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.

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 poplar trees which are expected to continue growing in size which will further contribute to the bar's impacts.

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. 

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 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 increase the flood and groundwater levels in 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 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.
• It will also 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 in quality 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 and wood debris where the river turns after the bridge.
• Realigning the gravel bar would result in safer navigation for river users.

There does not appear to be any technical, regulatory, or safety reasons to exclude a recreational wave from the project. From a technical perspective, this location is ideal for this type of feature due to the hydraulic and geotechnical conditions. Based on this, detailed design of the recreational wave will move forward, however its construction is still dependent on several factors including funding, regulatory approvals, and operational viability.

River engineering of the project has been conducted at the highest level possible for this type of structure and included research partnerships with both the University of Ottawa and the National Research Council of Canada (NRC). Through these partnerships a physical scale model of the proposed gravel bar realignment was constructed to confirm the performance of the proposed nature based solution.

Findings and lessons from this work were integrated into the project design. This work was partly funded 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. The construction schedule and impacts will be determined as we move further along in the design process. but will be dependent on funding and regulatory approvals. Please check this page for updates.