Guest blog:Rise of Blue-Green Infrastructure

Guest blog by Robert Brears who is the author of Urban Water Security, Founder of Mitidaption, and Our Future Water." @Mitidaption
Faced with climate change and environmental degradation many cities are turning to Blue-Green Infrastructure (BGI) solutions to enhance climate resilience as well as restore the health of ecosystems.
BGI is a strategically planned network of natural and semi-natural areas, ranging in size from rain gardens right up to green streets, that are designed and managed to deliver a wide range of environmental, economic, and social benefits including improved water quality (BGI captures and cleans storm water, ensuring waterways are healthier), reduced potential for flooding (BGI slows down and holds storm water allowing it to soak into the ground), enhanced resilience to climate change (BGI can use water as a resource for communities and natural habitats), reduced infrastructure costs (BGI reduces the volume of water entering the sewer system, increasing the lifespan of the sewers and reducing infra- structure maintenance costs), and increased space for communities and wildlife (BGI provides multiple mental and physical health benefits to communities as well as a sanctuary for urban wildlife and pollinators).

Amsterdam Implementing BGI at Different Spatial Scales
Amsterdam, facing rapid population growth and climate change threats, is developing various types of BGI at different spatial scales in both existing and new neighbor- hoods to achieve a variety of benefits including enhanced climate resilience, increased biodiversity, and improved human health. Specifically, Amsterdam’s BGI will increase the retention and reticulation of rainwater, all the while having a cooling effect on surface temperatures, provide habitats for indigenous plants and animal species, and provide opportunities for recreation and relaxation. The city’s range of BGI being developed includes green pocket parks and neighbourhood parks, which are small parks designed to not only manage storm water but also invite activity; green play streets which are streets that have been closed to traffic and turned into green spaces for people to meet and play in; and sidewalk gardens where residents are encouraged to create green facades or plant vegetation in bare soil around street trees.

LA’s Green Streets
Each year Los Angeles loses 58 trillion gallons of water to the ocean. To collect some of this excess water off the city’s impervious surfaces the Los Angeles Department of Water and Power (LADWP) is developing a storm water incentive programme for the infiltration and on-site use of storm water from industrial facilities as well as designing and     constructing     ‘green streets’, which are streets that reduce, treat, and capture storm water runoff close to its source. Both initiatives align with the Sustainable City pLAn’s goals of reducing  the purchase of imported water by 50% by 2025 and producing 50%  of  LA’s  water  locally  by 2035. Regarding the storm water incentive programme, all industrial facilities regulated by the Industry General Permit and within LADWP’s service area/areas of interest will be eligible to participate in the program. The total rebate amounts will be based on yield for each respective facility, with the rebate amount of USD 1,100/acre foot (AF) for infiltration and USD 1,550/AF for onsite reuse. Meanwhile, one green street being implemented is the Laurel Canyon Boulevard Green Street Project that will see a series of vegetated infil- tration swales and dry wells installed. During storm events, these BGI solutions will capture and treat stormwater runoff from an approximate 123-acre drainage area and infiltrate it into the San Fernando Groundwater Basin. During a normal year, the project will be able to replenish 13 million gallons of rainwater into underground aquifers.

Oslo Restoring its Waterways
The City of Oslo is one of Europe’s fastest-growing cities with its population in 2030 projected to be 30% higher than today. With a greater number of people facing climatic risks, Oslo is implementing a range of BGI strategies to create a more resilient, greener city including the restoration of its waterways. Oslo has 10 main waterways that run through its urban areas. Up until recently, these waterways were considered problematic for sewage and an obstacle to development. As such, large sections have pipes and cul- verts. However, these have predefined capacities and with more frequent and heavier rainfall the city faces increased urban flooding risks. In response, Oslo has decided to restore these waterways by reopening closed rivers and streams to handle storm water more effectively as well as create recreational spaces for people and facilitate increased habitat for biodiversity. One example is the Teglverksdammen Project which is a reopening of around 650 meters of the stream Hovinbekke.
The project has been planned and designed as a natural cleaning system with several sedimentation basins, a stream with water rapids, a small lake, and shallow waters with dense vegetation. Storm water from a nearby school is also safely led into the newly reopened stream.
New York City Incentivizing BGI on Private Property
New York City’s  BGI  aims to reduce Combined Sewer Overflows (CSO) into New York Harbour, in addition to providing multiple community and environmental benefits to the  city’s  neighborhoods  and residents in a cost-effective way. These secondary benefits include increased urban greening, urban heat island reduction, and more habitat for birds and pollinators. To incentivize BGI retrofits on private   property, the   city’s Department of Environmental Protection (DEP) will be releasing a Request for Proposals to procure a Program Administrator to launch and administer a new BGI Private Incentive Retrofit Program.
The five-year contract will have a value of USD 43-58 mil- lion with a goal of retrofitting 200 greened acres. DEP has also released a streamlined fast-track review process for private green roof projects funded through its Green Infrastructure Grant Program. The funding schedule sets reimbursement rates for green roof projects based on growing media depth and planted area.
These upfront reimbursement rates eliminate uncertainty over how much funding is available for potential projects and by giving this information to applicants in advance it means DEP can fast-track green roof grant applications, with anticipated design approval within 90 days from the submittal date.
Moving Forwards
A range of policies can be implemented by cities around the world to implement BGI solutions including retro- fitting public areas as well as encouraging the uptake of BGI solutions on private property.