Session B9 - Tools for multi-criteria and spatial planning

Geographic Information Systems (GIS) combined with Multi-Criteria Decision Analysis (MCDA) tools hold strong potential to support the spatial planning of blue-green infrastructure (BGI). They allow for the integration of diverse criteria while considering stakeholder preferences, producing maps that are interpretable for decision-making. This study examines the impact of integrating stakeholder preferences into urban BGI planning using the GIS-MCDA tool SSANTO, adapted for Québec, Canada. Preferences constitute a source of uncertainty, raising the question of whether the effort invested in eliciting them is justified by their influence on the results. Workshops were conducted to co-create and operationalize objectives and to determine the relative weights assigned by stakeholders. A global uncertainty and sensitivity analysis, based on 90,000 Monte Carlo simulations, assessed the impact of these parameters on spatial suitability maps. The results suggest that the collection of preferences could be optimized according to their actual influence, while confirming that stakeholder involvement remains essential. These findings provide key insights to guide strategic planning and enhance the effectiveness of GIS-MCDA tools for BGI implementation.

Urban flooding and Combined Sewage Overflow (CSO) spills are escalating due to climate change and urbanisation. This paper presents a holistic methodology for selecting Blue-Green Infrastructure (BGI) interventions using the CityCAT hydrodynamic model and spatial source-to-impact analysis. We demonstrate a novel strategic framework that proposes intervention placement to satisfy multiple Risk Management Authorities (RMAs) simultaneously. This method integrates engineering parameters with specific RMA priorities, such as reducing building exposure to flooding, improving roads’ conditions, and mitigating sewer spills from CSOs, while also incorporating co-benefits like amenity value. Results indicate that this integrated approach offers a promising alternative to traditional siloed planning by delivering targeted flood reduction while maximising amenity and environmental value.

The intensification of extreme rainfall events due to climate change is making conventional stormwater systems increasingly inadequate, prompting municipalities to explore more adaptive strategies. This study develops a multicriteria decision-support framework to compare grey and blue-green stormwater strategies across technical, environmental, financial and social dimensions. Eight alternatives are evaluated under an equivalent 1M$ investment scenario using 14 criteria. Hydraulic performances are simulated with a calibrated PCSWMM model applied to a 535-ha urban watershed in Montreal, Canada. The PROMETHEE method is used to determine the overall value of each strategy, in what constitutes a first application of this approach under a standardized investment scenario. The results show that bioretention, sponge parks and rain gardens perform best, while oversized conduits rank last. The proposed framework offers a transparent and transferable tool to support municipal planning and investment decisions for adaptation to extreme rainfall.

The SmartWater project is developing a digital urban planning tool – the Blue-Green Infrastructure Planner (BGI Planner) – to integrate decentralised stormwater management measures into planning processes at an early stage. The aim is to strengthen the climate resilience of urban areas, mitigate flood risks, reduce urban heat and lessen the pollution of Berlin's waterways. The BGI Planner is based on a modular structure and links geodata, checklists and effect simulations. In two pilot areas in Berlin, the effects of blue-green infrastructure are being analysed using models – in terms of flooding, water pollution, urban climate and water balance. Established modelling tools such as InfoWorks ICM, GERRIS/HYDRAX/QSim, ENVI-met and ABIMO are being used. Initial simulation results confirm the effectiveness of selected measures and form the basis for simplified evaluation models in the tool. In future, the BGI Planner will be used as a digital tool in Berlin's administration to support sustainable and climate-adapted urban development.