Ecological Modeling for Utoy Creek Watershed Restoration

Corresponding Author:
Kyle McKay, PhD, PE
Environmental Laboratory
U.S. Army Corps of Engineers
Email: kyle.mckay@usace.army.mil

Model Accessibility: An interactive version of this report may be accessed here. The underlying numerical code as well as an MS Word version of this analysis may be downloaded from this github repository.

DISCLOSURE: This website represents a preliminary and working version of decision models for a stream restoration study in Utoy Creek, Atlanta, Georgia. The project is led by the Mobile District of the U.S. Army Corps of Engineers (USACE) in partnership with the City of Atlanta. This site DOES NOT reflect agency findings or outcomes, and this is merely intended as documentation of methods and working notes for internal use. Please refer to the project manager for the Utoy Creek study, Alex Smith (alexandria.n.smith@usace.army.mil), for up-to-date information about the project. A final version of this report will ultimately be included as an appendix to the more detailed feasibility study report.

MISSING DATA AND METHODS: This analysis is missing a variety of information prior to sharing, specifically:
- Check that the objectives presented in Section 2.1 align with project objectives.
- Ecological data are being quality controlled and have known erros at this point (i.e., equal riparian areas for left and right bank). Additionally, we need to revisit whether year-0 should be equal to the FWOP for all alternatives.
- The Utoy Instream Model is also under development and subject to change. For instance, the current version removes hydrologic metrics as well as a few geomorphic metrics (BEHI).

1. Introduction

The Utoy Creek watershed drains the southwest portion of the City of Atlanta 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 modern challenges like flashy runoff from urban development. The majority of Utoy Creek’s watershed is situated within City of Atlanta boundaries; however, downstream portions of the watershed are within Fulton County. Two main tributaries, North and South Utoy Creeks, unite to form the main stem approximately five miles upstream the Chattahoochee River (EPA, 2016). The total combined length of the main stem and primary tributaries is approximately 22 miles (Walker, 2016). Including sub-tributaries, the total length of stream is over 50 miles in the Utoy Creek watershed. The total drainage basin is approximately 33.7 square miles with 64% developed and 18% impervious.

Figure 1. Overview of the Utoy Creek watershed.

In partnership with the City of Atlanta, the USACE’s Mobile District is leading a feasibility study of potential stream restoration actions in the Utoy Creek watershed. The study is authorized through the USACE’s continuing authorities program for aquatic ecosystem restoration (Section 206, WRDA 1996). In summer 2023, the project development team conducted preliminary project planning activities such as identification of problems and opportunities, setting ecosystem restoration objectives, and screening potential restoration sites. From fall 2023 to summer 2024, the project development team advanced restoration planning through actions such as field data collection, design of alternatives, ecological modeling, cost estimation, analysis of socio-economic benefits, and public and interagency meetings. This report summarizes…Specifically, this document…

This report does the following…Our objectives are…

2. Project Planning Framework

Decision support modeling builds from the planning framework established for a restoration study as a whole. As such, this chapter briefly reviews major components of restoration planning in Utoy Creek.

Plan Formulation Strategy

Restoration project planning sets the stage for all other design, analysis, or decision tasks. A sound plan formulation strategy clearly articulates a problem statement and objectives from which all choices about design or analysis flow (McKay et al. 2012). The USACE project development team identified objectives for the Utoy Creek restoration project through three primary means. First, USACE policies and budget criteria were used as a template for local objectives. Second, existing local plans and studies in the Utoy Creek watershed were examined. Third, project objectives were compiled from prior studies in the region (e.g., Proctor Creek and Butler Creek). Fourth, preliminary objectives were presented to technical and non-technical stakeholders at a charrette in May 2023. Based on these approaches, the following objectives were identified.

