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Article

A Phased Approach to Urban Stream Restoration Decision-Making in Utoy Creek, Atlanta, Georgia

by
Garrett T. Menichino
1,*,
Liya E. Abera
2,3,
Terry W. Rickey, Jr.
4,
Stephen P. Phillips
4 and
S. Kyle McKay
5
1
U.S. Army Engineer Research and Development Center (ERDC), Environmental Laboratory (EL), Jacksonville, FL 32259, USA
2
Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, TN 37831, USA
3
U.S. Army Engineer Research and Development Center (ERDC), Environmental Laboratory (EL), Oxford, MS 38655, USA
4
U.S. Army Corps of Engineers (USACE), Mobile, AL 36602, USA
5
ERDC-EL, New York, NY 10278, USA
*
Author to whom correspondence should be addressed.
Land 2025, 14(3), 449; https://doi.org/10.3390/land14030449
Submission received: 10 January 2025 / Revised: 12 February 2025 / Accepted: 15 February 2025 / Published: 21 February 2025
(This article belongs to the Special Issue Research in Urban Ecology: Application into Landscape Design and Green Infrastructure)
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Abstract

:
Urban watersheds undergo significant ecological change due to increased imperviousness, flashy hydrologic processes, channel evolution, the loss of riparian zones, and the fragmentation of movement corridors. Watershed restoration seeks to address these challenges simultaneously through site-scale actions coordinated at the basin scale. Ecological benefits, social outcomes, and monetary costs represent common metrics to inform decision-making on these programs. However, decision-making at the site and watershed scale may differ, and the accuracy and resolution of benefit and cost data should vary as project needs dictate. This paper presents a case study of urban stream restoration in Utoy Creek, Atlanta, Georgia, USA, where multiple partner organizations are planning a portfolio of stream restoration projects. Analyses were conducted to assess ecological benefits, social outcomes, and monetary costs at the watershed scale to inform site selection, at the site scale to guide restoration design, and then again at the watershed scale to identify an effective portfolio of sites. These scales each presented unique technical challenges and required the adaptation of analytical methods to suit decision-making needs. This case study is not presented as a comprehensive approach applicable in all urban systems, but instead a template for urban restoration practitioners to adapt to their unique watershed and planning contexts.

1. Introduction

Land use change in urban areas alters the hydrologic, chemical, and ecological processes of streams and riparian areas [1], which has indirect effects that fundamentally change channel geomorphology (e.g., Booth and Fischenich (2015) [2]), biodiversity (e.g., Roy et al. (2005) [3]), and ecosystem processes (e.g., Gao et al. (2022) [4]). Given the extent and pace of urban development [5], multiple industries have unsurprisingly developed to manage urban stream ecosystems using approaches such as stream restoration [6,7], stormwater management [8], landscape architecture along urban riverfronts [9], and design of nature-based solutions [10]. However, it is increasingly acknowledged that urban water management decisions cannot be made in isolation from community desires [11] and socio-economic outcomes [12,13]. Urban stream managers need decision-making methods and tools to support these diverse goals, transparently make trade-offs, and work toward integrated socio-ecological outcomes [14].
Urban water management decisions are rarely made at a single moment or in isolation of other factors; instead, most decisions are a series of nested choices that span spatial scales and are executed over long time horizons. Many stream management initiatives often begin with a prioritization or site selection phase, which can include a variety of ecological and social factors [15,16,17]. At a reduced number of locations, alternative management actions may then be developed and compared at the site scale to identify locally effective conceptual plans [14,18]. Formal design is then needed to inform the sizing of features, material selection, construction staging, and other site-scale design issues, which usually involves feature-specific design processes and manuals (e.g., bank protection, Baird et al. (2015) [19]). Following implementation, adaptive management and maintenance actions are typically triggered by yet another set of decision points based on monitoring data or condition assessments [20,21].
Information needs and tolerable uncertainty shift as stream management projects evolve through these various phases and decision contexts. Similarly, plans and designs mature as projects proceed from site selection to conceptual design to constructed realities. A fundamental challenge for many stream management projects is identifying the “appropriate” level of analytical complexity [22] needed to make a particular decision in light of constrained time and resources [23]. The complexity of data and monitoring needs are, thus, common themes in many aspects of stream management ranging from hydraulic engineering [24] to ecological modeling [25] to cost estimation [26].
This paper addresses an important question in watershed restoration, namely, how do we ensure that restoration decisions are matched to the appropriate resolution of data and models throughout the planning and implementation process? Specifically, we use a case study in the Utoy Creek watershed (Atlanta, Georgia, USA) to demonstrate how analytical choices can (and should) vary as projects advance from broad-scale site screening to detailed site-level design and, finally, to watershed-scale portfolio analyses. We argue that project success in urban streams depends on balancing project goals, available resources, and decision timelines with methods that provide sufficient ecological, social, and economic information without overburdening planners, engineers, or stakeholders. Although we frame our study around “stream restoration” in Utoy Creek, the ideas, concepts, and lessons learned about tailoring analyses to match specific decision points are broadly applicable to other areas of urban ecosystem management. Our approach serves as a template for urban restoration practitioners to adapt to their unique watershed and planning contexts, which aligns with other recommendations for context-driven stream restoration [27].

