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Storm drainage system

Stormwater is the water from rainstorms or melting snow that goes into the storm drains (or catch basins) in the road through an underground pipe system to the river.

It is the City of Calgary's responsibility to control the volume and quality of stormwater that is released into the river. The City helps ensure appropriate water use and drainage with the Drainage Bylaw, Lot Grading Bylaw and the Community Standards Bylaw.

For common questions about our stormwater system, visit the Storm Drainage System FAQ.

Our stormwater drainage system

Our collection system for stormwater includes the following:

Catchbasins (storm drains)
These are the main way water gets into the underground pipe system. The metal grates that can be seen at the edge of the road are only a portion of the catchbasin structure. Under the side walk is a barrel that collects the water. The barrel is attached to a pipe that allows the water to be whisked away.

Overland Conveyance System
This includes the eavestroughs on buildings and the concrete gutters that can be found behind houses in newer areas, grass, swales, roads or lanes. The water is kept above ground until it reaches the nearest catch basin.

Underground Pipe System
This consists of different sized pipes. The smaller pipes feed the larger pipes which are closer to the river. These pipes direct water to the river by way of gravity and some are large enough to drive a car through.

There are three different types of ponds that can collect water and each serve different functions.

Storm Pond Infographic

What is a Storm Pond?
Click for larger image.

  • Dry Pond
    This pond is dry 90% of the time and can have playing fields in it. They fill with water during heavy downpours and can take as long as 24 hours to drain once the rain stops.
  • Wet Pond
    This pond always has water in it but the water will get much deeper during a storm. The wet pond can help clean the water that comes off the roads because it allows the water to slow down, at which point the heavy dirt and garbage will settle to the bottom.
  • Wetland
    This is similar to a marsh or a bog; it contains plants and the water is quite shallow before a storm. The plants that grow in the wetlands filter out the fertilizers and pesticides that some people put on their lawns. A wetland can clean the water better than a pond.

The outfalls are the exit points from the pipe system to the river. there are more than 300 of them in Calgary.

Low Impact Development (LID)
LID is an approach to land development (or re-development) that works with nature to manage stormwater (rainwater and snowmelt runoff) where it falls.

LID employes principles such as preserving and recreating natural landscape features, and minimizing hard surfaces to create functional and appealing site drainage. LID treats stormwater as a resource rather than a waste product.