The Government of Alberta manages the production of Flood Hazard Area maps, which identify the areas of land that would be impacted by river flooding during a 1:100 design flood. This means a flood that has a one per cent chance of occurring each year. The flood hazard areas are divided into different zones based on the level of intensity of the flood water.

The maps reflect the existing flood mitigation infrastructure in place at the time of the studies. Going forward, revisions to the Flood Hazard Area maps will be considered when flood mitigation, like the Springbank Off-stream Reservoir on the Elbow River and flood barriers, are constructed or upgraded.

Flooding can cause damage to property, hardship to people and loss of life. Cities use Flood Hazard Area maps to guide local decision-making that will help keep people safe and protect their properties from floods.

A 1:100, also known as a 100-year flood, is a flood that has a one per cent chance of happening in any given year, or a 22 per cent chance of happening during the lifetime of a 25-year mortgage. This doesn’t mean that once a 1:100 flood occurs, it won’t happen again for another 100 years. It’s possible for major floods to happen in back-to-back years. And in the face of climate change, it’s possible this will lead to changes in how the frequency of flooding is calculated in the future.

Over time, smaller floods tend to occur more often than larger floods. For example:

• A 1:10 flood has a 10 per cent chance of happening in any given year.
• A 1:200 flood has a 0.5 per cent chance of happening in any given year.

The draft updated Flood Hazard Area maps reflect the latest understanding of a 1:100 flood risk across the province, including Calgary.

The province has adopted a new approach for flood hazard area mapping. This approach divides the flood hazard area into four categories (two of which are new) that reflect the level of risk:

• Floodway: An area where flows are deepest, fastest and most destructive. New development is typically discouraged in this zone.
•  High Hazard Flood Fringe (New): An area outside of the floodway where the flow during a 1:100 flood would be deeper (greater than 1 metre) and/or faster (greater than 1 metre/second) than the rest of the flood fringe.
  
• Flood Fringe: An area where the flow during a 1:100 flood would be shallower, slower and less destructive than the High Hazard Flood Fringe. This is an existing classification, but the boundaries may have changed.
  
• Protected Flood Fringe (New): An area where dedicated existing flood mitigation infrastructure (such as City-owned and maintained flood barriers) protects the area to at least the 1:100 flood level.
  

The existing Overland Flow Zone designation is being removed, as these areas are being incorporated into the other zones as appropriate.

Visit Bow and Elbow River flood study engagement for more information on draft flood maps for Calgary, including additional resources on flood studies and frequently asked questions.

The new Flood Hazard Area maps will replace previous maps that were developed in 1983 and updated in 1996.

The Government of Alberta released a set of updated draft inundation maps in December 2020 that show anticipated flooding for various flood sizes. The inundation maps are informing the Government of Alberta’s updates to the Flood Hazard Area maps.

Now that the draft updated Flood Hazard Area maps are available, the Government of Alberta is seeking public input. Visit floodhazard.alberta.ca to view Calgary’s map and provide input to the province. 

Many of Calgary’s older communities were built on rivers’ floodplains. Over the decades, our understanding of the flood risk in these areas has improved, leading to safer building practices.

Since the 2013 flood, changes have been made to the Municipal Development Plan and Land Use Bylaw to provide guidance and better regulate development within the Flood Hazard Area.

Today, some property-level flood-proofing is required through building regulations during renovations and new builds. Measures may include:

• Building the main floor above the flood level
• Installing sump pumps and backflow valves
• Elevating furnaces and electrical panels

Other voluntary actions can further reduce damages to homes, such as installing water alarms in the basement or finishing the basement with easy-to-clean materials. You can also get more tips for reducing flood damage.

As part of the Calgary River Valleys Project, floodplain policies and regulations are being reviewed and modernized to protect and enhance our river valleys, while helping shape more resilient river communities and guide updates to the Land Use Bylaw and the Calgary Plan.

Flood hazard areas are not shown on the draft updated map for the Elbow River, downstream of the Glenmore Dam. Flows are currently being re-assessed to include the effect of the Springbank Off-stream Reservoir (SR1), which will be operational in 2025. The flood mitigation provided by SR1 will have a significant impact on 1:100 flood flows along the Elbow River. It will also reduce flood flows in Calgary on the Bow River downstream of the confluence with the Elbow River, but there will be less impact on the Bow than on the Elbow. The potential impacts of SR1 on a wide range of flood flows are being currently assessed and will be reflected in flood maps when the reservoir is operational. We can estimate, however, that with SR1, a 1:100 flood will look more like the current 1:5 flood map. 

There will still be risks that exist in the Elbow River Valley with SR1 in place. As such, some regulation will still be required to ensure these risks are adequately addressed in development planning and building design. Potential risks include:  

• Risk of a larger flood than both the SR1 and the Glenmore Reservoir can handle 
• Risk of increasing flood flows due to our changing climate 
• Risk of high groundwater in the river valley due to high river levels during and after flood events 

The Elbow River is one area within Calgary’s Flood Hazard Area map, which is part of the larger mapping study that covers the whole province. 