2. Study Site

The Utoy Creek watershed drains urban and suburban parts of Atlanta, Georgia, into the Chattahoochee River (Figure 1). This small-to-middle-order stream is within the Piedmont region of the southeastern United States, and Utoy Creek exhibits many common characteristics of regional streams such as historical channel degradation due to poor sediment management as well as modern challenges like flashy runoff from urban development [28]. Two main tributaries, North and South Utoy Creeks, unite to form the main stem approximately five miles (8.0 km) upstream of the Chattahoochee River. The total combined length of the main stem and primary tributaries is approximately 22 miles (35.4 km) [29]. The drainage basin is approximately 33.7 square miles (87.3 km2) with 64% developed land uses and 18% impervious cover. The total length of channels is approximately 60.3 miles (97.0 km), which corresponds to a watershed drainage density of 1.8 miles per square mile (1.1 km per km2).
From 2022–2025, the U.S. Army Corps of Engineers (USACE) and the City of Atlanta partnered on a feasibility study of potential stream restoration actions in the Utoy Creek watershed, which is authorized through the USACE’s aquatic ecosystem restoration program (Section 206 of the Water Resources Development Act of 1996). A sound restoration strategy clearly articulates a problem statement and objectives, from which all choices about design or analysis flow [30], and the project team identified objectives for the Utoy Creek restoration project through four common agency practices [31]. First, agency policy was consulted to understand higher-level organization goals [32]. Second, existing local plans and studies in the Utoy Creek watershed were examined for potential themes and goals [33]. Third, project objectives were compiled from prior studies in the region (e.g., the neighboring Proctor Creek watershed) [34,35]. Fourth, preliminary objectives were shared with technical and non-technical stakeholders at a public meeting for input and refinement (May 2023, Terry Rickey Jr., personal communication). The following objectives were identified based on these methods.
  • Restore flow regimes to best attainable conditions achievable in altered urban environments by decreasing peak flows and hydrologic flashiness.
  • Improve channel geomorphic conditions.
  • Reduce sediment loading from the stream bed and banks.
  • Increase instream habitat for a diverse assemblage of local fauna.
  • Increase the connectivity of the channel for the movement of aquatic species.
  • Improve riparian conditions supportive of a diverse aquatic and riparian community.
The first objective focuses on hydrologic outcomes, which are important for achieving geomorphic and ecological outcomes [8]. This objective was addressed by a different set of management actions (e.g., stormwater control features), models (e.g., distributed hydrologic models), and cost drivers (e.g., maintenance of retention features). These analyses are described in project documentation, but they are not included in this paper to maintain the focus on reach-scale stream and riparian restoration actions [36].

3. Methods and Results

In pursuit of project objectives, different information was required as planning proceeded from early watershed-scale problem screening to site-level design, and a three-phase approach to analysis was developed to inform decision-making (Table 1). First, initial activities focused on screening sites to a focal set of locations aligned with project objectives. This phase applied high-level assumptions and preliminary data on ecological benefits and costs to first reduce 107 potential sites to 66 based on feasibility, and then further screen them down to 22 for a more detailed analysis. Second, alternative analyses were conducted at a reduced set of sites based on additional field and desktop data, the development of conceptual designs, the execution of ecological models, and the estimation of construction costs. Third, site-scale recommendations were combined at the watershed scale to develop different investment “portfolios” of potential restoration actions, and additional socio-economic data were compiled to contextualize ecological benefits and monetary costs.
The following sections describe each of these analytical phases separately and show how information was passed between phases to create an overall narrative about restoration planning. In this section, the methods and results are presented together to better reflect the decision-making for each phase on the Utoy Creek project. English units and U.S. dollars are used in this section to align with decision-makers’ expected form of outputs and minimize confusion about unit conversion in journal and agency documentation (e.g., conversion of indices like “habitat units”). All analyses were conducted using the R Statistical Software package version 4.4.0 and project documents were developed using R Markdown and GitHub to facilitate real-time documentation and increase transparency. All analyses and numerical code may be downloaded from the GitHub repository.

