How to Do It: Measure for Green Infrastructure Success

At the 2011 GreenBuild in Toronto, Jim Schuessler, ASLA, BNIM, and David Dods, URS Corporation, a dynamic landscape architect and engineer duo, outlined lessons learned from two years of research into stormwater management best practices in sites across Kansas City. Sampling results from rain gardens, bioswales, “treatment trains,” and other green infrastructure systems, they explained how collecting data and measuring results is key to determining what types of approaches are most effective and cost-efficient. Given more communities are integrating man-made stormwater management systems that mimic nature into the built environment, their research has value.

Dods said it’s important to “think like a raindrop.” In nature, rain evaporates, or hits trees, where it’s captured by leaves, and then rolls down trunks into the soil. There, it’s absorbed slowly into the soil and captured by plant root systems. In prairie systems, grass roots can go down 10-15 feet into the soil. Not only do the roots and soils capture water, they also remove pollutants. In nature, water and land connect: there’s a gradual change that “creates intimate connections.” In contrast, with urbanization, this process of natural water management has been broken. When water hits paved surfaces, it rushes right off, into stormwater drains, collecting toxic particulate and disolved building, lawn, and car waste in the process. Dods did an experiement on his roof and found from “roof to drain,” it took 1 minute 17 seconds for water to flow off his roof and parking lot into drains, leaving no time to filter out pollutants and capture excess water.

In four test sites across Kansas City, Dods and Schuessler used a range of high-tech gizmos to measure a range of ecological functions: A teledyne (ISCO) machine, which “looks like a keg,” was used to sample water flow every five minutes. Bubbles of air determine when water has entered the system, and this turns on the machine. Piezometers, or monitoring wells, are used to figure out how much water moves through a site. Rooftop tipping buckets (rain gauges) help the team figure out rainfall flow. Soil samples and soil moisture rates were also taken and measured to determine how the soil material changed.

The sites include a highly urban site at a downtown mission, which featured an infiltration basin; two locations at the headquarters of Applebee’s, with a rain garden and “treatment train,”; and another site at the University of Kansas, which included a rain garden and detention basin.

The downtown mission test site, which cost some $70,000 to design and build, had three sets of basins that move water through a level of steps. The idea is that each step will capture any overflow from the previous level. A combination of rocks, soils, and sands successfuly captured 1-inch of stormwater. But the team found that this was due in part to a subterranean basin found underneath the site. Schuessler said the lesson learned was that “soil and site characteristics have a huge impact on how a site functions.” It’s then important to do test pits to see what the conditions really are.

In the first site at Applebee’s Headquarters, overflow from the roofs were moved through to a set of rain gardens in plazas below. Four roof drains help distribute the water flow. The data said that the rain garden systems had “modest pollutant removal” results – some 50 percent of pollutants were removed through the system. However, they  found that the rain gardens were under-sized and couldn’t hold 1-inch of run-off. Still, they found that “distributing flows instead of using one big pipe” was key to moving towards a system with greater ecological function.

The other site of the Applebee’s site was a “treatment train” designed to capture stormwater runoff from 15 acres of parking lots and clean water for the 5 acres of water in a nearby public retention basin. Sediment “forebays” included deep rock-covered sand filters that successfully removed many pollutants. “These sand sponges cleaned water before they moved towards the wetlands,” said Schuessler. U-shaped wetlands then create wildlife habitats, although, interestingly, they were designed to be geese-proof. As Dods explained, geese like water surrounded by turf grass so they can have a clear view and guard against the predators. The only issue: water fowl feces wreck havoc on water quality. As they explained, geese were negatively affecting water quality in the wetland — adding bacteria — before the grasses grew in. There were other issues with sediment entering the wetlands, but Schuessler explained this was due to other client work on site.

Lastly, University of Kansas’ site, which was designed by that university’s landscape architecture students, divided streams of water leaving the roof into 11 separate streams. Plants were added and placed based on their tolerance for water. “There were different moisture zones, creating a set of micro-ecosystems,” Dods explained. As a result, it took 1 hour and 20 minutes for water to move through the vegetated systems, being cleansed in the process.

