Disambiguating Concepts of Fairness in Stormwater Management: A Review of Economic Efficiency and Equity

To confront the converging challenges of failing infrastructure, climate change, degraded water quality, and fewer undeveloped lands, many municipalities are establishing stormwater utilities (SWUs) to allocate a dedicated funding source to stormwater management (SWM) services. As a public service, creating a “fair” SWU by defining collective values that reflect community and municipal needs is crucial. However, the prevalent professional discourse surrounding SWUs often conflates “equity” with “economic efficiency” when they are two theoretically separate concepts, which obscure concerns raised by service beneficiaries. This paper unpacks ideas of fairness based on a systematic literature review that frames SWM financing in terms of economic efficiency and SWM services in terms of distributional, procedural, and structural equity. The distinction of which is important to set appropriate expectations between SWUs and beneficiaries.


Introduction
Cities across the United States and internationally face the converging challenges of deteriorating and insufficient stormwater infrastructure and uncertainty posed by climate change (Cesanek et al., 2017;Milly et al., 2008;Postel, 2010).Inadequate stormwater management (SWM) can lead to public health and safety threats (Gaffield et al., 2003;Kessler, 2011;Sanders & Grant, 2020), water quality concerns for receiving waterbodies (Rodak et al., 2019;Zhou, 2019), and issues surrounding resource allocation, accrued benefits, and adverse impacts (Elshall et al., 2020;Wilfong & Pavao-Zuckerman, 2020).Concepts that re-envision stormwater as a resource rather than a hazard incorporate multi-purpose solutions built on closed-loop water management systems that address these and other sustainability challenges (Brown et al., 2009;Crosson et al., 2020;US Water Alliance, 2016).These SWM solutions often include low-impact development, green infrastructure, nature-based solutions, or other multi-benefit soft infrastructure that moves away from singular-purpose hard or gray infrastructure (Dhakal & Chevalier, 2017;Prudencio & Null, 2018;Pyke et al., 2011;Wang et al., 2020).However, the nature of stormwater originating from disparate land parcels with varied ownership can pose difficulties in implementing effective, large-scale soft solutions, especially in urban locations (Lim & Welty, 2018).Additionally, funding and capacity issues have long been barriers to implementing forward-looking solutions in SWM (Stormwater Infrastructure Finance Task Force, 2020).The growing acceptance and movement toward multibenefit soft solutions that are decentralized with distributed benefits has led to an increased need to reconsider how and where to deploy SWM solutions, who is responsible for reducing runoff, what is financed and how, who should be involved in planning processes, and the associated social implications.
Even though pollution in stormwater runoff is the leading cause of water quality degradation in the U.S., investment in SWM often lags behind drinking water purveyance and wastewater management (Stormwater Infrastructure Finance Task Force, 2020).Unlike drinking water and wastewater, which are conventionally governed by utilities, new SWM projects compete with other municipal public works programs for funding and prioritization when no dedicated stormwater enterprise fund exists for a municipality.In response, cities are increasingly adopting stormwater utilities (SWU) to assess stormwater fees, which create a designated revenue source for use on stormwater-related infrastructure, management, or maintenance.There are over 1,700 SWUs across the U.S. and Canada (Campbell, 2019;Kea et al., 2016), and an increasing number of cities worldwide are adopting a stormwater fee model (Tasca et al., 2017).Having a dedicated fund for SWM systems ensures that all beneficiaries directly pay to address this ubiquitous issue, which can also serve to raise awareness of stormwater issues.Furthermore, programmatic incentives or credit systems can encourage individual landowners to adopt behaviors and practices that reduce runoff from their property.Still, municipalities often face conflicting demands from citizens, where communities expect more and better public service but resist paying taxes or fees (Boulton et al., 2022;Grigg, 2019).Perceptions of fairness are shown as a key part of the discourse to build community buy-in and political feasibility in public services and resource management (Jorgensen, 2003;Mankad et al., 2015).In practice, community perceptions of fairness are not limited to technical aspects of SWM and might be highly influenced by contextual historical, socio-economic, political, and environmental factors.
