Let the rain drain – supporting low impact development within the GRCA

Stormwater runoff occurs when rain or snowmelt flows off hard surfaces rather than being absorbed by vegetation and soils. In urban areas, these hard surfaces include roads, parking lots, driveways, sidewalks and roofs. In order to prevent street flooding, stormwater drains quickly remove water from hard surfaces. The water then travels through underground pipes, eventually entering stormwater ponds, local creeks or Lake Ontario untreated.

Stormwater causes problems to the quantity and quality of our local creeks. Since a stormwater system is meant to move water quickly, a large amount of water enters local creeks, increasing the volume and flow of water. This increased amount and flow of water can be a public safety hazard and can also cause creek bank erosion and alteration or destruction to fish habitat.

Water quality is also affected due contaminants (gas, heavy metals, salt, bacteria, sediments) from roads, driveways and parking lots. This water contamination not only affects the quality of water for fish, insects, birds but also our source drinking water – Lake Ontario.

There are many types of pervious (porous) surface materials; however the basic water conservation function is the same – drainage into soils rather than surface runoff. Pervious concrete is one such product that has a similar durability to concrete, within certain applications, but with stormwater management benefits due to its porous nature. Rain or snowmelt drains through the open spaces within the pervious concrete rather than running off its surface. The environmental benefits of pervious concrete include increased groundwater recharge, reduced surface runoff rates and volumes, reduced water contamination through natural filtration, and reduced flash flooding through increased drainage capacity. Even with the use of pervious concrete, it is important to reduce potential contaminants that exist on our roads, parking lots and driveways, and increase the amount of natural vegetation within urban areas.

In order to support local capacity to design and install pervious concrete, the Ganaraska Region Conservation Authority (GRCA), in partnership with Concrete Ontario, hosted a lunch and learn seminar on pervious concrete systems. Over 30 engineers, architects, municipal staff and contractors learned about pervious concrete pavement systems, engineering properties and typical construction techniques that have been used on completed Ontario projects.

To learn more about low impact design systems such as pervious surfaces, please contact the GRCA at stewardship@grca.on.ca. Funding may be available to install systems (pervious surfaces, rain gardens, soakaway pits) to help manage stormwater on a property.