Happy Waskoone Giizis (Flower Moon)! As the old saying goes, “April showers brings May flowers”. I came across a little guide book on planting a “design-a-relationship garden” from Ojibwe.net, and it’s really interesting to hear how plants relate to one another to form a complete, happy garden. Each plant species is one of the following:

• Badakide (“it stands up”) - tall plants that shine with a vibrant and outgoing personality

• Babaamoode (“it crawls about”) - shy, quiet ground cover plants that protect the soil

• Aasonige (“it supports others”) - plants that hold up the garden structure, reliable and trustworthy

Can you build a garden of native plants that form these relationships? What about one that maintains these relationships throughout all seasons, with blooms at different times of the year? The Ojibwe.net guide is a great starting point! Don’t know any native plant nurseries? The 1000 Islands Master Gardeners have a great guide that gives you plenty of options!

Announcements

• Join us at the Kingston Climate Summit on June 3rd and 4th! We’ll be hosting a workshop on multispecies cities to get you thinking from the perspective of our ecological kin and to help us understand how they experience our urban environment. Registration required, $35.

• Did you know Kingston is now certified as a bird-friendly city? Come celebrate world migratory bird day with us at Lakeside on Saturday May 9. Meet some of the birds of Lakeside: summer residents settling in and migrants passing through. We’ll have a bird trail, a scavenger hunt, an obstacle course, tree and shrub seedlings to take home & more! Registration required, but free.

Stop floods with green infrastructure

It’s been a rainy few weeks here in eastern Ontario, and it seems like every few days Environment Canada sends out rain/flood warnings. It might seem like these warnings aren’t affecting you much, but the truth is that the increasingly volatile weather events caused by climate change are creating higher costs for building and maintaining infrastructure. This is particularly easy to see when it comes to stormwater infrastructure (the pipes that rainwater drain into, as well as pumping equipment and treatment plants).

Enter green infrastructure. Unlike “gray” infrastructure, like pipes and buildings, green infrastructure refers to natural systems and processes that are created by our Ecological Kin. The Green Infrastructure Ontario Coalition includes the following examples in their definition of green infrastructure:

• Urban forests

• Green stormwater systems

• Green roofs and green walls

• Urban agriculture

• Parks and open space

• Natural heritage

• Other elements that store water or help it to infiltrate into the soil, such as permeable pavement and rain barrels

Let’s take a closer look at what makes green and gray infrastructure so different.

Green or gray?

What specifically distinguishes gray and green infrastructure? What are the benefits or disadvantages of the two? Let’s make a table:

Gray infrastructure is well understood (at least as far as managing stormwater in urban areas) and is something that developers and municipalities are familiar and comfortable with. It’s also something that generally takes up less space at ground level, because it is buried underground, freeing up space for new buildings and other infrastructure. However, this comes with some major drawbacks: the cost to build, maintain, and replace gray infrastructure is very high, and continues to increase, whereas, once implemented, green infrastructure acts independently of humans and generally doesn’t require much maintenance. This means that, although gray infrastructure appears more convenient and practical than green infrastructure, it becomes much less convenient in the long run.

Green infrastructure can also refer to benefits beyond water management, such as reducing air and noise pollution and countering the urban heat island effect, but most of the time, the term is used to refer to natural water management systems (which often have those additional benefits). This is why you may also sometimes hear the terms “blue infrastructure” or “blue-green infrastructure”. Green infrastructure is also sometimes referred to as “low-impact development” (LID).

How does it work?

Green infrastructure doesn’t “remove” water from the watershed, so how is it beneficial for water management?  We can understand what’s going on based on this simplified water cycle formula which is included in the Ontario Ministry of the Environment, Conservation, and Parks (MECP)’s draft low-impact development guideline:

P = R + I + ET

We see that precipitation (P) is transferred to one of the following “forms” of water:

• Runoff (R), where water accumulates on the surface of the ground and flows along slopes and through channels

• Infiltration (I), where water flows into the soil rather than staying on the surface

• Evapotranspiration (ET), which is the combined effect of both evaporation from the surface of water, and transpiration, where plants release water vapour to cool themselves (basically plant sweat)

The important thing to know is that gray infrastructure exists to manage runoff. Urban areas consist of large amounts of impervious surfaces, such as concrete, which do not allow water to infiltrate into the soil. This means that, besides some evaporation (which is generally considered negligible on impervious surfaces with drainage), all of the water landing on a road or other impervious surface becomes runoff. If runoff is not managed (i.e. if the water has nowhere to go), then it pools and creates floods, so gray infrastructure collects the runoff and moves it to somewhere where it will not have a significant impact (e.g. a large body of water, which is typically considered “outside” the watershed). That said, many jurisdictions simply release water downstream of their political boundary, essentially making it “someone else’s problem”.

Green infrastructure, on the other hand, includes many other mechanisms for managing rainfall. Of course, runoff still occurs on permeable surfaces if the soil becomes saturated, but generally, green infrastructure makes use of the following principles:

• Vegetation absorbs water, which is subsequently transpired

• Leaves and irregular surfaces that water can land on allow for greater levels of evaporation (larger surface area)

• Green spaces, ponds, and other elements of green infrastructure allow water to infiltrate into the soil.

The most important aspect of green infrastructure is infiltration. Water doesn’t disappear from the water cycle by infiltrating into the soil; rather, water stored in the soil or in bodies of water is released more gradually. Flooding happens when we get a sudden influx of water:

• Water levels in lakes and rivers rise because the rate at which water is transferred “out of the watershed” is less than the rate at which it is added

• Similarly, pipes and gray infrastructure have a maximum discharge rate which can be exceeded by heavy rainfall, meaning that water can back up into city streets. Water treatment plants are also sometimes forced to discharge untreated water because too much water is coming in at once.