Calgary’s new Flood Hazard Area map reflects current flood risk and is based on the 1:100 inundation map published by AEPA in 2020. Because the new Flood Hazard Area map reflects updated risk, including completed flood barriers, some areas on the map will now be shown as “protected.” Not releasing the Flood Hazard Area map for Calgary until SR1 is complete would mean delaying the public release of the latest understanding of how a 1:100 flood would impact all areas of Calgary, not just along the Elbow River.

The goal of the Government of Alberta is for the post-SR1 flood map to be ready as soon as SR1 is operational. Of course, this is dependent on having determined operating procedures and new mitigated flows, and various factors could potentially delay completion of the maps. 

Regulation in the flood zones is the jurisdiction of The City of Calgary. Until the new Flood Hazard Area maps are finalized and City of Calgary policies and bylaws have been updated, development applications will continue to be assessed according to existing regulations. The City also considers information from the draft updated Flood Hazard Area map to provide advisory comments for further resilience. As always, applicants may draw on additional information in support of their applications. 

Both The City of Calgary and the Government of Alberta recognize the importance of having timely maps that reflect current, actual risk. Structural mitigation under construction or in planning phases are not yet reflected in new maps, such as the Sunnyside Barrier. Once projects are completed, the province has a process for reassessing the impacts on calculated flood levels and flood maps and will consider impacts to the flood map. In some cases, including for the Sunnyside Barrier, post project scenarios have been modeled and are addressed in the accompanying PDF report.

Insurers produce and use their own flood maps and have indicated they do not typically use government flood maps.  Both The Government of Alberta and The City of Calgary are happy to speak to property owners about how their property is mapped and can provide information for insurers upon request. Calgarians can contact 311 to inquire about the status of mapping, applicable bylaw regulations, advisory information or development implications on their property.

No. Provincial flood studies focus on river flood hazards – the situation when high water escapes the river and inundates the floodplain. However, many riverside communities in Calgary may experience basement flooding when heavy rain or higher river levels cause changes in the groundwater table. As part of the Calgary River Valleys Project public engagement on floodplain policies and regulations, we’ll use our technical understanding of river conditions to explore the potential for property-level regulations to better manage this risk.

Many of Calgary’s older communities were built on rivers’ floodplains. Over the decades, our understanding of the flood risk in these areas has improved, leading to safer building practices. 

There are a number of actions that have advanced The City’s land use and flood resilience context, including the 2014 updates to flood hazard area regulations in the Land Use Bylaw (LUB) and updates to Section 4.4 of the Municipal Development Plan (MDP).  

As part of the Calgary River Valleys Project, floodplain policies and regulations are being reviewed and modernized to protect and enhance our river valleys while helping shape more resilient river communities and guide updates to the Land Use (Zoning) Bylaw and the Calgary Plan.   

We are committed to engaging with Calgarians and all interested parties prior to making any policy and regulatory revisions.

The following policy and regulatory directions have been raised for consideration and will frame key discussions in Calgary River Valleys Project – Stage 2 engagement:

• How to align planning and development decisions with investments in flood protection.
• How to ensure Calgary’s buildings are equipped to bounce back from increasingly severe floods as our climate changes.
• How to account for different types of flood risk, including both overland and groundwater flooding.

The City of Calgary is not responsible for the development of flood hazard mapping.

Flood hazard maps are developed by the province and provide important information about the most current understanding of our community’s flood risk. The draft mapping released in January by the Government of Alberta reflects the latest understanding of a 1:100 (1 per cent chance) flood risk based on updated the 1:100 flood inundation map released in 2020 and introduces a new mapping approach for the regulatory flood zones, including the new High Hazard Flood Fringe classification. Provincially led public engagement on their new mapping approach took place January 12 to February 12, 2024.

The province has developed two FAQs to help answer common questions about their flood study, available at Bow and Elbow River flood study engagement | Alberta.ca.

The new provincial approach to mapping includes the new High Hazard Flood Fringe designation. The purpose of this new zone is to identify areas outside of the floodway where the flow during a 1:100 flood would be deeper (greater than 1 metre) and/or faster (greater than 1 metre/second) than the rest of the flood fringe.

When the High Hazard Flood Fringe is both fast and deep, it is the second highest flood risk category after Floodway. ​

When a High Hazard Flood Fringe Area is only deep (not fast) and, particularly, when it is surrounded by the Flood Fringe Hazard Area, the overall flood risk is lower. The City of Calgary is choosing to look carefully at this distinction within the high hazard flood fringe, to ensure that updated regulations are in line with the flood risk. ​

Historically, these areas would have been mapped as floodways, but because this designation is the most restrictive and has significant implications on developability, in established communities, the province has designated these areas as High Hazard Flood Fringe instead of Floodway. This allows municipalities more flexibility in how these areas are regulated, to continue to function as thriving communities.