3.1. Watershed-Scale Site Screening

The Utoy Creek watershed presented many potential restoration opportunities across the basin, but limited resources constrained the number of actions possible through this joint study. Site screening was conducted to explore the “solution space” and reduce the number of potential opportunities to a smaller set for more detailed data collection. The goals of this analysis were threefold: (1) to remove locations misaligned with agency missions, (2) to eliminate ineffective options, and (3) to preserve sites with high potential for achieving socio-ecological objectives. Throughout this study, “site” and “reach” are used interchangeably, as each site corresponds to a distinct stream reach. In general, we use “site” when discussing plan formulation, cost analysis, and screening, and “reach” when referring to watershed-scale location and context.
The watershed was delineated into 107 stream reaches based on a desktop analysis of tributary junctions, discrete changes in riparian or channel conditions, and other locally important social factors such as road crossings or land ownership. Reaches varied in length but were selected to be somewhat homogeneous relative to ecological condition and anticipated management strategies. A site-naming convention was established from downstream to upstream, in which numbers were branched at major tributary junctions and letters indicate reaches within those tributaries. These reaches serve as the basic unit of analysis of all site screening and subsequent restoration planning. Aerial photography, hydrographic data, and land use cover were used to eliminate 41 reaches that were expected to be infeasible for restoration (e.g., active reservoirs or highly confined reaches between major roads) or outside of the scope of agency actions (e.g., small headwater tributaries are uncommon locations for USACE actions).
Ecological conditions were assessed for the remaining 66 reaches using semi-quantitative scoring during rapid site visits in March 2023 [36]. All metrics were scored on a 0–20 scale, where 0 was non-functioning and 20 was ideal, and data were subsequently binned as poor, marginal, suboptimal, and optimal for decision-makers (Figure 2A). Instream metrics were selected based on common field assessment methods (i.e., Barbour et al. (1999) [37], Bjorkland et al. (2001) [38], Rankin (2006) [39], McKay et al. (2024a) [40]) and included evaluations of geomorphic stability, bank erosion, physical habitat features, and floodplain connectivity. These metrics were grouped to align with project objectives for channel geomorphology, sediment loading, instream habitat, and connectivity. A parallel riparian scoring system was drawn from metrics used in existing assessments and was based on sources of organic carbon, nutrient uptake mechanisms, temperature and light regimes, habitat structure, and movement corridors [41]. Scoring metrics were aggregated into separate 0–1 indices of habitat quality for instream and riparian condition. These habitat quality metrics were multiplied by instream and riparian areas to quantify the number of “habitat units” at each site.
The primary objectives for this study are related to ecological outcomes, but urban restoration often requires secondary contextual information on socio-economic outcomes [42]. A 0–20 scoring system comparable to ecological condition was developed for five categories of societally relevant outcomes [36], perceived to align with common concerns raised in this community [43,44]. First, resilience to disturbance was assessed with the logic that urban systems often experience high levels of unpredictability due to floods, rapid land development, or other unexpected events like spills. Second, social benefits and equity of actions are important considerations, which were scored relative to alignment with other agency activities (i.e., flood risk management), visibility and accessibility with residents, and perceived community support for this location. Third, esthetic and recreational opportunities were included to account for potential educational access and community use. Fourth, this study focuses on ecosystem restoration opportunities, but water quality management is a key consideration for city water managers. Finally, the intangible benefits were assessed at this site with the assumption that observers may be aware of other qualitative benefits of acting at a given location (e.g., ease of real estate acquisition, synergy with ongoing management, strong stakeholder support). Social metrics were averaged and normalized into a 0–1 index (Figure 2B) and multiplied by site area to create a “social unit” comparable to “habitat units”.
At each site, one restoration alternative was developed to reflect the maximum amount of restoration potential at the site. These actions were primarily based on stages of channel evolution and associated restoration actions as well as existing riparian land uses [2,45]. Ecological condition scores were adjusted for these future conditions with restoration actions, and the net effect of restoration between the with and without project condition was used as the metric of ecological “lift” or benefit at the site. A relative metric of construction cost was developed from unit cost data at prior restoration sites (e.g., cost per linear foot of bank protection) and combined with site-specific quantities (e.g., length, area, fill volume). These costs were not reflective of fully burdened cost estimates, but provided a metric for relative comparison of sites (Figure 2C). The social benefit metric was assessed for each site, but the metric only addresses the social value of the location itself, not an effect of restoration actions.
Ecological benefit and monetary cost estimates were analyzed using cost-effectiveness and incremental cost analysis (CEICA, McKay et al. (2024b) [46]), which provides a mechanism for examining the efficiency of alternative actions (see Robinson et al. (1995) [47] for methodology). Cost-effectiveness identifies actions with the highest environmental benefits for a given level of cost or the least cost for a given level of environmental benefit. An “efficiency frontier” identifies all plans that efficiently provide benefits on a per cost basis. Incremental cost analysis is conducted on the set of cost-effective plans and sequentially compares each plan to all higher cost plans to reveal changes in unit cost as output levels increase. Specifically, this analysis examines the slope of the cost-effectiveness frontier to understand the marginal cost increase of the next level of investment. Plans emerging from incremental cost analysis efficiently accomplish the objective relative to unit costs and are typically referred to as “best buys”.
CEICA was applied four times to screen restoration actions across the Utoy Creek watershed. Sites were aggregated into three regions for the mainstem, north tributary, and south tributary. Within each region, all combinations of sites were considered up to a maximum of five actions per region. Separate prioritization of actions distributed sites across the watershed and reduced the potential combinations of actions to a level that was numerically feasible. For each combination, ecological benefits and investment cost were summed, and these combined actions were subjected to CEICA. Social outcomes were analyzed separately from ecological benefits and were analyzed for the watershed with the goal of identifying societally important portions of the watershed and potential alignment with ecological outcomes.
The overarching goal of this analysis was to reduce the number of sites by removing ineffective sites and maintaining sites with high potential for socio-ecological benefit. Sites were advanced if one of four criteria were met: (1) identification based on CEICA, (2) high potential ecological benefit, (3) low cost per unit of ecological benefit, and (4) high potential social benefits. This inclusive approach to site screening was used in part because of the high uncertainty in estimates of ecological benefit, social benefit, and investment cost, and a more rigorous screening approach had the potential to eliminate effective sites. While our approach aimed to retain all sites with identifiable potential, in watersheds with many candidate sites, a more restrictive threshold may be necessary. Future applications of this framework may consider adjusting the screening criteria based on study-specific constraints such as project scope, budget, or stakeholder priorities. Twenty-two sites were advanced for site-level alternative development based on this analysis (Figure 2D).

