Improving flood protection in Alberta

By Gaven Tang and Wolf Ploeger

The devastating floods that ravaged through Alberta in June 2013 caused as much as $5 billion in damage in the province. It was a harsh reminder of the widespread destruction that can be caused by a 1-in-100-year (Bow River) or a 1-in-500-year (Elbow River above Glenmore Reservoir) flood event.

In the years since, Alberta has become an example to follow in how to prepare for what comes next, taking a responsible approach to flood awareness, protection and resilience. The work that has taken place in just over a decade has prepared the province for the reality that someday, perhaps in the not-so-distant future, another extreme weather event will materialize in the region.

Using smart infrastructure solutions informed by innovative data solutions, communities can take significant steps in protecting residents from a once-in-a-lifetime natural disaster.

Leading up to 2013

Before explaining the measures that have taken place since 2013, it’s important to understand the situation prior to this.

By 2012 WSP had completed detailed flood mapping for the City of Calgary that indicated that the flood resilience of low-lying areas such as downtown (including the famous Stampede Grounds) and many residential areas along the Bow and Elbow Rivers was at a level of a 25- to 50-year flood event. The City of Calgary then asked WSP to develop a flood response plan. We prepared detailed maps and figures that would inform City staff where to implement temporary flood protection measures like sandbagging, dirt berms or other barriers, and at what height, depending on the expected severity of the predicted flood impacts. This allowed for a rapid and targeted response as it was known that the response time to a significant flood would be less than 24 hours.

The insights generated from the work completed just in time before the 2013 flood provided a comprehensive road map for the City to respond to the extreme rain event in June which resulted in the once-in-a-generation flows in the Bow and Elbow Rivers.

It is important to note that the flood damage wasn’t nearly as severe as it may have been thanks to some of the infrastructure that was already in place and the additional protection provided by the temporary barriers that were quickly set up. Proactive operation of the The Glenmore Dam helped reduce the impact of flooding along the Elbow River from a 1-in-500-year to an approximate 1-in-100-year level downstream of the dam. Within the Bow River catchment upstream of Calgary, several dams also helped to attenuate (hold back) flood waters. Without this infrastructure already being in place, the devastation would have been far greater than the widespread damage that occurred.

Severe flooding also occurred along several other rivers that originate in the eastern Rocky Mountains slopes such as the Highwood River, Sheep River and the Red Deer River.

Delivering Solutions

As the region cleaned up the mess left behind by the widespread flooding, government action followed closely behind. Within a few months, the provincial government offered to purchase some properties at assessment value, most impacted by the floods. This allowed homeowners in the most vulnerable area to re-locate if they desired to, rather than work to rebuild their properties and improve their resilience.

The city and province then joined forces to do a cost-benefit analysis of the flood resilience measures that could be implemented relatively quickly. We worked with another consultant to provide a comprehensive list of the projects that could be undertaken (groundwater pumps, berms, floodwalls etc.) to then determine what would present the best overall value. From there, the governments were able to work together to determine the investment needed to address projects from the list on an annual basis.

Then there was the large-scale work that was needed. It was recognized that additional storage capacity was needed upstream of the City, and not enough could be added to the existing infrastructure. The proposal was brought forward for the Springbank Off-stream Reservoir, which would provide protection along the Elbow River. The 3,700-acre dry reservoir, located approximately 15 km west of Calgary, would help divert millions of litres of water during a flood event which could then be slowly released back into the watershed when the system could bear it. Completed in the first half of 2025, the 29-metre tall, 3.8 km long storage dam and reservoir will now protect residents along the Elbow River.

An upgrade was also recommended, and completed, for the existing Glenmore Dam within the City on the Elbow River. The installation of a series of new 2.5-metre-high steel gates has added significant additional capacity, estimated at upwards of 10 billion litres. The new Springbank Reservoir and the upgraded Glenmore Dam will be operated in tandem to achieve optimal reduction of flood flows.

The province also led an extensive program for many municipalities to develop flood mapping for their community, maps that would allow them to understand vulnerabilities and act on them. Our team has been fortunate to develop numerous of these maps throughout the province, which has led to new investments in flood resilience and better flood awareness.

Lastly, the province will move forward with the next phase of designing a new dam on the Bow River upstream of Calgary to provide additional flood and drought resilience.

The work done to date, especially on the Elbow River and within the City of Calgary, has created significant improvements to the community’s overall flood resilience. From significant vulnerabilities at the 25-to-50-year flood event level in 2012, the City is now in a place where notable widespread flooding is not likely to occur for floods smaller than a 200-year event. That level of improvement has and will continue to create infrastructure and property damage savings in the billions of dollars. And work to further improve this is still ongoing.

Thanks to the ongoing government commitments to improving resilience in the Calgary region and beyond, Alberta residents and property owners are now far less exposed to the potential impacts of a substantial flooding event.

Wolf Ploeger is the Director, Water Management, Earth and Environment, Prairies and North for WSP in Calgary, Canada. Gaven Tang is a Group Manager and Principal River Engineer for WSP in Calgary, Canada.