Green Stormwater Infrastructure Research Articles

Performance assessment of stormwater GI practices using artificial neural networks

This study evaluates the performance of a suite of stormwater green infrastructure (GI) practices at the Belknap Campus, University of Louisville. In lack of instrumentation within individual GIs, and detailed drainage and sewer information, data mining procedures and artificial neural networks (ANN) were used. Two separate Back Propagation Neural Network Models (BPNNMs) were developed to estimate the reductions of flow volume and peak flow rates within the combined sewer system. The results from developed BPNNMs showed that following the construction of stormwater GIs at the Belknap campus, downstream wet-weather related flow decreased. The developed BPNNMs showed that the flow volume reduction and the peak flow attenuation rates had averages of approximately 33% and 61% per storm event, respectively. The flow reduction rates generally were lower for larger storms. Similarly, the peak flow rates decreased by increase of maximum intensity values per storm. However, further analysis indicated that even for large storm events, with long durations, the GIs had a positive impact on mitigation of combined sewer flows. Additionally, using rainfall data and downstream sewer flow in conjunction with artificial neural network modeling, was determined to be an effective technique for evaluating the combined hydrological performance of a suite of stormwater GIs.

From the household to watershed: A cross-scale analysis of residential intention to adopt green stormwater infrastructure

Improved stormwater management for the protection of water resources requires bottom-up stewardship from landowners, including adoption of Green Stormwater Infrastructure (GSI). We use a statewide survey of Vermont paired with a cross-scale and spatial analysis to evaluate the influence of interacting spatial, social, and physical factors on residential intention to adopt GSI across a complex social-ecological landscape. Specifically, we focus on how three GSI practices, (“rain garden (bio retention),” “infiltration trenches,” and “actively divert roof runoff to a rain barrel/lawn/garden instead of the street/sewer”) vary with barriers to adoption, and household attributes across stormwater contexts from the household to watershed scale. Private landowners, who may be motivated more by on-site and neighborhood stormwater problems, may gravitate toward practices like infiltration trenches compared with practices (e.g., rain gardens) perceived to serve stormwater function over larger areas. Diversion of roof runoff was found to be more likely to be a part of a larger assembly of green behaviors. Improved stormwater management outcomes at the watershed, town, neighborhood, and household levels depend on adaptive approaches and adjusting strategies along the rural-urban gradient, across the bio-physical landscape, and according to varying norms and institutional arrangements.

Benefit-cost analysis of stormwater green infrastructure practices for Grand Rapids, Michigan, USA

Grand Rapids, Michigan, USA is a medium-sized city located within the Lake Michigan watershed. Grand Rapids spends a considerable amount of money managing stormwater. Impervious surfaces collect and concentrate volumes of water and associated sediments and pollutants creating flooding, erosion, and pollution problems especially, for downstream communities. An ecological paradigm has emerged that places stormwater quantity and quality within the context of integrated watershed management. Stormwater quantity can be reduced and quality can be improved by, for example, mimicking natural hydrology. Detailed benefit-cost analyses, however, are still lacking. Therefore, the research team estimated the economic benefits and costs of various green infrastructure (GI) practices. Each GI practice was standardized to treat 84.95 m3 (3000 ft3) of stormwater per 25.4 mm (1.0 inch) event plus the first 25.4 mm of stormwater from larger events. This equates to about 3030 m3 (107,000 ft3) of stormwater per year. A benefit transfer approach was used to estimate the net present value (NPV) of capital, operations, and maintenance costs, as well as the direct and indirect benefits. The suite of benefits varied for each GI practice and included flood risk reduction; reductions in stormwater volume, total phosphorus, total suspended solids, and air pollution; scenic amenity value; and CO2 storage. A 3.5 percent discount rate was applied to all costs and benefits, and each practice was analyzed over 50 years. Conserved natural areas had the largest NPV at $109/m3 of water quality volume (WQv) reduced, followed by street trees at $46/m3 WQv, rain gardens at $37/m3 WQv, and porous asphalt at $21/m3 WQv. Infiltrating bioretention basins and green roofs had negative NPVs of $-3.76/m3 WQv and $-47.17/m3 WQv, respectively. If the green roof is used to attain certification such as Leadership in Energy and Environmental Design, then the net benefits turn positive. This paper will help both academic researchers and stormwater managers in the Great Lakes region and beyond understand the relative benefits and costs of stormwater GI so cost-effective practices can be implemented. The calculations presented here form the basis of the www.RainwaterRewards.com stormwater GI calculator.

