Go Rain Gardens, Go Green Roofs
by Nancy Sartor
Gardening is civil and social, but it wants the vigor and freedom of the forest and the outlaw. -- Henry David Thoreau
Think massive building development has no effect on your water supply? Think again. Urban sprawl—whether it’s residential, commercial or industrial—diminishes the amount of green space in our communities, causing storm water runoff to pollute our water supply, harm fish and wildlife and make recreation areas unsafe.
ago—long before skyscrapers dominated downtown and gated communities gobbled
up suburbia—runoff from rain and snow simply seeped back into the earth.
But today’s burgeoning development has obliterated much of our green space,
causing storm water runoff to traverse a serpentine path that is literally paved
with toxic debris. From organic particles and pesticides, to fertilizers, gas
and oil, water runoff is well tainted by the time it hits the city storm drains
that feed directly into our streams, rivers and lakes. Here in the Twin Cities,
almost all storm water eventually ends up in the Mississippi River—not only
a natural treasure, but also the source of much of our drinking water.
Rain gardens and green roofs
are eco-friendly technologies that combat storm water runoff and other environmental
problems, such as urban island heating, which occurs when high summer temperatures
in cities over-burden cooling systems and increase pollution. Implemented in Europe
for decades, these sustainable, best management practices are gaining popularity
in the United States.
Rain gardens are perennial gardens (native plants work best) situated in slight
depressions or swales that capture and filter storm water before absorbing it
back into the soil. It’s a landscape system designed much like a forest
habitat, where the density of plants and trees naturally provides a spongy layer
to soak up water and return it slowly to the earth. Rain gardens are located
where runoff water from roofs, driveways and other hard surfaces can be directed
into it. More elaborately designed rain gardens use small swales and buried
tubing to redirect water runoff to other areas. In addition, rain gardens add
beauty to any landscape.
The average amount of runoff from a roof is 24,000 gallons per year—enough
water to fill 600 bathtubs. Rain gardens capture this runoff and prevent the
transfer of pollutants, such as sediment, phosphorous, nitrogen, gas, oil and
a vast array of litter, to our waterways. In
addition to protecting fish, wildlife and vegetation, these mini-wetlands help
prevent flooding, recharge groundwater, provide habitat for birds and butterflies
and beautify communities.
The Minneapolis Blooms Program is part of the Committee
on Urban Environment (CUE), established by the Minneapolis City Council
in the early 1960s. In 2001, budget constraints cut all of its funding, but
CUE still operates with volunteers, donations and grants.
Joyce Vincent is co-chair of the Minneapolis Blooms program. She said there’s
a lot of interest in rain gardens. “Last year we offered 18 rain garden
workshops and expected to serve about 300 people. We actually had over 500 people
attend and 400 people on the waiting list. I was amazed that there was that
great an interest.”
year Minneapolis Blooms has doubled its number of free rain garden workshops,
which begin in March and run through May. Each workshop consists of two sessions.
The first session focuses on the value of rain gardens and design options. Two
weeks later, participants meet with landscape architect interns and master gardeners
for customized, hands-on design strategies.
“We’ve got a dozen landscape architect interns from the University
of Minnesota College of Architecture and Landscape Architecture, who we’ve
trained further in rain gardens and native plants,” said Vincent. “And
we have five master gardeners, so people can come back and get one-on-one advice
and consultation.” In addition, Vincent said the program is offering on-site
consultations. “We’re offering on-site consultations at a very low
cost of $20 to have a couple of interns go to your home and help you design
your rain garden.”
Workshop participants will also receive a $75 reimbursement form that they can
apply toward installation costs (which vary, depending on size and design) or
native perennial plants. For a complete schedule, or to register for a rain
garden workshop, go to MinneapolisBlooms.org
or call 612-673-3014.
Green roofs are another sustainable technology that has increased in popularity
and practice. Corrie Zoll, director of the GreenSpace
Partners Program, part of the Green
Institute, said that calling green roofs a trend would be putting it modestly.
“There’s been an explosion the last few years,” he said. “It’s
a global trend that we’re finally catching up with here [in North America].
In Germany, about one in eight buildings have a green roof top.”
Zoll said green roofs are becoming popular in North American cities such as
Toronto, Winnipeg, Vancouver, Seattle, Portland and Atlanta, and that Chicago
boasts more than two million square feet of green rooftops.
What is a green roof? Basically one that’s partially or completely covered
with plants. Specially engineered and landscaped with native plants, a green
roof typically lasts two- to three-times as long as a regular roof. It can dramatically
reduce heating and cooling costs, as well as manage storm water runoff.
“It’s this last issue that is really driving green rooftops in the
city of Minneapolis right now,” said Zoll. “In Minneapolis, as in
other cities in North America, storm water management has become the number
one environmental issue.”