Upstream solutions on the Bow River are critically important for Calgary.

The City of Calgary continues to advocate to the province for an upstream reservoir on the Bow River, recognizing the importance of a project of this nature for both flood resilience and water security in our community.

Completing an upstream reservoir on the Bow River is an important long-term milestone at least 14 years away. There is much work, like design and regulatory review, that needs to be completed before a preferred option is selected, approved and funded. 

Based on the options being explored, it’s unlikely that the reservoir would be large enough to completely mitigate a 2013-level flood without the need for additional community-level measures in some vulnerable, low-lying communities.

If new dams or reservoirs dedicated to flood mitigation are built in the future, and if their impact on flood flows is established to be dependable and significant, the province will re-evaluate hydrology assessments and hydraulic modelling and consider flood map revisions once final construction is completed, if appropriate. In the meantime, the Government of Alberta’s agreement with Trans Alta to operate the Ghost Dam for flood mitigation provides some level of protection on the Bow River for small and moderate sized floods. This 5-year agreement was renewed until April 2026.

The feasibility study for the Bowness flood barrier was completed in April 2021. The results from the study showed a barrier would be effective at helping reduce damage that may be caused by overland flooding. The project would need to be built on private land, and we worked closely with the community throughout the studies. Through the engagement process, many community members wanted more details on the Government of Alberta’s plans for an upstream reservoir before progressing further with the barrier project. As a result, The City is not moving forward with further work related to a barrier at this time and has no project team or funding assigned.

Without any community-level structural infrastructure (i.e. flood barrier) in place in Bowness, we must rely more heavily on both a future upstream reservoir and property-level measures where flood-proofing and changes to permissible development and land use must play a more critical role in achieving greater flood resiliency.

There is currently no assistance available to homeowners located within the flood hazard area who wish to relocate. The properties purchased by the province following the 2013 floods were floodway-specific. The City did not purchase any properties at that time.

The City's 2017 Flood Mitigation Measures Assessment saw Council approve a primarily Protect in Place strategy. The Triple Bottom Line Assessment conducted as part of this work demonstrated that it would be more advantageous to protect communities than conduct significant buyouts and major land use redesignation.

Additionally, we have heard clearly from engagement that our river valley communities have unique cultural, historical and economic significance, so intensive assessment of further buyout has not been a favored resilience tool.

Insurers produce and use their own flood maps and have indicated they do not typically use government flood maps.

Both the Government of Alberta and The City of Calgary are happy to speak to property owners about how their property is mapped and can provide information for insurers upon request. Calgarians can also contact 311 to inquire about the status of mapping, applicable bylaw regulations, advisory information or development implications on their property.

The City of Calgary has a responsibility to be resilient to climate change by responding, preparing and adapting to the associated impacts. In order to prepare for climate change we need to understand what those changes will mean for our local region. Climate change is shifting precipitation patterns, increasing rainfall intensity, causing an earlier melting of the mountain snowpack and creating hotter drier summers. As a result, both drought and river flooding have been identified as top climate hazards for Calgary. 

Climate change is shifting precipitation patterns, increasing rainfall intensity and causing an earlier melting of the mountain snowpack. As a result, river flood hazards are increased for the Bow and Elbow River watersheds.

Updating our land use planning policy and regulations is a key action in Calgary’s Flood Resilience Plan as well as our Calgary Climate Strategy. As part of the Calgary River Valleys Project engagement on floodplain policies and regulations, we are exploring how climate change risk projections will be incorporated into today’s floodplain planning and development decisions and regulations.

The City of Calgary has a responsibility to protect public safety and ensure that our affordable housing options are not vulnerable to hazards such as flooding.  

Generally, floodplain planning aims to reduce the number of people living in flood impacted areas, especially areas where a higher risk of flooding remains. Basements (including living areas or secondary suites) are vulnerable to flooding because underground spaces can quickly fill with water, risking life or personal safety and property damage. During river flood events, basements can be flooded by overland floodwater, or high groundwater that enters the basement through cracks and drains.  Any changes being contemplated for below-ground living spaces only apply to a few areas in our communities, leaving many other areas that are safer and available for increasing housing choice.

It is important that The City of Calgary balances all these priorities, and continues to reduce flood risk while supporting safe, resilient, vibrant and affordable communities.

As our city continues to grow and the information available about flood risk evolves, it is important that we continue to revisit our land use policies and building regulations in flood hazard areas to guide how we plan and develop in river communities to make them more resilient.

Key outcomes of the Calgary River Valleys Project include adding updated river valley and flood hazard policy content in the Calgary Plan and updating Flood Hazard Area regulations in the updated Land Use (Zoning) Bylaw. The Land Use (Zoning) Bylaw Phase 3 engagement is being conducted by the City Building program and the new bylaw is anticipated to be updated in 2026.

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