Ecosystem services and U.S. stormwater planning: An approach for improving urban stormwater decisions

Green stormwater infrastructure (GI) is gaining traction as a viable complement to traditional “gray” infrastructure in cities across the United States. As cities struggle with decisions to replace deteriorating stormwater infrastructure in the face of looming issues such as population growth and climate change, GI may offer a cost-effective, efficient, and sustainable approach. However, decision makers confront challenges when integrating GI within city plans, including uncertainties around GI capacity and maintenance, resistance to collaboration across city governance, increasingly inflexible financing, accounting practices that do not incorporate the multiple values of GI, and difficulties in incorporating ecological infrastructure into stormwater management. This paper presents an ecosystem services framework for assessing the context-specific needs of decision makers, while considering the strengths and limitations of GI use in urban stormwater management. We describe multiple dimensions of the planning system, identify points of intervention, and illustrate two applications of our framework – Durham, North Carolina and Portland, Oregon (USA). In these case studies, we apply our ecosystem services framework to explicitly consider tradeoffs to assist planning professionals who are considering implementation of GI. We conclude by offering a research agenda that explores opportunities for further evaluations of GI design, implementation, and maintenance in cities.

Stormwater Quality Benefits of Permeable Pavement Systems with Deep Aggregate Layers

Green infrastructure (GI) stormwater control measures (SCMs), such as permeable pavement systems, are common practices used for controlling stormwater runoff. In this paper, two permeable pavement strips were studied to quantify their water quality performance. The quality monitoring was coupled with comprehensive rainfall analysis to investigate the effects of common rainfall characteristics on the quality performance of the systems. The pavements utilized deep aggregate layers to promote higher infiltration, and were installed in parking lanes of an urban neighborhood. Water quality samples were collected from upgradient stormwater runoff and from stormwater captured by the permeable pavements. In addition to total suspended solids (TSS), nutrients, and dissolved metals, this research also investigated bacterial contamination (Escherichia coli, E. coli). The results indicated that the two permeable pavement systems significantly reduced concentrations of TSS, E. coli, total phosphorus, and ammonia. The average reductions of TSS and E. coli between the two systems were 47% and 69%, respectively. It was also observed that pollutant loadings in the stormwater runoff, as well as pollutant reductions, were affected by the intensity of sampled rainfall events. Thus, it is suggested to consider the effects of rainfall characteristics when reporting the water quality benefits of stormwater GIs.

Temporal Evolution of Green Stormwater Infrastructure Strategies in Three US Cities

Over the last several decades, interest in green stormwater infrastructure (GSI) has rapidly increased, particularly given its potential to provide stormwater management in conjunction with other ecosystem services and co-benefits such as urban heat island mitigation or habitat provision. Here we explore the implementation of GSI in three US cities – Baltimore (Maryland), Phoenix (Arizona), and Portland (Oregon). We examine the trends in GSI construction over several decades, highlighting changes in implementation rates and GSI types with concurrent regulatory and economic changes. Additionally, we discuss the implications of these GSI portfolios for ecosystem service delivery in urban areas. Results indicate that Portland’s quantity of GSI is approximately ten times greater than the quantity of GSI in Phoenix or Baltimore. However, Baltimore has the most diverse portfolio of GSI types. In Phoenix, regional stormwater policies focused on flood control have led to retention basins being the dominant GSI type for decades. In contrast, Portland and Baltimore both have had substantial changes in their GSI portfolios over time, with transitions from detention or retention basins and underground facilities towards filters, infiltration facilities, and swales. These changes favor increased water quality function as well as provision of other ecosystem services. Additionally, we find evidence that each city followed a different GSI implementation pathway, with Portland’s combined sewer overflow program influencing initial development of GSI, while state legislation and regional water quality pressures played a major role in Baltimore’s GSI development. By studying the evolution of GSI in these different cities, we can see the variability in stormwater management trajectories and how they manifest in different suites of benefits. We hope that continued research of GSI implementation and performance will identify opportunities for future improvement of these infrastructures.

