Peak flows in Calgary

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Peak flows in Calgary

Bow River Shuttles writes: "We received this very interesting email on June 25 from Mac Hickley of Calgary River Valleys. If you thought our recent flood was a once-in-a-lifetime 1:100 or 1:300 year event, think again."

Hello Friends of Calgary River Valleys,

I would like to respond to some comments and requests for information regarding the flood events of this past weekend.


Firstly, the CRV Board of Directors would like to extend their deepest sympathies to all those who have been displaced or harmed by the floods. Our volunteers and staff have worked hard for many years to anticipate and plan for this kind of occurrence in the city, to raise awareness and encourage policies to mitigate damages, and to reduce the level of risk to the public and public infrastructure. We believe that the CRV mission has never been more valid than it is now.

Secondly, the response by emergency services, City employees and Calgary City Council has been professional, comprehensive and well managed. Our heartfelt thanks and appreciation go to everyone who is working on or helping with recovery efforts. While dynamic and flood-prone rivers are certainly not unique among world cities, we are confident that the local response has been as fast and effective as it could be anywhere, especially in the face of dangerous and variable natural conditions.

Thirdly, CRV will continue to work closely with our partners in local communities, the City of Calgary and Government of Alberta to rebuild, recover and celebrate our rivers and riparian areas. If you have any further questions or would like more information, please contact me any time.

Finally, FYI – here’s a few peak flow figures** (ref: Government of Alberta website) as measured at three river gauging stations:

• Elbow River at Sarcee Bridge (i.e., above Glenmore Dam):

On Friday 21 June at 00:00:00 (midnight), the Elbow peaked at 543.208** cms (cubic metres per second).

Based on projections from the Calgary Floodplain Study (1983), this was between a 1:20 and a 1:50-year** flood event.

• Elbow River below Glenmore Dam:

On Friday 21 June at 03:00:00 (3 am), the Elbow peaked at 555.926** cms

Based on projections from the Calgary Floodplain Study (1983), this was less than a 1:50-year** flood event.

• Bow River at Calgary:

On Friday 21 June at 07:00:00 (7 am), the Bow peaked at 1682.913** cms

Based on projections from the Calgary Floodplain Study (1983), this was a just a touch more than a 1:50-year** flood event.
In comparison, the peak flow in 2005 was 791 cms and was considered about a 1:10-year event on the Bow River.

**NB: Estimating the return period of a flood event based on flow rates is tricky at best and in some ways futile. For water-cooler discussions, you may like to consider the following points:

- Estimated return-period projections were calculated via a computer model in 1983 as part of the Calgary Floodplain Study.

- Flow data posted to the government website are preliminary and subject to confirmation and perhaps amendment in the future.

- Attached for your reference is a graph showing historical peak river flows on the Bow River in Calgary.


Please take care and when you have time, consider providing whatever help you can manage to return Calgary’s riverfront areas to a cleaner, healthier state.

Thanks very much,
Mac.

Mac Hickley, MEDes, RPP, MCIP
Calgary River Valleys

http://www.calgaryrivervalleys.org/

T: 403 268-4867, F: 403 268-6906
PO Box 2100, Stn M, Code # 414
Calgary, AB T2P 2M5

Calgary Water Centre - Bldg. 'M'
2nd floor - 651 25th Avenue SE

Calgary River Valleys champions and engages the public in the protection, appreciation and stewardship of Calgary's rivers, creeks, wetlands and watershed resources.

We are the voice of your rivers.