Dods and Schuessler had 10 key takeaways, which resulted from their comprehensive data collection and measurement experiements:

1. Preserve existing landscapes. It’s easier to preserve than rebuild natural functions.
2. Development disturbs soils. Dods said “construction destroys top soils and plant material” so beginning a new project requires restoring site soils so native plants can take root again. Also, “erosion is the enemy of stormwater management best practice,” largely because metals stick to sediment. The goal then is to reduce the movement of soils so you capture sediment that has absorbed metal particulates.
3. Site characteristics inform design. Schuessler noted that soil types and levels of compaction below ground will obviously have impact on how successful an ecological stormwater management system is.
4. Size is important. Properly sized sites can maximize stormwater capture and pollutant removal while saving money.
5. Distribute systems. There shouldn’t be one failure zone.
6. Diversify. “Divere systems are resilient. Nature is diverse,” said Dods. In this case, diversity relates to plant species as well. If one plant type dies, the system can still function.
7. Plant material is important. “Match plants to moisture zones,” argued Schuesller. Test plants to see what kind of ecological function they provide.
8. Keep designs simple to get the best results.
9. Low-cost designs can be effective.
10. Make the landscape beautiful so people want to be there and learn how these systems actually work.

Image credit: ASLA 2011 Student Awards General Design Honor. Co-Modification Joseph Kubik, Student ASLA, Graduate, University of Pennsylvania
Faculty Advisor: Mark Thomann

Urban Forests = Cleaner, Cooler Air

Watch an animation from ASLA’s “Designing Our Future: Sustainable Landscapes” online exhibition that explains how urban forests fight air pollution and the urban heat island effect. See how cities can add in millions of trees, while ensuring the trees themselves live long, healthy lives.

Poor air quality has led to an explosion of asthma cases and other health problems among vulnerable populations including children, the elderly, and low-income residents. Each year bad air causes two million deaths worldwide. Also, in the U.S., there have been 8,000 premature deaths from excessive heat over the past 25 years. Urban heat islands, which are caused, in part, by sunlight being absorbed by paved surfaces and roofs, lead to higher surface temperatures, up to 90 degrees. Atmospheric air temperatures are also higher: in the day by up to 6 degrees, and at night, by up to 22 degrees. Vulnerable populations also face greater risks of heat exhaustion.
(Sources:  Heat Island Impacts, U.S. Environmental Protection Agency (E.P.A.), World Health Organization (WHO))

Increasing the tree canopy in cities is one way to fight both poor air quality and urban heat islands. Research shows significant short-term improvements in air quality in urban areas with 100 percent tree cover. There, trees can reduce hourly ozone by up to 15 percent, sulfur dioxide by 14 percent, and particulate matter by 13 percent. U.S. trees remove some 784,000 tons of pollution annually, providing $3.8 billion in value. Furthermore, a single large healthy tree can remove greater than 300 pounds of carbon dioxide from the atmosphere every year. In fact, New York City’s urban forest alone removes 154,000 tons of CO2 annually. Through their leaves, trees also provide evaporative cooling, which increases air humidity. Shaded surfaces may be 20-45 degrees cooler, and evapotranspiration can reduce peak summer temperatures by 2-9 degrees. (Sources: Heat Island Mitigation: Trees and Vegetation, U.S. Environmental Protection Agency (E.P.A.), “Sustaining America’s Trees and Forests,” David J. Nowak, Susan M. Stein, Paula B. Randler, Eric J. Greenfield, Sara J. Comas, Mary A. Carr, and Ralph J. Alig, U.S. Forest Service.)

Some other benefits: Urban forests reduce energy use by providing shade in the summer and wind breaks in the winter, reduce stormwater runoff, remediate soils, and provide animal and plant habitat. Trees have economic benefits: they increase property value. Lastly, trees have positive cognitive effects and may even help improve moods. (Sources: Does Looking at Nature Make People Nicer?The Dirt, “The Restorative Effects of Nature in Cities,” The Dirt, “Sustaining America’s Trees and Forests,” David J. Nowak, Susan M. Stein, Paula B. Randler, Eric J. Greenfield, Sara J. Comas, Mary A. Carr, and Ralph J. Alig, U.S. Forest Service.)

In the U.S., cities take up just three percent of land but contain 80 percent of the population. Cities may take up a relatively small share of all land now, but are projected to consume an area the size of Montana between 2000 and 2050. Two-thirds of the planet is expected to live in cities by 2050. With rapid urban growth, it’s essential that trees remain, whether along streets, in small pocket parks, or big green spaces. A 40 percent tree canopy is a challenging but worthy goal for every city to reach. (Sources: American Forests Tree Canopy Goals, “Projected Urban Growth (2000-2050) and Its Estimated Impact on the U.S. Forest Resource,” David J. Nowak and Jeffrey T. Walton, U.S. Forest Service, “Sustaining America’s Trees and Forests,” David J. Nowak, Susan M. Stein, Paula B. Randler, Eric J. Greenfield, Sara J. Comas, Mary A. Carr, and Ralph J. Alig, U.S. Forest Service.)

