Implementing blue-green infrastructures in cities – A methodological approach considering space constraints and microclimatic benefits

• Method to systematically assess street usage and space availability for BGI implementation in existing and densely built urban areas. • Prospective scenarios freeing up space availability maintaining street functionality. • Microclimatic assessment of BGI implementations & identification of effective scenarios. In the context of globally rising temperatures, the imperative for climate change adaptation measures in cities is becoming increasingly apparent. Blue-green infrastructures (BGI) are recognised for their heat mitigating effects. However, urban settlements frequently face spatial constraints, that hinder their implementation. Consequently, this article introduces a methodological approach to systematically describe and assess urban street space to indicate possible space availability for BGI implementation in dense urban areas. We propose two scenarios, one context sensitive and one more disruptive, to free up and increase available space by altering current street usage while maintaining initial street functionality. Compositions of BGI were implemented in the scenarios according to space availability and their anticipated heat mitigation potency. Microclimatic computer simulation served to assess related temperature reducing capacities of the newly implemented BGI. The methodological approach was applied in a historic part of Vienna, Austria. Investigations clearly showed a positive correlation of the extent of BGI implementation and the reduction of physiological equivalent temperature (PET). Correlating space consumption and temperature reducing capacity of BGI implementations revealed differences in microclimatic and spatial efficiency. Most efficient reductions of PET were observed when 10–25 % of street surface was allocated for BGI. Our study suggests that allocating around 10 % of street surface for new BGI implementation can lead to considerable reductions of PET emphasising the potential for effective urban heat mitigation strategies. The results and the method developed provide new insights and possibilities for strategic urban planning, implementing heat mitigation strategies in dense urban areas while supporting existing concepts for the sustainable transformation of cities.