Critical document: Flood Mitigation Options Assessment Report
Executive summary now available publicly
In May 2017, the City of Calgary released the Flood Mitigation Options Assessment Report, prepared by the IBI Group and Golder Associates.
The report is a further and more refined study to the initial study work conducted by IBI in 2015 (available here). The research used sophisticated modelling data to provide a cost-benefit analysis to various upstream and community-level mitigation options being analyzed in the months after the 2013 flood. The results clearly suggested that, on a cost/benefit ratio analysis, the Springbank Off-stream Reservoir (SR1) was the optimal first upstream mitigation project for the Elbow River. But it was not a “triple-bottom-line” assessment that would include environmental and social costs alongside economic costs.
The full May 2017 Flood Mitigation Options Assessment Report is available here, in all its 371 page glory (click “Add to Cart” and then “Checkout Now” and then “Submit Order” and then “Download”). It is a more comprehensive and definitive study of flooding impacts to Calgary and the cost/benefit analysis of the various mitigation options.
Because of the heft and complexity of the report, CRCAG asked the City to provide an “executive summary” for distribution to the public. This took a while (and we greatly appreciate Water Services’ efforts in this), but the “Flood Mitigation Options Assessments Study Summary” report has now been posted.
Note:
It’s a bit confusing because this “Flood Mitigation Options Assessment Summary” is posted on the “Flood Mitigation Measures Assessment Report” webpage, which is a different 14-page report issued following the City’s community consultations last year. This is the report, which was approved by Council in April 2017, upon which the City is proceeding with its local area mitigation work (including the proposed Bowness berms).
Highlights from the Flood Mitigation Options Assessments Study Summary
Below, we’ve cut and pasted verbatim excerpts that caught our eye:
The Key Conclusion:
Based on the results of this study and other work undertaken since 2013, The City recommended an informed flood resiliency and mitigation strategy, which was approved by Council in April 2017. Subsequently, an implementation plan was approved by Council in June 2017 that outlined a combination of watershed and community level mitigation that allows flexibility and adaptability in managing flood risk.
The recommended scenario is Scenario 8, which has the lowest residual average annual flood damages, and provides the most timely and equitable protection to communities at risk of flooding from the Bow and Elbow Rivers.
Recommended Scenario: #8
Upstream reservoirs on the Bow River (upstream of Calgary) and Elbow River (SR1).
Low-height barriers for Sunnyside, Bowness and Pearce Estates on the Bow River.
1:200 barrier for the downtown core.
While The City of Calgary can implement some mitigation measures within its jurisdiction, it is essential that upstream mitigation is built to provide the level of protection needed for Calgary. The City will continue to support and advocate for upstream mitigation on both the Elbow and Bow Rivers.
As approved by Council, work is already underway to fund, design and construct barriers to complement a potential new reservoir on the Bow River that would achieve equitable protection for all at-risk communities across the city.
The City has implemented several lessons-learned from the 2013 flood, and continues to improve forecasting, emergency response, citizen education and communication, and preparedness for citizens, businesses and city departments.
Other non-structural solutions, such as policy, regulations, education, incentives and selective property buyouts are being explored to complement structural measures and provide further flood resiliency for Calgary.
Other Observations
- The study results showed that the Springbank Reservoir (SR1) on the Elbow River removes a significant portion of flood risk, as does the current 5-year agreement between the Government of Alberta and TransAlta to operate the Ghost Reservoir on the Bow River for flood mitigation. Together, these measures reduce the city-wide flood risk by another 30%. This scenario has a very high benefit-cost ratio of 3.2. It does, however, leave a high residual risk ($45.2 Million per year), largely on the Bow River, as the level of protection provided in this scenario is not as high on the Bow as the Elbow.
- The study acknowledges that while not developing in a floodplain eliminates flood damages, historic development patterns have led to a complex relationship between cities and floodplains, and the social and economic value of development in floodplains is significant.
- Buyouts of properties in a hypothetical floodway based on a 200-year flood were assessed as a mitigation solution. The results showed this measure is one of the most costly, even though it did not provided mitigation to all properties at risk of flood damage. While the study acknowledged flood damages would be completely eliminated for the bought-out properties, the high cost of purchasing the properties made it the only scenario that was not cost-beneficial.
- Property ownership and development within Calgary’s floodplain is diverse, spanning many land uses and demographics. The cost of buying out all properties at flood risk in Calgary and converting them to parkland is extraordinarily high (over $2 Billion) – far more costly than any other mitigation option assessed. Not all properties have to be bought out to reduce future flood damages. Buying out select properties, however, leaves many other properties still in need of protection. The financial and social implications of buying properties must be considered very carefully.
- The study suggests that flood insurance should not be relied on to achieve acceptable levels of protection. The costs and levels of risk involved suggest that premiums for unmitigated homes are not viable for most property owners. Insurance is a tool to redistribute the financial risk of flooding, not prevent flood damages.
Please take the time to read at least the shorter Flood Mitigation Options Assessments Study Summary. It’s a critical document.
Regards,
Your CRCAG Board