Influence of governance structure on green stormwater infrastructure investment

Communities are faced with the challenge of meeting regulatory requirements mandating reductions in water pollution from stormwater and combined sewer overflows (CSO). Green stormwater infrastructure and gray stormwater infrastructure are two types of water management strategies communities can use to address water pollution. In this study, we used long-term control plans from 25 U.S. cities to synthesize: the types of gray and green infrastructure being used by communities to address combined sewer overflows; the types of goals set; biophysical characteristics of each city; and factors associated with the governance of stormwater management. These city characteristics were then used to identify common characteristics of “green leader” cities—those that dedicated >20% of the control plan budget in green infrastructure. Five “green leader” cities were identified: Milwaukee, WI, Philadelphia, PA, Syracuse, NY, New York City, NY, and Buffalo, NY. These five cities had explicit green infrastructure goals targeting the volume of stormwater or percentage of impervious cover managed by green infrastructure. Results suggested that the management scale and complexity of the management system are less important factors than the ability to harness a “policy window” to integrate green infrastructure into control plans. Two case studies—Philadelphia, PA, and Milwaukee, WI—indicated that green leader cities have a long history of building momentum for green infrastructure through a series of phases from experimentation, demonstration, and finally—in the case of Philadelphia—a full transition in the approach used to manage CSOs.

Estimating effective impervious area in urban watersheds using land cover, soil character and asymptotic curve number

ABSTRACTKnowledge of the effective impervious area (EIA) or the degree to which impervious surfaces are hydraulically connected to the drainage system is useful for improving hydrological and environmental models and assessing the effectiveness of green stormwater infrastructure in urban watersheds. The goal of this research is to develop a method to estimate EIA fraction in urban watersheds using readily available data. Since EIA is dependent on rainfall–runoff response and cannot be solely determined based on the physical characteristics of a watershed, the EIA is linked with the asymptotic curve number (CN), a watershed index that represents runoff characteristics. In order for the method to be applicable to ungauged watersheds, the asymptotic CN is predicted using land cover and soil data from 35 urban catchments in Minnesota and Texas, USA. Similar data from 11 other urban catchments in Wisconsin and Texas, USA, are used to validate the results. A set of runoff depth versus EIA fraction curves is also developed to assess the impact of EIA reduction on discharge from an urban watershed in land-use planning studies.

Soil Media CO2 and N2O Fluxes Dynamics from Sand-Based Roadside Bioretention Systems

Green stormwater infrastructure such as bioretention is commonly implemented in urban areas for stormwater quality improvements. Although bioretention systems’ soil media and vegetation have the potential to increase carbon (C) and nitrogen (N) storage for climate change mitigation, this storage potential has not been rigorously studied, and any analysis of it must consider the question of whether bioretention emits greenhouse gases to the atmosphere. We monitored eight roadside bioretention cells for CO2-C and N2O-N fluxes during two growing seasons (May through October) in Vermont, USA. C and N stocks in the soil media layers, microbes, and aboveground vegetation were also quantified to determine the overall C and N balance. Our bioretention cells contained three different treatments: plant species mix (high diversity versus low diversity), soil media (presence or absence of P-sorbent filter layer), and hydrologic (enhanced rainfall and runoff in some cells). CO2-C and N2O-N fluxes from all cells averaged 194 mg m−2 h−1 (range: 37 to 374 mg m−2 h−1) and 10 µg m−2 h−1 (range: −1100 to 330 µg m−2 h−1), respectively. There were no treatment-induced changes on gas fluxes. CO2-C fluxes were highly significantly correlated with soil temperature (R2 = 0.68, p < 0.0001), while N2O-N fluxes were weakly correlated with temperature (R2 = 0.017, p = 0.04). Bioretention soil media contained the largest pool of total C and N (17,122 g and 1236 g, respectively) when compared with vegetation and microbial pools. Microbial biomass C made up 14% (1936 g) of the total soil C in the upper 30 cm media layer. The total C and N sequestered by bioretention plants were 13,020 g and 320 g, respectively. After accounting for C and N losses via gas fluxes, the bioretention appeared to be a net sink for those nutrients. We also compared our bioretention gas fluxes to those from a variety of natural (i.e., grasslands and forests) and artificial (i.e., fertilized and irrigated or engineered) land-use types. We found bioretention fluxes to be in the mid-range among these land-use types, mostly likely due to organic matter (OM) influences on decomposition being similar to processes in natural systems.

Implementation of Green Stormwater Infrastructure to Meet Water Quality Goals in Texas

Implementation of Green Stormwater Infrastructure to Meet Water Quality Goals in Texas

Green Infrastructure, Green Stormwater Infrastructure, and Human Health: A Review

