Urban Resilience Through Hybrid Measures: Strategies for Stormwater management

More intensified events such as extreme precipitation are increasingly occurring in urban areas, leading to waterlogging (surface water accumulation) and pluvial flooding. These events adversely affect urban assets, facilities, and critical infrastructure networks, causing not only financial damages but also disruptions in accessibility and essential services.

Climate adaptation is therefore essential to address these hazards. Since climate change is already underway and its impacts cannot be fully prevented, adaptation strategies must be prioritized. Climate adaptation measures vary in scale, functionality, and composition. The composition of these measures can be defined by the degree of integration of natural (green) and engineered (grey) elements. This range forms a hybrid spectrum, where green and grey components are combined and designed for synergistic performance (Figure 1).

Hybrid measures provide various benefits such as reducing flood events by enhancing infiltration, increasing storage capacity, and delaying runoff in terms of both volume and timing. Additionally, they contribute to several co-benefits as: urban aesthetics, mitigate heat stress, and promote biodiversity. Considering these measures in urban planning frameworks is crucial for creating multifunctional spaces that address both hydrological, ecological and social challenges.

The study focuses exclusively on urban hybrid measures and collects expert interviews to capture practical insights into their design, implementation, and performance. Interviews are aimed to develop a structured classification of urban hybrid measures based on spatial scale, cost, and multifunctional benefits. Experts identified key challenges, including maintenance and governance, and to provided several examples of successful implementations with key lessons learnt for international knowledge exchange. The study concludes with recommendations that link tested design principles and operational practices to scalable strategies for resilient urban water management with key messages related to finance, governance and institutional challenges with practical guidelines for the design, implementation and maintenance ensuring a long-term efficiency of hybrid measures.