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Calgary Underground Diversion Study (Calgary Tunnel)

This government-funded study, directed by the City of Calgary, determines the feasibility of diverting water underground during flood conditions.

Flood water would be diverted underground along Heritage Drive from Glenmore Reservoir to the Bow River.

The final report is available on the City of Calgary's website.

Estimated impact on flood mitigation

An underground diversion with an internal tunnel diameter of 8 metres could accommodate a peak flow of approximately 500 cubic metres per second. A larger version of the underground diversion with a 9.5 metre tunnel could accommodate a peak flow of approximately 700 cubic metres per second. The peak flow rate of the Elbow River entering Glenmore Reservoir during the June 2013 floods was approximately 1,240 cubic metres per second.

Project status

Multiple flood mitigation options upstream of Calgary are being considered. The Alberta government is reviewing the Calgary underground diversion feasibility study and consulting with the City of Calgary and other impacted communities to identify the best options for flood mitigation.

Government is creating a new cost benefit tool to more accurately assess the value of each flood mitigation project. This will be used to determine whether the tunnel is the ideal choice for Calgary.