The purpose of this paper is to disambiguate concepts of "fairness."This paper is motivated by the often imprecise use of the terms "equity" and "equitable" in professional stormwater discourse, where their liberal usage-primarily related to financing-is a means by which deeper and more complex justice issues are often dismissed.To give a concrete example, in exploring the possibility of establishing a SWU for the island of O'ahu, Hawai'i (also the City and County of Honolulu), residents raised wide-ranging concerns regarding fairness (Kearns West et al., 2020).However, public replies revealed that the terms "equity" and "equitable" were often used in response to various community concerns about fairness.In particular, the idea of establishing a stormwater fee and credit system was described as "more equitable" compared to the current financing model deriving revenue from property taxes and highway funds (AECOM et al., 2020), when the concept is more technically described as economic efficiency.The messaging of SWUs being described as "more equitable" is promulgated by major U.S. federal, national, and regional organizations, including the U.S. EPA (Stormwater Infrastructure Finance Task Force, 2020;US EPA, 2008), the National Association of Flood and Stormwater Management Agencies (2006), National Association of Clean Water Agencies (2014), Georgia Association of Water Professionals (2018), the National Governors Association (Buchheister et al., 2022), and other gray literature related to SWUs (McIntosh & Vicari, 2016).While understandable that "economic efficiency (The term "efficiency" on its own can take on different meanings in different disciplines, and therefore can also be an ambiguous term, in addition to having different meaning in everyday lexicon.For example, in terms of water use, it can be used to describe conservation and the reduction of wasteful water use.In water quality science, efficiency can refer to the efficacy of a certain medium's ability to remove pollutants.Efficiency in engineering can refer to productivity of a build or design)" may be clunky and technical for a daily lexicon, I argue that using the term "equity" too loosely and frequently as a mode of eloquence can harm public trust if used without true reflection on its contextual implications (Beyond stormwater, cultural scholars have coined the terms "fakequity" or "faux-equity" to describe the hollow use of the term equity, which ultimately serves to perpetuate structures of exclusion rather than addressing real social justice issues (Hadley et al., 2022)).Irrespective of colloquial usage, it is important to clarify these concepts to set the right expectations and objectives around SWUs and SWM services and planning, whether in the literature or in public discourse with community residents.Moreover, precision in these concepts is critical as "rate methodology/ equity and fairness" was documented as the leading cause of legal challenges to stormwater utility fees in a U.S. survey of 73 municipal, state, and federal stormwater service practitioners (Black & Veatch, 2021).Distinguishing financing as an "input" and implementation as an "output" of SWM services helps disambiguate the concepts of fairness.That is, economic efficiency can be used to understand fairness in financing models for SWUs, and concepts of equity explain fairness in SWM services and programs.This paper presents a systematic literature review of concepts of fairness in SWM, which can be unpacked into economic efficiency in SWM financing and distributional, procedural, and structural equity in SWM services.The paper provides an overview of the methods used, followed by two main sections.The first section connects stormwater financing to economic theory, exploring the concept of fairness through the lens of economic efficiency.The second section discusses the literature that defines and analyzes fairness in SWM services, focusing on distributional, procedural, and structural equity.The paper concludes with a brief summary.

Methods
For this paper, I conducted a literature review to define "fairness" in stormwater financing and services.I followed PRISMA methods for systematic reviews and meta-analyses (Moher et al., 2009).I used the search strings "stormwater justice," "stormwater equity," "stormwater socioeconomics," and "stormwater fee efficiency," or variations thereof, using the Web of Science search engine.As shown in Figure 1, the number of publications related to stormwater financing or aspects of fairness has been increasing, especially within the last 5 to 10 years.I chose to focus on "stormwater"-as opposed to terms such as "drainage" or "flood prevention"-to better capture the contemporary management concept of water as a resource rather than a hazard (Cousins, 2018).However, the strict use of the word "stormwater" may impose a U.S.-centric focus to this literature review.
My literature search found 239 publications published between 2000 and 2022.After filtering out proceedings or meeting abstracts, book chapters, and editorial material, I was left with 198 articles.For the screening process, I read through abstracts to identify studies that conducted an analysis or developed a research method relevant to furthering the understanding of equity issues in SWM and services.I looked for papers that directly addressed questions of economic efficiency or equity in SWM (e.g., How is SWM financed?Who benefits from SWM services?Who is included in planning?How are known equity issues being addressed?).At this step, I kept 78 articles for further assessment to look for an evaluation of at least one aspect of economic efficiency or equity issues in SWM, definitions of equity or justice in terms of SWM, an analysis of issues of equity or justice in relationship to SWM, or a discussion of SWUs, fees, credits, willingness-to-pay for SWM.For example, I excluded papers motivated by an equity or justice issue, but did not specifically study the issue.In all, I conducted a full-text review of 67 papers for methodology and justice concepts related to stormwater.Of these, 8 focused on economic efficiency concepts, while the remaining 59 added to the discussion on equity in SWM services.Through these search criteria, there was a clear gap in literature discussing stormwater financing explicitly in terms of economic efficiency.

Financing Models
Funding is often a significant barrier to updating stormwater infrastructure and providing effective services while also meeting federal water quality regulations (Allerhand et al., 2009;Cousins & Hill, 2021;Stormwater Infrastructure Finance Task Force, 2020).Under a traditional public works financing model, stormwater systems and management are funded through taxpayer sources, such as the general fund or road fees, and compete with other priorities for a proportion of the monies.In the face of increasingly inadequate infrastructure, climate change impacts, water quality regulations, land use change, and competing public works budgeting, many municipalities are establishing SWUs to create a separate revenue source for SWM services (Brisman, 2002;Grigg, 2013).SWUs create enterprise funds that allow municipalities to establish a dedicated and predictable revenue source for proactive SWM services (US EPA, 2008).Among the financial advantages, McDonald and Naughton (2019) find SWUs to be an effective means for increasing per capita funds for stormwater services compared to municipalities without SWUs.In addition, stormwater fees are increasingly advantageous as a direct funding source for climate change adaptation efforts, especially in coastal cities facing rising sea-level impacts (Bloetscher et al., 2011).
