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Frequently asked questions - flood mapping

Below are frequently asked questions related to Flood Mapping in Calgary. For more information about what the City of Calgary is doing to be ready for flooding, visit our Flooding in Calgary page.

What should I do if I live in a flood hazard zone or inundation area?

For residents whose property is located in a flood hazard zone or inundation area, we recommend you visit our Flood Readiness page. This resource can help you identify your flood risk and take steps to prepare for future flooding.

My area says "inundated" but I wasn't flooded in 2013 - How accurate are the maps?

The 2013 event, according to current data, was about a 1:70 year flood on the Bow River, a 1:200 year event on the Elbow River above Glenmore Dam, and a 1:70 year event on the Elbow River below Glenmore Dam.

Actual inundation during a flood may be different than inundation mapping because the size of the event may not line up exactly with the size of the event mapped. Also, maps do not take into account emergency response measures that prevent inundation, such as building or raising flood barriers such as berms.

There is some uncertainty when statistically analyzing and predicting events like flooding. While inundation maps show the best available estimate of flood levels and inundation areas, many factors influence the accuracy of the estimates:

  • Changes to the bed, banks and pathway of the river
  • Operation of dams and reservoirs along the river during a flood
  • New or altered mitigation measures not included when the maps were created

The City of Calgary and the Province of Alberta work together to update flood mapping. After the 2013 flood, which significantly changed the river in some areas, we completed a new hydrologic and hydraulic analysis and created new inundation mapping. The Province is also currently updating inundation and hazard mapping for Calgary as part of their Flood Hazard Identification Project.

Why do I have two values for the designated river flood elevation for my property?

In some areas, the river level and inundation shown on the inundation maps (2015) for the 1:100 year return period event is different than the inundation in the flood hazard mapping (1983).

This is because the flood hazard map was created in 1983, we have collected more data, which changes the statistical and hydrological analysis, and the watershed and river have changed. In general, the 1:100 year river flow and elevations at most locations has increased from the 1983 analysis.

Since late 2011, property owners have been advised of both the official designated flood elevation as per the Land Use Bylaw (based on the flood hazard mapping) and the most up-to-date recommended designated flood elevation (based on the inundation mapping) for their specific property.