Is Green Infrastructure a Universal Good?
University of California, Davis | CLUE Lab
Green infrastructure is being used more and more in cities to provide environmental and social benefits. Planners often assume that green infrastructure is good for all places and all people in their cities. In this research project, we questioned that assumption and asked, is green infrastructure a universal good? We explored whether the use of green infrastructure has promoted equity.
We found that issues with the planning, siting, design, and maintenance of green infrastructure can limit the benefits it provides, particularly in areas that are less privileged. However, we suggest that green infrastructure can be a positive feature of cities if all people affected by it are equitably involved in planning and decision-making.
What is green infrastructure?
The term “green infrastructure” can mean many things. It can refer broadly to networks of natural areas, parks, and other green spaces. However, it is often used more specifically to describe locations modified to reduce and treat stormwater runoff using plants, soils, and landscape features.
For this project, we mainly use the second definition—we focus on green infrastructure features designed to manage stormwater runoff. This type of green infrastructure is often called green stormwater infrastructure, or GSI.
Stormwater runoff is a big concern in cities. The amount of runoff in urban areas tends to be greater than in undeveloped areas because impervious surfaces like roads, parking lots, and buildings prevent rain from sinking into the soil. Runoff can travel quickly to streams through pipes and other “gray” infrastructure, carrying nutrients, sediments, and other pollutants.
GSI is often promoted because it can help control the amount of stormwater runoff that reaches streams and other water bodies, as well as the amount of nutrients and sediments in that runoff. At the same time, it potentially provides other benefits for urban areas such as pollinator habitat, local cooling, and beauty.
Rain gardens are a popular type of GSI. They are shallow depressions located to capture stormwater runoff and let it sink into the soil, and they are often planted with ornamental plants.
Bioretention facilities are similar to rain gardens, but include engineered drainage systems and structured layers of soil, sand, and other materials to filter stormwater. They may release filtered stormwater to gray infrastructure systems.
Green roofs replace typical roof construction materials with plants and engineered soils, capturing stormwater before it runs off.
Not all GSI includes plants. Rain barrels capture and store stormwater, while permeable pavement allows runoff to soak into the soil.
Other common types of GSI not pictured include swales, berms, and stormwater ponds and wetlands.
Learning from green stormwater infrastructure in Baltimore
We studied GSI in Baltimore, Maryland, a city of around 600,000 people located on the Chesapeake Bay.
In Baltimore—as in many cities in the United States—a history of racial segregation has contributed to a highly uneven and inequitable distribution of wealth, power, education, and resources across the city. Practices and policies of disinvestment and discrimination led to the segregation of Baltimore’s African American population into certain less desirable areas of the city.
Baltimore’s total population peaked in the 1950s with a post-war economic boom. After that time, closing factories and migration to the suburbs contributed to a population decline of about 30% in the second half of the 20th century, leaving many neighborhoods in decline and tens of thousands of vacant properties across the city. Today, some of these vacant properties are being used as sites for GSI.
One of the motivations for GSI in Baltimore is preventing nutrients and sediments from reaching the Chesapeake Bay. The Chesapeake Bay has been severely impacted by nutrient pollution, leading to declines in aquatic ecosystems and fisheries. The United States Environmental Protection Agency (U.S. EPA) has established limits for the amount of nitrogen, phosphorus, and sediments that may go into the Chesapeake Bay and its tributaries, and GSI is one of the strategies that Baltimore can use to meet this limit.
All of these factors contribute to making Baltimore an important place to study equity and green infrastructure. In addition, the city is home to the Baltimore Ecosystem Study (BES), a long-term investigation that has produced influential social and ecological research about urban systems for more than 20 years. As a BES project, our research builds on this body of knowledge and the relationships developed over time in Baltimore.
Do city plans for green infrastructure in Baltimore address equity?
Baltimore currently has eleven city plans that address green infrastructure. Most of these plans focus on the ability of green infrastructure to control and filter stormwater, but some incorporate efforts for greening and neighborhood revitalization.
These plans commonly refer to the need to improve equity and justice, and they emphasize community involvement. However, equity remains poorly defined, and plans include few requirements to ensure equitable design, implementation, and evaluation of green infrastructure projects.
