Gray to Green (G2G): User Guide and Documentation

A decision support tool for transitioning to vegetation-based stormwater management. A product of the University of South Florida in partnership with the University of Florida and Thomas L. Singleton Consulting with grant funding assistance from the U.S. Forest Service.

The Gray to Green (G2G) decision support tool is a GIS-based toolkit that guides users in transitioning from conventional “pipe and pond” (gray) stormwater management systems designed to drain, direct, and quickly dispatch and dispose of stormwater to vegetation-based (green) stormwater management systems designed to slow, spread, soak, and manage stormwater as a valuable resource for people and the environment.

G2G follows a volume-based approach to manage stormwater. It promotes the protection of green infrastructure and the use of ecosystem services and trees to reduce stormwater runoff volumes, velocity, and pollutant loads. It utilizes GIS to help users identify potential areas for protecting and restoring green infrastructure and the natural pathways for water and siting 11 low impact development (LID) best management practices, including Green roofs, Pervious pavement, Constructed wetlands, Rainwater harvesting, Bioswales, Wet ponds, Tree plantings, Infiltration trenches, Dry ponds, Rain gardens, and Infiltration basins.

It utilizes Excel to help users quantify water volume and pollutant load reductions as well as other benefits for different development scenarios. This is done as part of one continuous and strategically designed treatment train.

The strength of G2G is the scenario testing which allows users to see what happens when you maximize the use of green infrastructure and LID practices. It expands the understanding of what is possible for users both with and without practical experience using LID practices. It provides the necessary context for protecting green infrastructure and the natural pathways for water which is critical to defining problems and developing comprehensive solutions at both the site and watershed scales. Although there are very sophisticated models for evaluating stormwater designs, they require special expertise to run and are not easily applied or commonly used for planning, regardless of the scale. Planners, resource managers, scientists, and engineers can use G2G to guide project planning for urban reforestation, new development and redevelopment, stormwater retrofits for water quality enhancement and flood reduction, and community resilience and adaptation to climate change.

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