What is Green
Infrastructure?

Most of us think of roads and pipes when we think of infrastructure. But Green Infrastructure (GI) is necessary for a healthy community. Parks, natural spaces, trees, and stormwater management are all necessary for protecting and restoring our unban streams, rivers, and water supplies. Green Infrastructue refers to the set of technologies we use to manage urban stromwater runoff in a way that approximates the management we see in nature. Such nature-based solutions to urban stormwater problems include water harvesting, green roofs, permeable pavement, and rain gardens - all of which are considered Green Infrastructure.

1Durham and
Ellerbe Creek

The most densely developed areas of the City and County were built along and on top of the headwaters of Ellerbe creek. The creek receives almost half of all the stormwater runoff from the city creating a huge problem for Ellerbe creek. The 2010 Durham "State of Our Streams" Report lists numerous pollutants in the creek that are directly related to excess stormwater runoff. Ellerbe Creek has been on the list of North Carolina’s most polluted water bodies since 1998 and stormwater pollution makes the creek nearly uninhabitable for aquatic life and at times dangerous for people.

2Ellerbe Creek
and Falls Lake

Ellerbe Creek is the dirtiest stream in the Falls Lake Reservoir Watershed. High levels of nitrogen and phosphorous contribute to the current pollution problem in Falls Lake causing algae blooms and elevated bacteria levels leading to human health hazards, fish kills, drinking water contamination, and closed recreational beaches in the lake. Clean-up goals for the reservoir are in place and call for a 40% reduction in nitrogen and a 77% reduction in phosphorus. To restore clean water to the creek, the City of Durham will need to spend hundreds of millions of dollars using traditional stormwater management practices. A new innovative approach was developed to address these problems relying on integrating green infrastructure (e.g. rain gardens, green roofs, permeable pavement) into the city’s urban landscape to absorb and filter polluted stormwater and slowly release the cleaned, cooled water into the creek to restore its health and make it a more valuable resource for the community.

3Stormwater
Management

A city’s urban landscape has not been designed or built to manage stormwater to protect and restore water quality. Traditional stormwater management consists of a network of pipes that collect stormwater, removing it as quickly as possible from the landscape and pipe it directly into nearby creeks and rivers. In contrast, Green Infrastructure mimics the natural landscape; water is cleaned through a network of stormwater management practices that capture and filter rain where it falls. Green Infrastructure reduces stormwater runoff and improves the health of surrounding waterways.

4Project
Goal

Demonstrate a new approach to stormwater management by integrating green infrastructure into the urban landscape to begin the restoration of the hydrologic balance in Ellerbe Creek. These changes can make the creek an important asset for the community and add value throughout the city. An additional goal was to show that these techniques can help the city comply with regulation to clean up Falls Lake Reservoir.

5Stormwater
Runoff

1 inch of rain falling on a square foot of surface area yields approximately 0.6 gallons of water. So in a 1 inch rainstorm, a 1,500 sq ft roof will produce about 900 gallons of stormwater!

That runoff is a major source of pollution for Durham’s streams. It washes trash, fertilizer, bacteria, heavy metals, and other pollutants sitting on those surfaces into the creek polluting the clean water. Stormwater also moves more quickly across these hard surfaces dumping more water into the creek in a shorter span of time. This destroys wildlife habitat and increases the likelihood of erosion and flooding.