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Bowness Flood Barrier FAQ

What is the Bowness Flood Barrier project?

The Bow River is an integral part of the Bowness community. Being so close to the river means there will always be a risk of flooding. In Bowness, flooding can happen when the flow rate is approximately 850 cubic metres per second (m3/s), which has a 12 per cent chance of occurring each year. For context, the ‘normal’ spring flow rate ranges from 70 - 400 m3/s.

In 2016, The City hired external consultants to update the Provincial Flood Damage Assessment study for Calgary, and to assess and recommend future resiliency and mitigation measures. The resulting document, the Flood Mitigation Measures Assessment (FMMA) report, was approved by Council in spring of 2017. Recommendations include a combination of watershed-, community- and property-level mitigation solutions to create a flexible and adaptable flood risk management program.

The Bowness flood barrier project was one of the recommendations from this study. Much of the riverfront property is privately owned in Bowness and The City will work with individual property owners to gather their input, and discuss their concerns and ideas as the detailed design work gets underway.

Why does the strategy include a flood barrier in Bowness?

The report proposed several recommendations that would work together to support flood protection efforts on the Bow River. These include a new upstream reservoir, modified operations of the Ghost Reservoir, and flood barriers in the neighbourhoods of Bowness, Sunnyside, and Pearce Estates Park in Inglewood. Homes, buildings and other infrastructure in Bowness are impacted when river flows reach levels of 850 m3/s. The flood barrier will protect buildings, streets and infrastructure up to flow rates of 1,230 m3/s. There is a 5 per cent (or 1 in 20) chance that such floods will occur in any year.

Once Bowness is protected by the barrier so that flows of 1,230 m3/s can pass through Bowness without damage, the upstream reservoirs (including the existing Ghost Reservoir) can be operated to provide better flood mitigation for all downstream communities. In combination, upstream reservoirs with the Bowness flood barrier can mitigate much larger floods than the reservoirs could alone.

What stage is the project currently in?

The proposed Bowness Barrier project is currently in the preliminary design phase. This phase will extend from fall 2018 to fall 2019. This phase consists of gathering feedback from community members, conducting site surveys and completing engineering studies and analyses.

Throughout the preliminary design phase, the project team will be working with individual property owners to gather their input, discuss their concerns and develop ideas to be potentially incorporated into the finalized preliminary design options.

These design options are tentatively scheduled to be ready in spring 2019 for review and will be presented to riverfront property owners at that time.

How is the project being funded?

A detailed project plan is in the process of being developed, but it looks like the project will be funded 70/30 between the Province and City, respectively.

The City is also actively working to determine Federal funding opportunities to support any flood mitigation work, which would have similar cost share obligations for The City.

Is a barrier a cost-effective solution?

The completed conceptual design work included a high-level cost-benefit calculation. Estimates of the economic benefits of the barrier were calculated based on the amount of flood damages that will be prevented once the barrier is in place.

As we proceed through the detailed design stage, the cost-benefit will be refined and confirmed. The final cost-benefit of the project will depend on complexity of the final design (e.g., location, extent and type of barrier), property easement agreements, and construction costs.

What studies have been done on groundwater?

Groundwater was modelled during the development of the barrier concepts. This was a high-level study based on generalized soil types. During detailed design, the soil types and groundwater will be investigated in more detail. By understanding how groundwater and the river interact, we’ll better understand the potential impact from groundwater flooding to the community. We expect to learn:

  • Site specific details on the ground conditions, geology, aquifer(s) and groundwater surface water interaction.
  • How quickly changes in the river water levels lead to changes in groundwater levels.
  • How high the groundwater level rises from various flood events.
  • To what extent do changes in the river level affect groundwater.

The information gained from this study will help evaluate the effectiveness that various flood barrier designs have in reducing the impacts associated with rising groundwater levels during floods.

How will the barrier deal with local and private lot drainage?

Study of local lot drainage will be conducted as part of the technical design process and the barrier will be designed with detailed consideration of local topography.

What level of protection is the project trying to achieve?

Homes, buildings and other infrastructure in Bowness are impacted when river flows reach levels of 850 m3/s. The flood barrier will protect buildings, streets and infrastructure up to flow rates of 1,230 m3/s. There is a 5 per cent (or 1 in 20) chance that such floods will occur in any year.

Once Bowness is protected by the barrier so that flows of 1,230 m3/s can pass through Bowness without damage, the upstream reservoirs (including the existing Ghost Reservoir) can be operated to provide better flood mitigation for all downstream communities. In combination, upstream reservoirs with the Bowness flood barrier can mitigate much larger floods than the reservoirs could alone. With the three part plan in place, Bowness would be protected from flood events up to the 200 year return period flood event.

If the detailed design work hasn’t been completed how do you know that barriers are the right choice?

Technical studies have shown that even with a potential new upstream dam, local flood protection is also required to protect Bowness. The location, type and extent of the final structure will be determined during the detailed design.

As part of the preliminary design process, the project team is gathering detailed information about each property, consulting with home owners and community members and conducting technical studies, including geotechnical and groundwater studies. All of this information will be taken into consideration into our recommendation of what the best flood barrier for Bowness will look like.

Does The City really need to build all of the planned barriers? Can’t it just build some?

Although the detailed, technical design work has not yet been completed, we know that the final solution will need to be fully constructed in order to provide adequate flood protection for Bowness.

When will I know where and how my property will be impacted?

It is too early to provide details about specific properties with any certainty. We have not yet entered the detailed design phase, so while we have an idea of which properties will be affected, we don’t understand the full extent to which they would be affected.

How many homes will be affected by this project?

