Great Calgary Flood Tunnel

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As another part of our series on flood tunnels, below we look at the future Calgary flood tunnel project that was announced in November 2013 as a potential part of a large flood mitigation project for the city.

Anti-flood tunnelling was once described by the Canadian city of Calgary’s mayor Naheed Nenshi as “science fiction”. But things change and this kind of flood mitigation engineering is now being championed by the province of Alberta’s premier, Alison Redford.

Calgary Floods of June 2013

Following devastating floods in Alberta in June 2013 that killed four people, displaced thousands and caused over C$6bn (US$5.5bn) in damages, the premier, at the Alberta Urban Municipalities Association convention in November 2013, announced feasability studies into three major flood mitigation projects, including a 6km (3.75mi) long stormwater diversion tunnel taking water from the Glenmore Reservoir on the Elbow River, to the Bow River. Other parts of the flood mitigation project for Calgary include plans to build a dry dam for the Elbow River near Bragg Creek, and also run a diversion channel around High River.

In the event of a flood, the 8m (26ft) wide Great Calgary Flood Tunnel would be used to divert Elbow River waters through a six kilometre long passage below 58th Avenue, and away from the inner city, at a peak flow rate of 500 cubic metres (132 000 gallons) per second. The alternative of aligning the tunnel below Heritage Way may also be investigated. Estimates in various media reports for the cost of the flood tunnel range from $200 million to $300 million.

The province ordered environmental reviews and public meetings on the route of the diversion tunnel, which is one of a total of C$830m (US$759m) in projects recommended by a flood advisory panel.

Although Mr. Nenshi said he was originally sceptical about the diversion tunnel scheme, he has accepted the advice of water management experts from the Netherlands after they told him: “This kind of thing is very common, and it actually makes a lot of sense.”

The City of Calgary, which will build and operate the flood management tunnel with funding assistance from provincial and national levels, has retained the services of water resources and design consultants to assist with investigating mitigating solutions. The aim is to move ideas quickly into the design and construction phase rather than just undertaking feasibility studies, many of which already exist.

Scott Edelman, an expert who has given evidence about flood mitigation to the United Nations, said: “I have seen disasters across the globe and Alberta is ranking in the top ten per cent in how you are reacting to the flood … what I am seeing is unbelievable cooperation. I am seeing leadership from the very highest level … You have the ingredients to impact future generations.”

Sources: Calgary Sun; The Globe and Mail; Tunnel Talk; Alberta; Canada