The most prevalent method by which stormwater fees are calculated is based on a measure or metric of total impervious surface area (ISA) as a key driver of surface water runoff (Kea et al., 2016).One commonly used metric uses an Equivalent Residential Unit (ERU), which bases the fee on the average ISA of a single-family residential parcel (Tasca et al., 2019).Non-residential properties are then charged based on the ratio of the impervious area of the parcel to the ERU.Other models include flat fees, water usage-based fees, and tiered fees based on total ISA (Kea et al., 2016;US EPA, 2008).Many municipalities also offer credit systems that provide fee breaks for property owners who implement runoff reduction practices on their property (e.g., rain gardens, rain barrels, downspout disconnections) (Doll et al., 1998;Gmoser-Daskalakis, 2019).
The decision about which fee structure to adopt for a SWU is influenced by several factors.Administrative burden and available capacity can be major limiting aspects for incorporating greater complexity into a stormwater fee (Fedorchak et al., 2017).For example, a flat fee is an administratively undemanding means of charging a stormwater fee but may appear "unfair" because property characteristics are not considered (Tasca et al., 2017).Data availability can also be limiting and create greater administrative burdens.ERU-based fees attempt to reduce the data acquisition and administrative burden while considering some degree of property characteristics.Enforcement is an issue for a SWU that differentiates it from other utilities, where no individual service can be cut in the advent of non-payment.Therefore, it is useful to tie the stormwater fee to a water or power bill to have a mechanism for enforcement (Campbell, 2019).A successful SWU also requires legal viability and political feasibility, which can be shaped by public perception and trust (Grigg, 2013(Grigg, , 2019;;Hsu et al., 2020).Moreover, issues of who bears the burden of costs overlap with perceptions of fairness in administering an SWM financing mechanism.

A Welfare Economics Framing
According to the literature search, there are few studies that explicitly connect or discuss SWUs through the economic lens of efficiency.However, neoclassical economics provides a useful lens to understand stormwater financing and its implications on fairness before situating the financing mechanisms into a particular legal, political, and community setting.Focusing on volumetric runoff, there are two theoretical framings that well describe SWM systems and their financing.The first considers SWM services and infrastructure as a public good (Burnett & Mothorpe, 2018;Geaves & Penning-Rowsell, 2016;Jorgensen, 2003), which are defined as assets or services that are non-rivalrous and non-excludable, meaning everyone has access and no one's consumption reduces the usefulness to others.The traditional method of stormwater financing is based on bundling stormwater services as part of municipal public works funded by tax revenue, to which all public works projects are prioritized relative to one another (Grigg, 2013;Stormwater Infrastructure Finance Task Force, 2020).With this financing model, entities such as tax-exempt properties may benefit from stormwater services but do not Water Resources Research 10.1029/2023WR035743 ARIK contribute revenue to the funding pot, in economic terms, free-riders.The second framing considers stormwater and associated pollution as an externality (Lindsey, 1990;Milon, 2019), which is an adverse impact to society's resources created by individual activities.
In welfare economic theory, economic efficiency reflects policy that maximizes net benefits to society (i.e., the general equilibrium system is Pareto optimal).Both free-riders and externalities are market failures that lead to a sub-optimal market equilibrium (Gillingham et al., 2009;Medema, 2020;Trivić, 2019).These market failures have respective solutions (Jenkins, 2014;Keohane & Olmstead, 2007), which are reflected in certain SWU financing models (Parikh et al., 2005).To correct the free-rider problem, SWUs effectively detach SWM services from public works and fund them separately through user fees.This is a mechanism to require all service beneficiaries to pay a fee, for example, regardless of tax-exempt status.To correct the problem of externalities, certain SWUs incorporate an approximate of the differential cost of stormwater runoff from a property (This concept mirrors the concept of a Pigouvian tax (Parikh et al., 2005).However, in the US, the use of the word "tax" can be problematic in both political and legal arenas (Grigg, 2019; National Association of Clean Water Agencies, 2014), where terming charges either a "tax" or a "fee" has specific legal criteria based on policy purposes and outcomes).These charges are often based on a proxy for ISA, such as an ERU-based fee or a tiered fee based on ISA.
