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Storm drainage system

Stormwater is the water from rainstorms or melting snow that goes into the storm drains in the road through an underground pipe syst​em to the river.

We ensure appropriate drainage with the following:

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

Our stormwater drainage system

Storm drains (catchbasins)

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 and underground systems

Overland includes 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 is made up of different sized pipes. The smaller pipes feed the larger pipes which are closer to the river. These pipes take water to the river via gravity and some are large enough to drive a car through. Learn more in ourCloud to River brochure.


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

Dry Pond - This pond is dry 90% of the time and can have playing fields in it. They fill with water during heavy rains and can up to 24 hours to drain once the rain stops.

Storm Pond - This pond always has water in it but the water will get much deeper during a storm. They 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 - Like 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.