Final Report: Performance and Effectiveness of Urban Green Infrastructure: Maximizing Benefits at the Subwatershed Scale through Measurement, Modeling, and Community-Based Implementation

EPA Grant Number: R835555
Title: Performance and Effectiveness of Urban Green Infrastructure: Maximizing Benefits at the Subwatershed Scale through Measurement, Modeling, and Community-Based Implementation
Investigators: McGarity, Arthur E , Hobbs, Benjamin F. , Rosan, Christina , Welty, Claire , Heckert, Megan
Institution: Swarthmore College , University of Maryland - Baltimore County , The Johns Hopkins University , Temple University
Current Institution: Swarthmore College , Temple University , The Johns Hopkins University , University of Maryland - Baltimore County
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 2013 through September 30, 2017 (Extended to September 30, 2018)
Project Amount: $1,000,000
RFA: Performance and Effectiveness of Green Infrastructure Stormwater Management Approaches in the Urban Context: A Philadelphia Case Study (2012) RFA Text |  Recipients Lists
Research Category: Watersheds , Water

Objective:

(1) Evaluate selected Green Infrastructure (GI) demonstration projects in the Philadelphia CSO area to measure and model technical performance.

(2) Develop methodology for creating zones of green infrastructure that encompass attributes influencing performance, benefits, and costs of GI practices, in the context of community- based adaptive implementation.

(3) Develop quantitative GI benefit-investment functions for each zone for maximization of benefits and minimization of costs through evaluation of multiple benefits.

(4) Incorporate benefit functions into tools for evaluation, optimization, and adaptive implementation of GI practices to facilitate transfer of this project's results to other urban centers.

(5) Incorporate STEM learning at multiple levels in all phases of the project.

Summary/Accomplishments (Outputs/Outcomes):

This broadly interdisciplinary research program included a year of monitoring at three Green Infrastructure (GI) sites that control stormwater runoff in Philadelphia's Wingohocking Sewershed, which is the largest of the city's Combined Sewer Overflow (CSO) areas. The data obtained were used to calibrate an advanced 3-D subsurface flow model to evaluate the effectiveness of these and future GI installations. The data have also been documented and archived in a publicly available database. This work demonstrates the power of using a coupled surface-subsurface model to account for all water balance components at a GI site. In particular, we have illustrated the temporally-variable nature of the infiltration process as affected by precipitation and evapotranspiration. This kind of approach, as demonstrated for one year at our sites, can be applied more broadly to other sites and for any length of time, given that inputs are available for use in the model. We have also calculated the potential for widespread adoption of GI technologies throughout the city to substantially reduce CSO flows of sewage into the city's rivers and creeks, while also taking into account costs and community co-benefits. Our research team has engaged community partners at each stage of the project to assure that our results and conclusions will be useful to Philadelphia's neighborhoods and city government during the city's GI adoption process. We have developed a geographical method for calculating an "equity index" to examine to what extent GI benefits are helping to improve measures of social equity across the city. The GI equity index is important because it can: (1) change the conversation about equity in GI planning using careful data analysis and Geographic Information Systems (GIS) that take into account both socio-economic and built environment variables; (2) provide a visualization tool that communities can use to understand underlying conditions and the existing placement of GI; and (3) serve as a tailored framework for communities to weigh their priorities, putting more power in their hands.

We have developed new decision support tools that evaluate placement of GI technologies on landscapes at the hydrological subwatershed level and in neighborhood zones of green infrastructure where the community co-benefits of GI have the potential to improve the quality of life of the residents. We have developed a tool called the Community Storm Water Investment Strategy Evaluation (StormWISE) model. StormWISE is linked to EPA's Storm Water Management Model (SWMM) from which it obtains quantitative CSO reduction benefit functions for each GI zone. StormWISE also links to input on community stakeholder priorities in GI zones where it is applied to generate "weighted GI co-benefit functions." CSO reductions and weighted co-benefits are both linked to the amount of runoff volume managed by different kinds of GI technologies such as rain gardens, infiltration tree trenches, and rain barrels.

Two cases studies demonstrate the application of StormWISE, through a web app developed for this project, in two Philadelphia GI zones: (1) the entire Wingohocking sewershed in North Philadelphia, and (2) a zone in West Philadelphia's Overbrook Neighborhood, in the Mill Creek sewershed, where a "Green Commercial Corridor" is being planned on Lancaster Avenue (U.S. Route 30). These case studies incorporate up-to-date GI costs for Philadelphia, provide estimates of the long-term benefits and costs over a wide range of GI adoption intensities, and enable prioritization of the available GI technologies. We have used the web app to demonstrate the StormWISE methodology to our project's community partners and have received valuable feedback on its applicability to green infrastructure development. Our results show Community StormWISE to be a valuable tool for informing polices that guide green stormwater infrastructure investments in Philadelphia, with potential for application in other urban areas.

We have developed and tested the potential for extending our GI evaluation methods to deal with uncertainties in GI performance and costs through adaptive management strategies. We have successfully advanced fundamental research on stochastic modeling of multi-stage adaptive decision making to reduce uncertainties and improve long-term outcomes of public infrastructure investments. We have developed a stochastic and multi- stage formulation for application in the StormWISE modeling framework, and we have applied it to a case study in Philadelphia's Wingohocking sewershed zone to examine our research's potential for reducing future uncertainties related to the city's long-term CSO reduction goals.

