How Green Infrastructure Handles Atlanta's Stormwater Problem

Atlanta receives about 50 inches of rainfall per year — more than Seattle — and an increasing proportion of that rain falls on pavement. The result is a chronic stormwater problem. Green infrastructure is a cost-effective solution that does the work of pipes and basins while adding ecological value.

Atlanta's relationship with water is complicated. The city sits atop a watershed that drains into both the Chattahoochee and the Ocmulgee river systems. Its soils — primarily red clay Piedmont soils — have low permeability when compacted, meaning water runs off rather than infiltrating. And the decades of development that turned forests and fields into parking lots, rooftops, and roads have dramatically increased the proportion of the watershed covered in impervious surface.

The practical consequences are visible to any Atlantan who has seen a neighborhood creek rise several feet in twenty minutes during a heavy storm, or who lives near a low point in the road grid that floods predictably after significant rainfall. Less visible but equally real: combined sewer overflows, where the city's older sewer system — designed to carry both sewage and stormwater in the same pipes — overflows into creeks and rivers during heavy rain events, releasing partially treated waste into the watershed.

What green infrastructure means in practice

Green infrastructure is an umbrella term for approaches that manage stormwater by keeping it as close to where it falls as possible, rather than rushing it off-site through pipes and channels. The specific techniques include:

Rain gardens are shallow, planted depressions that collect runoff from roofs, driveways, and streets and hold it long enough for it to infiltrate into the ground and be taken up by plant roots. A well-designed rain garden handles the runoff from a typical residential roof in most storm events without any of that water reaching the street or storm drain. The plants in a rain garden — ideally natives adapted to both wet and dry conditions — also filter pollutants from the water as it percolates through the soil.

Bioswales are vegetated drainage channels designed to slow and filter stormwater rather than simply convey it. Unlike a concrete stormwater channel, which moves water as fast as possible, a bioswale holds water in plant-filled media that slows velocity and allows infiltration. They are commonly installed along street rights-of-way and in commercial parking areas.

Permeable pavement replaces conventional impervious asphalt or concrete with materials that allow water to pass through — either porous asphalt and concrete mixes, or interlocking paver systems with open joints. Permeable pavement is particularly effective in parking lots, where a large impervious surface can be made to infiltrate a high proportion of runoff with minimal change in function.

Green roofs cover rooftops with engineered soil media and plants, absorbing rainfall that would otherwise run off immediately. They also reduce the urban heat island effect and extend roof membrane life. Green roofs are expensive to install and require structural support; they are most cost-effective on new construction.

Tree canopy is green infrastructure in a form that often goes unrecognized as such. A large mature tree intercepts thousands of gallons of rain annually on its leaf and bark surfaces, releases water slowly through transpiration, and contributes to soil structure that supports infiltration. This is part of why canopy loss and stormwater problems are directly linked.

Atlanta's stormwater and consent decree context

Atlanta operates under a federal consent decree related to its sewer system, requiring significant investment in reducing combined sewer overflows. The city has spent billions on gray infrastructure — tunnels, tanks, and pipe upgrades — under this agreement. Green infrastructure is part of the city's strategy for meeting the consent decree's requirements at lower cost than gray infrastructure alone, and the city's Department of Watershed Management has deployed rain gardens, bioswales, and street-side green infrastructure projects in multiple neighborhoods.

The pace has been slower than advocates would like. Gray infrastructure projects are simpler to permit, easier to quantify for regulators, and more familiar to the engineering firms and city staff managing the work. Green infrastructure projects are often smaller, distributed across many locations, and require landscape maintenance skills that differ from traditional infrastructure maintenance. Building the institutional capacity to deploy and sustain green infrastructure at scale is a process the city is still working through.

What homeowners can do

Residents can deploy green infrastructure at the property scale without city involvement. Disconnecting a downspout — redirecting it from the storm drain to a rain garden, rain barrel, or vegetated swale — is a simple intervention that measurably reduces runoff from a single roof. The City of Atlanta's Watershed Management department has historically offered rebates or assistance for residential downspout disconnection; check the current program status.

Replacing lawn area with native groundcovers, shrubs, and trees increases the permeability and infiltration capacity of a residential lot. Lawns — particularly the fescue lawns common in Atlanta — have lower infiltration rates than diverse planted landscapes, and the compaction from mowing further reduces their capacity to absorb rain. Converting even a portion of a lawn to planted native beds is a measurable stormwater improvement.