In a growing trend, cities around the world have been installing Green Infrastructure (GI) in the form of vegetated landscapes that provide ecological benefits such as stormwater management, wildlife habitats, and temperature moderation (Tzoulas et al. Landsc Urban Plan. 61(3):11, 2007). Some GI, such as trees and green spaces, have positive impacts on human health. It is less clear how newer types of GI, such as rain gardens, green roofs, and bioswales, impact human health. These newer GI types are called Green Stormwater Infrastructure (GSI). Planners and designers need to know the extent to which GSI impacts humans. This systematic review does exactly that—we explore the published evidence regarding the relationships between GI and human health. We identified 55 peer-reviewed articles addressing these issues. Familiar types of GI, such as trees and green spaces, were found to be beneficial to the body (cardiovascular system, cortisol regulation, and pregnancy health), mind (attention capacity and mental health), and behavior (lower crime, better self-regulation, and more pro-social behaviors). We found much less research exploring the impacts of GSI on health. Our findings show that for some of the specific categories of GI, such as trees, considerable evidence exists on the impacts on human health. For other categories, such as rain gardens, green roofs, or biodiverse plantings, however, there is scant evidence of a health impact. We believe it is likely that these forms of GI do impact human health and that the reason for the scarcity of evidence is that few careful studies have examined the impacts of newer forms of GI on specific human health outcomes. Future researchers should investigate the health effects of type, dose, frequency, and duration of exposure to GI and GSI.

Hydrologic processes that govern stormwater infrastructure behaviour

AbstractUsing water budget data from published literature, we demonstrate how hydrologic processes govern the function of various stormwater infrastructure technologies. Hydrologic observations are displayed on a Water Budget Triangle, a ternary plot tool developed to visualize simplified water budgets, enabling side‐by‐side comparison of green and grey approaches to stormwater management. The tool indicates ranges of hydrologic function for green roofs, constructed wetlands, cisterns, bioretention, and other stormwater control management structures. Water budgets are plotted for several example systems to provide insight on structural and environmental design factors, and seasonal variation in hydrologic processes of stormwater management systems. Previously published water budgets and models are used to suggest appropriate operational standards for several green and grey stormwater control structures and compare between conventional and low‐impact development approaches. We compare models, characterize and quantify water budgets and expected ranges for green and grey infrastructure systems, and demonstrate how the Water Budget Triangle tool may help users to develop a data‐driven approach for understanding design and retrofit of green stormwater infrastructure.

Reducing Directly Connected Impervious Areas with Green Stormwater Infrastructure

AbstractThe emerging field of urban watershed protection often lacks a unifying goal to guide the efforts of many of its multidisciplined participants—planners, engineers, landscape architects, sci...

Maximizing Green Infrastructure in a Philadelphia Neighborhood

While the Philadelphia Water Department (PWD) is counting on Green Stormwater Infrastructure (GI) as a key component of its long-term plan for reducing combined sewer overflows, many community stakeholders are also hoping that investment in greening can help meet other ancillary goals, collectively referred to as sustainable redevelopment. This study investigates the challenges associated with implementation of GI in Point Breeze, a residential neighborhood of South Philadelphia. The project team performed a detailed study of physical, social, legal, and economic conditions in the pilot neighborhood over the course of several years, culminating in the development of an agent-based model simulation of GI implementation. The model evaluates a) whether PWD’s GI goals can be met in a timely manner, b) what kinds of assumptions regarding participation would be needed under different theoretical GI policies, and c) the extent to which GI could promote sustainable redevelopment. The model outcomes underscore the importance of private land in helping PWD achieve its GI goals in Point Breeze. Achieving a meaningful density of GI in the neighborhoods most in need of sustainable redevelopment may require new and creative strategies for GI implementation tailored for the types of land present in those particular communities.

A game theory analysis of green infrastructure stormwater management policies

AbstractGreen stormwater infrastructure has been demonstrated as an innovative water resources management approach that addresses multiple challenges facing urban environments. However, there is little consensus on what policy strategies can be used to best incentivize green infrastructure adoption by private landowners. Game theory, an analysis framework that has historically been under‐utilized within the context of stormwater management, is uniquely suited to address this policy question. We used a cooperative game theory framework to investigate the potential impacts of different policy strategies used to incentivize green infrastructure installation. The results indicate that municipal regulation leads to the greatest reduction in pollutant loading. However, the choice of the “best” regulatory approach will depend on a variety of different factors including politics and financial considerations. Large, downstream agents have a disproportionate share of bargaining power. Results also reveal that policy impacts are highly dependent on agents' spatial position within the stormwater network, leading to important questions of social equity and environmental justice.

Flash Flooding and Green Stormwater Infrastructure in Philadelphia: Areas for Further Improvement

Flash flooding is one of the dangerous catastrophes among the type of flood events. a. Flash flooding may occur in an area that may not even be located in floodplain zone. Because most flash flooding can take minutes or hours to develop with little warning and has high damaging potential, in this study, it was focused on identifying areas prone to flash flooding in the city of Philadelphia, which has many rivers and high development rates. For this reason, a Geographic Information System (GIS) analytical model was developed to find the most flash flood prone areas in Philadelphia, and analysis the relationship of our analysis results with the combined sewer area and the locations of green stormwater infrastructure projects.