These concepts reflect economic efficiency in theory but do not necessarily reflect community ideas of "fairness" nor politically feasible outcomes.While requiring all beneficiaries to pay into a SWU as a public good addresses one type of market failure, it does not yet capture the source of the stormwater issues that requires management.To this end, correcting externalities as a market failure requires beneficiaries to be charged for the marginal costs of the impact they cause.True externality costs are based on property size, land development, and natural characteristics (e.g., soil permeability, precipitation) (Rossman, 2015) and are, therefore, difficult to estimate individually for all service beneficiaries.However, there is legal precedent in the U.S. to base stormwater fees on ISA or a proxy thereof (National Association of Clean Water Agencies, 2014).Moreover, the fairness and political feasibility of these solutions should also be considered.Despite long-standing calls for studying equity and economic efficiency in SWUs (Doll et al., 1998), academic literature analyzing the social implications of stormwater utility fees and credits is generally limited.

Is Economic Efficiency Fair?
For a SWU, the theory of economic efficiency can be used to understand approaches to dividing the costs of SWM services among beneficiaries.What is perceived as "fair" depends on many factors that may or may not be related to economic efficiency.However, not properly accounting for the context of an SWM system may lead to designing price inefficiencies into stormwater fee structures.Economic efficiency is a theoretical price point that implies that one entity cannot become better off without making another entity worse off; it does not in itself lead to equity.This formulation can be used to consider what comprises mechanisms commonly used toward economic efficiency in stormwater financing: All beneficiaries pay into the service (i.e.,SWM is a public good,no free-riders) Pay for marginal negative impacts (i.e.,negative externalities are priced) Credit for positive contributions (i.e.,positive externalities are rewarded) The first component of correcting economic inefficiency is eliminating free riders by ensuring all beneficiaries pay.This on its own might be perceived as "fair."For example, municipalities in France can levy a tax for managing aquatic environment and preventing floods based on a predetermined budget and divided evenly amongst the tax base (Harle, 2015).In this case, social solidarity, where everyone pays equally into flood risk management, was preferred to ensuring everyone pays according to risk exposure (Arik et al., 2023;Verlynde et al., 2019).Flat-rate fees are a simple option for assessing SWU fees but tend to give large landowners a financial advantage (Kea et al., 2016).
The second component of correcting economic inefficiency is to price externalities by differentially charging landowners for negative impacts or offering financial breaks to those who reduce impacts.This financing Water Resources Research 10.1029/2023WR035743 ARIK structure not only aims to collect revenue to cover the costs of providing SWM services but is also often meant to disincentivize impacts while incentivizing best practices (Lu et al., 2013;Malinowski et al., 2020).However, even if pricing negative externalities appears to be a fair practice, it may also amplify underlying socioeconomic inequalities.For example, low-income households stand to be the most affected by stormwater fees, even if the fees comprise only a minor proportion of the overall cost of living (Porse et al., 2022).Other inherent patterns of development may also contribute to increasing socioeconomic inequality.For example, Laćan et al. (2020) found that lower-income households in San Jose had higher rates of soil sealing.If lower-income houses tend to have higher total amounts of ISA, a stormwater fee based on ISA would likely disproportionately impact those households.A stormwater fee that is not fully collected among property owners can also lead to a less economically efficient system, creating new issues of fairness.For example, in the case of Philadelphia, switching from water-meter to ISA-based billing for the stormwater fee resulted in many first-time customers (i.e., large land parcels with high ISA without previous water bills) becoming delinquent in paying these bills (Hsu et al., 2020).
Credit systems can also have similar regressive effects.Where stormwater fee reductions are offered, some studies have found that higher-income households are more likely to have the capital to invest in solutions on their property to reduce their fee, such as rain barrels (Ando & Freitas, 2011) or green infrastructure (Mandarano & Meenar, 2017), while lower-income households that are marginally more financially impacted by a fee may not have the capital to invest in solutions to reduce their fee.When credit systems are used to better capture the price of externalities, they can also be described by economic efficiency.
Ultimately, economic efficiency and socioeconomic equity do not necessarily go hand-in-hand and should not be conflated.In specific cases, correct water pricing may lead to improved social equity if increased revenue is then used to correct uneven distributions (Rogers et al., 2002).However, as Keohane and Olmstead summarize, "focusing on the net benefits to society as a whole ignores the identities of the winners and the losers-that is, an emphasis on efficiency obscures a consideration of distributional equity" (2007, p. 45).Though connections may certainly exist, what is "fair" on the financing side of SWM does not transfer automatically into "fairness" on the planning and provision of SWM, and vice versa.

Equity and SWM Services
An increasing number of studies in the literature explore various aspects of fairness in SWM services.In this section, I present a systematic literature review to understand the directions of study of various disciplines toward defining what is fair in SWM services.I define fairness in SWM services as equity in three parts: distributional, procedural, and structural.The goal of this systematic literature review was to understand what issues of equity are present and studied in the literature.

