ASLA Releases More than 475 Green Infrastructure Case Studies


The Environmental Protection Agency (E.P.A.) recently started a national rulemaking process, with the goal of creating a new, comprehensive program to reduce stormwater runoff. The E.P.A. announced that during this rulemaking it will evaluate green infrastructure design techniques that mimic natural processes to evapo-transpire, infiltrate and recharge, and harvest and re-use stormwater. Typical green infrastructure systems for managing stormwater include green roofs and walls, bioswales, rain gardens, bio-retention ponds, and permeable pavements. Street and park trees also provide great stormwater management benefits.

The E.P.A. asked ASLA to collect case studies on projects that successfully and sustainably manage stormwater. More than 300 ASLA members responded with 479 case studies from 43 states, the District of Columbia, and Canada. Not only do these projects showcase landscape architecture, but they also demonstrate to policymakers the value of creating green infrastructure policies and investing in these approaches.

Green infrastructure and low-impact development (LID) approaches, which are less costly than traditional grey infrastructure projects, can save communities millions of dollars each year and improve the quality of our nation’s water supply. Also, these systems provide multiple benefits: They store carbon, provide wildlife habitat, and clean and cool the air, creating more livable communities in the process.  

Here’s an analysis of the 479 stormwater case studies:

Project type:
Institutional/Education — 21.5% 
Open Space/Park  — 21.3%
Other  — 17.6%
Transportation Corridor/Streetscape  — 11.9%
Commercial  — 8.6%
Single Family Residential  — 5.5%
Government Complex —  4.2%
Multifamily Residential  — 3.7%
Open Space-Garden/Arboretum  — 2.9%
Mixed Use  — 1.8%
Industrial  — 1.1%

Estimated cost of green infrastructure:
$100,000–$500,000 — 29.2%
$1,000,000–$5,000,000 — 22.1%
$500,000–$1,000,000 — 13.2%
$50,000–$100,000 — 12.9%
$10,000–$50,000 — 12.1%
$10,000 — 3.5%

Green infrastructure type:
Retrofit of existing property — 50.7%
New development — 30.7%
Redevelopment project — 18.6%

How much impervious area was managed?
1 acre to 5 acres — 34.5%
5,000 sq/ft to 1 acre — 31.3%
greater than 5 acres — 24.8%
less than 5,000 sq/ft — 9.5% 

Did use of green infrastructure increase costs?
Reduced costs — 44.1%
Did not influence costs — 31.4.7%
Increased costs — 24.5%

Green infrastructure design approaches used:
Bioswale — 62.1%
Rain garden — 53.2%
Bioretention facility — 50.8%
Permeable pavement systems — 47.3%
Curb cuts — 37.9%
Cistern — 21.2%
Downspout removal — 18.1%
Green roof — 16.5%
Rain barrels — 5.7%

Other facts about the case studies:

  • 55 percent of the projects were designed to meet a local ordinance.
  • 88 percent of local regulators were supportive of the green infrastructure projects submitted.
  • 68 percent of the projects received local public funding.

Along with this effort, ASLA continues to work with Natural Resources Defense Council (NRDC) and American Rivers to promote green infrastructure policies.

View the 479 case studies organized by state.

Also, to learn more about green infrastructure, delve into Philadelphia’s cutting-edge program, watch an animation, and read an interview with Congresswoman Donna Edwards on her legislative proposal.

Image credit: Seattle Green Factor. City of Seattle Department of Planning and Development / Vulcan

The Primacy of Pathways

At Dumbarton Oaks, Suzanne Preston Blier, a professor at Harvard University, said not all landscapes are enchanted in the ancient Yoruban city of Ife in southwestern Nigeria, but many are.

Combining landscape architecture with a rich cosmological system, the Yoruban kings and Ifa priestly castes laid out Ife as a giant turtle, with criss-crossing pathways embedded with deep cultural and religious meaning. Much of this has been unknown to the outside world, until Blier and others at Harvard created AfricaMap, an open-source geospatial mapping Web site, to unearth the patterns underneath the buildings and vegetation. She said “technology may actually be key to uncovering the past.”

Some scholars put the earliest settlements at Ife at 350 BCE, with the kingdom reaching its peak as an artistic and cultural center around 1300AD.

Arriving in the area, Blier was “stunned by the landscape,” and the “amazing system of spatial engagement, buildings, and ritual pathways” that form the city.

The topography is like a “bolder hat,” with a palace and temple in the middle, and then a set of hills circling. The lowlands are continually covered in rain, providing fertile soils. Nowadays, the city is 50/50 Muslim and Christian. She said this “hybridity” is also reflected in the landscapes, which mixes baobab trees from the savannah with palm trees from the south.