3.2. Site-Scale Alternative Analysis

Stream and riparian restoration can be pursued through a diverse set of actions at a given location [17]. For instance, a site may require channel restoration using grade control features, bank protection actions, riparian forest management, or some combination of these actions. This phase of the analysis focused on the identification of effective combinations of restoration actions at the site scale with the goal of identifying conceptual restoration plans for each reach.
Site-scale data were compiled for the remaining 22 reaches based on field visits in October 2023. These field visits involved walking the length of each site to observe physical, ecological, and social factors (described below) as well as factors affecting project feasibility (e.g., utility crossings, staging). Potential restoration sites were also discussed with partners (e.g., greenway planners, watershed managers) to better understand ongoing management and potential barriers to restoration at a given location. Some sites were combined based on their potential for a single construction mobilization. These factors ultimately advanced eight locations for site-level alternatives development, which included 10 of the original reaches.
Interdisciplinary teams of engineers, ecologists, an economist, and an archeologist visited each location and developed potential restoration strategies. For each site, four alternatives were developed to present a range of potential ecological benefits and investment costs, including a no-action alternative, a large mobilization with all potential restoration actions included, and two intermediate solutions. Preliminary restoration actions and concepts were developed during field visits. Details of the specific alternatives considered at each site are provided in Abera et al. (2024) [36]. Depending on the site conditions, the alternatives ranged from a combination of actions, including channel reshaping, planform realignment, habitat improvement with instream structures, and riparian plantings. Following the field activities, a series of working meetings were conducted to refine ideas into conceptual alternatives. An interactive facilitation tool (www.miro.com accessed on 1 April 2023) was used to collect input and notes from all disciplines and team members, which served as a knowledge gathering space for alternatives. Site-scale concepts were then formalized into design formats to assess the quantities of restoration needed for ecological and cost models.
Ecological benefits were reassessed for instream and riparian outcomes using more detailed ecological assessment tools. Instream outcomes were assessed using a model developed for this project [36], which draws heavily from existing tools used nationwide [37,38,39], in neighboring basins [35], and from other comparable urban systems [34]. This instream model was organized around four modules for hydrology and hydraulics, geomorphology, physico-chemistry, and biology, which approximately correspond to the widely used stream functions pyramid [48]. The Riparian Ecosystem Function Index (REFI) is a rapid method for quantifying the ecological function of riparian zones based on the indirect effects of riparian zones on streams, the role of riparian zones as corridors, and the unique and important habitat provided for aquatic and terrestrial fauna [49]. These separate tools are intended to complement each other with the instream tool applied from streambank to streambank, and REFI applied from the top of the bank outward. Instream and riparian outcomes were summarized as “habitat units” (HUs) capturing the quantity and quality of the ecosystem at a given point in time.
Each ecological model was executed for four points in time for all alternatives (Figure 3A). Year-0 was assumed to be the existing condition and represents the pre-restoration, degraded condition of the site. Year-2 represents a point in time reflecting an initial increase in ecological benefits associated with restoration actions. In general, this time frame reflects instream benefits of the project, but riparian outcomes would not fully be captured. Year-10 was then assessed as a representative time frame for obtaining many of the riparian benefits. Year-50 represents a fully mature site with a developed multi-story riparian canopy and instream conditions adjusted to a new dynamic equilibrium. Both models were time-averaged (i.e., annualized). Instream and riparian outputs were summed as an overall metric of ecological benefits. For all sites, the benefits are reported as the ecological “lift” between the with and without project conditions (Figure 3B).
Life cycle costs were estimated for construction, monitoring, adaptive management, and long-term operations and maintenance (Figure 3C). However, these estimates are parametric and for comparative purposes only due to the exclusion of factors such as real estate, design, construction management, or cultural resources. Construction costs were compiled for each site-scale restoration action following standard cost engineering methods [26]. Monitoring and adaptive management are typically conducted over a ten-year window for USACE ecosystem restoration projects (Section 2036 of the Water Resources Development Act of 2007). The monitoring cost was estimated based on pre-construction sampling as well as 1-, 3-, and 5-year time points following construction with each event, including the collection of fish, invertebrate, bathymetric, and hydraulic data. Adaptive management was estimated as a proportion of the construction cost ranging between 7.5% and 25% depending on the site and alternative complexity. Operation and maintenance costs were estimated relative to quarterly general maintenance, bi-annual inspections, invasive species management, and the repair of structure features at a 25-year interval, which resulted in costs ranging from 1.2% to 16.7% of construction costs across sites and alternatives. All costs were annualized over a 50-year life span based on the policy-specified federal discount rate of 3.00% using the EngrEcon software package version 1.0.0 [50].
The ecological benefits and monetary costs for each of the four alternatives were then subjected to CEICA at the site scale (Figure 3D). These analyses provided a mechanism to examine the relative merits of different alternatives and elucidate trade-offs associated with levels of costs and ecological benefits. CEICA was executed using the ecorest R package [46]. The CEICA results were interpreted by an interdisciplinary team of 10–20 subject matter experts. At each site, each expert evaluated the relative merits of the alternatives through their disciplinary lenses such as ecological efficacy, engineering reliability, constructability, real estate constraints, cultural resources, economics, and other factors. The logic of decision-making was to visually examine the CEICA results, default to a decision array of best buy plans from incremental cost analysis, and then explore other cost-effective plans if appropriate. Site-scale recommendations were made along with the accompanying logic of each decision. Based on these analyses, no action was recommended at one site and restoration actions were recommended at seven sites.