Distributional Equity
Distributional equity refers to how burdens or benefits are allocated across SWM service beneficiaries.By and large, researchers study distributional equity issues through correlational or spatial analyses between underlying social factors and various parameters related to SWM.Although stormwater infrastructure placement will likely be highly related to hydrological design parameters, certain sociodemographic factors may also have an influence (Porse, 2018), leading to distributional inequality if the stormwater infrastructure does not provide an equal service across beneficiaries.For example, as Kuller et al. (2018) found in Melbourne, ad-hoc and opportunistic placement of water-sensitive urban design led to its overrepresentation in certain areas because of the disregard of socioeconomic factors.Li et al. (2020) found an uneven distribution of stormwater services in Ghent based on both social and environmental flood vulnerability factors, and proposed a method for identifying priority areas of green infrastructure to mitigate flood risk.Similarly, Meerow (2019) developed a web-based green infrastructure planning tool for New York City, Los Angeles, and Manila that identifies hotspots for multiple desired benefits beyond SWM.In fact, Seyedashraf et al. (2021) show that, regardless of the underlying social conditions, onesize-fits-all stormwater policies or objectives can themselves lead to distributional inequity.
The diversity of results of these studies reflects the fact that municipalities each have their own unique development patterns.For example, Baker et al. (2019) conducted the same spatial regression analysis for Portland, Oregon and Baltimore, Maryland.They found green infrastructure to be clustered in Portland and randomly distributed in Baltimore.Factors related to green infrastructure density in Baltimore were dependent on scale, Water Resources Research 10.1029/2023WR035743 ARIK where socioeconomic factors were significant only at the finer scale (i.e., U.S. Census tract) but not at the coarser scale (i.e., U.S. Census block group).On the other hand, median income was associated with green infrastructure density in Portland at both scales, with higher density in lower-income areas, in line with the findings of Chan and Hopkins (2017).The results of these two Portland studies suggest that programs promoting the strategic placement of green infrastructure by scoping both social and hydro-environmental needs may be used to correct existing distributional inequity.However, these studies do not assess whether the green infrastructure was effective or beneficial to these communities.
Other studies analyze the distribution of outcomes of benefits of SWM or absence of management, especially as related to socioeconomic factors.For example, Liang et al. (2019) analyzed trash generation and accumulation in Los Angeles in local water bodies and stormwater conveyance systems.They found that trash accumulation was related to the occupation and socioeconomic status of residents.Dixon et al. (2021) used crowdsourced data to identify whether socioeconomic patterns exist in the occurrence of reported problems.They found that a majority of reported stormwater infrastructure issues occurred in neighborhoods of vulnerable socioeconomic status, suggesting inadequate maintenance of critical infrastructure.In Atlanta, Lockaby et al. (2016) found that lowincome households, older houses, and housing density strongly correlated to West Nile virus risk factors related to combined stormwater-sewer overflow.Horvath et al. (2022) found that areas with greater poverty experience degraded water quality in nearby urban streams in Detroit, Michigan.Similarly, a study conducted in Inverness, Scotland showed that affluent neighborhoods have higher ecological quality of sustainable drainage systems than neighborhoods of less income (Miró et al., 2018).Other studies of the distribution of outcomes make the connection to problems of structural inequalities because of known underlying demographic and socioeconomic issues (Herreros-Cantis & McPhearson, 2021;Nyelele & Kroll, 2020;Shokry et al., 2022;Wendel et al., 2011).Overall, these studies to understand the spatial distribution of outcomes underscore the need to analyze distributional equity issues contextually before planning and implementing solutions.

Procedural Equity
Strategic prioritization and investment to improve the distributional outcomes may not necessarily comport with community needs or wants.This indicates the importance of including SWM beneficiaries in stormwater programs and planning processes.Procedural equity refers to the community's right to participation and transparency.Many studies evaluating procedural equity employ qualitative approaches, surveys, or mixed methods, and evaluate programmatic aspects such as outreach, knowledge, and participation.Studying outreach is critical, where the success of a project can largely depend on community relationships to stormwater projects and infrastructure.For example, Meenar et al. (2020) conducted field surveys of the appearance, context, and public perception of green stormwater infrastructure in Philadelphia.Their findings suggest that a lack of information can lead to low maintenance and social divestment.Similarly, Leets et al. (2022) suggest that successful tree planting programs involve targeted outreach, public-private partnerships, and significant community participation.Citizen perspectives can also be useful for better understanding the values that communities place on naturebased solutions and urban rivers (Naserisafavi et al., 2022).
Other papers study knowledge and willingness to participate, which could be related to the effectiveness of outreach programs.In Belo Horizonte, Brazil, Drumond et al. (2022) surveyed residents about stormwater knowledge and process and found that male respondents over 40 years old reported knowing more about SWM than other participants.However, they found no connection between greater knowledge and willingness to coparticipate in SWM, nor socioeconomic variables.In a study conducted in Knoxville, Tennessee, Mason et al. (2019) found that residents generally had moderate to high interest in backyard green infrastructure even though the participants had low to moderate awareness.Across three longitudinal studies in Charlotte, North Carolina, Scarlett et al. (2021) found that underserved groups were more willing to participate in SWM programs, which was linked to a heightened concern for flooding.Knowledge of potential ecological benefits can also lead to community involvement, as was the case for Cáceres, Spain in implementing sustainable drainage systems (Sañudo-Fontaneda & Robina-Ramírez, 2019).
