c.zevenbergen@un-ihe.org

With the intensifying frequency and severity of extreme weather events, coupled with rising sea levels, societies and ecosystems worldwide are under pressure (IPCC, 2022). Urban areas, in particular, face critical challenges from extreme rainfall, drought, water quality degradation, and land subsidence, leading to severe damage and disruptions. Traditional water infrastructure, designed under less volatile conditions, now frequently fails, while ongoing socio-economic changes amplify the consequences and reduce tolerance for these interruptions.

In response, significant adaptation efforts are underway, using a variety of approaches in urban and rural settings. In cities, methods such as Nature-based Solutions (NBS), Ecosystem-based Adaptation (EbA), Low Impact Development (LID), Water Sensitive Urban Design (WSUD), and the Sponge City concept have gained traction, incorporating blue-green infrastructure (BGI) to mitigate the impacts of urbanization. By integrating BGI with grey infrastructure, cities aim to upgrade and regenerate stormwater systems, thereby reducing reliance on traditional monofunctional approaches.

Evidence confirms that BGI enhances water management and resilience to flood and drought conditions, but its effectiveness in multi-functional, blended urban environments requires further exploration. In particular, the design of BGI systems to withstand and adapt to extreme weather events—those beyond typical design parameters—remains an area in need of rigorous study. A deeper understanding of BGI’s collective performance at different urban scales is essential to optimize resilience, manage extremes, and maximize broader environmental and social benefits.

• Discuss barriers and facilitators for integrating BGI with existing grey infrastructure to enhance resilience to extreme weather events in cities.
• Share best practices and insights from global case studies, emphasizing restoration, transformation, and regeneration using BGI.
• Present models and decision-support systems to operationalize and scale blended grey-BGI strategies across diverse urban settings.