Locations for green infrastructure in Baltimore are often prioritized based on stormwater management. However, the city’s plans highlight the socioeconomic benefits of GSI. If stormwater concerns and socioeconomic concerns do not occur in the same places, then equity goals could be jeopardized.
While Baltimore does have these municipal plans that include GSI, the city itself has implemented very little GSI at this point. Some city plans even expect that private developers will be installing GSI.
Therefore, GSI currently found in Baltimore has mostly been installed opportunistically as individual, unconnected projects.
The term “infrastructure” implies a system. However, GSI currently on the ground in Baltimore has not been planned, installed, or maintained in a systematic way.
What motivates green stormwater infrastructure in Baltimore?
There are two main reasons that GSI has been installed in Baltimore.
1) Maryland state law requires that GSI be used whenever possible to make up for the impacts of construction. GSI installed for this reason has to meet engineering standards to ensure that it works properly when installed. Once these standards are met, this GSI also counts toward the city’s stormwater management requirements set by the U.S. EPA. We call this regulatory GSI, and we found that it makes up around 60% of all GSI in Baltimore.
The City of Baltimore is responsible for maintaining a database of regulatory GSI, but has limited staff to keep it up to date. We are grateful to city staff for taking the time to provide us with their database and help us work with it.
There are 419 constructed GSI facilities in the city’s database that we included in this study.
2) A lot of GSI projects in Baltimore have been installed by non-governmental organizations (NGOs) and community groups to serve organizational missions and leverage funding opportunities. Most of these existing GSI projects have not fulfilled regulatory requirements, and many are unknown to city agencies. We call this non-regulatory GSI, and we found that it makes up around 40% of all GSI in Baltimore.
Non-regulatory GSI has not been systematically tracked in Baltimore, and documentation is highly variable among different organizations. A large part of this research project has been devoted to putting together a database of non-regulatory GSI projects, and we’ve been grateful for the help and information provided by NGOs working on GSI in Baltimore.
We identified a total of 293 non-regulatory GSI facilities in Baltimore.
Where is green stormwater infrastructure located in Baltimore?
We found that when GSI is installed by many different institutions—each acting individually to meet regulatory requirements or organizational goals—it can lead to concerns about distributional equity.
We looked at the distribution of regulatory and non-regulatory GSI projects in Baltimore relative to different characteristics of the population, using data from the 2017 American Community Survey 5-year estimates at the census block group level. We considered race, income, education, and vacancy rates. In addition, we mapped impervious surfaces in the city and used parcel data to determine whether GSI facilities were located on private or public land.
Explore the maps below to see where GSI is located in Baltimore relative to characteristics of the population and landscape.
We found that regulatory and non-regulatory GSI installations show different patterns.
Predominantly African American areas are less likely to have regulatory GSI facilities, and this pattern accounts for differences in income, education, and vacancy, as well as the area and impervious cover of census block groups.
On the other hand, non-regulatory GSI projects are relatively common both in low-income areas with predominantly African American populations and in high-income areas with predominantly white populations.
This pattern may be due to the fact that some NGOs specifically work to bring GSI to underserved neighborhoods, while other non-regulatory projects are sought and funded through grant applications. Populations with higher levels of privilege are more likely to have the resources and connections necessary to apply for GSI grants successfully.
Areas with higher vacancy rates were also more likely to have non-regulatory GSI facilities, while level of education in the population was not related to the distribution of GSI for either regulatory or non-regulatory facilities.
We found that GSI projects located on public land tend to be in more disadvantaged areas than GSI projects on private land.
More of the GSI on public land is non-regulatory.
- Only 17% of regulatory facilities are on public land.
- In contrast, 65% of non-regulatory facilities are on public land.
So, while disadvantaged areas may have relatively greater access to GSI on public land, more of these facilities are non-regulatory. There are positives and negatives to this. On one hand, non-regulatory GSI is often designed with more community involvement. On the other hand, these GSI facilities may not meet the same requirements as regulatory facilities, and sometimes also rely on communities for maintenance.
It’s important for both city and NGO planning to consider current patterns of GSI distribution to ensure that new facilities are increasing distributional equity and not increasing burdens.
Is green stormwater infrastructure in Baltimore providing benefits, and for whom?
Whether GSI is installed for regulatory or non-regulatory reasons, there is an underlying assumption that it will provide benefits to urban areas. However, just because GSI can provide a number of benefits doesn’t mean that all GSI does provide those benefits.