3.3. Watershed-Scale Portfolio Analysis

Site-scale recommendations were then reassessed at the watershed scale to understand the benefits of the overall investment. This system-scale analysis asked “Which combinations of sites and actions create a logical portfolio of recommendations?”. The analysis also sought to reduce uncertainties in key decision metrics (e.g., moving from parametric to more refined cost estimates) and conduct ancillary analyses to understand the social context of this suite of restoration actions.
Every combination of the sites was examined (128 “plans”), and the ecological benefits and monetary cost were summed across sites. These watershed-scale plans were then assessed using CEICA (Figure 4), with the results again interpreted by an interdisciplinary team. All plans remained within the USD 10 million federal funding limit set by the USACE program under which the project was conducted, making them financially viable. Outside of this study, budget constraints will vary by project, and future applications should account for project-specific limits. The watershed-scale scope of the project encouraged the consideration of the spatial distribution of projects to include both North and South Utoy Creeks. Some plans include logical sets of geographically clustered actions (i.e., Sites 17F2M, 17D2E, and 17B as well as Sites 2A and 2B), which could be sources of efficiency in construction mobilization and ecological outcomes. Finally, one site (Site 3F) included some novel restoration approaches, such as introducing beavers into a parkland reach with low infrastructure risk, allowing for a more process-based restoration approach. At this site, the value of innovation and learning was weighed relative to the monetary cost of this investment. Based on these and other factors, the team sequentially considered each best buy plan and developed a rationale for the next incremental investment. Ultimately, the recommended action included all seven remaining sites, which collectively provide 117 habitat units of ecological lift at an anticipated construction cost of USD 4.5M (Table 2).
Prior analyses emphasized project outcomes relative to ecological criteria (i.e., the primary project purpose) and investment cost. However, urban water management projects are embedded within cities, and social outcomes often enrich decision-making and contextualize the benefits of investments. This analysis considers two factors commonly raised by decision-makers: the social equity of restoration investments and the economic benefits of construction actions.
The benefits of stream restoration are sometimes inequitably distributed among communities [43], and equity has been cited as an important aspect of water resource decision-making writ large [51]. The distribution of restoration benefits among the residents of Utoy Creek was analyzed using tract-level census data to examine patterns relative to population density, gender, age, race and ethnicity, income, and employment [52,53,54]. Table 2 presents select data on income and employment rates as representative examples of how restoration benefits are inequitably distributed. For instance, unemployment rates at Sites 17F2M, 17D2E, 17B, and 19A are high relative to the state and county averages of 3.4 and 4.1 percent, respectively. These types of data helped contextualize and justify the inclusion of sites that may not be as justifiable based purely on ecological rationale. While these data on distributional equity are important, this analysis does not directly address procedural and recognitional equity issues beyond traditional public meeting formats, which are acknowledged challenges in this particular watershed, and leaves opportunity for future improvement to restoration planning practices [43,44].
The impacts of restoration on employment, income, and output of the regional economy were considered as additional context for the recommended actions. An input–output macroeconomic model (i.e., USACE’s Regional Economic System) was used to address the impacts of construction spending on the local economy [55]. The regional economic analysis estimated direct, indirect, and induced effects to the local region as measured through jobs (primarily short-term construction-oriented positions), gross regional product, labor income, and sales. Restoration actions at these seven sites are estimated to result in 125 jobs and USD 13.7M in gross regional product in the local area and 232 jobs and USD 17.8M in gross regional product in the State of Georgia.
The portfolio analysis ultimately carried forward all seven site-scale recommendations from the prior analysis; however, the analyses helped “tell the story” of Utoy Creek restoration decisions. The system-scale CEICA provided a mechanism for recording the quantitative and qualitative arguments supporting restoration at each site, which was crucial for justifying each increment of investment. The secondary analyses of community demography and economic production also provided context for decision-makers about the collective benefits of restoration not only to the ecosystem, but also to the city. Overall, this analysis provided an important step of narrative building, which is often omitted or qualitatively justified in watershed restoration.