Toronto’s Cutting-Edge Approach to Green Roofs

New data collected by Green Roofs for Healthy Cities says Toronto’s cutting-edge green roof by-law, which came into effect in January 2010, has resulted in 1.2 million square feet of new green space across commercial, institutional, and residential developments. Toronto’s by-law requires green roofs for all new developments with gross floor area over 2,000 square meters.  According to the city, the green roof requirement is graduated, ranging from 20-60 percent of available roof space, so as buildings move up in size, the percentage area of green roof that needs to be installed also increases. If building owners can’t or won’t add green roofs, they can provide a cash payment instead, which gets funneled into other green roof programs in the city. In April 2012, the same regulations will apply to industrial buildings. 

Toronto provided Green Roofs for Healthy Cities with data on the impact of the by-law: More than 125 full time jobs were created, 435,000 cubic feet of stormwater was captured, 1.5 million KWH of energy were saved, and there was a “tangible reduction” in the local urban heat island effect. Other pluses: the green roofs may be improving air quality, creating wildlife habitat, and offering new rooftop recreational and food production opportunities. In addition, the organization says the new green roofs may help lengthen the lifetimes of the roofs, “saving building owners money” and reducing landwill waste over the long-term. 

Steven W. Peck, Hon. ASLA, Founder and President, Green Roofs for Healthy Cities, pointed to models run by the Canadian government, outlining the benefits if the green roof roll-out scales up: “Environment Canada modeling has demonstrated that an area covered by 10 million square feet of green roofs, the size of 10 Queens Parks, would reduce temperatures in that area by 1 to 2 degrees centigrade and will help save tens of millions in energy costs by reducing the peak load demand. Environment Canada scientists have estimated that the energy savings on heating and cooling generated by 10 million square feet of green roofs in Toronto are over 15 million KWH, the equivalent of running 29,593 60 Watt light bulbs year-round. Stormwater run-off reductions also increase to well over 3.6 million cubic feet annually.”

According to their data, Toronto was just behind Chicago in terms of the total square feet of green roof added in 2010. Chicago uses a set of incentives and expedited permitting processes to promote green roof installation but unlike Toronto, has no green roof requirement.

On top of the progressive rule-making, Toronto, like Chicago, has been smart about making its green roofs public. Last year, the city added a novel green roof park to its City Hall (see image at top). The project, which was designed by local firm PLANT architects, in effect extends ground-level park land and a broader urban revitalization effort through to one of the city’s most symbolic public spaces.

Learn more about Toronto’s green roof by-law and “eco-incentives” program, which a number of cities are now evaluating.

Image credit: (1) Toronto City Hall Green Roof / PLANT Architects, (2) Green roof data, 2010 / Green Roofs for Healthy Cities

How Will You Help Make D.C. the Greenest City in the Country?

Washington, D.C.’s leadership has requested input from all D.C. residents as it develops a new “unified vision” and “comprehensive framework” for a more sustainable Washington, D.C. The end goal: to connect sustainability with economic development and become the number-one, most sustainable city in North America. Washington, D.C. is currently ranked eighth in a recent Economist Intelligence Unit report sponsored by Siemens.

Landscape architects, architects, and planners are on the front lines of creating a more sustainable country and capital city. On issues ranging from stormwater management to land use, transportation to green building, these professionals are trained to think daily about sustainability, while also protecting the public’s health, safety, and welfare.

On Tuesday, October 11th from 12:30 to 2:00 PM, local members of the American Society of Landscape Architects (ASLA), the American Institute of Architects (AIA), and the American Planning Association (APA) will welcome representatives from the District of Columbia Office of Planning and Department of Environment to discuss Mayor Vincent Gray’s forward thinking SustainableDC Initiative and share their expertise on how to work collectively to help make D.C. the greenest city in the country.

Bring your own bold ideas. The presentation and discussion, which are open to the public, will go for about an hour. Then, feel free to join us for a tour of the award winning ASLA Green Roof immediately following the program.

When?: Tuesday, October 11, 12:30 PM
Who Can Attend?: Design professionals and the general public
Where?: American Society of Landscape Architects (ASLA), 636 Eye St NW (between 6th and 7th), Washington, D.C. 20001 (Metro: Gallery Place-Chinatown)

For more information or to RSVP, please contact ASLA representative Kevin O’Hara at or 202-216-2370. Please be sure to RSVP by Monday, October 10, 2011.

Image credit: Capital Bikeshare Station / Urban Indy