Friday, June 28, 2013

UPDATED: FLOOD 2013 ~ Bow River Historical Floods to 1870 (AB Government)

UPDATED:  Mayor Nenshi's update today highlighted that the current flow is vastly reduced but still double (2X) normal flow (listen HERE).  A request has been made to further lower the release rate from Transalta's facilities.

This historical graph puts the Flood 2013 into perspective.  While the flow of the Bow has been managed to a great extent, there have been a couple past events that are magnitudes greater.  Whether one wishes to refer to a 1:10/50/100/500 yr event, the flood of 2013 only represented 67% of the known and measured peak flood a couple of centuries ago (ca 1870), and barely breached the 1:20 limit.  Modernization of society has dampened the impact to some degree (i.e., lower amplitudes in variation), but from a proximity and wealth perspective, the effect has been dramatically intensified.



Anonymous said...

Good graph showing frequency. The last 80 years look like anomalous.
Also, I heard from a source in a relevant City dept that max flow last Friday was closer to 2000 m3/s.

Tahoe said...

Ghost dam was completed in 1929. Bearspaw dam was completed in '54. I believe these may have had a significant influence over flood magnitude. Such tempering of flows is beneficial to downstream users, but if capacities of the reservoirs is exceeded - then their influence becomes rather negligible. Thanks for the comment - much appreciated!