Dynamic design of green stormwater infrastructure

This paper compares ongoing research results on hydrologic performance to common design and crediting criteria, and recommends a change in direction from a static to a dynamic perspective to fully credit the performance of green infrastructure. Examples used in this article are primarily stormwater control measures built for research on the campus of Villanova University [1,2]. Evidence is presented demonstrating that the common practice of crediting water volume based on soil and surface storage underestimates the performance potential, and suggests that the profession move to a more dynamic approach that incorporates exfiltration and evapotranspiration. The framework for a dynamic approach is discussed, with a view to broaden our design focus by including climate, configuration and the soil surroundings. The substance of this work was presented as a keynote speech at the 2016 international Low Impact Development Conference in Beijing China [3].

Equitable distribution of green stormwater infrastructure: a capacity-based framework for implementation in disadvantaged communities

ABSTRACTThis study seeks to understand the factors that influence the variability in distribution of public and private sector investments in green stormwater infrastructure (GSI) projects across the diversity of neighbourhoods in the City of Philadelphia, PA, U.S.A. using indicators of community context and capacity. For this study, context is defined as characteristics of disadvantaged communities and capacity as factors that facilitate individual and collective action. Community context and capacity are deemed integral to the success of the Philadelphia GSI programme as the Philadelphia Water Department is relying upon collaborative approaches to facilitate public investments in neighbourhoods and voluntary implementation of GSI practices on publically and privately owned lands. Private sector investments in GSI mandated by stormwater regulations for new construction and major rehabilitation also are assessed in relation to these two sets of indicators. The geographic information systems and statistical analyses reveal an inequitable distribution of GSI projects, which largely is driven by market forces. The paper concludes with a community capacity-based framework to prioritise public sector investment in disadvantaged communities to achieve more equitable distribution of GSI projects and associated benefits.

The research of gray space design of architecture based on green stormwater infrastructure application

Green stormwater infrastructure has become an important issue in the development of modern ecological city. However, the research about green stormwater infrastructure combined with architecture is not sufficient, for which usually focus on community planning in meso scale or landscape design in micro scale. The green stormwater infrastructure associated with building can be as green roof, vertical greening and gray space etc. Through data collection, case analysis and field research, the paper combined with architectural ecology and aesthetic mainly studies the public space closely connected with building easily accessible to citizens, which can be called gray public space. Based on the introduction to concept, principle and composition of green stormwater infrastructure and the basic connotation of gray space, the wisdom of the Chinese traditional architecture and building group in the rainwater utilization is draws out. Chinese traditional courtyard, alleys and garden not only build landscape utilizing stormwater and related infrastructure, but also collect rainwater for recycling or seeping directly into the ground. After the comparison of traditional gray space and the one based on stormwater utilization, three gray space models based on green stormwater infrastructure are summarized, such as separation-association based on the landscape function, half-association based on purifying stormwater to drainage and complete association based on recycling stormwater. Finally, this paper explains and confirms the three models through the rain and sewage separation system and purification system in the courtyard of Sidwell Friends School.

Quantitative analysis of impact of green stormwater infrastructures on combined sewer overflow control and urban flooding control

Stimulated by the recent USEPA’s green stormwater infrastructure (GSI) guidance and policies, GSI systems have been widely implemented in the municipal area to control the combined sewer overflows (CSOs), also known as low impact development (LID) approaches. To quantitatively evaluate the performance of GSI systems on CSO and urban flooding control, USEPA-Stormwater Management Model (SWMM) model was adopted in this study to simulate the behaviors of GSI systems in a well-developed urban drainage area, PSW45, under different circumstances. The impact of different percentages of stormwater runoff transported from impervious surfaces to the GSI systems on CSO and urban flooding control has also been investigated. Results show that with current buildup, GSI systems in PSW45 have the best performance for low intensity and short duration events on both volume and peak flow reductions, and have the worst performance for high intensity and long duration events. Since the low intensity and short duration events are dominant from a long-term perspective, utilizing GSI systems is considered as an effective measure of CSO control to meet the long-term control strategy for PSW45 watershed. However, GSI systems are not suitable for the flooding control purpose in PSW45 due to the high occurrence possibility of urban flooding during or after high intensity events where GSI systems have relatively poor performance no matter for a short or long duration event.