Over the past several decades, a gravel bar has been forming in the Bow River under the Louise Bridge that connects 10 Street N.W. to downtown. Since the 2013 flood in Calgary, the 10 Street Gravel Bar under the bridge has grown dramatically in size, increasing flood risk to neighbouring communities.

The primary purpose of this project is to mitigate flood risk, while exploring the best possible configuration of the gravel bar for future river safety, recreation and accessibility. A recreational wave is also being explored as part of the project.

Gravel bars form naturally in rivers from sediment movement. They become a concern when they form in and around bridges and constrict flow of the river.

• The 2013 flood resulted in a dramatic increase in size of the gravel bar.
• Since 2013, the gravel bar has become covered with plants including trees which are expected to continue growing in size, increasing flood risk to the area.

The continued growth of the bar and its plants increases the flood risk to the surrounding area, by blocking water flow through the bridge and reducing its capacity.

• This increases water levels upstream that can overflow into the adjacent neighborhoods.
• It also causes erosion along the opposite bank and bed of the river which can put infrastructure, including bridges, outfalls and pathways at risk.

The aerial images below show the gravel bar’s increase in size after the 2013 flood. The green dashed line indicates the riverbanks before the flood, and the purple dashed line indicates the banks after the flood.

Aerial image of project area in 2012 (before flood)

Aerial image of project area in 2014 (after flood)

The approach to lowering flood risk is to realign the gravel bar. This means that the gravel and soil would be removed and redistributed within the area of the river using a nature based approach.

• Realignment of the gravel bar would provide long-term flood mitigation benefits and be the most environmentally beneficial and stable solution.
• We can improve fish and riparian habitat in the area and naturalize the south bank by redistributing the removed materials.

There is a natural wave adjacent to the gravel bar which has been used for recreation such as river surfing.

• This wave has been decreasing as natural sediment movement continues to occur and the gravel bar increases in size.
• The area is hazardous for river rafters and floaters since they need to navigate around the gravel bar and can get stuck on the boulders where the river turns after the bridge.
• Realigning the gravel bar would result in safer navigation for river users.

The project team has conducted a feasibility study to look at incorporating a permanent recreational wave as part of this project. We are working with the Alberta River Surfing Association and the Alberta Whitewater Association who provide expertise and represent river recreation user groups. 

Through partnership with the National Research Council of Canada (NRC), we are assessing the project reach using a physical scale model of the proposed gravel bar realignment. The model will evaluate the performance of the Preliminary Design under a range of river flow conditions. After each run-through we will adjust our design to better address flooding and erosion risks and improve design longevity.

Findings and lessons from this project will be integrated into new guidelines for nature-based solutions which are currently being developed by the NRC. This project is funded in part by the NRC’s Climate Resilient Built Environment Initiative, in support of delivering the Government of Canada’s Adaptation Action Plan, and towards achieving commitments under the National Adaptation Strategy.

The 10 Street Gravel Bar project is occurring in parallel with several other City projects and initiatives that will work in coordination with one another to deliver their mandates. These include:

RiverWalk West
Calgary’s Downtown Strategy
Harvie Passage
Sunnyside Flood Barrier

We are currently in the Detailed Design phase, from October 2024 to September 2025. The construction schedule and impacts will be determined as we move further along in the design process. Please check this page for updates throughout the project.