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Types of flooding

Types of flooding

There are many types of flooding that can have a big impact on Calgary. Learn more about the types of flooding that can happen in your community or surrounding area.

Flooding can occur at any time with little or no warning. The period between May 15 and July 15 is when we are likely to experience flooding because this is when we receive our largest rainfalls.

People who live on flood ways or flood fringes should pay particular attention to weather warnings and conditions during that time.

You can also learn more about river flow rates, river triggers and related effects, as well as how river flooding occurs in Calgary.

Types of floods in Calgary

Overland flooding
This flooding happens when water overflows from the banks of creeks, streams, rivers (Bow and Elbow) or lakes.

Depending on how severe the flooding is, the water can slowly creep up into backyards or it can rapidly spread throughout the streets with little warning. In winter, frozen catch basins, storm drains or piled snow, combined with quick thawing and/or rain, can cause overland flooding, which can enter basements or garages.

Basement seepage
This type of flooding occurs when water is absorbed by the soil and raises the level of the underground water table. Water seeps through the soil and eventually reaches the foundation of your home. The water works its way into your basement through cracks and holes, or through joints in the home's foundation.

Basement seepage can also happen in homes near rivers because of elevated river levels due to either spring or summer high-water levels or winter ice jams.

Sewage backup
Water on flooded streets or high groundwater may drain into the sanitary sewer system. This overloads the sanitary sewer pipes and can force sewage back through the sewer line and into your basement. If you are experiencing a sewage backup, please contact 311. To help our crews before arrival, view oursewage backup guide.

Stormwater backup
The City of Calgary's stormwater system empties into the Bow and Elbow rivers through large pipes. When the rivers rise, or there is excessive rainfall, water can flow back into the stormwater pipe system and spill back onto streets through stormwater drains.