Further fundamental research has investigated whether the location of GI sites within a hydrological drainage zone can have an effect on the magnitude of CSO reductions achieved. We investigated key factors that affect the timing of runoff and basin discharge, including network travel time, time to fill-up GI, and rainfall duration. We compared the effects of GI site placement in two different climates by using long-term precipitation for both Philadelphia and Seattle.

Finally, we performed statistical analyses of Philadelphia green infrastructure installation cost data to obtain variability statistics for use in stochastic and multistage GI planning models. We found significant differences in the variability of costs depending on funding source and project scale. Public projects have much greater variability than private projects. Also, smaller projects have much greater variability than larger projects. We extended the cost variability analysis by examining labor and materials costs for individual line item inputs to GI construction projects.

We expect our research findings, and the tools we have developed, to help improve the nation's ability to protect its urban watersheds and ecosystems through better understanding of the costs, benefits, and performance of GI technologies. The following lists of our project's outputs and outcomes summarize our accomplishments.

The research has been covered in academic media. The Spring 2017, Volume CXIV, Swarthmore College Bulletin article by Kate Campbell, "A Spark, Then Room to Grow" featured coverage of this project's community engagement in Philadelphia under the heading "From Scrub, New Growth" and connected these activities with the support received from the College's Lang Center for Civic and Social Responsibility. The Academic Minute Podcast of National Public Radio and the Association of American Colleges and Universities featured project PI Arthur McGarity explaining the problems associated combined sewer overflows and summarizing this project's findings.

Conclusions:

  • Refined methodologies, developed with data and models from our field sites, for accurate lifecycle performance assessment of GI practices at the site level.
  • A publicly available database containing field observations from our monitored sites.
  • Refined methodologies for evaluation of cost effective, adaptive GI implementation strategies at the subwatershed scale employing a realistic cost model and multiple benefit metrics including runoff and CSO load reductions as well as ancillary benefits affecting community livability and equity in the distribution of those benefits.
  • Case study applications of methodologies developed through our research to specific green infrastructure zones in Philadelphia.
  • A web app to enable our community partners to evaluate and critique our methods through case studies in two GI zones: the North Philadelphia Wingohocking Sewershed and a West Philadelphia Green Commercial Corridor development in the Mill Creek Sewershed (Overbrook neighborhood).
  • Reports, peer reviewed papers in journals and conference proceedings, one Ph.D. dissertation, one Masters project, five undergraduate theses, national conference presentations, regional conferences, invited lectures, public databases, transferrable tools, and STEM education at the K-12, undergraduate, and graduate levels, documented in our technical report Appendices 1 and 2.
  • Increased national capabilities for assessing and implementing cost-effective and adaptive GI practices for urban stormwater management at the subwatershed level, especially in cities with combined sewers.
  • Community input at all stages of our research that enhances prospects for our research to assist in efforts to bring about widespread, successful implementation of green infrastructure.


Journal Articles on this Report : 5 Displayed | Download in RIS Format

Other project views: All 56 publications 5 publications in selected types All 5 journal articles
Type Citation Project Document Sources
Journal Article Heckert M, Rosan CD. Developing a green infrastructure equity index to promote equity planning. Urban Forestry & Urban Greening 2016;19:263-270.
abstract available   full text available
R835555 (2016)
R835555 (2017)
R835555 (Final)
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  • Journal Article Lim TC, Welty C. Effects of spatial configuration of imperviousness and green infrastructure networks on hydrologic response in a residential sewershed. Water Resources Research 2017;53(9):8084-8104.
    abstract available  
    R835555 (2017)
    R835555 (Final)
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  • Journal Article Lim TC, Welty C. Assessing variability and uncertainty in green infrastructure planning using a high-resolution surface-subsurface hydrological model and site-monitored flow data. Frontiers in Built Environment 2018;4:Article 71 (15 pp.).
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    R835555 (Final)
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  • Journal Article Heckert M, Rosan CD. Creating GIS-based planning tools to promote equity through green infrastructure. Frontiers in Built Environment 2018;4:Article 27 (5 pp.).
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    R835555 (Final)
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  • Journal Article Hung F, Hobbs BF. How can learning-by-doing improve decisions in stormwater management? A Bayesian-based optimization model for planning urban green infrastructure investments. Environmental Modelling & Software 2019;113:59-72.
    abstract available   full text available
    R835555 (Final)
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  • Supplemental Keywords:

    GI community co-benefits, StormWISE Investment Model, GI Equity Index, GI cost uncertainty, temporally-variable infiltration process, Stochastic Multi-stage Investment Planning Model

    Relevant Websites:

    Main project website Exit

    Philadelphia Keeps Stormwater Out of Sewers to Protect Rivers

    Progress and Final Reports:

    Original Abstract
  • 2014 Progress Report
  • 2015 Progress Report
  • 2016 Progress Report
  • 2017 Progress Report