Flood Mitigation Program

In 2013 the Town of High River, Alberta was struck by a major flooding event, leading to the evacuation of 13,400 people and resulting in damage to 6300 structures which spurred the implementation of flood mitigation actions. The town undertook multiple interventions to both lessen the likelihood of the Highwood river flooding the town and also to reduce the vulnerability of the townspeople should the river overtop its banks again.

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Understanding and Assessing Impacts

Situated not far South of Calgary, the Town of High River finds itself in a strange position of facing both increasing droughts and increasing floods as global climate change continues to shift weather patterns. While not much research has been conducted on the Highwood River, which flows through High River, the Bow River, of which the Highwood River is a tributary, is expected to increase its annual flow by about 42% in some models. These models also indicate that this increased flow will come as the result of higher occurrences of intense rainfall, both of these being factors that could play into another flood like the one High River experience in 2013. The total damage from flooding during the event in 2013 was in excess of $5 billion, and remains one of Canada’s costliest disasters ever. Having lived through a disastrous flood, the Town had a very good idea of exactly what sorts of improvements were needed to be better prepared for future floods. This reduced the need for extensive flood mapping and hand-wringing about the costs; people had seen the damage that can occur. The town received substantial funding from the Provincial government in order to enact the desired changes.

For additional climate information, look at the Resources section of this example (below).

Identifying Actions

Many flood protection plans are based on a theoretical model of what might happen should a flood occur. The Town of High River saw first hand exactly what occurs when their river overtops its banks and therefore knew exactly what parts of town were most vulnerable. Knowing exactly where the flooding was likely to occur immediately moved the Town’s planners onto the next phase of determining how to reduce harm from the next flood. It was determined that a mixture of physical hardening and managed retreat would be implemented. This hybrid strategy adopts what some would call a ‘safe-to-fail’ in that it expects the (now reinforced) banks to be overtopped eventually and works to reduce the number of people and structures in the potential flood area. Perhaps to most important aspect of this work is the singularly united political will towards building back better in the wake of a disaster. The Town took the opportunity presented by the destruction to remodel its downtown business core into a more attractive locale and reports indicate that people find the newly-developed region more attractive and livable than before. A proactive and creative planning process, with plenty of input and support from the Provincial Government, recognized the opportunity to make improvements to the community itself while also increasing its resilience to flooding.

Implementation

There were three main components to the flood mitigation program. First, the construction of dikes, built to 1-meter above the 2013 flood height. Several of these are completed, with several more on the way. Secondly, a major bridge that created a chokepoint in the river was removed and is scheduled to be rebuilt in a better position. And finally, a program designed to leave ‘room for the river’ in which properties were bought out and people moved away so that the river’s natural course could be widened, allowing for reduced flow rates and a larger buffer between the river and homes. By 2018, the Town had invested over $200 million in flood protection improvements.

Outcomes and Monitoring Progress

High River is now considered by some to be one of the most secure communities in the nation against flooding. One of the primary factors contributing to the success of this program was the unified political will to make positive changes in the wake of disaster. This is credited with allowing for an expansive program of mitigation strategies. The outcome of creating a more attractive and livable downtown core was a great example of the synergies that can be realized with proper planning and a little creativity.

Next Steps

There are still several more dikes in the planning and construction phases. There is also the need to maintain vigilance in ensuring that future governments do not relax the restrictions about building in the flood zone, maintaining the ‘room for the river’ that was implemented in the immediate response.

Resources

Link to Full Case Study

Additional Resources: 

 

Using climate change projections enables better adaptation decisions, as it allows you to better understand how the climate may change.  To learn how to choose, access, and understand climate data, visit ClimateData.ca’s Learning Zone.

For more information on variables that may be useful in work related to flooding, visit ClimateData.ca and click “Explore by Variable”. Here you will find pertinent future climate projections related to flooding including: