Green Infrastructure: Green Roofs is part of a series of posts that explore some of the Best Management Practices (BMPs) of Green Infrastructure and Low Impact Development (LID) for both urban and rural applications. The IRWP is currently working with our local cities, counties and organizations to implement green infrastructure and LID elements within the Illinois River Watershed. Watch for these demonstration projects in public spaces to see first-hand non-point source management in action!

For thousands of years, humans relied on natural roofs [made from sod, mud or straw] to keep their homes cool in the summer and warm in the winter. Today, “green roofs,” the next generation of those earlier thatched roofs, are slowly sprouting up throughout our cities. As of June 2008, there have been roughly 8.5 million square feet of green roofs installed in the U.S. (U.S. EPA). But it’s not just the heating and cooling benefits that drive the rooftop garden movement; these are also shown to reduce runoff, which can improve water quality and protect our watershed.

1_Green roof at CBUpon entering Crystal Bridges Museum, you will find an exquisite green roof on the north side.  Source: ArkansasLife 

Green roofs are exactly as they sound: roofs that contain plants and a growing medium (special soil mix). They can vary from a lower-maintenance roof with drought-resistant plants (such as sedum), pre-planted modules, to a roof with full landscapes of grasses, perennials and trees. They have a wide range of use from industrial to small-scale, and can cost anywhere from $10 – $25/square foot (US EPA). The design and systems offered can vary to fit the user’s needs, as it all depends on  your location, sun/shade requirements, load capacity and outcomes you are looking for, i.e. rain reduction, energy efficiency, aesthetically pleasing landscape view, etc.

2_Example GR TrayExample of a modular green roof tray. Source: Eco-Roof 

Plants help to absorb heat, capture rain, and filter pollutants as the water moves through the system. Green roofs can also reduce the amount of water moving off of the roof by absorbing and slowing down runoff. An added benefit also includes providing habitat for our birds, butterflies and important insects.greenroofvolunteers

Volunteers from Sam’s Club and Anheuser Busch help to install the green roof at the IRWP Watershed Sanctuary. Source: IRWP

Green roofs are becoming more important and valuable to Northwest Arkansas, as we seek natural alternatives to treat non-point source runoff. Here at the Watershed Sanctuary, we have a green roof demonstration that was installed in November 2014. With the help of volunteers from Cabela’s, Sam’s Club, and Anheuser Busch, we installed a 27’ by 14’ green roof that used a modular planting system of pre-planted sedum on half of our pavilion. The other half (metal roof) will be used as a control to measure and compare reduction in runoff, thermal heat and we will be capturing water from each side into rain barrels. We worked with Eco-Roofs who helped determine the load capacity and type of system that would work best for our application. This will be a great learning tool for visitors and students to learn more about the green infrastructure that works in our area. We look forward to having this demonstration as part of our Learning Center experience.

4_IRWP GRSedum, a drought-tolerant, low-maintenance plant, is planted on the IRWP Watershed Sanctuary Green Roof. Source: IRWP

The Illinois River Watershed Partnership works to improve and restore the Illinois River Watershed through public education, water quality monitoring, and conservation/restoration projects. Check out our website for current events that continue to educate stakeholders of the Illinois River Watershed about Green Infrastructure and Low Impact Development, as well as events that offer volunteer opportunities to make a positive difference! 

Related Posts:

Green Infrastructure & LID: Bioswales

Green Infrastructure & LID: Permeable Paving

Green Infrastructure & LID: Tree Wells

Additional Resources:

U.S. EPA: Green Infrastructure

IRWP: Handbook of Best Management Practices