We found that GSI in Baltimore is extremely variable in terms of type, design, size, and maintenance. Some of these factors vary with characteristics of the population.
Different types of GSI don’t provide the same benefits.
Most non-regulatory GSI projects in Baltimore are small rain gardens or micro-bioretention facilities, or areas where pavement is removed and planted with turf or other vegetation.
Regulatory GSI projects also include many larger rainwater detention areas and stormwater ponds.
Even GSI facilities of the same type can be designed so differently that they provide very different benefits.
For example, a "micro-bioretention" facility can look like a well-kept flower garden…
...or merely a depression in the lawn.
GSI facilities can also degrade very quickly if not maintained, and they vary widely in size.
We looked at more than 70 different bioretention facilities and rain gardens in Baltimore, and gave each one a score for aesthetics, habitat, and stormwater value—three factors that often motivate GSI.
We found a range of scores for each factor, but there was no large difference overall in scores between regulatory and non-regulatory facilities.
However, for regulatory facilities, better scores were found in less affluent neighborhoods, while for non-regulatory facilities, better scores were found in more affluent neighborhoods. This result may reflect differences in design, as well as the fact that many non-regulatory facilities rely on community time and resources for maintenance.
How is green stormwater infrastructure maintained in Baltimore?
Maintenance of GSI is an important consideration that tends to be inadequately addressed. GSI facilities require maintenance to keep vegetation healthy and attractive, as well as to remove trash, sediments, and other materials brought in with stormwater.
Regulatory facilities must have long-term maintenance plans before they are approved. However, these plans are often privately contracted and unenforced, yielding a variety of maintenance outcomes.
For non-regulatory facilities, maintenance is a challenging issue. Long-term funding for GSI maintenance is rare—in fact, most grants only cover installation—and not all organizations can support a GSI facility over a long time period. In some cases, maintenance has been assigned to community volunteers, often without additional support or fully accounting for differences in capacity. Mixed results with maintenance practices that rely on community volunteers have more recently led to a shift toward reliance on partnerships and institutional capacity building. All of these factors contribute to variable outcomes.
Lack of communication or knowledge about GSI facilities across different city agencies can also lead to undesirable maintenance practices. For instance, GSI facilities may be unwittingly weed-whacked by maintenance crews, reducing their capacity to manage stormwater.
Maintenance is recognized as a problem by NGO leaders and other professional stakeholders, but sustainable solutions for GSI maintenance require system-wide changes. Ultimately, resources, burdens, and accountability for GSI maintenance must be planned with consideration for the fact that different communities have different capacities to maintain GSI, and that they may also require different levels of long-term financial and logistical support.
How do people perceive green stormwater infrastructure in Baltimore?
People’s perceptions of GSI can differ based on their relationships to GSI, the types of GSI they interact with, and how the GSI is situated in the larger system. To better understand these different perceptions, we interviewed residents who live near GSI facilities in Baltimore, as well as stakeholders involved with GSI installation and management.
Many residents who help maintain GSI in their neighborhoods feel that GSI promotes positive environmental change—it adds beauty, promotes community stewardship, and serves as a source of neighborhood pride. However, negative perceptions of GSI emerge from system-wide problems like poor communication about on-going maintenance practices and needed mechanical repairs.
Residents are often unsure of how NGOs or city agencies are supposed to support existing GSI facilities, and most residents perceive the city as responsible for GSI regardless of who implemented the project.
Some city officials express concern that poorly maintained non-regulatory facilities erode public trust in their mission to ensure that Baltimore meets regulatory requirements for water pollution limits.
In turn, some NGO stakeholders feel constrained by bureaucratic procedures that can be expensive and time-consuming, such as the review of engineering plans by city agencies.
These issues highlight how important it is to engage and communicate among all communities and stakeholders affected by GSI to reduce misunderstanding and clarify expectations, needs, and standards of care.
Increasing the equity of green stormwater infrastructure
Our research suggests that in order for GSI to be more equitable:
- The perceptions of all stakeholders must be included throughout the process of planning, design, implementation, maintenance, and evaluation.
- GSI must be treated as a system. Each individual installation should address local needs, desires, and capacities, but all installations should be considered collectively to promote social equity in their distribution, maintenance needs, financial support, and evaluation.
