Enhancing Resilience and Sustainability with Blue-Green Infrastructure

Urban areas worldwide are facing significant challenges from climate change and environmental degradation. Recently, in early September, Hong Kong experience the unleashed torrential rainfall brought by the remnants of Super Typhoon Haikui. This downpour shattered previous records dating back to 1884, resulting in the longest duration of Black Rainstorm Warning Signal and turning the city into an inundated landscape.[1]Alarming instances of extreme weather have sadly become the "new normal" in the era of climate change. In response, city planners are increasingly embracing innovative approaches that integrate nature-based solutions into urban design.[2]One such approach that is gaining momentum is blue-green infrastructure, which recognises the vital role of water and green spaces in creating sustainable and resilient cities[3].

Global average June temperature by year, compared with pre-industrial average (Image source: Berkeley Earth)

Torrential rainfall flooded MTR station in Hong Kong (Image source: BBC News)

Blue-green infrastructure encompasses an interconnected system of natural and engineered components designed to effectively manage water resources while delivering numerous environmental, social, and economic benefits. It combines traditional "gray" infrastructure, such as stormwater drains and sewers, with "blue" elements like rivers, lakes, and wetlands, along with "green" components such as parks, green roofs, and urban forests.[4]By emulating natural hydrological processes and integrating vegetation, blue-green infrastructure enhances water management, reduces flood risk, improves water quality, and promotes urban biodiversity.[5]

Green roofs in Singapore (Image source: ArchDaily)

The use of blue-green infrastructure offers a wide range of benefits for urban areas. Firstly, it helps mitigate climate impacts by reducing the urban heat island effect, enhancing air quality, and providing natural cooling through shading and evapotranspiration.[6]The green spaces and water bodies act as natural filters, improving air quality by reducing pollutants.[7]Additionally, blue-green infrastructure reduces stormwater runoff by promoting infiltration into the ground, and mitigating the risk of urban flooding.[8]

Urban heat island (Image source: World Meteorological Organisation)

Furthermore, blue-green infrastructure provides numerous social and economic advantages. Access to green spaces and water bodies enhances the overall physical and mental health of urban residents by creating opportunities for recreation, relaxation, and community interaction.[9]These spaces also contribute to the cultural identity of cities and promote a sense of place. Research has shown that proximity to nature and green spaces can reduce stress levels, improve cognitive function, and foster a sense of belonging among residents.[10]

Economically, blue-green infrastructure has been shown to increase property values, attract investments, and stimulate local economies through tourism.[11]Well-designed green spaces and water features can enhance the aesthetics of urban areas, making them more appealing to residents, businesses, and visitors. Moreover, the planning, design, and maintenance of blue-green infrastructure create employment opportunities, particularly in landscape architecture, horticulture, and environmental management.[12]

Environment, social, economic and public health benefits of blue-green infrastructure (Image source: USEPA)

Several successful case studies have demonstrated the positive impact of blue-green infrastructure on cities. In Copenhagen, Denmark, the city has transformed its harbor into a vibrant waterfront district that incorporates blue-green infrastructure.[13]Its innovative stormwater management system incorporates green roofs, rain gardens, and permeable pavements, effectively reducing flood risk while enhancing the aesthetic appeal and livability of the area.[14]

Permeable pavement design (Image source: Farley)

Singapore is another notable example of a city that has embraced blue-green infrastructure. The city-state, known for its limited land area and high population density, has implemented initiatives such as the "ABC Waters Program".[15]By creating a network of rain gardens, bioswales, and naturalized water bodies, Singapore has made substantial advancements in water management, reduced flood risks, and created attractive community spaces.[16]These blue-green features not only serve practical purposes but also enhance the livability and visual appeal of the city.

Kallang River under the ABC Waters Programme (Image source: Singapore's National Water Agency)

Incorporating blue-green infrastructure into urban planning requires collaboration among diverse stakeholders, including policymakers, urban planners, developers, and local communities.[17]It is essential to consider the unique characteristics and needs of each city when designing blue-green infrastructure projects. Factors such as climate, topography, available space, and existing infrastructure should be taken into account to ensure the implementation of the most effective and appropriate solutions. Comprehensive planning and long-term maintenance strategies are crucial to ensure the sustainability and longevity of blue-green infrastructure projects.[18]

Blue-green infrastructure presents a promising approach to urban planning that addresses multiple challenges faced by cities today. As urban areas continue to expand, the implementation of blue-green infrastructure becomes increasingly crucial in creating sustainable and livable cities. It is imperative for the government to take the lead in prioritising and investing in blue-green infrastructure, fostering the transformation of cities into resilient, inclusive, and environmentally friendly urban spaces.