Temporal evolution of blue - green infrastructure and perceived benefits: a case study for urban context of Colombo, Sri Lanka

Abstract

In contemporary urban planning, flood mitigation through blue–green infrastructure (BGI) is a central pathway to climate-resilient urban form. This article examines the temporal evolution and perceived benefits of BGI at Diyatha Uyana Park, and Bellanwila Park in urban context of Colombo. A mixed-method approach combines temporal land-cover mapping, flood-inundation analysis, and community perception surveys to understand how BGI systems have changed over time and how these changes influence both hydrological performance and user experience. Temporal analyses across pre-BGI, immediate post-BGI, and matured BGI periods reveal significant expansion and stabilization of blue-green networks. Flood-inundation maps for peak rainfall events in 2016 and 2024 demonstrate a measurable reduction in flood extent where BGI elements have become more connected and ecologically mature. Community responses further validate these spatial findings. Reported benefits include reduced flash flood during heavy rain, improved thermal comfort, enhanced visual quality, and increased use for relaxation. Overall, the temporal evolution and perceived benefits at Diyatha Uyana Park and Bellanwila Park shows that planned BGI, designed as multifunctional, and connected systems can reduce urban flood risks while elevating spatial quality and community wellbeing in Colombo.