Phase 1 – Feasibility study update
Thanks to everyone who provided their input on the feasibility of a community flood barrier in Bowness.
After extensive community engagement and technical studies, the feasibility study is complete. We have advised Council that we do not plan to move forward with design and construction of the flood barrier at this time.
Although the flood barrier is technically feasible, after listening to the community we heard support for flood mitigation solutions; however, a number of concerned residents raised significant questions about the Government of Alberta’s plans for an upstream reservoir, what can be achieved and how it could work with a potential barrier to reduce their risk of flooding.
We recognize there are two key Government of Alberta initiatives underway - the Bow River Reservoir Options study of upstream mitigation on the Bow River and updates to Calgary’s Flood Hazard Area maps – once completed, these will inform Bowness’ remaining flood risk and may influence cost-benefit of the potential barrier. This project is complex and community feedback reinforces the decision to take the time to get more clarity on the Province’s upstream plans before proceeding further.
Since we are not seeking direction at this time, this update will not be part of the public agenda and discussion at the UCS Committee meeting on April 28.
ABOUT THE PROJECT
When the June 2013 flood caused the Bow and Elbow Rivers to spill into the streets of Calgary, Bowness was one of the worst hit areas of the city. Many residents faced significant property damage or the permanent loss of their home, and long-term impacts to their mental health. No one wants this to happen again, so we’re exploring the feasibility of an overland flood barrier, to help keep the community safe, vibrant and make it more resilient.
The proposed overland flood barrier is one of the flood protection measures in Calgary's Flood Resilience Plan. The plan is a three-layered approach where the overland barrier would work with upstream flood protection, provided by a new reservoir on the Bow River, and modified operations at TransAlta's Ghost Reservoir. Working together, these measures would help us better manage our flood risk and avoid the type of damage we saw in 2013.
BARRIER DESIGN OVERVIEW
Overland flood risk in Bowness today
The results of the river modelling show two key low-lying areas along the river in Bowness in the map below. These areas are the source of overland flooding in the community. Approximately 160-180 properties, including roads, vital public infrastructure and a long-term care facility are at risk overland flooding when the river is flowing at 1,230 m3/s.
Area #1: East of Bow Crescent to 67th Street
Water begins to enter the community and cause overland flooding in this area when the river is flowing at 690-800 m3/s.
Area #2: East if 60th Street and ending at the Hextall Bridge
Water begins to enter the community and cause overland flooding in this area when the river is flowing at 830 m3/s.
Proposed flood barrier alignment and design
Location: The red line illustrated in the map below shows the potential for an overland barrier alignment that targets the two key low-lying areas on the north and south ends of Bow Crescent.
Total length of the flood barrier: 1.9 kilometers. It is divided over two sections that target the low-lying areas along the riverfront.
Number of properties identified for a flood barrier: 75 riverfront properties. Negotiated easements would be required with individual property owners.
No increased flood risk to neighbouring downstream communities: Given the width of the Bow River and floodplain, the overland flood barrier has a small impact on affecting the water levels and does not increase the risk of flooding in downstream communities (e.g. Montgomery).
Estimated cost: $25-35 million. This range accounts for different feasible alignments on individual properties that carry different costs and the variability in land costs. Following further engagement, a more refined cost estimate will be used in the evaluation of the feasibility of the overland flood barrier.
- The barrier may include a combination of flood walls, retaining walls and earth berms depending on the alignment and property-owner preference.
- Majority of properties (60%) would require an overland barrier that is 1 meter high or less.
- The minimum overland flood barrier height is 0.4 meters, and the maximum overland flood barrier height is 1.7 meters.
- The barrier design does not and will not, incorporate, any design for public access or an access road.
In the next two years as the Government of Alberta completes their upstream reservoir feasibility study and flood hazard area map updates progress, we will share this information with the community and how a flood barrier would work with a new upstream reservoir to provide greater protection. From there we will re-assess and determine how to proceed.
The risk of overland flooding hasn’t changed in Bowness and while that risk remains, we will continue our work to keep the community safe.
The modified operations of TransAlta’s Ghost Reservoir was recently renewed until 2026, which will help reduce the risk of smaller floods (up to a 1:20 event) until other mitigation is constructed. In the event of a flood, our emergency response plans are ready to help keep residents safe.
The Bowness Flood Mitigation Working Group was established in spring 2019 to build mutual trust and understanding amongst all stakeholders and support and strengthen stakeholder engagement during the study and research components of the Preliminary Design Phase. The Bowness Community Association, Bowness Responsible Flood Mitigation Society and The City of Calgary agreed to jointly establish the Bowness Flood Mitigation Working Group in May 2019.
The Working Group provides advice to The City of Calgary Bowness Flood Barrier Project Team and advocates for full consideration of the interests of all stakeholders, including the directly impacted residents and businesses, in the community of Bowness in determining the best flood mitigation solutions for the community.
Purpose of the Working Group
As representatives of the larger community of Bowness, the Working Group is committed to providing advice to The City of Calgary Bowness Flood Mitigation Project Team. Meetings will continue throughout the Preliminary Design Phase until such time as City Council makes a decision on the next phase of the Bowness Flood Barrier, which is anticipated in Q2 2020. The Working Group may continue to meet after that date if deemed appropriate.
The Working Group will support The City barrier team engagement activities, with a focus on ensuring the Bowness community and directly impacted residents are fully informed, have the opportunity to provide input and have confidence the Bowness community is treated fairly, respectfully and equitably when compared to the rest of Calgary relative to flood protection.
For more information, visit bownessfloodmitigationworkinggroup.ca.
PROVIDE YOUR INPUT
Thanks to everyone who provided their comments on the feasibility of a community flood barrier in Bowness. Engagement for this phase is complete
Based on engagement we completed with the Bowness Flood Mitigation Working Group, social criteria were identified to help evaluate the feasibility of an overland flood barrier in Bowness. As part of the online evaluation, we’re asking the community to help rank the importance of each criteria and to comment on the benefits and concerns they have with an overland flood barrier. A summary of the feedback received from the community will be posted on the project’s webpage.
Your feedback will help determine the feasibility of an overland flood barrier and inform our recommendation to Council on the next steps.
We would like your help determining the importance of each of the Bowness flood barrier social criteria. The social criteria (in no particular order) and its description are found in the table below. The table also gives you some 'guiding questions' which are useful to consider when determining the importance of each social criteria. Once ranked, the social criteria will be used by the project team during the evaluation process of the overland flood barrier.