4. Discussion

The Utoy Creek case study has been presented here as an example of common challenges in stream restoration decision-making. All projects are, however, limited by their decision context, and Utoy Creek is no different since it was scoped around a specific geography; the mission and goals of two agencies; and time, financial, data, and analytic resources available to the team. While tailored to this focal system, the case study uses comparable approaches to stream prioritization activities in other urban areas like southern California [16], Charlotte, North Carolina [17], Seattle, Washington [56], and Melbourne, Australia [57], and many of the techniques and methods used in Utoy Creek may have broader applicability than the narrow confines of this project context.
One notable difference between Utoy Creek and some existing watershed restoration projects is the use of restoration cost in prioritization at all scales. The relative merits of a site depend not only on ecological and social benefits, but also the constraint of cost [57]. Cost-effectiveness and incremental cost analyses have been recommended as mechanisms for describing return-on-investment of conservation and restoration writ large [14,47,58], and the Utoy Creek case study strongly reinforces the importance of cost data as critical information at all scales of decision-making. Unfortunately, cost estimates and methods are often less available than physical and ecological data or available in disparate formats and this gap represents a crucial research need for urban stream management [27,59].
Social outcomes and processes are increasingly acknowledged as crucial drivers of stream restoration efficacy [11,60], and an equity-oriented perspective has been recommended as a mechanism to provide context and identify opportunities to address fundamental community needs [43]. The Utoy Creek study provides an incremental step forward toward these goals by including social outcomes in both site screening and watershed-scale decision-making, which broadened the scope of agency-led restoration activities to include common community-driven goals [11]. However, the analysis of social outcomes was constrained by resources, time, and alignment with the ecological project focus (i.e., site screening used simple scoring and watershed prioritization used demography as a proxy for equity), and more nuanced and detailed analytical methods are emerging for assessing the equity of stream restoration actions (e.g., Yaryan-Hall and Bledsoe (2023) [17], DeJong (2024) [61]) that could be used in future studies. Furthermore, distributional issues are only one dimension of equity, and procedural and recognitional forms of equity are crucial for facilitating community involvement [51]. In fact, community engagement and inclusion in the decision process have been identified as major issues in historic stream management activities in the Utoy Creek watershed specifically [45] and more broadly across Atlanta’s urban watersheds [44]. While an incremental step forward, the Utoy Creek study used only traditional public engagement methods (i.e., occasional formal meetings), which did not overcome many common challenges in engaging communities in stream restoration such as enhanced roles in problem identification [62], a focus on ecological over social outcomes [45], complex relationships between institutional roles and missions [62,63], or including communities in the interpretation of results [11,44]. An enhanced model of engagement could include sustained relationship building, increased frequency or duration of public engagements, mechanisms to encourage participation (e.g., alternative time or incentives), or alternative mechanisms for input (e.g., web applications).
Multiple disciplines played important roles in analysis of Utoy Creek’s stream restoration actions (e.g., engineering, ecology, cost estimation, environmental justice), and all decisions hinged on multiple lines of evidence compiled through interdisciplinary dialog [64]. At each of the three phases of analysis (Table 1), extensive dialog was required among team members to understand the necessary level of effort to make informed decisions [22,25]) relative to resource availability and tolerable uncertainty [23]. Furthermore, the results were jointly interpreted with all disciplines represented, which led to important observations about constraints, analytic uncertainties, and the relative merits of alternatives. These conversations were crucially important to ensure that a given discipline’s perspective was not providing information at a lesser or greater resolution than others, and these choices highlight the important roles of interdisciplinary dialog and effective project management in navigating stream restoration projects.
The three scales of analysis in this study point to the need for both site- and system-scale information to make informed decisions about stream restoration priorities. The need for systems thinking is well acknowledged in a range of restoration and water management guidance (e.g., de Vries et al. (2021) [65]), and the nested hierarchy of river systems is often cited as a major driver of the need for systems thinking (e.g., Polvi et al. (2020) [66]). However, for Utoy Creek, analyses were scoped to move from the watershed scale to site scale and then back to the watershed scale (rather than unidirectionally from watershed to site). The context provided by moving between scales was crucial for understanding the effects of decisions in Utoy Creek, and interactive restoration prioritization tools (e.g., Beck et al. (2019) [67]) could provide a useful mechanism for transitioning between scales and engaging communities in stream restoration analyses and decisions. Additionally, the site screening process tended to favor larger, lower-watershed reaches where ecological lift was more quantifiable, while smaller upstream reaches often scored lower in potential benefit. Future applications of this framework may consider a more specific evaluation of upstream restoration benefits for sediment and water quality improvements.