Green infrastructure stores water, then releases it more gradually, reducing water level rises and also reducing the demands on gray infrastructure. Water absorbed by green infrastructure often bypasses gray infrastructure entirely, as water that has soaked into the soil is released directly into rivers and other bodies of water.

Costs of Infrastructure

Now that we have a good sense of what green and gray infrastructure is, let’s take a more detailed look at the costs of gray and green infrastructure. There is so much information available about green infrastructure (let’s call it GI from now on) that it’s really quite daunting to dig into. Let’s start with some quick facts:

• A survey of 479 case studies where GI was implemented found that overall costs were reduced in 44.1% of cases, while costs increased in only 22.5% of cases.

• The US EPA found that, in most cases, GI was cheaper to implement than a gray infrastructure system with an equivalent water management capacity. More specifically, a study of 17 cases in 2007 found that, on average, GI costed 25% less than an equivalent gray infrastructure solution.

• Data from Seattle, WA, showed that, on average, street designs incorporating GI resulted in cost savings of roughly $330 per square foot of development area (~$3,500 per square metre), while the City of Chicago found that equipping alleys with permeable pavements and rain barrels, planting trees, and disconnecting downspouts are 3-6 times more cost effective than a grey infrastructure solution.

Although these numbers are exciting, it’s hard to know what the actual projects would look like, so let’s take a look at some case studies!

Case Study 1: Elm Drive in Mississauga

In 2011, Elm Dr in Mississauga was reconstructed to improve rainwater treatment and management. Before the reconstruction, the street had grassy ditches on either side of the road which fed directly into the city’s sewer system, and provided basically no treatment or runoff reduction. In addition to rainwater management improvements, the project replaced broken asphalt and added a sidewalk to the south side of the road, along with curbs and a parking layby.

The street segment, which runs between Joan Dr and Kariya Dr, receives rain runoff from a total of 0.646 hectares (6,460 m² , roughly 2.5 times the size of Springer Market square), of which 51% is impermeable. The project consisted of installing six bioretention cells (basically gardens that store and treat water), as well as replacing traditional solutions for the parking layby and sidewalk with permeable pavement. Credit Valley Conservation (CVC) collected data to measure the effectiveness of the solutions, and found that:

• 80% of rainfall events produced no outflow

• Rainfall events of 2-25 mm produced only 7% of the outflows expected from grey infrastructure

• During a “100-year storm” event (i.e. a storm that has a 1% chance of occurring in any given year), the peak outflow rate was reduced by 60%, and 30% of the total runoff volume was absorbed by the bioretention cells.

• Generally, during storms, peak outflow rates were reduced by at least 54%, and up to 95%

These are huge impacts seen by what is a relatively minor change to the street. Not only were these impacts far more effective than predicted (the 100-year storm peak outflow rate was expected to be reduced by only 13%), the GI installed cost 18% less than an equivalent grey infrastructure solution! As an added bonus, these bioretention cells are prettier and support more biodiversity.

The report from CVC includes some details about maintenance, and the main issues identified were related to litter clogging the permeable pavement or bioretention filters, as well as snow being pushed onto the bioretention cells (adding more litter/debris and potentially harming plants). In terms of costs, the report states that the City pays a contractor $1,000-2,000 per year to maintain the bioretention cells, and CVC contributes 60-70 hours of volunteer maintenance a year.

Case Study 2: Honda Canada Campus in Markham

Another report by CVC details the impacts of GI on the Honda Canada campus, a site 17.9 hectares in size (179k m² , roughly 1.5 times the size of City Park), which is 65% impermeable (with twice as much parking as building area). To address runoff concerns related to the campus, a number of different GI solutions were implemented:

• A large underground cistern used to irrigate a soccer field on the site

• Many vegetated biofilters spread throughout the site

• Permeable pavement in some parts of the parking lot

• A bioswale along the western property boundary

• A dry pond that collects rainwater when the cistern and biofilters overflow

CVC found that these measures reduced the total volume of runoff from the entire site by 30-35%, with roughly 6% of the total rainfall being reused for irrigating the soccer field. Peak outflow rates were also reduced by 65-79%. The overall cost implementing GI instead of gray infrastructure was originally estimated to come at a 10% premium, but in the end it costed 5% less.

Summary

These two case studies, as well as research more broadly, show that green infrastructure has the potential to simultaneously reduce construction costs, reduce maintenance costs, and improve the environment in many different contexts. Whether it’s the City upgrading our roads or private companies building new developments, green infrastructure is arguably the best way for us to build resilience in face of a changing climate. However, we need a concrete policy solution that will incentivise developers to implement these kinds of solutions.

Generally, when a new development is built, a municipality imposes development charges to make up for the added construction and maintenance costs to extend utilities and public services to that development. The City of Kingston’s development charges pamphlet includes details on the fees they charge, but (at least as far as I can tell) there is no provision for reducing the costs of stormwater fees if green infrastructure is incorporated into the development. Providing developers with the ability to reduce fees by maintaining existing vegetation or implementing other stormwater solutions could be an excellent way to incentivise adopting green infrastructure.

After a number of hours of research, I still feel like I’m only at the tip of the iceberg when it comes to green infrastructure, so I’m planning to write another article about this at some point in the future. Stay tuned!

-Robert