Can Green and Grey Infrastructure Improve Urban Water Systems?
Human activity in cities is known to decrease biodiversity in the surrounding environment. Living in modern society, however, requires the building of systems that inherently use land and resources that may harm wildlife and ecosystems. Managing water runoff is a particularly tricky problem. So how do we meet today’s standard of living while maintaining the natural world around us as much as possible? The answer may lie in green infrastructure.
Green infrastructure is any natural approach to water runoff treatment and helps to protect or reinvigorate the natural water cycle. While heavily dependent on the local ecosystem, improvements include the upkeep and revitalization of forests, wetland restoration, green roofs, mangroves as damming implements, rain gardens, permeable pavers, and other natural remedies to water cycle issues. Green infrastructure techniques can be scaled up or down to include various types of projects including the collection of water, limiting water waste, and even assisting with water treatment by naturally filtering particles. There is a wide array of benefits to this type of infrastructure, including positive outcomes in water quality and quantity, air quality, climate resiliency, and habitat restoration.
Green infrastructure can be pricey, as it relies on the local ecosystem’s ability to naturally maintain projects, despite using less fabricated material. For example, mangroves as flood barriers can only be utilized in coastal environments as the trees grow only in brackish water, limiting their use in inland areas. There are also ongoing maintenance costs on top of the high cost of entry to these projects. Some experts, however, find that these projects can potentially save money in the long run, as they can withstand natural disasters more readily than manmade infrastructure can.
Grey infrastructure, on the other hand, refers to human-made structures that assist with processing water runoff, including dams, water treatment facilities, floodwalls, drains and pipes, bioswales, roadside ditches, and several other systems. We have systems and infrastructure that drain waterways, protect flood zones, supplement local irrigation, and facilitate treatment of water runoff for repurposed use and consumption. These are critical aspects of modern societal living, and structures that we likely could not live without.
Source: Taguchi et al. 2020
Still, there are some important negatives to consider when it comes to the implementation and overuse of grey infrastructure. First, the cost of grey infrastructure programs can be quite high, as many involve vast digging projects and the installation of proper drainage setups. Additionally, the ongoing maintenance costs of grey infrastructure can continually plague city governments and taxpayers as constant upkeep is required—especially compared to green infrastructure, which can largely go undisturbed with low maintenance.
Second, some grey infrastructure projects, especially older ones, risk contaminating the water supply or improperly performing their functions, such as waterway filtering, posing risk to people living near the system.
Third, some grey infrastructure disturbs native habitats and disrupts the biodiversity of natural water systems in the area. Dams, for example, can disturb fish and aquatic systems via their implementation, despite providing energy benefits to people downstream.
City planners choose to implement various projects based on the benefits that they can provide residents of the area. Until recently, these projects mainly consisted of grey infrastructure due to their perceived efficacy, impact, and economic factors like job creation. Planners now, however, have more choices and the ability to implement green infrastructure projects, which can have similar benefits to grey infrastructure ones but do not harm the local environment as much.
Instead of choosing one over the other, the scientific community suggests an approach that reconciles positive aspects of both green and grey infrastructure systems, what many call the “green-grey approach.” The World Bank and World Resources Institute released a joint report on integrating both green and grey infrastructure which suggests the implementation of green projects like forests and wetlands alongside grey infrastructure projects. Such solutions can be in concert with projects that already exist or targeted interventions that support an area of the green infrastructure that is inadequate or unable to meet the need of an entire community.
Another vital benefit of the implementation of more green infrastructure projects is from a health equity and environmental justice standpoint. If the creation of these green systems can increase water quality and access to resources for a wide range of communities, there can be significant benefits to communities that have historically faced injustices and inequality. It is important to remember that the history of infrastructure projects in the United States has disproportionally affected BIPOC communities.
Moving forward, engineering projects should implement green infrastructure wherever possible to leverage the benefits of natural remedies to city planning issues. Grey infrastructure, while subject to valid environmental criticism, still has great value to city planning when naturally occurring solutions are not available or too expensive. It is also necessary for city planners, when implementing future green infrastructure programs, to ensure that racial and ethnic injustices are not repeated. Through cohesive green-grey approaches, modern city planning can be low-cost, climate-friendly, and ethical.