The archeological elements of Ife follow closely the current city. Yoruban cities were “centrally planned.” Ife’s palace was an “ancient center, with a garden environment.” The back of the palace was a historic forest used to grow herbs and medicinal plants. Buildings formed a square courtyard in the center where rainwater was collected. In ancient Yoruban culture, when people died, they were buried in their living or bedrooms. She discussed how this was important in the distinction between interior and exterior spaces.

Yoruban mythology centers around two primary figures: Obatala and Odudua. Obatala was sent down from the heavens (on a chain or boat) to create earth, but instead got drunk on palm wine. So the supreme god sent down his younger brother who managed to finish the job.

As a result, Obatala is considered the sky god, and is associated with ritual power, while Odudua is associated with earth, and earthly political power. “These are the cosmological heroes,” but they also stand for “the division of Ife and different dynastic rulers.” Obatala is connected with the first dynasty, while Odudua is with the second.

Along with sky and earth, there is light, which is represented in the mica Yoruban kings where in their crowns. Mica is spread throughout the soil in Ife so “when it rains, the pathways become glittery and enchanged landscapes, powered by light.”

Unearthing the city’s turtle shape via AfricaMap, Blier found that each of the four main gods in Yoruban religion had different spaces associated with different roles, which “coincide with Ife divination.”

There were also divisions according to family, and a ward system that follows those lines. Each have different pathways.

She emphasized the “primacy of pathways” and their role in preserving “time – past, present, and future.”

Also, chiefly compounds with old and new dynastic leaders have specific locations around the palace, with guaranteed “viewsheds” that allow the priestly caste to “keep the king in view and in check.” The viewsheds actually represent the political landscape as well.

Kings in Yoruba never die but turn into natural elements, “skeuomorphs,” kind of large stone sculptures. In the same vein, she said “buildings never die” here. Earth homes crumble and then locals reuse the mud to create new homes. Buildings are simply reinvested with new life. “You can see very modern buildings next to decrepit ones on the same street corner.”

Blier added there is a larger renewal of life in Yoruban culture and “pathways are key to this.” The pathways to one temple, for example, need to be freshly cut for each ceremony, but according to ancient plans. Once cleared, these paths that “quietly engage with history” become “very public spaces” in which anyone can go in. There are also vertical paths or “holes” that priests use to connect with the spiritual world.

While each ancient city in Africa is unique and can’t really be compared, Blier said AfricaMap is also uncovering “similar” examples elsewhere. The ancient Dahomey kingdom is actually organized around the model of a serpent eating itself. “It has a python urban plan.”

Learn more about the Ifa religion and Yoruban culture through the Osun-Osogbo Sacred Grove, a UNESCO World Heritage site. Also, check out Harvard University’s WorldMap, a beta version that builds on AfricaMap. It can be used to “overlay historical maps, including period maps,” provides “base mapping for different contexts,” along with geospatial visualizations of data on population, ethnicity, and economic and environmental indicators.

Image credit: Ife / Blackpast.org

Solar Decathlon 2011 Innovations: Constructed Wetlands, Edible Landscapes, Rain Gardens, and More


The Solar Decathlon, a design competition and public education program run by the U.S. Department of Energy, returns to the National Mall this year, where it will be open September 23 – October 2. Like the competition two years ago (see earlier post), teams of architecture and landscape architecture students from universities around the world compete to design, build, and then operate the most “cost-efficient, energy-efficient, and attractive” solar-powered home. The team that reaches optimal energy production, maximizes all efficiencies, and combines design excellence with affordability, takes home the top prize. 

In 2009, Team Germany beat out all the top talent from the U.S. and Asia with their innovative cube home entirely covered in solar panels. Given all the fundraising needed to create these projects (some of these model homes cost hundreds of thousands to create), not many of the schools from 2009 appear again this year. A whole new set of competitors are in play.

All projects have the requisite solar photovoltaic or solar thermal systems installed in various places on or around the home, but in terms of integrated site design, the University of Maryland’s WaterShed was the most innovative project this year. An attempt to create a “micro-scale ecosystem,” the project truly integrates building and landscape and uses “living systems,” or constructed wetlands to recycle and reuse greywater from sinks and showers. In combination with the wetland, exterior native plantings, edible gardens and walls, and a green roof mean the site will not only be highly energy efficient but will also be extremely water efficient and have zero stormwater run-off. 

