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Implementation of green infrastructure to improve water quality and reduce flood risk within the Colewood Creek watershed

Sandy Springs, Georgia

Featured image for the project, Implementation of green infrastructure to improve water quality and reduce flood risk within the Colewood Creek watershed

City Green Park

This project seeks to address polluted stormwater runoff entering streams and reduce flood risk.

With a scientist on board to do specific modeling experiments we can determine if/how green infrastructure could help improve water quality. Also, we hope to reduce the flood hazard in a small watershed (Colewood creek) that is fully within the City’s boundaries.

If successful, we can use this project as a role model to raise awareness on the impacts of untreated stormwater runoff. Also, we would like to build collective pride in solving this problem with community involvement and acceptance.

Many residents of Sandy Springs are aware of flooding implications to our community, these stories are always covered by local media. Through this project, we hope to bring a heightened awareness to the detriments of water pollution/contamination to our creeks, rivers and watersheds. Buy-in from our community could lead to many residents contributing to this cause by taking individual measures to help keep contaminants from entering waterways on their properties.


Sandy Springs is a city in northern Fulton County, Georgia. It is a suburb of Atlanta, with a population of approximately 110,000. Sandy Springs has ample green space, great educational institutions, and a booming economy. While the City was officially incorporated in 2005, the vision for the community began decades before. The community prides itself on containing over a dozen premium parks, including three that are run by the National Park Service. The average annual rainfall in Sandy Springs is 53.2 inches, and the average elevation is 1060 feet (323 meters).

Several decades of water sampling indicate that stormwater runoff pollutes streams in Sandy Springs. New developments must work to reduce or eliminate runoff that picks up pollutants while flowing into the City’s watersheds. The challenge is to design a solution for flooding and improve poor water quality within the watersheds.

The intent of this project is, with the help of a scientist or scientists, to determine through modeling if and how green infrastructure could help improve water quality and reduce flood hazards in a small watershed that lies completely within the City’s boundaries. These results could then be used to reach out to the public in order to demonstrate benefits of green infrastructure. Creating community awareness of degraded water quality within the confines of the City could help create additional support for this type of project. Flooding that occurs after intense storms receives media coverage, but water quality often does not. If successful, this project could be replicated on a larger scale, in other watersheds in Sandy Springs, and across the region.

The specific scope of Phase 1 of this project is to deliver preliminary modeling to help support the community awareness and buy-in of the implementation of green infrastructure to improve stream water quality, and, if feasible, reduce flood risk within the City’s Colewood Creek watershed.

Colewood Creek Watershed


Project Description:

This project will require a scientist who can model the risk of flooding and the potential for green infrastructure to improve water quality. Modeling the impact of green infrastructure will be the most complex and challenging aspect of the project. Bringing in an outside scientist and expert in modeling will corroborate Staff findings and strengthen the credibility of the project. Through watershed modeling, the scientist will determine the volume of water that needs to be filtrated and infiltrated, and the preferred locations for the implementation of green infrastructure. This information will then be used to educate and encourage residents to retrofit voluntarily with green infrastructure.

A goal for this project is to increase community awareness of the impacts of untreated stormwater runoff. Community acceptance and involvement are critical to the outcome. After completion of the project, City Staff hope to develop a program to deploy green infrastructure in the Colewood Creek watershed and measure improvements in water quality.

Staff will give status updates to the Mayor and City Council at its regular meetings, in the community newsletter, on the City website, and at professional conferences. As issues related to stormwater runoff are encountered by all jurisdictions in the region, the Metropolitan North Georgia Water Planning District should be able to help disseminate project results.

Follow-up phases could include an assessment by the City of different incentives and supporting tools for the construction of green infrastructure. If a critical mass of green infrastructure is implemented, the success of the initiative will be measured through regular water quality monitoring and observation or reporting of flooded areas after rain events. Once proven effective, the program could be scaled up and expanded to other watersheds in the City.


Timeline and Milestones:

The project is expected to take approximately eight months, starting immediately after identification of a scientist. The proposed timeframe for presenting the team’s preliminary findings would be in early November 2021. Annual priorities are chosen at the beginning of the calendar year, and the budget for the fiscal year is adopted in the first quarter. Thus, having an implementation strategy designed by the end of 2021 would be ideal.

The end goal of this project is to demonstrate that small, decentralized green infrastructure can improve water quality and, potentially, decrease flooding.

Project Team

Community Leaders:

Catherine Mercier-Baggett, AICP

Catherine Mercier-Baggett, AICP

Catherine serves as the first Sustainability Manager for the City of Sandy Springs, after leading the Planning and Zoning Division for four years. She previously worked at other municipalities and as a designer at consulting firms. She grew up in Montreal, Canada, where she studied urban design, landscape architecture, and ecology. She can talk endlessly about green stormwater infrastructure, urban nature, and sustainable development.


Alexandra Horst, AICP

Alexandra Horst, AICP

Alexandra is Planner III at the City of Sandy Springs. She has been in Community Development since 2016 and is passionate about planning, the environment, sustainability, and science.  A native of Sandy Springs, she has a B.S. in Geography (Environmental Emphasis) and a Water Resources Certificate from the University of Georgia, a Master’s degree in Urban Planning (Land Use and Environmental Planning Concentration) from the University of Michigan, and a Master’s in Real Estate Development from the Georgia Institute of Technology.


Community Scientists:


Dr. M.A. Karim, P.E., BCEE, F.ASCE is a Professor of Civil Engineering at Kennesaw State University. Dr. M.A. Karim has more than 30 years of experience in teaching, research, government regulations and consulting. He has a B.Sc. and M.Sc. in Civil Engineering from Bangladesh University and Technology and a Ph.D. in Civil/Environmental Engineering from Cleveland State University. He has experience in the area of soil and sediment remediation/decontamination, environmental management, statistical hydrology, and engineering education, to name a few of his areas of expertise.

David S. Ancalle, P.E., is a Project Manager with CA Engineering. David has 7 years of hydrologic and hydraulic modeling experience with over 125 projects completed in 8 states (including some in Sandy Springs). P.E. in Georgia.

Eric Smith is a Project Engineer with CA Engineering. Eric has 1 year of hydrologic and hydraulic modeling experience including experience with large-scale watershed models with more than 2000 pipes. Prior experience with stormwater systems in Sandy Springs. Prior experience with HEC-RAS and SWMM

Other individuals will be contributing to the project on an as-needed basis.


Community Science Fellow:

Rosanne McConnell

Rosanne McConnell

Rosanne is a student at Scripps Institution of Oceanography, pursuing a Master of Applied Studies in Climate Science and Policy. Rosanne was a federal Air Traffic Controller and spent 20 years in the military in the Washington, D.C., Air National Guard as a weather forecaster for F16 fighter squadrons. Through the Air Force, she received associate degrees in Meteorology and Information Technology. She also has a Bachelor of Science in Professional Aeronautics from Embry Riddle University. She is an ocean lover and can often be found at the beach below Scripps in La Jolla, California.

Collaborating Organization(s)