HSCA Position re Flood Mitigation Measures

November 19, 2016 by CRC Action Group in News

Hillhurst-Sunnyside Comm. Assoc. Position on Flood Mitigation Measures

 

From our Friends at the HSCA

 

The City of Calgary recently held a series of facilitated workshops, as part of a broader public engagement plan, to obtain input to various flood mitigation strategies to protect all of Calgary. These strategies include upstream mitigation infrastructure on the Bow and Elbow rivers, local area berms and flood walls, development policy options, and a combination of these.

 

For information on this public engagement, go to: “engage.calgary.ca/flood”

 

The folks with the HSCA who have dedicated countless hours on behalf or their community and all of Calgary to address the many issues resulting from the 2013 flood, have allowed us to post their position summary, to let you know their views and what’s important to this great neighbourhood. Their comments have relevance for all Bow and Elbow river communities. Thanks in particular to Charlie Lund for his tireless efforts, and those of that core team:

 

HSCA position summary:

 

1. Establish an appropriate flood protection standard of 1:350 instead of the inadequate 1:100. Some climate change has happened and it is important for our infrastructure to be adapted to the new reality of increasingly frequent extreme events.

 

2. Increase the Sunnyside berm height and add a groundwater barrier to protect the community now while waiting decades for upstream mitigation. The Sunnyside berm improvements are justified by estimated annual avoided flood costs. Protection for Sunnyside must match the protection provided to the expensive condos downtown and must compensate for the ill-advised reinforcement of the Prince’s Island Park Causeway.

 

3. Build at least one new dam upstream of Calgary, but recognize that construction is likely decades in the future – economically sensible in-city barriers can be built quickly to complement. Implement permanent management improvements at TransAlta’s reservoirs while enabling rapid lowering of Ghost reservoir to balance flood, drought and recreational purposes.

 

4 Do not depend on ineffective bylaw/code changes – instead build reliable, resilient flood mitigation. Non-structural measures must respect the character of existing communities and must be effective for all existing structures. Note that the City recently relaxed rules for basement secondary suites.

 

5. Infrastructure must protect against reasonably foreseeable future floods and move Sunnyside down to medium risk so that affordable flood insurance could be available to protect against residual risk. One measure of the adequacy of community flood mitigation is that flood insurance is available and affordable.

 

Detailed Points:

 

Berms and Dams

 

1. Protecting Sunnyside is cheaper than buying out properties and converting to parkland

 

− Must buy out all properties or no properties for a given community (Sunnyside)

 

− Buy-outs are the only option if the community cannot be made safe

 

− Sunnyside assessed total market value (2016): $929M

 

− Plus City facilities, plus demolition, plus park development

 

2. Establish appropriate flood protection, likely in the 1:200 – 1:500 return rate range

 

− Use survey of flood protection standards elsewhere as guidance

 

− Note that 1:1,250 used for critical infrastructure in Netherlands

 

− Consider combined effect of upstream mitigation and local barriers

 

− Move Sunnyside into a low-medium risk category, so flood insurance becomes affordable

 

3. Design with reasonably foreseeable storms in the Bow basin, not storms centred on the Elbow or south.

 

4. Increase Sunnyside berm height to protection standard plus 0.5m freeboard

 

− Compensate for provincially funded Prince’s Island Park Causeway reinforcement

 

− Further increase as required to balance any shortfall or delay in upstream mitigation

 

− Address ground water contribution – install below grade barriers as required

 

− An improved berm for Hillhurst Sunnyside has strong triple bottom line benefits

 

− Consider berms for all river communities and build where economic while waiting for upstream dams.

 

− Average annual avoided flood costs of $12M/y for Sunnyside provides strong incentive to build now.

 

− Berms must protect to the same standard on both sides of the river (eg. if expensive downtown condos will be protected to 1:200 then the mixed Sunnyside neighbourhood across the river must be 1:200).

 

5. Remove obstructions to flow in the river channel

 

− Eliminate rock bars before vegetation makes them barriers

 

6. Implement all practical Bow River upstream mitigation options.

 

− Expedite Bow Valley Working Group process and implement recommendations

 

− Support at least one new Bow River dam upstream of Calgary, but recognize that construction is likely decades in the future – economically sensible in-city barriers can be built quickly to complement.

 

− Implement permanent management improvements at TransAlta’s reservoirs

 

− Enable rapid lowering of Ghost reservoir to balance flood, drought and recreational purposes

 

7. Build reliable, resilient flood mitigation – do not depend on ineffective bylaw/code changes

 

− Building codes should reflect existing community and upstream flood protection

 

− Non-structural measures must respect the character of existing communities and must be effective for all existing structures.

 

− Note that it is City policy to increase density in inner city neighbourhoods, one example being the recently relaxed rules for basement secondary suites.

 

8. Infrastructure must protect against reasonably foreseeable future floods, with affordable flood insurance to cover residual risk.

 

− One measure of the adequacy of community flood mitigation is that flood insurance is available and affordable.

 

Pumps and Pipes

 

9. Much of Sunnyside flooding is caused by water piped in from the upper plateau (Banff Trail etc)

 

10. The Hillhurst Sunnyside Community supports a rainfall design basis of 1:5 with river gates closed, down from the 1:50 usual standard for established communities and the 1:100 standard for new communities.

 

− The 1:5 standard is a balance of protection and cost, considering the type of weather systems likely when the river gates must be closed.

 

11. Implement Upper Plateau Storm Drainage Separation Project to keep large volumes of rain water off Sunnyside streets when the river is high.

 

− Enables proper handling of upper plateau rainfall, without damaging Sunnyside.

 

− “Shovel ready” project with initial engineering study estimate of $37M

 

− Identified as a “Potential Future ACRP Eligible Project”, but the value is more than ACRP is intended to support. This could be a good project for Federal Green Infrastructure funding.

 

− One way or another we need to find a way to fund and move this project forward ASAP.

 

12. Fully implement Hillhurst-Sunnyside Storm Water Pump Station Project to lift water over the berm when the river is high and the outfall gates are closed.

 

− Consistent with designs for new communities – but no room in Sunnyside for storage basins

 

− The four storm water pump stations are required at river levels of only 1:20 or below – these are “no regrets” projects regardless of any upstream mitigation.

 

− These projects are “shovel ready” with an initial engineering study estimate of $40M total

 

13. Support rebuilding of the Sunnyside Pump Station #2 (which is already ongoing)

 

14. Support Sunnyside Pump Station #1 on the 2016 City of Calgary Alberta Community Resilience Program (ACRP) priority list (already on the list).

 

15. Build Hillhurst Pump Stations #3 & #4 – they are identified as “Potential Future ACRP Eligible Projects” or could be good projects for Federal Green Infrastructure funding.

 

− Need to find funding to move these projects forward ASAP

 

16. Support rebuilding the Sunnyside Sanitary Lift Station (which is already ongoing).