Using plants native to this region, which creates habitat for local birds and insects, architecture and landscape architecture students at UMD constructed the wetland right outside the home’s floor-to-ceiling bathroom window so it’s clear that water from the sinks and shower flow outside to the wetlands, where the water is then cleaned and reused to irrigate the landscape.

However, their landscape also does more than clean and recycle wastewater, it also produces food. Veronika Zhiteneva, a student with the UMD team, explained that a garden plot with vegetables can help a family in their model home “live more sustainably and with greater self-reliance.” Near the garden plot, there’s also an edible wall made of twisting grape vines. 


The building’s green roof, which was grown by LiveRoof, is comprised of 150 2.5-inch deep trays, which feature six different types of sedum. Placed on the north side, the green roof not only reduces energy use by 25 percent, but also slows down and absorbs any stormwater. Any excess rainwater not captured by the roof is then soaked up by the surrounding native plants. 


In fact, the entire project, from the wetlands and native plantings to the garden and edible wall to the green roof, are designed to ensure the home only offers positive impacts on the surrounding environment. Scott Tjaden, another team member, said “our inspiration is the Chesapeake Bay,” which has suffered major impacts from agriculture and stormwater run-off. Indeed, of all the projects in this year’s Decathlon, WaterShed seemed to offer the more thoughtful approach — it places high value not only on energy efficiency, but stormwater management, water efficiency, and biodiversity too.  

Among the other 19 model homes on the Mall, a theme this year was edible landscapes. A student from the Middlebury College team (see below) said these homes “offer an opportunity to produce your own food.” Their project had an indoor “greenhouse wall shelter” for growing herbs and seedlings that could be moved outside to the garden plot once they grow larger. “The local food movement is part of living sustainably.” The team from the University of Illinois at Urbana-Champaign also added an edible garden around the exterior of their home.


Parsons The New School of Design and Stevens Institute of Technology worked with Habitat for Humanity to create a real home that will be turned over to a family in the Deanwood neighborhood of Washington, D.C. once the competition is over. Parsons said the family was actually brought into the design process early on and they requested a rooftop food garden, which will be accessible via the second floor of the home. One fun element was a Parsons-designed cookbook offering recipes for the foods grown in the home. In addition, their home is designed to have zero stormwater runoff: a rain “spigot,” which funnels water into a rain garden, captures any stormwater coming off the roof. Any excess runoff will be stored in a 2,000 gallon tank buried under the house and then reused for irrigating the landscape. Eventually, when the home is put in place in Deanwood, two bioswales will be installed at either ends of the house to capture stormwater. Their project is also designed using PassiveHaus technologies, including extra thick walls and glazed windows.

Victoria University of Wellington, which is representing New Zealand in the competition, elegantly integrated a range of New Zealand landscapes into the form of their home. As visitors enter the house, they “begin at the beach,” with a landscape of grasses and sand-binding plants that “mimics the New Zealand coastal landscape.” Further in, around the home, there are a “mosaic of shrub land,” here innovatively incorporated into plots around bench seating. Behind the house, there’s a “forest edge” that replicates the “conifer-broadleaf forest which the most complex and diverse in New Zealand.”


Lastly, there are alpine zones featuring “unique flora” and another productive landscape offering opportunities for growing herbs, veggies, and fruits. The landscape provides water efficiency and stormwater management value.


Team New York from the City College of  New York came up with another unique approach that uses 30 percent less water than the conventional home: Shower and sink wastewater is recycled and reused. Also, some 30,000 gallons of rainwater will be captured via external banks of native plants that a landscape architecture faculty advisor helped select and install. New York’s project is designed to be placed on top of the roof of an existing New York City building in an effort to “increase density and encourage car-free living.” This approach is made possible by a “dunnage” system that distributes load through steel beams. The idea is to then plant a green roof around the rooftop home that will function as a yard and garden.


Innovative use of materials, including non-conventional materials and building waste, was another big theme running through the homes. The best example of this was the team from Appalachia State University, which beautifully reused corrugated iron as siding and internal walls, along with a natural, locally-sourced bark siding that is “soaked, flattened, and then kiln-dried” into sheets that last up to 80 years. One student said the bark is a “by product of the lumber industry.” Very smart reuse of a little-considered material.


Explore the 20 teams on the National Mall this year. In 2009, more than 300,000 visited the Decathlon in 10 days. Get there early this year to avoid long lines.

Image credits: Krista Sharp / ASLA

Research Shows Nature Helps With Stress

Michael Posner, professor emeritus at University of Oregon who studies attention, says that our brains gets fatigued after working for long periods of time, “particularly if we have to concentrate intensely or deal with a repetitive task.” Taking a break may or may not help deal with stress during high-pressure times. What’s crucial is the type of break taken: According to The Wall Street Journal, taking a stroll in the park “could do wonders” while drinking lots of coffee will just be further depleting. Also, in other instances, not taking a break at all may be the best course, simply powering through can be “more effective than pausing.”  