5. Conclusions

Several key lessons may be learned from this study on Utoy Creek that can guide restoration planning in other watersheds (Table 3). Overall, the Utoy Creek watershed restoration study highlighted how restoration decision-making evolves over the life of a project and should not be treated as a monolith. Three phases of analysis were tailored to decision needs of different points in project planning. Interdisciplinary dialog was critical to developing information on ecological, cost, engineering, and social outcomes at the “right” moment in the planning process, and results were interpreted with all team members to ensure that each perspective and bias was represented in the recommendations. While this approach was fruitful for integrating diverse lines of evidence, aspects of community engagement and the broader participation of non-technical audiences could be strengthened. The Utoy Creek stream restoration study is, thus, offered here as an incremental attempt to bring ecological, cost, and social data into common decision-making processes. However, stream restoration planning is a challenging endeavor and significant research is needed to blend disciplinary, institutional, and community perspectives in the management of urban waters.

Author Contributions

Conceptualization, G.T.M., L.E.A. and S.K.M.; methodology, G.T.M., L.E.A., T.W.R.J., S.P.P. and S.K.M.; formal analysis, G.T.M., L.E.A., T.W.R.J., S.P.P. and S.K.M.; investigation, G.T.M., L.E.A., T.W.R.J., S.P.P. and S.K.M.; writing—original draft preparation, G.T.M., L.E.A. and S.K.M.; writing—review and editing, G.T.M., L.E.A. and S.K.M. All authors have read and agreed to the published version of the manuscript.

Funding

The U.S. Army Corps of Engineers (USACE) and the City of Atlanta funded project planning through the Mobile District’s Utoy Creek Ecosystem Restoration Feasibility Study.

Data Availability Statement

Most data presented in the study are openly available in the UtoyDecisions Github repository at https://github.com/USACE-WRISES/UtoyDecisions. Any additional data not on the Github repository are available on request from the corresponding author.

Acknowledgments

We acknowledge the support of the U.S. Army Corps of Engineers (USACE) and the City of Atlanta for their contributions to project planning and research through the Mobile District’s Utoy Creek Ecosystem Restoration Feasibility Study. Also, the USACE’s Ecosystem Management and Restoration Research Program supported development of this publication. This paper presents parts of the overall Utoy Creek study, and the results do not necessarily represent the outcomes of the USACE project planning process, which are available on request from the authors or agency. The project team also included many internal and external collaborators, who provided data and guidance critical to this effort, some of whom included Alex Smith, Tom Jester, Kevin Dodd, Micah Wiggins, and Brenna Mickal. The opinions expressed here are those of the authors and not necessarily those of the agencies they represent. The involvement of Liya Abera was supported by an appointment to the Department of Defense (DOD) Research Participation Program administered by the Oak Ridge Institute for Science and Education (ORISE) through an interagency agreement between the U.S. Department of Energy (DOE) and the DOD. ORISE is managed by ORAU under DOE contract number DE-SC0014664.

Conflicts of Interest

The authors declare no conflicts of interest.