These studies suggest that willingness to participate is independent of knowledge, and thus the question becomes, who actually participates?Kanoko Maeda et al. (2018) found that independent of knowledge, homeowners were more likely to implement best management practices than renters.However, they also found that knowledge was uneven, where renters and members of homeowner associations within their sample had less knowledge of Water Resources Research 10.1029/2023WR035743 ARIK stormwater best management practices compared to homeowners.A study conducted in Philadelphia showed that among surveyed residents, those who participated in green infrastructure programs tended to be White, younger, wealthier, and with a higher educational level than those who did not (Conway et al., 2022).They suggested that their findings might be related to the type of housing, which may be further related to socioeconomic and demographic variables.Saywitz and Teodoro (2021) studied factors related to adopt-a-drain participation in Houston, Virginia Beach, and Seattle, and found that demographic variables were generally more predictive of participation than flood risk.A study in Melbourne comparing coastal municipalities found that those with 50% or more natural vegetation tended to have a stronger commitment to Water Sensitive Urban Design (Morison & Brown, 2011).In general, these studies highlight the importance of procedural equity in outreach programs and co-participatory stormwater programs, where strategic efforts may be necessary to improve equality.Some studies overlap with distributional equity, proposing that improved procedural equity can lead to improved SWM outcomes.That was the case for Raleigh, North Carolina as described by Hasala et al. (2020).They found that green infrastructure placement, taken into consideration with local knowledge and historical realities, can produce similar results of hydrologic analyses but can serve to facilitate greater trust between the beneficiaries and stormwater managers.Local knowledge and preferences can also be incorporated into tools and models.For example, as part of the tool created to prioritize locations for multi-benefits, Meerow (2019Meerow ( , 2020) ) weights green infrastructure parameters according to surveyed desires of residents.Co-learning can also be a means to improve SWM outcomes.For example, Meyer et al. (2018) found that enhancing co-learning between residents and researchers led to increased resilience knowledge of participants while increasing data collection from residents in a neighborhood of Houston, Texas.Community can be key contributors to identifying and prioritizing problems or problematic areas that need particular attention.For example, interactive tools can be used to engage the community in identifying infrastructure or drainage problems (Hendricks et al., 2018;Jelks et al., 2018;Meyer et al., 2018).Interactive tools and engagement methods can also be used to help communities understand tradeoffs in outcomes and improve planning processes (Christman et al., 2018;Heckert & Rosan, 2016, 2018;Jordan et al., 2022;Kaykhosravi et al., 2019;Meerow, 2019).Such decision support tools can be used to identify community needs and wants in the face of particular constraints.Ultimately, these studies suggest that inclusive planning or co-learning processes lead to better outcomes for the community and more strategic implementation of projects.However, as Tubridy (2020) found in the case of an urban park redesign project in Copenhagen, if cocreation excludes certain people, it can lead to further vulnerabilities and distributional inequalities for those already disadvantaged from enjoying benefits.Thus, procedural equity can be critical to a just stormwater planning process.

Structural Equity
If there is structural equity in a stormwater system, the existing institutional structures ensure that no group of households bears a disproportionate share of negative impacts.The concept is easier to further define in terms of its opposite, where structural inequity is the systemic exclusion or privileging of certain groups of people leading to long-standing distributional and procedural inequities.Compared to distributional and procedural inequity, which may be unintended byproducts of environmental, infrastructural, or institutional processes, structural inequity in SWM reflects patterned detrimental actions.As such, it is tantamount to environmental injustice.Environmental justice issues are recognized to affect many cities.However, in evaluating 119 planning documents from 19 U.S. cities, Hoover et al. (2021) found that green infrastructure siting criteria rarely explicitly discuss environmental injustice.Without correcting for known injustices, structural inequality will likely persist and grow.Through a case study of Pittsburgh, Pennsylvania, Finewood et al. (2019) argue that to take a purely technocratic view of siting green infrastructure by focusing on stormwater-based metrics misses an opportunity to include historically disenfranchised communities.Nonetheless, many studies considering environmental justice dimensions focus mainly on structural aspects of distributional equity.
As previously discussed, the results of studies by Baker et al. (2019) and Chan and Hopkins (2017) showing higher green infrastructure density associated with lower-income areas in Portland, Oregon, suggest programs promoting both social benefits alongside hydro-environmental benefits can lead to the strategic placement of green infrastructure.However, contrary to what was found in Portland, many studies find opposite trends between socioeconomic factors and green infrastructure placement.For example, Shokry et al. (2022) found green resilience infrastructure to be concentrated in wealthier and gentrified neighborhoods of Philadelphia and the exclusion of neighborhoods with higher percentages of minority population groups.In New York City, Herreros-Water Resources Research 10.1029/2023WR035743 Cantis and McPhearson (2021) found that areas with larger portions of White residents with higher income had greater access to ecosystem service benefits of green infrastructure compared to areas with a higher proportion of people of color.They suggest that the distributional inequity of access to climate-regulating benefits of green infrastructure would reinforce or exacerbate potential structural injustices.Looking closer at the Bronx neighborhood of New York City, Nyelele and Kroll (2020) found that disadvantaged socio-demographic and socioeconomic areas received disproportionately lower ecosystem services provided by tree cover conditions.A comparative study within the same city of Tampa, Florida pointed to similar results, where the inner-city East Tampa residents had significantly less access to desirable urban green space and water features, potentially compounding known socio-demographic inequalities.They suggest that integrated SWM could potentially be a corrective solution to underlying environmental injustices (Wendel et al., 2011).
