Cities Turning to Blue-Green Infrastructure
Cities are turning to Blue-Green Infrastructure (BGI) to manage excess stormwater while protecting biodiversity.
Traditionally, cities rely on grey infrastructure — pipes and drains — to remove stormwater from sites as fast as possible. These drainage systems are usually part of a wider sewer system that manages both stormwater and wastewater. In combined systems, the mixed water is sent to wastewater treatment plants.
Combined systems are overwhelmed easily during heavy rainfall, increasing downstream flooding risks. They also directly transport excess stormwater into waterways exposing people to pathogens and toxins and impacting aquatic life. They also completely fail during extreme weather events, i.e., cloudbursts.
Blue-Green Infrastructure
Cities are turning to BGI to manage water quantity and improve water quality. BGI includes semi-natural and natural systems that restore the natural landscape while managing stormwater. BGI range in size, including rain gardens, green walls, green streets, and urban forests.
A key aspect of BGI is its multifunctionality. This means BGI can perform several functions and provide several benefits on the same spatial area. For example, a green wall can reduce stormwater runoff and improve water quality, while also decreasing the urban heat island effect, improving the insulation of the building, and providing a habitat for species.
BGI also provides multiple environmental, economic and social co-benefits to urban communities, including enhanced biodiversity, protection from climate change, green jobs, reduced infrastructure costs, and spaces for recreational and social activities.
Berlin’s Rainwater Fee
Berlin is encouraging businesses to incorporate BGI on their premises as part of its Berlin Strategy for Biodiversity Preservation. The city’s water utility, Berlin Wasserbetriebe, has increased its rainwater fee from EUR 1.804 per square metre of drained ground per annum (per m²/year) to EUR 1.840 per m²/year. The aim is to encourage BGI solutions that manage rainwater in both new and existing buildings. BGI could result in a partial or full waiver of the fee.
New York City’s Green Infrastructure Grant Program
New York City’s Department of Environmental Protection (DEP) offers the Green Infrastructure Grant Program to encourage private property owners to retrofit their roofs with green roofs. DEP offers workshops to explain programme eligibility requirements and guide users through the online application. Funding for each green project is based on the green roof area and soil depth, with projects only valued at $50,000 or more able to apply.
The Take-out
Cities can use various fiscal tools to scale up blue-green infrastructure.