Clear thinking on stormwater
New approaches to rainfall and snow melt have environmental and financial benefits.
Into each city, a little rain must fall. If we were to update that truism for our era of climate change, it would be a lot of rain—and other forms of precipitation.
According to the Prairie Climate Centre, Calgary’s future includes wetter springs, drier summers and snowier winters. These are some of the changes The City’s Climate Resilience Strategy confronts. The strategy, released in 2018, seeks to adapt to and mitigate the effects of climate change. It’s all designed to cope with extreme weather events without losing critical services like clean drinking water or power supply.
One focus is on stormwater, which presents both a challenge and an opportunity. A challenge because more rainfall means handling stormwater becomes critical. An opportunity because handling it properly can produce financial and environmental benefits.
As it flows toward the Bow and Elbow rivers, stormwater gathers sediment and pollutants. Calgary’s stormwater system includes catch basins, wet ponds, dry ponds, and wet lands. It also includes a vast network of underground pipes. Even so, only a small portion of the water collected goes to a wet pond or wetland where solids and pollutants can settle out.
Given the expense and impracticality of installing bigger pipes, we need new approaches. Increasingly, that means things like rain gardens, green roofs and permeable pavements. These forms of low-impact development (LID) are becoming more common in Calgary and other cities. LID lets nature take its course. It uses landscaping to slow the flow of stormwater, letting it evaporate or soak into the ground rather than heading for the storm sewer.
Stormwater management fits with the Municipal Development Plan’s goal of creating a greener Calgary. As such, progress is monitored. The most recent report contained good news and bad news. Water quality in the Bow has improved, with a reduction in the amount of solids reaching the river. On the other hand, the percentage of land covered by impermeable surfaces continues to climb.
The latter has implications for the health of the watershed and illustrates that work remains to be done. It also proves you can be standing on solid environmental ground even while standing on porous concrete.