Overarching objective: Improve instream conditions suitable for a diversity of aquatic organisms (e.g., fish, crayfish, salamanders, benthic macroinvertebrates, turtles).
- Restore channel geomorphic conditions to less disturbed conditions.
- Reduce sediment loading from the stream bed and banks.
- Increase instream habitat for a diverse assemblage of local fauna.
- Increase connectivity of movement corridors for aquatic species

Overarching objective: Improve riparian conditions supportive of a diverse aquatic and riparian community. - Restore natural sources of organic carbon (i.e., energy) within the system.
- Increase floodplain connectivity to support biogeochemical cycling.
- Improve temperature and light regimes.
- Increase riparian habitat to support native biodiversity.
- Increase connectivity of movement corridors for riparian species

Overarching Objective: Restore flow regimes to a best attainable condition. - Decrease peak flows.
- Decrease hydrologic flashiness.
- Improve watershed capacity to attenuate high flows.

Secondary Objectives: Pursue socio-economic outcomes while restoring instream and riparian systems.
- Increase resiliency to disturbances (e.g., watershed development, climate change, large floods).
- Promote social benefits and equity.
- Promote aesthetics and recreation.
- Improve water quality (e.g., TSS, zinc, nutrients).

In pursuit of these objectives, different information was required as planning proceeded from early watershed problem screening to feasibility-level design. The USACE project development team developed a three-phase approach to analysis of the Utoy Creek watershed restoration (Table 1). In phase 1, activities focused on screening sites to a focal set of locations aligned with USACE objectives. This phase used a suite of high-level assumptions and preliminary data on ecological benefits and costs to reduce 60+ potential restoration locations to a more workable 20 sites for more detailed analysis. Phase 2 focused on feasibility-scale analysis of these 20 sites including collection of additional field and analytical data, development of conceptual designs, execution of ecological models, and estimation of cost. This phase ultimately focused on producing site-scale recommendations of restoration actions. Phase 3 examined the portfolio of recommended actions at the watershed-scale, which analysis of ecological outcomes as well as other project effects (i.e., development of a narrative about the “comprehensive” socio-economic benefits of an investment). These phases required a series of assumptions regarding each analytical step, which are briefly presented in Table 1. Additional information on discipline-specific assumptions can be found elsewhere in feasibility documents.

Table 1. Overview of the three-phase approach to Utoy Creek analyses.

Scoping Issue	Site Screening (Aug 2023)	Site-Scale Analysis (Chapter 2)	Watershed-Scale Analysis (Chapter 3 and 4)
Primary purpose of analysis	Screen out sites to a smaller set for more detailed data collection and analysis	Identify cost-effective restoration actions at each site.	Develop an effective portfolio of sites for the watershed.
Formulation of alternatives	ERDC identification of a conceptual action based largely on channel evolution	Field-based identification of needs followed by multi-disciplinary discussion of actions into a conceptual plan, which was then formalized into a suite of actions and quantities	All combinations of sites with recommended actions
Number of alternatives	Two: future without project and maximum build out	Four: future without project, maximum build-out, two intermediate solutions with varying levels of cost and benefit	One per site
Ecological Benefits	Simple habitat unit based solely on scoring sites relative to project objectives.	Separate instream (UIM) and riparian (REFI) models parameterized by a combination of field measurements, analyses, and judgement. See Figure 1.	Sum of site-scale habitat units for the recommended action.
Cost	Rapid, qualitative cost estimates based on prior unit cost	Site-specific, rough order of magnitude (ROM) cost engineering analyses	Sum of site-scale costs for the recommended action
Treatment of Time	Snapshot 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 project	Use of annualized benefits and costs from site-scale recommendations
Other Social Effects	Preliminary, qualitative field assessment for relative comparison among divergent sites	None	Combined metric based on field assessment, census data, and public input, which is aggregated for groups of nearby sites
Regional Economic Development	None	None	None
National Economic Development	None	None	None

Blah, blah, blah.

Site Screening

Insert brief description of site screening?

2. Ecological Model Development

Insert introduction.

Utoy Instream Model (UIM)

Insert description of UIM.

Model Structure and Concept (Liya)

Insert description.

Module 1: Hydrology and Hydraulic (Liya)

Insert description, equations, and methods as needed.

Probably about 1 paragraph per variable.

Module 2: Geomorphology (Liya)

Insert description, equations, and methods as needed.

Module 3: Habitat

Insert description, equations, and methods as needed.

Module 4: Connectivity (Kyle)

Insert description, equations, and methods as needed.