Many studies suggest that strategic placement of infrastructure that provides multi-benefits can help ameliorate spatial injustices and structural inequalities, and are developing tools for strategic programming.For example, Homet et al. (2022) found an overlap in some neighborhoods of Philadelphia between social and built environment vulnerabilities.They suggest a method for including multi-aspects of vulnerability to prioritize green infrastructure projects to provide multi-benefits to underserved communities.Almeter et al. (2018) developed a semi-quantitative prioritization scheme to identify a tree planting strategy based on maximizing multi-benefits.They found that multi-objective benefits favored planting in historically disadvantaged U.S. Census block groups in Durham, North Carolina, compared to single objectives.Though not a tool for strategic infrastructure placement, Castro (2022) conducted a Monte Carlo simulation of the social and environmental efficacy of nature-based solutions in Houston.The study found that notable improvements are potentially achievable by considering income disparities with no strong differences in runoff and pollution reduction, suggesting that opportunities for socioeconomic benefits are not mutually exclusive of environmental benefits.
However, these studies are based on presumed benefits for green infrastructure, while other studies show the importance of considering potential impacts and continued evaluation throughout the lifecycle of a project.For example, Meenar et al. (2022) conducted semi-structured interviews of community residents regarding green infrastructure in Camden, New Jersey, and found that green infrastructure projects do not automatically guarantee environmental justice and health equity.Green infrastructure redevelopment projects can also have adverse social impacts.For example, in Minneapolis, Minnesota, Walker (2021) found that gentrified tracts receive a majority of green stormwater infrastructure.This is largely because green stormwater infrastructure is incentivized in areas where the City is planning redevelopment where it is easier to install larger projects at lower costs.Ultimately, these impacts of green infrastructure-related gentrification can potentially lead to displacement (Chan et al., 2021).To consider social vulnerability aspects for rebuilding after a flooding event, Rezende et al. (2020) developed an indexing tool to incorporate socioeconomic capacities into discussions of flood risk management.These studies indicate the importance of both strategizing social benefits and accounting for potential social impacts of green infrastructure projects.
Focusing on correcting distributional inequity to address environmental injustice will likely be insufficient without involving the affected communities in the process.As Tubridy (2020) found in Ghent, the exclusion of community groups can reinforce inequalities in procedures and outcomes.Wang and Palazzo (2021) found that although the Sponge City program in Baicheng, China has led to improved distributional equity outcomes, there are still insufficient mechanisms to support public participation and acknowledgment of the history and needs of different community groups.In Sydney, Coyne et al. (2020) critically analyzed the history of a river through archival research and the evolving relationship between urban communities and water infrastructure.Based on their research, they propose a Culturally Inclusive Water Urban Design framework aimed at democratizing the development of urban waterscapes.Heck (2021) conducted ethnographic and archival research on a wastewater redevelopment project in St. Louis, Missouri and found that the redevelopment relied on "geographies of racial capitalism" by not assessing benefits beyond cost savings and stormwater retention.The study further suggests that structural inequalities such as racism or historical injustices can also create systemic barriers to participation or can be propagated through the planning process.Alternatively, in a Houston neighborhood plagued by a long history of localized flooding and exposure to contaminants, Oti et al. (2019) demonstrate that citizens can be effective participants in monitoring and contributing data about their local environment.Several environmental justice studies evaluate stormwater infrastructure through the lens of Urban Political Ecology as a method to analyze economic, spatial, political, and social issues that surround projects that aim to provide multi-benefits (Finewood, 2016;Finewood et al., 2019;Tubridy, 2020).Nóblega-Carriquiry (2022) proposes a framework Water Resources Research 10.1029/2023WR035743 ARIK based on Urban Political Ecology to evaluate the role of citizens, the impacts, and the power dynamics of sustainable urban drainage systems.
There are also policy, budgetary, and institutional aspects to environmental justice issues concerning SWM.For example, in Sweden, Glaas et al. (2018) suggests that change has only been realized where urban water management has aligned with planning processes, stifling systemic change.The budgeting process can be a tool to either enforce environmental injustices or pursue spatial justice, as Koopedi (2022) describes for Ekurhuleni, South Africa, a post-Apartheid city.Davis et al. (2022) highlight U.S. Federal regulatory failures to address wastewater contamination of waterways that disproportionately impact Black, Indigenous, and other communities of color.