Recent research shows that taking a stroll through a natural setting can boost performance on “tasks calling for sustained focus.” “Taking in the sights and sounds of nature appears to be especially beneficial for our minds.” In fact, Dr. Marc Berman and fellow researchers at the University of Michigan found that “performance on memory and attention tests improved by 20 percent after study subjects paused for a walk through an arboretum. When these people were sent on a break to stroll down a busy street in town, no cognitive boost was detected.” (see an earlier post on Berman’s research).  

Even just looking at photos of nature in a quiet room has a greater cognitive boost than walking down a busy urban street. “In a follow-up study, the researchers had participants take a break for 10 minutes in a quiet room to look at pictures of a nature scene or city street. Again, they found that cognitive performance improved after the nature break, even though it was only on paper. Although the boost wasn’t as great as when participants actually took the walk among the trees, it was more effective than the city walk, says Dr. Berman.” 

You may actually not even have to enjoy the park, botanical garden, or arboretum to get the benefit. Dr. Berman said: “You don’t necessarily have to enjoy the walk to get the benefit. What you like is not necessarily going to be good for you.” For them, just looking at images of nature engages “our so-called involuntary attention, which comes into play when our minds are inadvertently drawn to something interesting that doesn’t require intense focus, like a pleasing picture or landscape feature. We can still talk and think while noticing the element.” In contrast, walking down a busy street is exhausting over long periods because we are on the look out for cars and bicyclists, and people bumping into us.

Important information for landscape architects working in dense urban areas: People also don’t have to live near a nature-rich environment to get some benefits. “A quieter city street with interesting natural elements to look at, such as containers of plants, could do the trick, too.” Berman and his researchers are still trying to figure out what kind of natural elements work best in terms of cognitive boosts. He is now at the Rotman Research Institute in Toronto where he and his colleagues are also trying to find out whether nature can help people with anxiety or depression.   

More and more exciting research is coming out on how nature can improve mood (see earlier post) or lower hospital rehabilitation times (see earlier post). Urban designers like Jan Gehl (see an interview) have long argued that landscape architecture educators and, really, those from all design professions, need to make courses on improving human health and well-being a central component of curricula. While therapeutic garden designers have long focused on these issues in the healthcare realm, perhaps some innovative landscape architecture programs will start adding required courses that cover all the research done by the Dr. Bermans of the world, which seem to be quickly zooming in on what forms of nature have the greatest health impact.

Public health, epidemiology, and medical programs would also do well to bring in landscape architects and other design professionals into research tracking the causes of epidemics like cancer, obesity, diabetes, depression, and nervous disorders, using positive and negative examples of urban landscapes as test-beds for research.

Read the article.

Image credit: Harvard University Arboretum / Photo Challenge. Pingsi

Vancouver Gets Parklets


San Francisco may have started something with its innovative Pavement to Parks or “parklet” program, which turns transportation infrastructure into public spaces. New York City is also a leader, given its recent decision to redesign sections of Broadway as permanent pedestrian malls. Now, Vancouver has gotten on board with its own Viva Vancouver program that features a set of eight streets that have become new mini-parks. Vancouver says these new spaces are “people places” designed to give residents “extra space to walk, bike, dance, skate, sit, hang out with friends and meet your neighbours.”

One brand new parklet, Parallel Park, which cost just $18,000, features a new deck-like structure in place of two parking spots and includes built-in seats and wood-cubed tables. Designed by Travis Martin, Associate ASLA, currently employed with landscape architecture firm van der Zalm + Associates, this pocket public space is made of clear cedar.


On the Facebook site for Parallel Park, there are more details on how the space is designed: “There is a lean bench on the left. The benches along the back alternate between working and lounging heights. The box seats or tables are placed to provide seating for individuals, couples or groups of 4-8.”


According to The New York Times, turning underused transportation infrastructure into new public spaces isn’t just happening at the small scale either. With the success of the second phase of The High Line park (see earlier post), cities like Chicago, Philadelphia, Atlanta, and St. Louis are also now looking at how to reuse their own abandoned railways.  

Learn more about the projects in Viva Vancouver and see more photos. Explore San Francisco’s Pavement to Parks initiative, which recently expanded.

Also, see a Google Sketchup animation focused on how to transform transportation infrastructure into public spaces.

Image credits: Parallel Park / BriteWeb and Viva Vancouver