Landscape architect Craig Wilson works for Kandiyohi Development Partners, a
firm that specializes in sustainable land use, renewable energy and clean technologies.
Wilson said there are some green roofs in Minneapolis that have been around
“For example, the garage in the back of the Bell Museum, I believe that
green roof has existed for 70 or 80 years,” he said, adding that green
roofs outlast conventional roofs. “If you think about it, it makes sense.
If you cut down on the ultra-violent radiation, which is really what causes
a lot of problems with rubber and tar because the temperature variation in summer
causes those materials to expand and contract, not to mention the fact that
the sun is a lot more powerful than people realize—it just breaks down
materials. Except for plants, of course, which actually use the energy. What
happens is [green roofs] shield those vulnerable materials and enable them to
last longer. So while green roofs tend to be more expensive with up-front costs,
over the long term they are actually less [costly] if they’re well constructed
and well designed.”
According to Wilson, one of the biggest misconceptions about green roofs is
that they’re leaky. “People perceive green roofs as leaky, but when
you learn about the technology and you understand how it works, you realize
that they’re not prone to leaking more than any other roof,” he
explained. “ There’s one layer that’s like a water-proofing
membrane, there’s another layer that’s a root barrier protection.
There are a lot of different layers of things that are protecting the roof.
And when you come to understand how ultra-violet radiation really wreaks havoc
on roofs, and how green roofs really help in all these other ways, I think people
will get over that ignorance.”
rain gardens, green roofs work best when they are landscaped with native plants.
Wilson said it generally takes two or three years for a green roof to establish,
and that some irrigation is needed during that time. “But once it’s
established, if it’s designed well, it should be low to no maintenance
if you’re using native plants and sedums,” he said.
Other green roofs in Minneapolis include the Crowne Plaza Hotel (which has had
its green roof since the 1970s), parts of the Loring Greenway, the Phillips
Eco-Enterprise Center (where the Green Institute is located), University of
Minnesota buildings and Brits Pub. The new Central Library in downtown Minneapolis
also has a green roof.
More green roofs are planned throughout Minneapolis, including one for City
Hall and one for Lund’s. Zoll sited the new Lunds going in downtown, and
said green roofs are not just for expensive developments. “There are condos
at 24th and Chicago—that building’s going to have a green rooftop.
So is the Green Leaf Lofts at Franklin and Nicollet. It’s not just high
Creating dense green space in urban areas is critical for environmental health.
“In the future, what I think is going to happen, particularly in the downtown
core, is that we’re going to have a lot more buildings, a lot more density,
a lot more people walking around, and we’re not only going to have more
green space, we’re going to have a higher quality green space,”
said Wilson. He added that in addition to rain gardens and green roofs, living
walls reduce storm water runoff and urban island heating.
“Living walls are important because they have a lot of benefits. Imagine
the southwest side of a building in August, with a lot of air conditioning units,
and how hot it gets out there. Plant material, just like on top of a roof, can
take that temperature down considerably and cool those air conditioning units,”
he said. “The other thing that’s really important about living walls
is that as we increase density in the city—which is a good thing for the
environment because what it does is release pressure in outlying areas that
should remain wild—we need to create as much green space as possible,
and one fantastic opportunity is just to green the walls.”
Both Zoll and Wilson agree that local governments generally support sustainable
technologies. “Councilmember Lisa Goodman is a big supporter of green
roof tops. She’s been the biggest driver of the popularity of green roofs,”
said Zoll, adding that Councilmember Sandy Colvin Roy was instrumental in making
sure that a green roof was included on the Central Library.
say that politically there has been a real shift, at least with the politicians
I’ve worked with in the city of Minneapolis,” said Wilson. “I
think there was a lot of skepticism at first, and now they’ve really embraced
it because they fully understand the technology. There are a lot of developers
and architects and landscape architects who are now interested in exploring
Wilson, who has also worked on writing sustainable public policies, said that
green technologies are good for the environment and offer cost savings to consumers.
He said the storm water utility fee credit is one way for residents and business
owners to save money, although he admits that the policy needs revision so that
it is more accessible to homeowners.
“Basically if you’re able to retain a certain amount of your storm
water on site from a variety of methods—green roofs, rain gardens, etc.—you’re
able to apply for a credit on your storm water utility bill. What that tries
to do is reimburse people for good behavior so the state doesn’t have
to invest a much more costly infrastructure down the road.” Wilson also
said the city of Minneapolis will soon be unveiling its new green roof policy.
Green Roofs for Healthy Cities, a Toronto-based network of public and private
organizations, is a good source for information on green roofs. The organization
is holding its annual international conference in Minneapolis next year. For
more information, go to GreenRoofs.net.