Developing communities and informal settlements face deeper policy issues and infrastructural exclusion.For example, Nanekely et al. (2016) conducted field surveys of communities in Erbil City, Iraq.They identified policy issues and gaps related to the sustainable management of drainage systems connected to water shortage issues.Kikwasi and Mbuya (2019) show that communities living in informal settlements in Dar es Salaam are at a high risk of flooding because of insufficient or non-existent drainage networks.In the Gaya District of Bihar, India, Rashid and Pandit (2020) evaluated the willingness of rural communities to pay for and participate in wastewater and SWM.Because of a lack of infrastructure, rural residents go to nearby villages to dispose of wastewater in the drainage system.The findings suggest that access to infrastructure influences people's willingness to pay for infrastructure.They further suggest the importance of including oft-absent or excluded communities in planning processes.

Discussion and Conclusion
This paper seeks to disambiguate ideas of fairness in stormwater financing from equity issues in SWM services.The word "equity" is increasingly being used in stormwater discourse, especially as related to describing fair distribution of service charges for SWUs.Drawing from the theory of economic efficiency, I argue that the term "equity" is often misused in this context because economic theory suggests that only maximizing the net cost benefits of a system does not account for distributional equity, and thus, the concepts are not necessarily complementary.I further define equity issues in SWM in terms of distributed, procedural, and structural equity, as laid out in Table 1.While academic literature studying and defining issues of equity in SWM services is expanding, there is still limited discussion of SWM financing, especially through the lens of economic efficiency.In practice, there are strong cost-recovery, political, and legal considerations to take into account in any given setting that will shape the financing structures of a SWU.Issues of "fairness" will always evolve within the social context in relation to implementation and fee structures based on the community's values.However, using appropriate and explicitly defined terminology related to issues of fairness in stormwater financing or services can help facilitate the implementation and administration of SWUs that take into account community values.Murray et al. (2023) provide a useful example of defining the New Zealand Infrastructure Commission's core infrastructure funding and financing principles in terms of price efficiency, fairness and equity, administrative criteria (i.e., simplicity, transparency, practicality), and revenue sufficiency.
Within the body of literature on equity issues surrounding SWM, a large majority of which studies green infrastructure, nature-based solutions, or sustainable urban drainage systems.Distributional equity studies are often spatial or correlational studies that analyze the outcomes of stormwater infrastructure in terms of density or placement of infrastructure, beneficial services, or the absence of management or services.Studies of procedural equity focus on outreach, dispersion of knowledge, willingness to participate, and demographics of those who do participate.These studies tend to be qualitative or semi-quantitative, using field studies, surveys, interviews, or document reviews.There can be overlap between distributional and procedural equity issues.Specifically, many studies suggest improved distributional outcomes through community engagement, co-learning, and citizen science or place-based knowledge.The overlap can also represent deeper environmental justice issues, in other words, structural equity.Many studies discuss environmental justice issues in stormwater by showing that historically disadvantaged communities are often excluded from green infrastructure and redevelopment benefits unless these structural inequities are specifically addressed.Even so, these types of projects can have ancillary detrimental effects if they do not match community needs or desires.This points to the need to improve procedural equity when addressing environmental justice issues.Structural inequity can also be propagated through deeper policy, institutional, and budgetary processes.Collectively, these studies indicate the importance of considering Water Resources Research 10.1029/2023WR035743 and addressing equity in context and with the community.Promoting stormwater fees as "more equitable" to garner community acceptance without fully considering underlying equity concerns may only add to perceived fairness issues.

Table 1 Concepts That Contribute to Community Perceptions of "Fairness" in Stormwater Management Financing and Services
Economic efficiency-maximizing the net benefit of a system such that all SWM beneficiaries pay into the service as a public good, each paying according to their marginal impact (e.g., the amount of stormwater runoff produced by the development of their property, infiltration loss, or stormwater pollution) Fairness in stormwater financing-financing structures (e.g., stormwater fees and credits, taxes) that recover costs of implementing and administering SWM while taking into account the values of the service beneficiaries and meeting relevant legal criteria Distributional equity-all SWM beneficiaries receive a level of service that accords them an equivalent level of SWM and safety as everyone else Procedural equity-all SWM beneficiaries are accorded the ability to access information, programs, and planning processes to provide input into development and administrative processes Structural equity (environmental justice)-SWM services, infrastructure development, and planning procedures adjust to ameliorate historical infrastructural, institutional, or environmental injustices that are related to long-standing distributive and procedural inequities, especially concerning patterned under service or exclusion of people of a particular race, heritage, identity, or economic standing, or systematic or strategic privileging of services for specific people over others

Figure 1 .
Figure 1.Meta-analysis of literature using Web of Science search results related to stormwater utilities and equity concepts.The respective search terms are shown on the right.The bar graphs showing the total number of publications correspond to the left axis, and the line graphs show the total number of citations on the right axis.