The work that has been completed to date identified approximately 130 riverfront properties within the proposed barrier alignment. That said, because the technical design work has not yet been completed, this number could change.

What is the proposed height of the barriers?

From the conceptual design, we have an idea of potential barrier heights. However, the unique elevation (height) of the riverbank is a key factor in determining the height and location of the barrier for each property and this be refined during the technical design phase. Our initial conceptual work reflected that barriers may range anywhere from 0.5 metres (1.5 feet) in height in some areas to 2.0 metres (6.5 feet) in height in other areas. The average barrier height over the length of the project is 0.8m (2.62 feet).

What will the barrier look like?

The City’s conceptual work looked at earthen berm barriers as well as floodwalls. Once we enter the detailed design phase, we will analyze where those barriers should be placed, how they function, how tall they are, and aesthetics.

It’s important to note that because much of the riverfront property in Bowness is privately owned, The City will work with individual property owners to gather their input, and discuss their concerns and ideas as the detailed design work gets underway.

How do I find out if a barrier is planned for my property?

The flood protection work in Bowness focuses on the area along the river’s edge, roughly between the CP Rail tracks and the Shouldice Bridge.

As part of the preliminary design phase, The City is meeting with private property owners to better understand the unique characteristics of their property and discuss ideas on how to best integrate the barrier into the existing landscape while protecting the community.

Citizen and community engagement is a critical piece of this project. We realize the potential impacts and are committed to working with you to ensure that you have the information you need and the right channels for sharing your thoughts, concerns and ideas.

What process does The City use to engage with property owners?

On September 20, 2018, The City hosted an information session with riverfront property owners to provide them with an update about the project, discuss upcoming timelines and engagement opportunities. Beginning in fall 2018 and continuing into spring 2019, The City would like to meet one-on-one with individual to seek their input into the preliminary design of the barriers.

Will the process be the same as it was for the Inglewood Flood Barrier?

The Inglewood Flood Barrier project occurred between, approximately, 1998 and 2011. It protects the community of Inglewood from river flooding. The barrier is located on public land and 12 private properties. As the local context, geography, design requirements, community, land owners and economic context are all different, this project will draw on lessons learned from the Inglewood project, but will not be the same.

Would a barrier on my property reduce my privacy?

The purpose of a barrier is to provide flood protection. Unlike barriers on public property that might be suitable for recreational access, The City recognizes that privacy is of concern to property owners along the river. Therefore, public access in Bowness is not being considered. We will work to maintain privacy and security on private property as part of the design process.

Would a barrier incorporate public access for recreation along the riverbank?

The City has no plans to create public access or encourage recreation along the barrier or riverbank in front of private property in Bowness.

How would trees be impacted during the construction of the barrier?

Minimizing the impact on trees is an important consideration of the proposed Bowness Flood Barrier project. We understand the value trees serve in providing natural habitats, reinforcing the riverbank, and contributing to the natural environment that exists along the Bow River.

We are still in the preliminary design phase of the project, so it is too early to determine how many trees will be impacted, but our objective is to design a structurally effective barrier that is integrated into the environment while minimizing the impact on existing trees as much as possible.

To achieve this objective, over the next year we will be taking an inventory of all the trees that fall within the proposed alignment of the flood barrier.  We will be assessing the species, age and health of the trees and determining which trees would impact the construction of the barrier. While the loss of some trees will be unavoidable, efforts will be made to select trees for removal that are at the end of their life or otherwise unhealthy.

In addition, during our one-on-one site visits with riverfront property owners, we are working directly with residents to identify trees that have a special significance to property owners. From there, we will determine what avoidance or mitigation measures we can put in place to avoid cutting these trees.

As part of our restoration of the natural environment we will work with homeowners to plant as many replacement trees as possible on the site.

How do I find out if my property is at risk of flooding?

There are a number of maps that are available on The City’s website that can help citizens determine their flood risk. For more information, visit Calgary.ca/floodinfo and click on the ‘Mapping’ section to view maps that can show you whether your property is at risk.

What if I am planning on selling my property? What can I tell prospective buyers who ask about the Bowness barrier project?

Homeowners are free to discuss the project with potential buyers, using The City’s website as a resource. Since the project is still in the early stages of planning, the website will be the best resource for up-to-date project information.

Why is The City not buying out the properties at risk of flooding?

From a financial perspective, it was deemed impossible to purchase all properties in the current flood hazard area. The buy-out costs have been estimated to be up to several times greater than the cost of developing new upstream mitigation. The costs that would be associated with building demolition, conversion of properties to parkland, and incentives to assist homeowners to relocate make this too costly an option. Property buy-outs are also very disruptive to communities and have significant impacts on property owners.

Would barrier design include river bank erosion protection?

Erosion potential of the adjacent bank would be assessed during the barrier design. Where required to create a stable barrier, erosion protection will be incorporated into the design.

Would a barrier increase flood levels on the opposite bank or in downstream communities?

Part of the design process includes verifying the impact that any potential flood protection measures could have on flood levels both upstream and downstream. Studies to date show that the impacts of a barrier would be negligible.

How would barriers affect riparian areas or aquatic habitats?

Protecting the riparian habitat in all of our rivers and streams is important to The City. The City has a Riparian Action Program, which aims to protect riparian habitat. The impact to the riparian areas of all projects are carefully considered and where possible, riparian restoration is undertaken.

With the exception of 2013 and 2005, Bowness hasn’t flooded in a long time. How great is our risk to flood again?

It’s true that Calgary had several decades without a flood event, however, with a changing and warming climate, extreme rainfall and floods are expected to happen more frequently.

Updated November 2018