi-criteria decision-making framework is developed to compare grey and blue–green stormwater strategies across 14 technical, environmental, financial, and social criteria. Hydraulic performance was simulated using a calibrated Personal Computer Stormwater Management Model (PCSWMM) of a 5.35 km2 urban watershed in Montreal, Canada. The novelty lies in integrating a standardized investment constraint at a watershed scale, in a simulation-based multi-criteria decision analysis framework, allowing direct comparison on a common economic basis. The eight evaluated options are oversized pipes, underground chambers, permeable pavers, blue roofs, green roofs, rain gardens, bioretention systems, and sponge parks. The Preference Ranking Organization Method for Enrichment Evaluations II (PROMETHEE II) multi-criteria approach was used to determine the overall value of each strategy. Results show that bioretention, sponge parks, and rain gardens achieve the highest rankings, all dimensions considered, while oversized pipes rank lowest. The proposed framework offers an adaptable tool to support municipal planning and investment decisions.
