The swollen Bow River, as seen from a helicopter in June 2013. (CBC) In the five years since the 2013 flood that cost us lives and treasure, Alberta been preparing for the next major flood.
Berms and other local mitigation projects in Calgary and High River protect communities from rising water. The Springbank reservoir project, once built, will provide significant upstream mitigation on the Elbow River. Calgary faces 3.9% chance of ‘1-in-100-year’ flood before major mitigation is built on the Elbow
But the Bow — ah, the Bow.
Five years on, we’ve not built any new upstream mitigation projects on Calgary’s major river to protect the city and other communities, nor will shovels be in the ground for years to come.
Further, a report for the city estimated it would cost $2 billion to buy all floodplain property in Calgary alone, which is politically and economically unlikely. We could have been smarter in building this city, but we’re stuck with it now.
And so, as we think ahead to the dangers of future flooding, upstream mitigation is inevitable.
What might that look like?
There are a lot of options. The most workable were narrowed down for the provincial government in a 2017 report by a group of experts and stakeholders called the Bow River Working Group (BRWG).
It has been convened to produce several studies on Bow River mitigation. The group is comprised of technical water management experts or representatives from municipalities, First Nations, and major river licence holders. These bright water-nerds are the folks who’ve devised our best options for the Bow River.
The options outlined in the BRWG report are big. They’re expensive. And they each come with complications. What we need
The report gives two sets of recommendations, depending how much flood risk we want to live with — a target maximum flow rate on the Bow River in Calgary of either 1,200 or 800 cubic metres per second (cms). For comparison, the Bow River peaked at 1,750 cms during the 2013 flood.
The higher number, that 1,200 cms maximum, gives moderate protection, but evacuations would still be required. The lower number provides better protection, though parks and underpasses would still be flooded. A flooded pathway that passes underneath Calgary’s Centre Street Bridge is seen in this file photo from June 2013. (CBC) The recommendations are largely the same for either: a handful of smaller must-have measures, plus a menu of three new reservoir options. For moderate protection, we must pick one new reservoir to build; for higher protection, we must choose two of the three.
First, let’s look at a couple must-have measures which the report recommends for both the higher- or lower-protection scenarios. The easy stuff
The Ghost reservoir, that man-made lake west of Calgary, acts as something of a catch-hold for water on the Bow. The report says the speed with which the reservoir can be drained to make room for an imminent flood — known as the drawdown rate — should be increased. This would be a comparatively minor upgrade.
As well, the report recommends that both the Ghost reservoir and Barrier Lake be used for "flood operations." That means putting in place a plan to drain extra water out during flood season so the reservoirs could absorb a surge of water.
TransAlta operates both facilities for hydroelectricity, and the province has an agreement in place for flood measures at both, along with Upper and Lower Kananaskis Lakes.But these are merely the hors d’oeuvres of Bow River flood mitigation.Now, for the main course — three options for big, expensive, complicated projects. Choose one or two, depending on how much protection you want. Option […]
(Visited 4 times, 3 visits today)