Rain Gardens 4 Resilience
WHAT WAS THE RAIN GARDENS 4 RESILIENCE PROGRAM ABOUT?
Beginning in 2017, with support from Alberta Environment and Parks, the Alberta Low Impact Development Partnership built rain gardens in the Bow, Battle, North Saskatchewan and Oldman watersheds.
Longer-term Educational Goals
The project has a longer-term goal to educate property owners and landscaping trades about the importance of managing runoff at home, and address barriers to implementation and provide inspiration and resources for future installations. We built ten rain gardens in 2017, two in 2018, and one in 2019. We'll be following them and developing resources from our learnings, including rain garden designer and rain garden installer certifications. We've also been using our learnings to design and construct community hubs in Calgary and Edmonton in 2020-22.
Read more about the Community Hub program.
Three of these rain gardens in Calgary are also being monitored for water quantity in the form of soil moisture and spill events. One of these has a weir. A fourth site is being monitored in a 'before' condition with shallow soil and was our final garden constructed in the fall of 2019, with 'after' monitoring starting in 2020.
BACKGROUND ABOUT CONTROLLING RUNOFF
WHY DO WE NEED TO CONTROL RUNOFF?
When land is converted from its natural or agricultural past use into urban uses, the roads, roofs, and land disturbance greatly exceed the capacity of what is left of the natural landscape to buffer floods and droughts, and to keep water quality at acceptable levels.
WHERE DOES RUNOFF COME FROM IN THE BUILT ENVIRONMENT?
We know that about one-half of runoff is generated by roads, and the remainder by the rest of the landscape. Roads contribute tremendous pollutant loads, and remedial solutions for quality-improvement, such as roadside and open-area bioretention, oil-grit separators, sacrificial ponds with sediment-removing forebays, and other more engineered interventions are needed to protect our wetlands, riparian areas, and receiving bodies from the burden of pollutants found on and transported by these hardened surfaces.
On the other hand, runoff generated on the rest of the landscape is relatively clean, and the primary objective for this rainwater is to keep it from becoming runoff at all, at the property level. At the same time, there is a significant quality payoff to keeping rainfall on lots, since atmospheric deposition on roofs routinely contains orthophosphate and other sediment-bound pollutants (primarily generated by certain agricultural land uses and by open construction sites). Holding these compounds at the lot-level means they will not concentrate to impair and shorten the life of other measures designed for treatment and flood control, or reach receiving bodies where they will contribute to eutrophication (algae blooms), for example.
I'VE NEVER HEARD OF LOW IMPACT DEVELOPMENT, WHAT IS THAT?
Low impact development is a comprehensive approach to managing runoff that harnesses natural landscape features and processes to restore the absorptive and assimilative capacity of the landscape and to recreate more natural rainfall recharge pathways, while still allowing land development to occur, but with reduced impact. Rain gardens are one part of the low impact development toolbox.
The Watershed Resiliency and Restoration Program was our primary funding partner for the Rain Gardens 4 Resilience Project. Learn more about the WRRP Program