Riparian Ecosystem Function Index (REFI) (KYLE)

Insert description of REFI. This can be shorter since it is documented elsewhere.

Model Testing and Evaluation

Insert brief description of model testing. Compare REFI with spreadsheet. Compare UIM with spreadsheet.

3. Model Application

Describe model application in Utoy Creek to obtain ecological benefits.

4. Summary of Ecological Outputs for Utoy Creek

In this section, yada yada yada. Blah, blah, blah.

References Cited

Abera L. and McKay S.K. 2024. Package ‘EngrEcon’. CRAN Reference Manual.

EPA. (2016). Total Maximum Daily Load Evaluation for Five Stream Segments in the Suwannee River Basin for Fecal Coliform. The Georgia Department of Natural Resources Environmental Protection Division, February.

Fischenich, J.C. 2006. Functional Objectives for Stream Restoration, EMRRP Technical Notes Collection (ERDC TN-EMRRP-SR-52). U.S. Army Engineer Research and Development Center, Vicksburg, MS. http://el.erdc.usace.army.mil/elpubs/pdf/sr52.pdf.

Grant, W. E., and T. M. Swannack. 2008. Ecological modeling: A common-sense approach to theory and practice. Malden, MA: Blackwell Publishing.

Harman, W., Starr, R., Carter, M., Tweedy, K., Clemmons, M., Suggs, K., & Miller, C. (2012). A Function-Based Framework for Stream Assessments and Restoration Projects (EPA 843-K-12-006). US Environmental Protection Agency, Office of Wetlands, Oceans, and Watersheds.

McKay S.K. and Hernández-Abrams D.D. 2020. Package ‘ecorest’. CRAN Reference Manual.

McKay S.K., Linkov I., Fischenich J.C., Miller S.J., and Valverde L.J. 2012. Ecosystem restoration objectives and metrics. ERDC TN-EMRRP-EBA-16. U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi.

McKay S.K., Pruitt B.A., Zettle B., Hallberg N., Hughes C., Annaert A., Ladart M., and McDonald J. 2018a. Proctor Creek Ecological Model (PCEM): Phase 1-Site screening. ERDC/EL TR-18-11. U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi.

McKay S.K., Pruitt B.A., Zettle B.A., Hallberg N., Moody V., Annaert A., Ladart M., Hayden M., and McDonald J. 2018b. Proctor Creek Ecological Model (PCEM): Phase 2-Benefits analysis. ERDC/EL TR-18-11. U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi.

McKay S.K., Richards N., and Swannack T.M. 2022. Ecological model development: Evaluation of system quality. ERDC/TN EMRRP-EBA-26. U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi.

McKay S.K., Athanasakes G., Taylor S., Miller W., Wagoner E., and Mattingly L. 2024. Qualitative Habitat Evaluation Index for Louisville Streams (QHEILS). ERDC/TN EMRRP-SR-92. U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi.

R Development Core Team. 2014. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. www.R-project.org.

Robinson R. Hansen W., and Orth K. 1995. Evaluation of environmental investments procedures manual interim: Cost effectiveness and incremental cost analyses. IWR Report 95-R-1. Institute for Water Resources, U.S. Army Corps of Engineers, Alexandria, Virginia.

U.S. Army Corps of Engineers (USACE). 2000. Planning Guidance Notebook. ER-1105-2-100. U.S. Army Corps of Engineers, Washington, D.C.

U.S. Army Corps of Engineers (USACE). 2011. Assuring quality of planning models. EC-1105-2-412. Washington, DC.

Wiest S., Menichino G.T., and McKay S.K. Forthcoming. Riparian Ecosystem Function Index (REFI). ERDC Technical Report. U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi.

Appendix A: Acronyms

• CEICA: Cost-effectiveness and incremental cost analysis.
  
• CoA: City of Atlanta.
  
• PED: Pre-construction Engineering and Design.
  
• ROM: Rough Order of Magnitude.
  
• TSP: Tentatively Selected Plan.
• USACE: U.S. Army Corps of Engineers.

Appendix B: Site-scale Alternatives

Do we want to dump all of the ecological model inputs or outputs here? It makes for a huge set of tables, but it is a good practice for transparency and reproducibility.