What is stormwater?
Stormwater is water from rainfall and melted snow that does not soak into the ground and becomes surface runoff. This surface runoff either flows directly into creeks, rivers and other natural areas or is channeled into storm sewers, which ultimately discharges into natural areas.
Why is stormwater a concern?
Managing stormwater is necessary to control flooding, stream erosion and water pollution. Before land is developed, rainwater can readily soak into soils, be absorbed by trees and other plants, evaporate into the air, or travel over land to receiving creeks, wetlands and other natural areas. When an area is developed with driveways, buildings and roads, the rain can no longer easily soak into the soil and travels over these hard surfaces as runoff, reaching a waterway much more quickly.
Major effects of floods include destruction of life and property. Flooding can cause damage to infrastructure like roads and bridges in urban areas and destroy farmland in agricultural areas. Southern Ontario, including Pickering, has experienced more frequent and extreme rainfall events over the past few years. During heavy rainfall, the storm sewer system can quickly become filled resulting in overflows, leading to flooding.
Reduced infiltration and evapotranspiration due to urbanization results in an increased volume of stormwater runoff reaching a waterway as surface flow. The increased volume of water can significantly alter the receiving stream characteristics and associated aquatic communities. Effects include stream widening, downcutting, sedimentation, bank erosion, and loss of tree canopy.
When stormwater runoff flows over hard surfaces such as roads, driveways, roofs and parking lots, it picks up pollutants from these surfaces. Stormwater then carries these pollutants into natural areas, creeks and rivers and into Lake Ontario. Stormwater pollutants originate from many different sources ranging from fuel and oil from our roads, to litter dropped on our streets, sediment from construction sites and pesticides and nutrients from agricultural areas.
What is Stormwater Management?
Stormwater Management is the planning for and controlling of stormwater runoff from precipitation and melted snow.
Stormwater Management Guidelines [PDF]
What types of Stormwater Management Practices does the City implement?
Pickering implements a variety of stormwater best management practices (BMP) and Low Impact Development (LID) measures including:
You can do a number of things to control stormwater before it reaches the storm sewer. The following measures help reduce the amount and rate of runoff coming off your property as well as reducing the amount of pollutants the run off carries:
Conveyance controls are used as the runoff travels down sewers and backyard or roadside swales. These measures help route the runoff back into the ground which reduces the amount of runoff and improves its quality. These include:
- pervious pipe systems (they have holes in them that allow the water to infiltrate the surrounding soil)
- pervious catchbasins
- grassed swales with gentle slopes
- oil/grit separators may be installed in the storm sewer system to remove oil, debris and large sediment as the runoff travels down the pipe
End-of-Pipe Stormwater Facilities
End-of-pipe stormwater facilities are the man-made ponds we see in our neighbourhoods. They receive stormwater runoff from a storm sewer or ditch, hold the water back for a period of time to allow pollutants to settle, and then discharge the treated water back to the receiving creeks, rivers, and other natural areas at a controlled rate to prevent flooding and erosion.
There are 3 main types of stormwater facilities:
Dry Ponds: Dry ponds are typically constructed in neighbourhoods to temporarily store water to prevent overloading the storm sewer system and reduce flooding in large storm events. The stored water gets released back into the storm sewer system at a reduced rate, preventing downstream flooding.
Infiltration Ponds: An infiltration pond is a special type of dry pond that requires sandy soils. It collects stormwater from the ground, improving water quality by filtering the runoff as it slowly passes through the soil. These ponds are also capable of recharging or replenishing the groundwater table.
Wet Ponds: The water levels in wet ponds rise and fall with each storm event, but the pond will always retain a certain volume of the water (known as the permanent pool).
Some of the larger facilities incorporate sophisticated control and monitoring systems with automatic gates to monitor and regulate the discharge. Wet ponds are intended to mimic natural lakes and often have healthy aquatic ecosystems, including fish, bird and waterfowl populations and may include man made wetland features. Recreational pathways are commonly incorporated into the designs and can be beneficial amenities to a community.
Can mosquitoes breed in these ponds?
No, mosquitos require stagnant water to breed. Although the ponds may not look like they are flowing, they always have water flowing in from the upstream storm sewer, and water flowing out, thus preventing mosquito development.
How many stormwater ponds does Pickering have?
Pickering owns and maintains 18 stormwater facilities, ranging from small dry ponds to very large wet ponds and artificial wetlands. There are also many private facilities servicing commercial and industrial buildings.
Most neighbourhoods built since the early 1980's have had some sort of ponds incorporated into them. Some dry ponds also provide recreational opportunities such as baseball and soccer fields. Wet ponds are often constructed adjacent to parks and include walking paths to allow you to view and enjoy the birds and animals that will inhabit the facility. Please note however that they are not suitable for skating or ice hockey, swimming, fishing or boating, and no camping is permitted. Next time you are out for a walk, have a look around and see if you can discover all the facilities in your neighbourhood.
How does the City of Pickering manage stormwater?
Currently, Pickering performs the following activities to manage our stormwater and mitigate the impact of stormwater pollution to the natural environment:
Operation & Maintenance
- cleaning of sewers, catchbasins and ponds
- removal of obstructions in creeks and watercourses (creek rehabilitation)
- street sweeping
- leaf collection
- site investigations (based on customer complaints or calls)
- watershed monitoring
- spill response
- flow and water quality monitoring
- provide quality and quantity control of stormwater in developing areas
- planting riparian buffers adjacent to streams
- public education/awareness
Capital Improvement Projects
- system rehabilitation, renewal and retrofit projects
- infrastructure projects (stormwater component)
Planning and Management
- emergency maintenance
- policy development
- stormwater management policies and guidelines