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Land 14 00449 g001
Figure 1. Utoy Creek watershed in Atlanta, Georgia.
Figure 1. Utoy Creek watershed in Atlanta, Georgia.
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Figure 2. Summary of site screening. (A) Existing ecological condition for instream and riparian areas. Instream condition is reflected by the inner color and riparian condition by the outer color. For instance, reach 2A has suboptimal riparian condition and marginal instream condition. (B) Qualitative metric of social outcomes. (C) Unit cost per linear foot (LF) based on the assumed restoration action and site-level quantities. (D) Sites advanced for additional analysis.
Figure 2. Summary of site screening. (A) Existing ecological condition for instream and riparian areas. Instream condition is reflected by the inner color and riparian condition by the outer color. For instance, reach 2A has suboptimal riparian condition and marginal instream condition. (B) Qualitative metric of social outcomes. (C) Unit cost per linear foot (LF) based on the assumed restoration action and site-level quantities. (D) Sites advanced for additional analysis.
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Figure 3. Site-scale analysis of restoration actions with an example from Site 17D2E: (A) ecological forecast for each restoration action, (B) time-weighted annualization of ecological outcomes, (C) life cycle cost estimation, and (D) cost-effectiveness analysis.
Figure 3. Site-scale analysis of restoration actions with an example from Site 17D2E: (A) ecological forecast for each restoration action, (B) time-weighted annualization of ecological outcomes, (C) life cycle cost estimation, and (D) cost-effectiveness analysis.
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Figure 4. Watershed-scale cost-effectiveness and incremental cost analyses.
Figure 4. Watershed-scale cost-effectiveness and incremental cost analyses.
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Table 1. Overview of three phases of analysis for Utoy Creek watershed restoration planning.
Table 1. Overview of three phases of analysis for Utoy Creek watershed restoration planning.
Site ScreeningAlternatives AnalysisPortfolio Analysis
Scale of AnalysisWatershedSiteWatershed
Primary purpose of analysisScreen out ineffective sites and identify a smaller set for more detailed data collection and analysisIdentify cost-effective restoration actions at focal sitesDevelop an effective portfolio of sites for the watershed as a whole
Key outputs for next phaseShortened list of candidate sitesSite-scale conceptual restoration plansRecommended portfolio of actions to request for construction funding
Formulation of alternativesPreliminary identification of a conceptual action based largely on stage of channel evolutionField-based identification of site-specific needs followed by multi-disciplinary dialog to develop 3–4 conceptual alternatives per siteAll combinations of sites with recommended actions
Number of sites66 sites reduced to 22 sites for additional analysis22 sites investigated, further reduced due to constraints, and combined 8 restoration reaches7 reaches recommended for further action and analyzed for additional outcomes
Number of alternativesTwo at each site: future without project and maximum build outFour at each site: future without project, maximum build-out, and two intermediate solutions with varying levels of cost/benefitOne per site
Cost EstimationRapid, qualitative cost estimates based on prior unit cost of construction actionsSite-specific, alternative-specific construction cost based on site-level quantities, access, mobilization, adaptive management, and maintenance (but not inclusive of real estate)Detailed cost estimate (Class 3, USACE 2016) for the recommended actions inclusive of major cost factors (i.e., construction, real estate, maintenance).
Ecological BenefitsScoring sites relative to project objectivesSeparate instream and riparian models parameterized by a combination of desktop analyses and field measurements and summarized as “habitat units”Sum of site-scale habitat units for the recommended action
Treatment of TimeSnapshot with and without project (i.e., no temporal forecast)Temporal trajectories over 50-year horizon based on years 0, 2, 10, and 50 and annualized over the life of the projectUse of annualized benefits and costs from site-scale recommendations
Socio-Economic OutcomesPreliminary scoring for relative comparison among divergent sitesNoneAnalysis of demographics surrounding sites and regional economic benefits of construction
Table 2. Summary of the recommended set of restoration sites and actions along with ecological benefits, restoration costs, and demographic statistics. Poverty and unemployment percentages are averaged across the nearest census tracts.
Table 2. Summary of the recommended set of restoration sites and actions along with ecological benefits, restoration costs, and demographic statistics. Poverty and unemployment percentages are averaged across the nearest census tracts.
SiteAlternativeEcological Lift (HU)Construction Cost (USD)Annualized Cost (USD)Unit Cost (USD/HU)Poverty Rate (%)Unemployed Rate (%)
17F2M36.8799,00055,1007200296.9
17D2E114.61,071,00071,8004900296.9
17B215.0881,00068,2004500296.9
2A131.4558,00046,300150080.4
2B124.5394,00040,100160080.4
3F14.8277,00036,0007500122.5
19A219.9552,00050,5002500204.0
All Sites 1174,531,000367,9003100
Table 3. Lessons learned from the Utoy Creek watershed restoration.
Table 3. Lessons learned from the Utoy Creek watershed restoration.
Lesson LearnedImportance and Added Value
Use multi-scale analysesEnsures that local restoration actions align with the broader watershed context and that downstream/upstream influences are adequately accounted for in decisions.
Document institutional knowledge in written reports as well as with data and model archivalFacilitates consistent decision-making over long project timelines and mitigates the impact of staff turnover by recording assumptions, design rationale, or input from stakeholders.
Integrate costs earlyAvoids advancing alternatives that are not feasible or cost-effective.
Justify projects through multiple disciplinary lensesCompiles qualitative and quantitative data for multiple objectives that may help contextualize or justify a particular action.
Tailor analytical detail to decision needs at each project phaseFacilitates dialog across team members about the merits of a particular piece of information relative to other project uncertainties.
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Menichino, G.T.; Abera, L.E.; Rickey, T.W., Jr.; Phillips, S.P.; McKay, S.K. A Phased Approach to Urban Stream Restoration Decision-Making in Utoy Creek, Atlanta, Georgia. Land 2025, 14, 449. https://doi.org/10.3390/land14030449

AMA Style

Menichino GT, Abera LE, Rickey TW Jr., Phillips SP, McKay SK. A Phased Approach to Urban Stream Restoration Decision-Making in Utoy Creek, Atlanta, Georgia. Land. 2025; 14(3):449. https://doi.org/10.3390/land14030449

Chicago/Turabian Style

Menichino, Garrett T., Liya E. Abera, Terry W. Rickey, Jr., Stephen P. Phillips, and S. Kyle McKay. 2025. "A Phased Approach to Urban Stream Restoration Decision-Making in Utoy Creek, Atlanta, Georgia" Land 14, no. 3: 449. https://doi.org/10.3390/land14030449

APA Style

Menichino, G. T., Abera, L. E., Rickey, T. W., Jr., Phillips, S. P., & McKay, S. K. (2025). A Phased Approach to Urban Stream Restoration Decision-Making in Utoy Creek, Atlanta, Georgia. Land, 14(3), 449. https://doi.org/10.3390/land14030449

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