The devastating flooding in southern Alberta could have critical lessons for all towns and cities located near rivers with subdivisions in flood zones. Chilliwack has been the victim of flooding in the past and it’s only a matter of time when spring melt and weather conditions will pull the elements together for a future encounter with a raging river.
Weather and geography came together in Alberta causing the perfect storm. A massive high pressure system held in place by a ‘loop’ in the jet stream that prevented an easterly low pressure system moving through are what turned a normal spring storm into a deluge. The system got stuck over the eastern slopes of the Rockies, pulling in moisture from Saskatchewan and the U.S. The unusual weather looping brought upside down temperatures. Whitehorse had beach front weather with highs of 25oC
An unprecedented 220 mm of rain fell in just 36 hours in one area of the Kananaskis. As the rain kept falling it added to the melting snowpack and last winter Alberta had record snows. In just 48 hours, the flow rates of the Bow, Elbow and Highwood rivers spiked five to ten times that of normal. Streams became rivers; rivers became 100 k/h torrents, picking up trees and car-sized boulders and ripping houses from their foundations with the ease of pulling daisies. On Thursday, the Elbow River peaked at 513 cubic metres per second. The entire crisis spilled into southeastern B.C. with flooding in the Elk Valley region.
This flood is far worse than the flood of 2005 that also took three lives and was then considered the province’s worst. Some $165 million were paid out in disaster service payments. This year’s flood, is considered at least four times worse. So far, three people have also tragically died.
Flooding is no stranger to the Fraser Valley. The Fraser River has reached flood stage 25 times in the last 100 years with the largest river flood in May 1894 when rapid snowmelt caused river levels to dramatically rise in both height and breadth triggering flooding from Harrison to Richmond.
The second largest flood was in 1948 by which time the valley was a busy, growing community of agriculture, industry and settlement. The Trans-Canada highway had been built and there were two transcontinental railway lines. Thousands of people were displaced and infrastructure damage included roads, bridges and hundreds of buildings. With the rebuilding came dykes and berms to keep the river in its channel.
No doubt Alberta (and many communities in Canada) will take a more critical look at building in flood zones. Already, criticism is being voiced that not enough attention was paid to the recommendations in a report following their 2005 flood.
In 2006 the Alberta government released its Provincial Flood Mitigation Report: Consultation and Recommendations. In addition to the key recommendation of establishing and keeping up to date information on flood zones, a strong recommendation was that building development should be stopped on flood risk areas. The report stated that undeveloped flood plains are the natural and most effective form of flood mitigation and selling land in those zones is the opposite of mitigation goals.
As the flood waters move through the river networks to Manitoba to drain into Lake Winnipeg, the sobering economic facts of this event will start to surface.
But other questions are also emerging. Is this a once in a lifetime event, or are weather events of this magnitude on the increase? Scientists can’t help but ask if more intense weather patterns bringing these levels of precipitation, melting, and flooding are in the future as the global climate shifts gears.
Many are trying to find out.