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Another way to effectively control water

The benefits of slowing, sinking and spreading rainwater, and how to promote this trend with landscaping customers


March 17, 2019
By Treena Hein

Topics
An archetype of a sustainable residential rain garden.

Rainscaping – landscaping strategies that reduce rain from flowing off properties and into surrounding bodies of water through stormwater drains or other means – is becoming a hot trend in Canada and around the world. Rainscaping includes the use of simple techniques like rain barrels and rain chains, but also the installation of more complex systems such as rain gardens and permeable paving.

Simply put, according to Clara Blakelock and Clifford Maynes of Green Communities Canada (who recently published a toolkit called Soak It Up) these “proven-effective technologies manage rain where it falls.”

How can you promote this trend with your clients and be ready to install the best rainscaping projects in their yards? First, let’s quickly review the benefits of the practice. First and foremost, rainscaping prevents pollutants from entering bodies of water – pollutants such as gas, oil, heavy metals and excess nutrients that may be picked up and carried in rainwater from the surfaces it flows over during a storm.

But while prevention of ecosystem and drinking water pollution is an important rationale for rainscaping, it’s far from the only one, especially in cities. Emily Rondel, coordinator of community engagement at Toronto and Region Conservation Authority (TRCA), notes that “as we experience more extreme weather events due to climate change,” increased threats of flooding, erosion and watershed change are also possible.

“We have much more frequent spurts of heavy rain and they tend to be more localized,” she explains. “These boom-and-bust weather patterns mean that our stormwater infrastructure is being taxed more heavily than ever before. The stormwater system dumps collected rainwater all at once into the nearest creek or stream, where water levels can quickly become high and water starts to move very fast. This affects the watercourse’s ecology, making it less effective habitat for plants and animals.”

However, when rainwater is aided by rainscaping to soak in and stay put or move underground to the nearest body of water, Rondel said streams, rivers and lakes do not fluctuate as quickly. By flowing through sediments in natural underground hydrological systems, rainwater is also filtered.  

Educating the public
In summer 2018, TRCA held a rainscaping workshop (future events are posted at https://trca.ca/get-involved/events/) in collaboration with Humber College. Other Canadian organizations that held similar workshops last year include the Bluenose Coastal Action Foundation (www.coastalaction.org) of Nova Scotia. Like the TRCA, Coastal Action promotes rainscaping for pollution reduction, flooding mitigation, recharge of groundwater and prevention of erosion, and has been working for the restoration, enhancement and conservation of ecosystems of the South Shore region of Nova Scotia since 1993.

“The workshop featured a presentation on DIY stormwater management solutions, a materials demonstration and a mapping exercise,” explains Samantha Battaglia, Coastal Action’s stormwater management projects technician. “Participants learned about rainscaping best practices, materials and maintenance, and started to develop a plan for their own property to help address flooding issues and make the most of the rainwater that falls on their landscape.”

Coastal Action has also hosted workshops where participants are guided to assemble their own 55-gallon rain barrel to capture roof water. In addition, within its “Green Streets Stormwater Project,” by the end of 2019, Coastal Action will complete 30 small-scale community projects in collaboration with various organizations and municipalities. Both vegetation and soil are used in these projects to slow down, absorb and filter stormwater runoff from impervious surfaces like parking lots, roads and sidewalks.  

Choosing practices
As with the proper application of any landscaping practice, rainscaping should be implemented with individual location characteristics in mind. “The site’s soil type, slopes, drainage patterns, available light, existing vegetation, type of impervious surface, space available for rainscaping, etc. will all be factors in determining which practice is best,” Battaglia says.

Rondel adds “learning about all the options is important before starting a rainscaping project. Luckily, most rainscaping features are relatively easy to install and intuitive to design. That being said, there are definitely right ways and wrong ways to rainscape, and education is key to avoiding mistakes.”

 One key item that Rondel says homeowners should think about off the top is how water moves over their properties. “Will water flow to the foundation of my home or that of my neighbours?” she invites homeowners to ask themselves. “Avoiding flooding is priority, and a badly-designed rainscaping feature might cause it. What is the capacity of the rainscaping feature I am building and does it align with the amount of water coming from my roof? That is, larger homes need larger rain features!”

If a property can accommodate one, Rondel recommends a rain garden as the best way to return rainwater to the ground instead of the storm drain. Rain gardens are garden beds that are specially designed to absorb rainwater, often from roofs, and they often have a depressed shape.

“The soil under the surface is less compact than in a regular garden, and the whole shape is designed to keep rainwater in while it slowly filters through the soil back to the groundwater,” notes Rondel. “They are simple to make, but very effective.”

However, she points out that rain gardens may not be suitable for heavily-sloped properties, as water will simply travel down the slope instead of settling in the garden.

Whatever rainscaping is planned or implemented, the very first thing any resident needs to do is disconnect the roof downspout. “In previous decades, many homes were built with rain gutters that emptied into a downspout that was directly connected to the storm drain,” Rondel explains. “This is obviously pretty problematic, so many municipalities (e.g. Peel and Toronto), recently introduced policies around mandatory-disconnected downspouts. Once your downspout is disconnected, you can then decide what to do.” She adds that if you are new to rainscaping and already have a disconnected downspout, “Try a rain barrel. It is very little work to install, and the benefits are almost instant.”

How to promote rainscaping
Before they can assist homeowners in designing and building rainscaping features, landscaping professionals should make themselves well aware of the different principles and techniques. Rondel believes that to ensure the longevity of a landscaping design, landscapers should make sure to work with the natural hydrology of each property. This, she says, will result in customers who “will be happy with their functional low-maintenance features.” Another point to keep in mind, she says, is that adding water-permeable paving is likely something that most customers will wait to do until they have to re-do their walkway or driveway anyway.

Battaglia believes a lot of promoting rainscaping with customers comes down to education, so landscaping professionals should both provide clear, concise descriptions of rainscaping practices to their customers and emphasize the diversity of benefits rainscaping offers to individual homeowners as well as community water quality. “I also find incorporating flowering plants that support pollinators into the plant palettes for rain gardens,” she notes, “or vegetated bioswales, can help increase the desirability of these gardens in residential areas.”

Bioswales
Rainscaping Iowa describes bioswales as “installed as an alternative to underground storm sewers and consist of permeable soil, a perforated subdrain, and subtle earthen berms. The bioswale is engineered so runoff from a 1.25-inch rain infiltrates through tile into the soil below. Bioswales differ from biocells in that they are implemented on sloped areas so that when larger storms occur, the above ground vegetation slows the flow of runoff, which is filtered and cleaned before draining into the nearest stream or waterbody. It is critical that bioswales are inspected and maintained periodically to ensure their continued performance.”