What is surface runoff pollution?
In a natural landscape, the ground has a dense cover of leaf litter and vegetation which acts as a sponge - absorbing and filtering most precipitation. When natural groundcover is removed, rainfall no longer soaks into the soil as readily as it once did resulting in surface runoff.
The U.S. Environmental Protection Agency estimates that a typical city block generates nine times more runoff than a woodland area of the same size.
Most precipitation that falls within the Coves Subwatershed becomes runoff which is channeled swiftly into ditches, creeks or storm sewers, then emptys into the Coves. Surface runoff becomes polluted along the way when it picks up pollutants (such as gas, oil, salt, chemicals, pet waste, sediment, pesticides and fertilizers) as it flows over lawns, along streets and through storm sewers. Surface runoff also results from events such as watering lawns and washing cars.
What are the effects of surface runoff?
Effects of surface runoff on the environment include the pollution of waterways into which runoff flows and erosion of land over which runoff flows. The pollution of our natural waterways makes them inhospitable to many native species and makes treatment of that water for human use more expensive. As runoff continuously gathers as it flows downstream, it gains greater energy. This water flow erodes the slopes of natural drainage channels and carries the eroded sediment to the Coves.
Coves water ultimately flows to Lake Erie, which is the source of drinking water for 11 million people
Another effect of increasing surface runoff is a reduction in infiltration of water into the ground which means that groundwater is not continually recharged and the supply is reduced. This makes it difficult for trees and other vegetation within that environment to harvest enough water to survive without human intervention through extra watering.
What can individuals do?
With a bit of attention paid to the water on our own properties, more clean water could be retained, leading to less polluted water entering the Coves. Ways to achieve this include reducing impervious surfaces and the channeling of water into storm sewers by:
- Reducing area covered by pavement and lawns
- Washing vehicles on the lawn instead of driveway
- Planting and mulching trees, shrubs and other vegetation
- Disconnecting eaves troughs from direct connections to storm sewers and directing them into your yard rather than down your driveway
- Capturing precipitation with rain barrels
- Never dumping anything into storm sewers
- Modifying the way you water your lawn/garden so that it doesn't run off into the storm sewer
- Plant a rain garden to manage surface runoff naturally
Follow the City of London's Outdoor Water Use Regulations
(City of London Water By-law W-3 is in effect each year from June 1 to August 31)
Street address ending with 0, 2, 4, 6, and 8
- Use water outdoors on EVEN numbered calendar days only.
Street address ends with a 1, 3, 5, 7, and 9
- Use water outdoors on ODD numbered calendar days only.
Plant a Rain Garden
Rain gardens are low-lying gardens with permeable soils optimally containing native plants because they have very deep roots. They are located in an appropriate location to intercept surface runoff.
Rain gardens promote the detention and infiltration of water into the ground. Installing a rain garden is an easy way for residental or commercial landowners to conserve water on their property and help reduce the effects of surface runoff.
Here is a technical worksheet which will guide you through all of the necessary steps for planning and installing your own rain garden.
Note: There is a formula within this worksheet which helps you calculate the appropriate size and depth of your rain garden based on an estimate of the volume of water it will receive and the infiltration rate of the garden. This formula is tailored specifically to use a rainfall considered extreme in London, Ontario (10cm/day). For other regions this number may need to be adjusted.
This slideshow will give you ideas of what types of native plants are appropriate for rain gardens in London, Ontario.